Animal health and diseases

BLACKFORDBY COLLEGE OF AGRICULTURE ANIMAL HUSBANDRY ANIMAL HEALTH (Compiled by Raphael Phiri) Introduction To understand diseases in an animal, it is necessary to know the animal in health and to know the conditions required to keep it in health.

Health -Is the condition in which all the organ systems and body structures are working in full harmony/functioning normally.

Certain conditions are necessary for health, they are: a) Suitable surroundings, b) Suitable food and water, c) Proper functioning of the body.

Characteristics/appearance of a health Animal -Alert, active and supports itself well (very aware of its surroundings) -Its eyes are bright, clean, normal blinking & without any discharges.

-Its ears are cocked-(upright always, attentive) -Its tail is continually swishing at attendant insects.

-Its coat is smooth and shows a sheen (shiny appearance) -Its muzzle should be cool, soft and shows beads of moisture over its surface.

-The animal continuously clears discharge from its nostrils with its tongue.

-Feaces shld be firm, urine straw coloured & passed out without any difficulty.

-Has a good appetite and drinks normally.

-Always with other animals (no self isolation).

-Pink mucus membranes.

-Moves easily and steadily with all its feet taking its weight.

The main causes of diseases; ●Direct contact btwn infected animals and non-infected. ●Ingestion of disease causing organisms in feed or water. ●Bites by disease transmission organisms (vectors) such as ticks, ---1

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●Dirty pens. ●Improper feeding.

ANIMAL DISEASES Definition: 1. A disease is an inability to perform physiological functions at normal levels even though nutrition and other requirements are met.

2. A disease is any alteration in the state of the body of an animal or of its organs which interrupts or disturbs its proper functions either caused by organisms or injury.

3. It is therefore any departure from health. *Disease can be described as, Acute, Sub-acute, Per-acute or Chronic.

1. Acute — denotes a disease that is quick on onset and the animal suffers for a short period. It does not denote the severity of the disease.

2. Chronic — a disease that is slow with onset and last for a long time. The animal suffers for a long time.

3. Sub-acute — something in between acute and chronic.

4. Per-acute — a disease that kills an animal quickly.

Definition of terms: Pathogen - is a disease causing organism.

Incubation period - period from time of infection to onset of clinical signs Clinical signs (symptoms) - observable signs that an animal is sick.

Sub-clinical signs a disease is present but can’t see any signs.

Endemic (enzootic) - common in a particular area in a particular population.

Epidemic (epizootic) - a disease occurs at a particular time within a population in a certain area, for one reason or another conditions become favorable.

Pandemic (panzootic) - huge numbers in a whole country or continent Zoonoses - diseases which can be transmitted between man and animals (e.g. Anthrax.

Notifiable Disease - a disease which you need to notify the state department of Veterinary Service, e.g. F.M.D, Anthrax, Brucellosis etc.

DIAGNOSIS -Is the process of finding out the disease and its cause. The process has got four main stages namely;

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●Case history This is the information supplied to the Vet by the farmer. This helps to find out what could have caused the sickness. Information to be reported includes; -about the animal -about the illness -about treatments and vaccinations done -about management ●Observation and Handling -observing the animal without touching it and one will be assessing things like animal condition, sex of the animal etc.

-Handling done to examine aspects like; temperature, pulse, breathing, mucus membranes and lymph nodes.

Temperature Pulse rate Breath rate

Cattle 38.5 70bts/min 30 br/min

Pigs 39 75bts/min 15 br/min

Sheep 39 80bts/min 20 br/min

Horses 38 35bts/min 12 br/min

●Post-mortem examination -In case an animal has died of an unknown cause. It is important to have a post-mortem done by the Veterinary department. The animal should be placed under shade whilst a report is made to Veterinary department. ●Taking of samples -Can be done either by the farmer or the Veterinary personnel. These are taken to confirm the cause of disease at the laboratory. *Animal diseases are grouped into two, namely, Infectious and NonInfectious diseases.

1. Infectious diseases - which are caused by pathogens (viruses, bacteria, protozoa, rickettsiae, helminthes and fungi)

2. Non-Infectious diseases - which are due to toxic/poisonous conditions, deficiency syndromes and production diseases.

Importance of animal diseases: 3

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-Results in animal loss to the farmer.

-High treatment and veterinary costs.

-Reduced production and loss of revenue.

-Export ban and loss of forex revenue.

-Zoonoses- some diseases can be transmitted from animals to humans and through animals products.

PREVENTION & CONTROL OF DISEASES Prevention is better and far much cheaper than cure.

There are several steps that a farmer can take to prevent or control diseases on the farm, these are: 1. Treatment 2. Slaughter 3. Quarantine 4. Biosecurity 5. Proper disposal of carcasses 6. Vaccination.

1. Treatment -Early treatment of diseases helps to minimize further spread of diseases to other animals.

2. Slaughter -consider cost of treatment vs. slaughter and production.

-consider also risk of spread of the disease.

-distance from animal health centre.

-official policy for the disease e.g. F.M.D, C.A, e.t.c.

-consider also welfare of animals.

3. Quarantine -basically means animals are separated for a period from rest of the herd.

-carried out with sick animals or new animals (recently purchased).

N.B. Feed quarantined animals and sick animals last.

4. Biosecurity -a farmer can prevent entry of external and new animals onto the farm.

-also involves entry of humans to the farm other than your workers -keep a closed herd i.e. you don’t buy in animals, don’t participate in shows.

5. Proper disposal of carcasses 4

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-all dead animals should be disposed of in a way that does not put other animals at risks.

This applies especially to the diseases with bacteria that can stay in the environment for long periods, e.g. Anthrax. *Dispose by burning or by deep burying.

6. Vaccination -an infected animal produces antibodies to fight off infection; these antibodies remain in the body even after infection is cured.

IMMUNITY -immunity is the ability to withstand infection.

Organs of immune system -bone marrow, lymph nodes, thymus gland, payer patches, bursa fabricus, spleen.

-all the above organs are responsible for the cellular type of defence.

We have a number of cells; T-lymphocytes—thymus derived lymphocytes.

B-lymphocytes—bone marrow derived lymphocytes.

Macrophages—secondarily involved in the clearance of infectious agencies by a process of phagocytosis and antibody production.

There are four types of immunity, namely; 1. Natural active immunity, 2. Artificial active immunity, 3. Natural passive immunity, 4. Artificial passive immunity.

1. Natural active immunity -is due to natural disease, -this is the type of immunity acquired by an animal that has been infected by disease and has recovered. After the infection the immune system produces antibodies which then remain in the body and the animal will have a natural immunity to that particular disease.

-This type is long lasting and sometime for a lifetime and is specific i.e. specific antibodies for a specific pathogen.

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2. Artificial active immunity -Due to vaccination, this is done by injecting an animal with a small amount of the bacteria or viruses which cause the disease and these then stimulate the production of antibodies and memory in the immune system.

3. Natural passive immunity -this is the type of immunity acquired by a young one when it drinks its mother’s first milk (colostrum). The antibodies pass from the mother’s blood into the colostrum and are ingested by the young one and pass into its blood giving it immunity.

-this immunity type is effective only for a short period of time.

4. Artificial passive immunity -an animal is serially infected until it produces a high amount of antibodies, then it is bled and blood given to another animal suffering from the same disease.

-this immunity type is short lived and there is risk of an allergic reaction.

VACCINES -A vaccine is a biological agent used to produce active immunity or is a biological substance which when introduced in the animal body in time, cause the production of antibodies.

-This biological agent will have been altered to retain its immunogenesis (capacity to activate the immune system) but will have lost its pathogenesis.

-Vaccines come in two forms, either dead or alive.

-they work for only one disease and sometimes for one strain of pathogens.

Properties of a good vaccine -should produce a life long immunity, e.g. C.A vaccine.

-should produce no adverse effects on animals, -should have long safe keeping qualities and still retains its immunogenesity.

Routes of administration.

1. Intramuscular—into the muscles (rump, neck, e.t.c.)

2. Subcutaneous—under the skin (neck, dewlap, e.t.c.)

3. Intravenous—into the vein (jugular vein) 4. Oral—via the animal’s mouth.

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Precautions to take when using vaccines -Use before expiry date.

-Do not mix two vaccines in one syringe.

-Do not vaccinate sick animals, stressed animals or those on a low plane of nutrition.

-Use clean syringes and needles free from chemicals.

-Use according to manufacturer’s instructions.

-If using drinking water it should be clean, cool and free from disinfectants.

-Store vaccines in a refrigerator;-a cold chain should be maintained from purchase to administration.

Interaction btwn management & diz. Occurrence Disease in farm animals is often the end result of inadequate management.

Management includes things like; calving management, housing, feeding & nutrition, animal handling, disease control e.t.c.

1. Calving management -calving in a dirt environment will predispose both the dam and the young one to infectious diseases.

-umbilical infection may occur so as may ingestion of pathogens in young animals.

-the mother may have infections of the vagina and/ or uterus.

-inadequate intake of colostrum milk predisposes the young animal to many infections.

2. Housing -overcrowding predisposes animals to respiratory and gastro-intestinal infections.

-overcrowding also results in accumulation of noxious gases such as ammonia which is very dangerous to animals.

-weak animals may be trampled and might not get enough feeding due to bullying.

NB. Temperature, humidity and ventilation, very important in animal housing.

3. Nutrition -animals on a low plane of nutrition are often prone to many diseases, this is becoz. their immune system is incompetent and well fed animals are better able to resist infections.

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4. Animal handling -poor handling of animals often cause stress to animals.

-transporting of animals in overcrowded and dirt trucks also cause a lot of stress to animals.

NB. Ensure you have good animal handling facilities and personnel are trained in humane animal handling. ***Stress causes immuno-supression.

How diseases can be transmitted 1. Host to host—contagious--spread by contact between animals.

2. Mechanical—same needle btwn animals, dehorning iron, contaminated bedding & soil.

3. Vector/intermediate host—ticks and snails.

4. Food and water source.

5. Wild life—act as reservoirs e.g. Foot & mouth and Rabies.

Epidemiology -Is the study of all factors which determine the occurrence and distribution of a disease.

-The occurrence of disease is a result of an interaction between multiple factors. This forms the basis of Preventive, Medicine, or Herd health management.

Disease causing agents 1. Virus -are minute organisms that can not be seen under a light microscope, and are so small that they can even cause an infection in bacteria.

-they don’t have a proper nucleus thus they can’t carry out their metabolic functions which result in growth.

-once inside the cell of an animal they takeover the control of animal metabolism, for the purpose of their multiplication and growth.

-when they are many of these viruses in infected cell, it will burst thereby spreading the virus to adjacent cells.

2. Bacteria -are single cell -consist of a thick outer structure (cell wall) -antibodies are aimed to destroy the cell wall.

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-the cell wall is made up proteins and polysaccharides -it is the configuration that antibody recognize with moisture and nutrients.

-bacteria can grow outside the body but under unfavorable conditions.

-some bacteria turn themselves into very resistance forms known as spores.

-spores can survive for many years e.g. clostridia bacteria.

3. Rickettsia -living organisms which can’t be grouped into bacteria or virus.

-they posses properties of bacteria and the other for virus e.g. Cowdria ruminantium for heartwater.

-most of these are transmitted by anthropods since they survive in the G.I.T of animals.

-they can briefly survive outside of the living cell.

4. Fungi -members of veg. kingdom.

-live on the skin or in the tissue, but most are external agents.

-consist of vegetative body called mycelium and have some filaments known as hyphae.

-can reproduce both asexual and sexual. *Mycoses –fungal infection/ invasion of the animal’s body and fungus will be multiplying there e.g. Aspergillosis, Ringworm. *Mycotoxicoses –the fungus grows outside the animal’s body (e.g. mouldy feed) producing toxins which upon ingestion by the animal may cause disease e.g. Aflatoxins.

5. Helminths -these are internal parasites, examples are; *Roundworms—wireworms, hookworms. *Flukes—liver flukes, bilharzias. *Tapeworms 6. Arthropods -these are external parasites, -they suck blood, irritate the animal and transmit diseases.

-examples are; ticks, flies, lice, fleas e.t.c.

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DISEASES A) GENERALIZED DISEASES 1. ABSCESS. -localised areas of puss accumulation. *localized - outside the body, normally due to tick bites/wounds (screwworm), navel. *Generalised - bacteria enter via navel, ulcers, wire damage, small wounds and then settle in the liver, lungs, kidneys, joints e.t.c.

-lymph nodes - carcass condemnation. *A generalised (internal) abscess may rapture leading to death.

Treatment.

-localised (external)—will soften and rapture, best to lance to drain properly (gravity), clean out with antiseptics, (iodine, dettol) -protect from screw-worm – apply fly repellant.

-antibiotics can be used after cleaning out the wound with antiseptic- to avoid secondary bacterial infection, (wound powder, healing wound oil.)

Prevention.

-prevent wounds in animals, and control ticks.

-work with clean instruments in clean environment.

-apply iodine/spirit on the navel at birth.

-attend to all wounds as soon as possible.

2. DIARRHOEA/ SCOURS. Causes; -sudden change of diet, -mouldy rancid feed, -poisons, -internal parasites, -bacteria, viruses and protozoa -overfeeding milk.

Signs; -white, yellow, grey, watery, bloody feaces.

-very bad smell depending on cause.

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Problems; -digestion and absorption disturbed -inflammation of the intestine lining -if not treated death from dehydration -recovered animals will have setback in growth/weight gain and poor growth. *Early detection and treatment vital to minimize loss.

Management of Diarrhoea (calves) -replace fluids plus electrolytes.

-oral rehydration Calves; -1 tablespoons salt -8 tablespoons glucose/sugar -3 litres water ***Give the mixture 3-6 litres per calf per day.

Or -1 cup glucose/sugar.

-1 teaspoon salt.

-1 teaspoon bicarbonate of soda.

-0.25 teaspoon permanganate.

-2 litres water. ***Give the mixture 4 litres/ 45kg body weight per day (24hrs).

Diarrhoea Treatment (calves) -oral antibiotics e.g. neomycin.

-oral rehydration.

-withdraw from milk for few days until diarrhoea is cleared.

Prevention (calves) -vaccinate mother (dam) before calving.

-provide clean and dry environment.

-if feeding milk from buckets, clean the buckets.

-ensure calf has enough colostrum milk.

Management of diarrhoea (Adults) 11

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1. Give 300g Kaolin to stop scouring.

2. Universal Remedy -0.25 kaolin -0.25 magnesium oxide -0.25 activated charcoal -0.25 tannic acid. ***Give 2-3 tablespoon by weight mixed with water.

3. Carron oil -0.5 linseed oil -0.5 calcium carbonate solution. ***Give half a litre of the mixture to an adult animal per day.

DEHYDRATION -Fluid loss from diarrhoea due to intake failure, not available, lack of thirstillness.

Signs of dehydration -sunken eyes -rapid loss of body weight -muscular weakness -anorexia (no appetite) Problems -Low blood pH (Acidosis) -Less urine – more waste products in blood (Toxic) B) BACTERIAL DISEASES 1. CLOSTRIDIAL DISEASES. -caused by clostridia bacteria known as anaerobic bacteria.

-produces powerful toxins that are lethal (dangerous, causing death) -examples of clostridial diseases are Pulpy Kidney, Quarter Evil, Tetanus and Botulism. a). Pulpy Kidney (overeating diz.)

-common in sheep -bacteria are naturally present in the intestines of sheep and cause no harm, but certain predisposing factors such as starvation result in the bacteria 12

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becoming pathogenic. They multiply and produce toxins that will cause death to the animal.

Cause:

--

Clostridium ovitoxicum

Risk factor: - affects animals on a high nutritional plane (in good body condition).

Clinical signs (symptoms) -anorexia -convulsions -eyes rolling -grinding of teeth -excessive salivation -sudden death Post-mortem -carcass decomposes rapidly -wool can be easily be plucked off -purple in skin colour -copper coloured liver -pulpy kidneys Treatment -No treatment for animals showing symptoms of the disease.

N.B. Antibiotics don’t work against toxins.

Prevention and control -feed rationing (strike a balance) -annual vaccination against Pulpy kidney; 1. Before deworming 2. Before entering feeding programme 3. Pregnant mothers. b). Botulism -is an acute often fatal poisoning of livestock which occurs after ingestion of toxins.

-the bacteria and toxins are present in the decaying carcasses.

-the botulism toxin is one of the most powerful toxins; the amount of toxin in a single rat can kill several animals.

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**Animals suffering from a phosphorus deficiency display pica & will pick up old bones & other foreign bodies and start chewing them. When a bone saturated with the botulism toxin is chewed, the animal will then die of botulism poisoning.

Cause:

--

Clostridium botulinum.

Clinical signs (Symptoms) -Signs usually appear 3 – 17 days after ingestion of toxic material.

-complete paralysis of all muscles develops within 24 hrs.

-paralysis of the jaw and throat muscles (inability to chew, swallow, feed and drink.)

-protruding tongue.

-salivation.

Treatment: -no effective treatment.

NB. Antibiotics do not work against toxins.

Control / Prevention: -annual vaccination against botulism.

-correction of dietary deficiencies (esp. supplementation of phosphorus & protein) -proper and hygienic disposal of carcasses.

-keeping animals out / away from animal cemeteries. c). Blackleg (Quarter evil) -an acute, infectious but non-contagious disease.

-the causing bacteria produce spores that are most resistant to heat & can survive many years in the soil. Infection results from ingestion of the spores and contamination of wounds.

Cause:

- Clostridium chouveoi

Clinical signs (Symptoms) -lameness -high body temperature (41°c) fever.

-limb muscles are swollen and painful.

-high heart rate (100-120 per min.)

-gas formation under the skin (can be felt over the affected muscle mass).

-death within 12-36 hrs after the onset of clinical signs.

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Post-mortem: -carcass decomposes very fast.

-thin blood stained fluid containing bubbles of gas.

-rapid clotting of blood.

-dark blood stained fluid with patches of dark red haemorrhage found under the skin.

-all body cavities contain excess fluid.

-spleen is swollen and firm.

-patches of haemorrhage present on internal organs including the heart.

Treatment: -high doses of antibiotics such as Penicillin will destroy the bacteria but not the toxin produced by the bacteria, therefore there is no treatment for animals showing symptoms.

Control /prevention: -annual vaccination (6 months – 2 yr olds, during summer and spring) -proper disposal of carcasses (burning or deep burying) -during outbreaks, take temperature twice daily & treat any animal with high temp. with high doses of penicillin. d). Tetanus (Lock-jaw) -an acute disease, the bacteria are present in the soil and kraal manure, natural inhabitant of the intestines of many animals esp. horses, but does not produce illness becoz it does not produce toxins in this state. When the bacteria gains access into a wound, they then produce a potent (powerful & effective) toxin. The toxin causes paralysis by translocation to the spinal cord along nerve fibres.

Cause:

--

Clostridium tetani

Clinical signs (Symptoms) -stiffness of muscles.

-animals can not eat or drink.

Treatment: -no treatment, but can treat stiffness with muscle relaxants.

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Control/ prevention.

-any wound on the animal must be cleaned thoroughly, flush out with hydrogen peroxide.

-Vaccination.

2. ANTHRAX. -is a disease of all warm blooded animals -infection takes place via the mouth when the spores are ingested from contaminated feed or animals displaying signs of pica. The organism produces a very resistant spore if exposed to air, which is why the carcass from an animal having died from Anthrax should not be opened up for postmortem, and should be destroyed by burning or buried at least 2m deep.

Cause:

--

Bacillus anthracis

Clinical signs -high temperature -tremble and shiver -swellings on the neck and chest -dark coloured blood almost tar like exudes from the nostrils and anus.

Treatment: -Antibiotics, Penicillin and Terramycin are effective if given early.

Prevention/ Control: -This is a specified diz and consequently the Veterinary Department must be informed and will then assume responsibility for its control.

-All animals in Anthrax areas should be vaccinated annually.

3. BRUCELLOSIS (C.A) -a highly contagious diz of cattle causing abortion in heifers and cows in the last third of pregnancy (third trimester) i.e. 6-9 months. This diz. Is a public health hazard as it also affects humans.

Cause:

Bacterium

---

Brucella abortus.

Transmission: -ingestion of contaminated feed or water, pastures can be contaminated by amniotic fluid from an infected animal.

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-ticks can also transmit the disease.

-transmission can also be through inhalation of contaminated air.

Clinical signs (Symptoms - Abortion in late pregnancy, or even birth at full time of weak, stillbirth.

Abortion result from the organism infecting the afterbirth as a result the foetus is not properly nourished and then dies and is expelled.

- Retained afterbirth or placenta.

- Increased incidents of metritis (prolonged calving to conception interval) **In humans, infection is manifested a general illness called Undulant Fever which is often confused with influenza or malaria. The main symptoms in humans are: - sweating, headache and fever periods.

The disease in humans can last for several months.

Treatment: -no treatment Prevention / Control: -Vaccination – heifers with S19 Brucellosis vaccine at 4-10 months of age.

-Culling of affected animals.

-Aborting cows must be strictly isolated until 3wks after abortion. **Meat from an infected cow is safe for human consumption.

4. FOOTROT. -is a diz. Of cattle, sheep and goats but sometimes pigs. It is an acute or subacute necrotic infection of the hoof and inter-digital space characterized by pain, severe lameness, fever and loss of condition.

-The bacteria occur normally in the intestines of the animal and enter the hoof thru a crack or tiny wounds in the skin infecting the superficial layers of skin before penetrating into deeper tissues.

Cause: Cattle - Bacillus necrophorus.

Sheep - Bacillus nodosus.

Risk factors: -muddy or moist conditions.

-small wounds from tick bites.

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-genetics.

Clinical signs (Symptoms) -lameness (1, 2 or all legs) -loss of appetite.

-reduced milk yield.

-Small wounds – (producing foul odours) -mass of rotten tissue.

-high body temperature.

-swollen foot (reddening of soft tissues of the inter-digital space) -animal may not bear weight on the affected leg, if one.

Treatment: -Clean the wound with local treatment – antiseptics, dettol, and iodine.

-Antibiotics – Tetracycline and Penicillin.

-Twice daily treatment of the feet with Formalin or 10% Copper Sulphate solution applied to the foot or mixed into a footbath and animals made to walk thru it every 4 - 5 days.

Prevention / Control: -Avoid muddy and moist condition.

-Paddock rotation.

-Isolate affected animals.

-Footbath with 10% Copper Sulphate, 5% Formalin or Zinc Sulphate.

5. CASEOUS LYMPHADENITIS. -A diz. of sheep and goats characterized by formation of abscesses in lymph nodes and internal organs, exerting little influence on the general health of the animal unless the diz. becomes generalised.

Cause: -- coryne bacterium -- Pseudo tuberculosis ***The organism can survive in puss infected soil for up to 8 months.

Clinical Signs: -Gross enlargement of one or more superficial lymph nodes.

-Abscesses normally rupture and thick green puss is discharged.

-Poor growth.

Post-mortem: -Caseous abscesses filled with greenish yellow puss occur in lymph nodes and some internal organs.

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Treatment: -Not usually attempted becoz. abscesses are encapsulated and antibiotics cannot reach the organism.

Prevention/ Control: -Avoid contamination.

-Lambing/ tail docking shld take place in a clean environment.

-Avoid sharing shearing equipment or sterilize btwn use.

-Surfaces contaminated with puss must be thoroughly cleaned.

-Shear young sheep first.

C) VIRAL DISEASES. 1. LUMPY SKIN DIZ (L.S.D.) -A specified diz. of cattle characterized by the sudden appearance of firm swellings/lumps on the skin and underlying tissue on all parts of the body.

Cause: -Two viruses are implicated, namely; Neethling strain which can be severe and a mild form caused by Allerton strain.

Transmission: -Biting insects.

-Unsterilised needles used btwn animals.

Clinical Signs: -High temperature.

-Reduced milk production.

-Loss of appetite (Anorexia).

-Pregnant cows may abort.

-Lumps appear all over the body i.e. on the skin, muzzle, neck, brisket, back, thighs and under the tail.

-Lumps grow to a size of 5cm in diameter, lumps then fall off leaving raw flesh.

-Animals show running eyes and salivate.

-Most affected animals also show one or more swollen, painful limbs and become lame.

Treatment:

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-No specific treatment for viral diseases, although antibiotic injections will assist in combating secondary bacterial infections.

Prevention/ Control: -Controlled effectively by vaccination. *Vaccinate annually before rainy season starts (Oct. /Nov.). **Advisable to inject the vaccine into the dewlap as some animals may develop a large swelling on the site of injection. Use sterile needles btwn each animal.

N.B. There are several Important Complications of Lumpy Skin Disease (L.S.D.)

1. Infertility and Sterility; -Cows and bulls are very often infertile for several months after L.S.D, but usually recover. Bulls may show permanent sterility if lumpy skin lesions occurred on the testicles.

2. Udder trouble; -One or more quarters may be lost owing to lumpy skin. Sometimes a month or longer after lumpy skin, small pieces of dead udder-tissue may become detached and float in the milk.

3. Breathing problem; -A small % of cases develop difficulty breathing a month or two after lumpy skin. This becomes worse and later on, the animal may gasp for breath with the mouth open and tongue protruding. On examination the windpipe will be found collapsed at some point or other.

2. FOOT & MOUTH DIZ (F.M.D) -Highly contagious viral diz of all cloven hoofed animals and man.

-Secretions and excretions of affected animals spread the virus.

-The virus cannot withstand heat but can survive in chilled meat for several months.

-The virus multiplies in blood and damages the mucus membranes of the mouth and tongue causing blisters that develop into superficial sores.

Cause:

---

F.M.D Virus.

Transmission: -Ingestion -Inhalation 20

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-Contact – a buffalo is a reservoir and carrier of the virus, transmission to cattle occurs when the two meet.

Clinical Signs: -Incubation period is 2 -5 days.

-Reduced milk production.

-Severe loss of weight (Due to anorexia).

-Salivation (foamy, ropy saliva).

-Slow chewing movement.

-Severe lameness.

-High body temperature.

-Blisters on mouth, gums, tongue, and btwn the hooves.

-The hoof breaks away from the skin, particularly at the back of the foot, resulting in Foot & Mouth Slippers.

Treatment:

--

None.

Prevention/ Control: -Vaccination annually.

-Slaughter (Eradication) -Imported animals to be kept in quarantine for a period.

-Separate buffalos from cattle.

-In the event of the diz being suspected, must be reported to the Veterinary Department immediately and they will take over control.

3. RABIES. -Highly fatal.

-Affects all mammals including humans.

-It is a Notifiable diz; suspected cases must be reported to the Department of Veterinary Services.

-It is transmitted through bite from infected animals, most commonly dogs and jackals. In the infected animal the virus is concentrated in the central nervous system (brain, spinal cord) and the salivary glands.

Cause:

--

Rabies virus.

Transmission: -Contact with contaminated saliva onto wounds/ cuts.

-A bite from a rabid carnivore.

Clinical Sings: 21

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-Incubation period is 2 -3 wks.

-Cardinal sign of rabies in all animals is a change in behavior – either Aggressive or unusually Placid – (calm & peaceful, does not easily get angry/ excited), wild animals will loose their fear of humans.

-Death.

-Symptoms of the diz. Can be divided into three phases; 1. The initial stage, -The animal becomes scared, restless, and disobedient the animal will snap into the air at imaginary objects.

2. The stage of increased irritability, * 2 -3 days after the first stage, the animal may bite if stroked or spoken to, or can appear very friendly. The animal will chew sticks & stones, will attempt to drink but is unable to. After a few days the animal will then go mad & bite anything it comes in contact with (Furious Stage) and then lie down exhausted as if unconscious.

3. The Hydrophobic Stage (fear of water) * 1 – 2 days after the second stage, the animal will be afraid of water and paralysis follows. The animal can not swallow and goes into fit when it sees water. It can not rise and then dies.

Clinical Signs (HUMANS) -Pain at the site of bite.

-Headache and fever.

-Confusion, excitement, salivation, convulsions and also hydrophobia.

Treatment: -None for animals. **For Humans; -Thoroughly disinfect the site of bite/contact using plain soap and water.

-Medical attention shld be sought for rabies vaccine and anti-serum treatment.

Prevention/Control: -Annual vaccination of cattle in rabies areas.

-Jackal eradication & dog vaccination will minimize the possibility of cattle contracting the diz.

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D) RICKETTSIAL DISEASES. -Rickettsias are small round organisms just visible with a light microscope, they are similar to viruses but larger, require living cells in-order to multiply, but resemble bacteria in that they have a cell wall & are susceptible to antibiotics.

1. HEARTWATER (Cowdriosis) -Is an acute diz. of sheep, goats and cattle caused by a Rickettsial organism which is transmitted by ticks (bont tick) -All year round, but mainly during rainy season due to high bont tick population.

Cause:

--

Rickettsia - Cowdria ruminantium.

Transmission: -Tick bites.

-Bont tick – Amblyomma habraeum is a specified pest.

Clinical Signs: -Incubation period is 10-14 days.

-High body temperature.

-Nervousness (twitching, bewildered, high stepping gait, aggressive) -Salivation.

-Rumination ceases.

-Convulsions.

Treatment: -Tetracycline antibiotics – e.g. Terramycin injection at double the normal dose is the drug of choice provided treatment is early before nervous symptoms appear.

Prevention/Control: -Vaccination.

-Tick control (good dip management) -Proper Paddock rotation.

2. PINK EYE (Opthalmia) -An infectious diz. of ruminants, characterized by corneal opacity, varying degrees of ulceration and weeping of the eyes.

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Cause: 1. Moraxilla bovis –for cattle.

2. Chlamydia psittaci – for sheep and goats.

Predisposing Factors: -Eye worm (Thelazia rhodesi) -U.V. Radiation.

-Dusty environment.

-Grazing in tall grass.

-Too high in fly population.

-Overcrowded.

-Other eye infections.

Transmission: -Flies.

-Contact.

Symptoms: -Deep red eyes.

-Cloudy eyes (opacity, whiteness) -Tearing/crying eyes.

-Eyes may develop into abscesses.

-In severe cases eyeball can burst.

Treatment: -Antibiotics, containing oxytetracycline - eye/wound powder, eye ointment.

Prevention/Control: -Fly control.

-Removal of manure from the feeding pens, (a.s.a.p).

-Veld & pasture management.

-Provide collars with insecticide to animals.

-Avoid overcrowding.

-Provide adequate shading to animals.

E) PROTOZOAL DISEASES 1. REDWATER (Babesiosis) -Is a protozoal diz. of cattle.

-It affects the red blood cells.

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-The diz. causes high mortality in adult animals.

-Most prevalent in rainy season due to high tick infestation.

Cause:

---

Babesia bigemina

Transmission: -Ticks – mainly blue ticks (Boophilus decoloratus) -Contaminated needles.

Clinical Signs: -Incubation period is 8 - 15 days.

-High temperature (40-42°c) -The animal will be off-colour (dullness) -Anorexia (loss of appetite) -Frequently lying down.

-Listless (feeling tired & not interested in anything) -Constipation, followed by watery diarrhoea.

-Red to brown colour of urine at later stage – Cardinal Sign.

-Labored breathing.

-Mucus membranes are pale in colour.

Post-mortem: -Anaemic carcass.

-Enlarged spleen and liver.

-Jaundice.

-Red urine in the bladder.

Treatment: -The most common used drugs are, Berenil and Imizol. *Berenil is dissolved in 12.5ml of water – is sufficient for treatment of 300kg body mass, by either intramuscular or intravenous injection. *Imizol is given at a dosage rate of 1ml per 100kg body mass.

As with most diseases, timely treatment is absolutely necessary to be successful.

Prevention/Control: -Effective means is by tick control. (Effective dip management) -Vaccination.

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2. JANUARY DIZ. (Theileriosis) -Is a Notifiable disease common in Dec.-March & most cases are recorded in Jan. -The disease affects the white blood cells.

Cause:

---

Theileria parva bovis.

Transmission: -Ticks – brown ear ticks-Rhipicephalus appendiculatus.

-Contaminated needles.

Clinical Signs: -Incubation period is 9-20 days.

-High temperature (41.5°c).

-Salivation – profusely.

-Listless.

-Swelling of lymph glands.

-Corneal opacity.

-Difficulty breathing.

-Lies down & dies with a white froth exuding from the nostrils.

Post-mortem: -Enlarged fluid filled lungs.

-Froth in the trachea.

-Ulcers may be present in the abomasums.

-Liver and spleen is enlarged.

-Swollen lymph nodes.

Treatment: -High doses of Oxytetracycline are slightly effective if administered early.

Prevention/Control: -Control brown ear ticks paying special attention to sites of attachment i.e. ears, horn bases and tail brushes.

-Buffalo/cattle contacts shld be avoided, buffalo are carriers of a closely related diz.

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3. GALLSICKNESS (Anaplasmosis) -A protozoan diz. Of cattle transmitted by ticks and affecting the red blood cells.

Cause:

---

Anaplasma marginale.

*A closely related parasite Anaplasma centrale differs from A. marginale in that;-it lies at the centre of the blood corpuscles (cells).

-it causes only a very mild illness, but stimulates the development of immunity.

-A. centrale is therefore used as a vaccine against Anaplasmosis diz.

Transmission: -Ticks – mainly blue ticks (Boophilus decoloratus), but also occasionally by red legged-ticks (Rhipicephalus evertsi) -Blood sucking flies.

-Contaminated needles.

Clinical Signs: -Incubation period is long, about 20-40 days.

-High temperature (40-41°C) -Anemia –due to the destruction of red-blood cells.

-Jaundice.

-Off-colour (dullness) -Anorexia.

-Reduced milk production in cows.

-Some animals may show nervous symptoms and become aggressive.

-Constipation.

Treatment: -Imizol, Oxytetracycline or Terramycin can be used at double dosage.

-Rumenotorics (gastro-intestinal stimulants) shld be give to stimulate digestion, e.g. molasses, vinegar, brown sugar or even Epsom salt.

-Also the animal shld be stabled and given ample fresh water and green feed.

-Injection of iron preparations are recommended to stimulate blood formation.

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Prevention/Control: -Effective dip management (tick control).

-Vaccination (using Anaplasma centrale)

4. TRYPANOSOMIASIS (Nagana) -A specified diz. of ruminants, not Zoonosis but can affect cattle and humans.

-The disease is called Sleeping sickness in humans.

-It is common in the north-west Binga, Gokwe e.t.c.

Cause:

---

Trypanosoma vivax and Trypanosoma congolense.

Clinical Signs: -Loss of body condition.

-High temperature.

-Anaemia Post-mortem: -Watery fat.

-Anaemic carcass.

-Fluid in the body cavities.

-Enlarged lymph glands.

-Blood is thin, watery and does not clot.

Treatment: -The drug Berenil is effective against the disease in cattle.

Prevention/Control: -This is a specified disease and is controlled by a branch of the Veterinary Department.

5. TRICHOMONIASIS -Is a contagious venereal disease of cattle causing infertility, pyometra (purulent discharge containing puss) and abortion.

Cause:

---

Trichomonas foetus.

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Clinical Signs: -Repeated irregular heat cycles (returns to service) -If pregnancy holds, possible abortion by the fifth month.

-The bull shows no evidence of symptoms.

Treatment: -Cows are not treated, sexual rest for 3-4 normal heats will usually result in spontaneous recovery.

-Bulls can be treated topically with various drugs, however treatment shld be conducted by a qualified veterinary surgeon.

Prevention/Control: -There is no vaccine against the disease.

-Keep a closed herd & to only buy in animals from clean herds.

-Artificial Insermination (A.I) assists in the prevention of the disease.

F) NUTRITIONAL DISEASES. 1. ACIDOSIS. -An acute or sub-acute over-ingestion of carbohydrates resulting in a drop in rumen p.h.

-Fermentation leads to a lowering of the rumen p.h with a consequent destruction of the normal rumen flora.

Cause: -Excessive ingestion of feeds rich in starch or sugars.

Clinical Signs: -About 8-12 hrs after feeding, the animal loses its appetite.

-The animal will show signs of indigestion and irritability.

-The rumen is usually distended (swollen becoz. of pressure 4rm inside) and loses its motility.

-Respiration becomes shallow and rapid.

-Feaces from the animal becomes very loose.

Treatment: -Re-establish the normal rumen faction as soon as possible – fluid & bicarbonate therapy to restore the normal acid base balance is necessary – 120grams or more sodium bicarbonate drenched to the animal.

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-In addition, 100ml of penicillin drenched to destroy the harmful bacteria that colonize the rumen.

Prevention: -Animals shld be introduced to high concentration rations slowly over a period of 7-10 days.

-Good quality roughage shld be available at all times.

-Animals shld not be allowed access to grain stores & shld exercise caution when permitting animals access to stover particularly if badly reaped.

2. UREA POISONING. -An acute often fatal over-ingestion of urea resulting in an elevation of rumen p.H. Cause: -Too rapid introduction of urea to an animal’s diet when animals are unaccustomed to it.

Clinical Signs: -Severe abdominal pain.

-Animal becomes weak.

-Difficulty breathing.

-Excessive salivation.

-Nervous symptoms, (excited/aggressive appearance). **With regards to nervous symptoms, the animals are found to adopt a reversing gait and in severe cases they may in fact run backwards.

Post-mortem: -The carcass is pretty negative, becoz. ammonia is so volatile, it dissipates rapidly and an elevated rumen p.H. is not often encountered.

Treatment: -The success or otherwise of the treatment depends on the quantity of urea ingested and how long after ingestion treatment is implemented.

-Vinegar is the remedy of choice as it neutralizes the alkaline rumen content and reduces the amount of ammonia absorbed. **Mix 750ml vinegar with an equal amount of water and molasses & drench the animal.

-Vinegar is mixed with water to eliminate its burning quality.

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Prevention: -Urea fertilizer shld be stored under lock and key.

-Introduce animals to urea slowly.

-In general, urea shld not constitute more than 3% of the concentrate ration. **As a rule of thump, an adult cow shld not be given more than 60grams of urea per day.

3. BLOAT. (Gas Bloat & Frothy Bloat) -Bloat is an excessive accumulation of gas in the rumen and reticulum due to inability to belch out gas which is constantly being formed by fermentation.

-It is categorized into Gas bloat and Frothy bloat, where gas bloat often accompanies urea and plant poisoning and frothy bloat most commonly occurs after grazing on rapidly-growing legume-dominant pastures e.g. lucerne.

Cause: -Overfilling of the rumen.

-Paralysis or malfunction of nervous control of eructation.

Clinical Signs: -Distention of the left flank.

-Labored breathing.

-Excessive salivation.

-Eructation eventually ceases.

-In severe untreated cases, collapse and death occurs.

Treatment: -Numerous commercial preparations are available, if unavailable 300ml of vegetable oil can be dosed to the animal.

-As a last resort, puncture of the left flank with a troachar and cannular can be resorted to.

Antibiotic injection must then be given to guard against secondary infections, like Peritonitis – a poisoned & sore condition of the inside wall.

Prevention: -Avoid predisposing factors.

-Allow animals to limited access to young rapidly-growing legume pastures, e.g. half an hour per day for a few days then increase to an hour.

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G) POISONINGS. -Many chemicals are kept on farms as insecticides, herbicides, acaricides (Dips), fertilizers, e.t.c and many plants are poisonous.

-In all suspected poisonings the following specimens shld be submitted for analysis; liver, kidney, muscle, rumen content and suspected source of poisoning.

The following routine shld be followed in all animals suspected of being poisoned; a) Remove the animals from the source of poisoning. b) Use specific antidote if poison is known. c) In the case of dip poisoning on the skin, hose the animal down thoroughly. d) Minimize absorption, if ingested, drench with Universal antidote consisting of;- 50g activated charcoal, 25g magnesium oxide, 50g kaolin and 25g tannic acid.

Mix with 2 litres of water, repeat 2-3 times.

1. Chemical poisoning; Poison Organophosphates

Source Clinical Signs Treatment Dips, Insecticides, Salivation, diarrhoea, Atropine herbicides. staggering 0,25mg/kg livemass, thru. i.v or i.m.

Chlorinated Dips, Insecticides.

Nervous symptoms.

Universal hydroantidote. carbons Arsenic Dips, Old mine Abdominal pains, Hypo (sodium dumps, wood Watery diarrhoea. thiosulphate) preservatives, 10ml/50kg I.V. herbicides. or 30mg/300ml water, drench.

Nitrates Fert, draughted Muscular weakness, Methylene blue fertilized crops, Respiratory distress.

20ml/50kg. I.V certain plants. or I.M. Urea Feed additives, Nervous symptoms, 750ml vinegar Fertilizers bloat, abdominal pains. mxd with molasses, drench.

Repeat several times.

Lead Old batteries, Blindness, nervous Ca. EDTA I.V. 32

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Paints.

symptoms.

Consult your veterinarian.

2. Fungal Poisoning: -When one considers that cattle are sometimes fed the worst grade of grain available, it is surprising that they can usually tolerate the challenge that they are subjected to.

-Mouldy and burnt maize is often incorporated in cattle rations, Diplodia fungus is a common fungal contaminant in maize fields and Ergot is frequently found growing on grasses such as Paspalum, rye, barley, and sorghum and is associated with many Mycotoxicoses.

Death diagnosed as haemorrhagic syndrome is probably as a result of mycotoxicosis.

Fungus Mould Diplodia zeae

Source Mouldy feed

Clinical Signs Generally diarrhoea & ill thrift May occur up to 2 wks later, muscular weakness, paralysis & death.

Infested, discolored maize, particularly when cattle graze poorly reaped lands.

Mycotoxins Mouldy maize Acute death. of and other aspergillus vegetation. & fusarrium spp.

Treatment Remove cattle from feed.

Remove ani. 4rm maize lands drench purgatives such as Epsom salts 500g for adult cows.

None.

Avoid feeding mouldy maize or herbage.

3. Plant poisoning: -There are many different plants in Zim. that are poisonous to animals and conditions which give rise to plant poisoning shld be avoided.

Factors predisposing to plant poisoning.

1. Veld fires – result in emergence of toxic plants. These plants which shoot first are usually poisonous plants e.g. tulp and slangkop.

2. Pre-summer growth – resulting in poisonous plants like tulp or slangkop coming out before adequate grass cover has established itself.

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3. Movement of animals – resulting in animals eating unfamiliar plants such as lantana camara.

4. Encroachment of toxic plants – resulting in rampant dominant species such as lantana camara establishing itself.

5. Drought – resulting in animals eating unfamiliar species of plants.

Plant poisoning can be avoided by; 1. Adopting rotational grazing, where known affected paddocks are avoided during danger periods.

2. Controlling veld fires with effective fire breaks.

3. Providing supplementary feed during winter.

4. Destroying poisonous plants by physical removal of them or resorting to chemical means by applying herbicides.

LANTANA CAMARA -Affects the liver.

-Animals are affected 4-5 days after exposure.

-Cattle are the most affected and also sheep & goats.

-Young animals are more susceptible than old ones.

-Exotic breeds especially those with light skin such as Friesian and jersey.

-Animals bred in areas with lantana may become tolerant.

-Lantana camara contains Lantanadene and this poison varies with soil type – Less toxic in light soils.

-The toxic damages the main cells of the liver (liver detoxinate poisons) and the liver gets affected and fails to remove bile colours from the blood.

-Affected animals are jaundiced, Lantana camara also damage kidneys and causes paralysis.

Symptoms; -Marked general signs of illness.

-Crusting around nose and eyes.

-Skin is thickened and rough especially on the white areas of the body.

-Animals affected stay in shed and is photosensitive.

-Young animals are the worst affected and there is jaundice.

-High temperature, breath and pulse rate.

-Inflamed skin, cracked and peeling off skin.

Post-mortem; -Enlarged yellow liver.

-Friable kidneys.

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-Cracked peeling off skin particularly of the muzzle.

-Discoloured kidneys.

Economic importance; -Loss of draught power (death of animals).

-Reduced growth rate.

-Reduction in production (meat and milk production).

Treatment; -Antibiotics can be used for the control of secondary infections.

-Liver protectants can be drenched e.g. Coffee.

-Provide shade.

-Multivitamins also help.

-Skin medication i.e. healing oil, caron oil e.t.c.

Prevention/Control; -Destroy toxic plants by stumping or use of herbicides e.g. Roundup, Tordon etc -Remove animal from source of poison.

H) PARASITES 1. EXTERNAL PARASITES -this group includes all the smaller animals or pests that attack our domestic animals from outside. a) The Nasal-worm of Sheep -the nasal-worm, or maggot of sheep does a fair damage, & there is only one kind of nasal-worm of sheep. The fly is grayish-brown and has tiny black spots all over its body. It has no mouth-parts and does not feed, consequently it lives at most for 14 days.

-the fly is active all year round, expect when it is very cold, & it deposits small maggots at the nostrils of sheep. Sheep become excited when flies are around, and they try to hide their heads between other sheep so as to avoid the fly. The small maggots then crawl up the nasal cavity and pass thru a small opening into the frontal sinuses that extends into the horn of horned sheep.

-the nasal-worm grows rapidly in the sinuses and may be fully-grown after a month. In summer the development in the sheep proceeds rapidly, but during cooler months the little maggots remain in the nasal cavity for a long time possibly as a result of the cool air inhaled by the sheep and the life cycle takes much longer.

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-the nasal maggot has two strong hooks at its front-end and its body is provided with small spines.

It obviously causes much irritation of the mucus membrane, resulting in copious secretion of slime on which the maggot feeds.

-when fully grown, the maggot is about 20mm long and has a number of dark, transverse stripes over its back. It crawls back into the nasal cavity and is sneezed out by the sheep. Then it penetrates into the soil to pupate and the fly emerges a few weeks later.

Symptoms; -the infected sheep’s nose is dirty and much slime flows out especially in the morning.

-the irritation in the head is very distressing causing the sheep to feed poorly and to loose condition.

-if sheep also have worm parasites, they will soon die of exhaustion. **A few nasal-worm will do little damage, but 10 or more per sheep are decidedly harmful and one may find up to 50.

Treatment; -the best time to treat is early in winter, and where nasal-worms are very troublesome two more treatments in Oct and Jan are desirable.

-while other nasal-worm remedies are available, Ranide and Dectomax are also highly effective. b) Blowflies -these are flies of which the larvae or maggots develop in carcasses, or in wounds on live animals or both. There are many different species, but we are concerned only with those that attack animals, such as the blowfly causing screw-worm.

The cattle-blowfly (Screw-worm) -The cattle screw-worm is a serious pest and is closely related to the sheep blowflies, but it is a separate species that lives in warmer regions and it attacks cattle.

-it is a dark-green fly, almost blue, with a short, stout body. It likes warmth and moisture and in wet summers it spreads over a large area.

-this fly breeds only in wounds on live animals, not in carcasses, and this then means that baits do not attract the fly.

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-the fly lays its eggs in any small wound, for instance in the bite of a tick, or the scratch produced by a thorn. The eggs hatch very soon and the little maggots burrow into the flesh of the animal.

-they penetrate deeply and one may therefore often see a swelling without an opening, which resembles an abscess. If this is cut open, it is found to contain the maggots and a mass of bloody debris.

-in other cases there is an open wound with the maggots at the bottom, packed close together and showing only their hind ends.

-the maggots complete their development in the wound in 3-7 days. They crawl out, drop off the animal and burrow into the soil. After a pupal stage lasting about a week the fly emerges.

-a maggot-infected wound is very attractive to screw-worm flies, with the result that it becomes further infected and grows rapidly larger. In this way very nasty wounds develop within a short time on cattle that are not inspected frequently.

Control; -Kill the maggots and protect the wound against re-infection. *This is not an easy matter, all sorts of remedies are used which stun the maggots, causing them to drop out. But they are only apparently dead and will recover in an hour or so later, pupate in the soil and develop into flies.

Substances such as petrol and carbolic disinfectants, which are often used, do not kill the maggots, they allow the screw-worms to breed and continue their existence, while the pest could be exterminated if all cattle were inspected every 4-5 days and wounds treated to kill the maggots & protect them against further re-infection. *Remedies such as Dazdust, Bromafix and regular dipping and hand dressing against ticks will do much to control screw-worm, since tick-bites are the most important points of attack of these flies. c) Tsetse flies; -tsetse flies are light brown in colour and resemble bees. The abdomen has six segments.

-they transmit Trypanosomiasis. The fly produces a full grown larva every 12 days depositing it close to water underneath a bush or stone. The larva burrows into the ground and turns into a black pupa. This stage can last up to 10 weeks after which the fly emerges.

Control; -notify the vet department and will takeover the control of the fly.

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*Tsetse flies are controlled by aerial application of insecticides that kill the adult fly. d) TICKS. -There are two types of ticks, hard ticks (Ixodidae) and the soft ticks also known as Tampans (Argasidae). The Tampans differ from the hard ticks in several important features, . Larvae of some species are non-motile and non-parasitic; they moult to the nymph, which then undergoes several moults feeding between each moult.

Nymphs finally moult to the sexually differentiated adults, which mate off the host before the female begins a series of feeds, after which she lays small batches of eggs. . Tampans are usually parasitic on their host only during their short feeding periods, measured in minutes or hours rather than days. For the rest of their time, they shelter, moult or lay their egg in suitable hidden places within the habitats of their hosts.

-The hard ticks will be discussed in detail as they are the ticks that cause severe economic losses to the cattle farmer.

There are three different types of hard ticks or Ixodidae ticks, the one host tick, the two host tick and the three host ticks.

One-host ticks -are those in which both moults take place on the host animal, so that the tick never leaves the host from time of attaching as a larva until it drops off as an engorged female.

All the Blue ticks (Boophillus) have such a cycle.

Two-host ticks -are those in which the first moult takes place on the host and the second moult on the ground, so that the adult ticks, when they emerge, must find a second host.

The Red-legged tick (Rhipicephalus evertsi) and the Bont-legged ticks (Hyalomma) species of Asia and Africa have a two-host life cycle.

Three-host ticks -are those in which both moults take place on the ground, so that nymphal ticks must find a second host and adult ticks a third host, when they emerge from their moults.

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The Brown ear-tick of Africa (Rhipicephalus appendiculatus) and Bont ticks (Amblyomma) have such a lifecycle.

The life cycle of the tick There are three motile stages in the life cycle of all the common cattle ticks, the tiny six-legged larva, the eight-legged nymph and the eight-legged adult (male & female). Between these three motile stages there are two moulting phases and characterized by the sloughing off of the outer skin, or cuticle, and reorganization of the body within it. The life cycle is completed by the productions of eggs whch are laid by the female after she has mated and finally engorged with blood.

From these eggs the larvae of the next generation hatch. Each of the motile stages must parasite a host animal, such as a cow, and take a meal of blood or body fluids. This is achieved by the tick piercing the host’s skin with its mouthparts and sucking blood or fluids from the host into its own body. It can then moults and pass on to the next stage of its life cycle. The larva sucks blood, becomes engorged before moulting to the adult male or female.

(Only at this stage is there overt sexual differentiation). The adults mate, usually on the host and the female tick takes her final blood meal and becomes engorged before dropping off the host and finding a sheltered, humid place on the ground in whch to lay her eggs.

The eggs Engorged females of the important cattle tick species lay betwn 2 000 and 20 000 eggs.

The eggs will hatch if they are exposed to constant low humidity or temp.

Night temps promote quick hatching provided the humidity is adequate to prevent desiccation of the eggs.

The larvae & nymphae The six-legged larvae find a host by climbing pinnacles of vegetation and attaching to any passing object. It may be their host of their choice or some other animal, but since confined cattle are creatures of habit, they will often pass the place where the previous generation of ticks dropped, and so provide a suitable host for the next generation.

Larvae and nymphae are tiny and light such that infestations may pass unnoticed except by close examination. They are very important, however, 39

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becoz they determine the level of later adult tick infestations. Furthermore, at one of these stages in two and three-host species, the tick may become infected with tick-borne diz such as East coast fever or Heartwater, which it will transmit to a host at a later stage; or an infection such as Redwater may be inherited thru the egg from the parent female and transmitted to a host by one of these immature stages.

Control of the larvae and nymphae is thus most important to overall tick control, particularly in two and three-host ticks, of which they usually infest at a different time of the year from the adults.

The adults The adults are sexually differentiated and usually mate on the host, following fertilization the female takes a final large meal of blood and drops to the ground to seek her egg-laying niche.

The male dies some time after mating.

TICK CONTROL. i. Dipping or Spraying The reason for dipping farm animals is to kill ticks, lice, mange mites, tsetse flies and other biting & nuisance flies.

Plunge dips are more effective than spraying (spray race or hand spray) becoz they wet the animal more thoroughly, particularly inside the ears and under the tail, but spraying enables gentler handling of sensitive animals e.g.

Daily cows. Spraying also has the advantage that the dip (acaricide) used may be changed at will and strategic applications for species control and the control of flies may be used.

Many factors determine the effectiveness of dipping; *The right dip must be used; some dips have weaknesses against certain ticks, while in other cases ticks may develop a resistance. *The manufacturer’s instructions must be followed precisely, (dilution rate, premixing techniques and precautions to be taken).

*All animals shld be dipped on dipping day; to ensure this, stockmen shld count animals before dipping. *Correct strength; under/over strength dipwash is very expensive in the long run becoz it leads to early development of resistance by the ticks. *Dip at the correct intervals; in most cases it is preferable to maintain weekly dipping. There are times, especially with brown-ear tick problem, when five day dipping is necessary.

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ii. Hand-dressing This can be used in conjunction with the hand-spraying method. This is a laborious, but entirely necessary procedure. It consists of treating the attachment sites of the two- and three-host ticks with tick grease or oil, or with a high concentration of the dipwash. It protects the sites against reinfestation for longer than the normal dipwash concentration and is thus valuable against fever carrying ticks, such as the brown-ear ticks, which can transmit disease after a comparatively short period of feeding. The treatment is carried out with a brush or swab, or with a knapsack sprayer, if concentrated dipwash is to be used. The main sites to be treated are the inside of the ears, round the scrotum or udder and under the tail. iii. Pour-ons This tick control consists of concentrated acaricide dissolved in a dispersible base and relatively small amounts are applied to the upper part of the animal from which the chemical spreads downwards and outwards to cover the whole body. Pour-ons are more costly than the most expensive dips, but some farmers will welcome them becoz they avoid the trauma and stress of the spray race or dip tank. Some have the added advantage that they are also effective against nuisance flies. They also carry the advantage of being insoluble in water, which means can be more effective in summer. iv. Injectables These are injected either subcutaneously or intramuscularly and distributed around the body thru the blood stream. When ticks suck blood they ingest the chemicals and are killed. This method is not yet in widespread use by farmers except for the control and treatment of mange mites.

Examples of drugs that are used here include Ivermectin (Ivormec速) and Doramectin (Dectomax速) and some Organophosphates.

LEGISLATION. In Zim the Animal Health Act ---- Cattle Cleansing Regulations --- exist to enforce dipping.

Thru-out the country from Nov to Jun all cattle have to be dipped at intervals not exceeding seven days and from Jul to Oct inclusive, at intervals not exceeding 14 days.

In the Regulation to dip means to submerge completely and wet thoroughly in a dipping tank containing an approved tick destroying agent (acaricide) at the correct dilution. Similarly, to spray means to wet thoroughly using an

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approved appliance. Ticks means, Blue ticks, Bont ticks, Brown-ear ticks, Red-legged and Bont-legged ticks.

**In Zim a herd of cattle is deemed tick infested if; i More than ten percent of the cattle in that herd have ten or more live ticks on them; or ii Ten or more engorged ticks are found on any one animal in the herd, or five or more engorged ticks are found on each of at least five animals in the herd.

N.B. Any owner of a cattle herd which is tick infested may be prosecuted.

* An authorized person may order the owner or person having charge of the cattle to produce them for inspection and counting at a particular time and place, and call upon the person to give him/her all necessary assistance.

He/she may also quarantine the property and give orders relating to tickinfested cattle. **Any person who contravenes or fails to comply with any provision of the regulations shall be guilty of an offence.

PROBLEMS (Diseases) CAUSED BY TICK TOXINS a) Sweating Sickness Definition: An acute febrile condition of calves and young cattle by the toxin of ticks.

Cause;

------------

Certain strains of Bont-legged ticks.

Symptoms; Incubation period is about 4 -10 days. This is followed by high temp, listlessness and inappetence, and the most consistent finding is a wet eczema spreading from the base of the ears down the neck and between the front and back legs. Eventually it can spread over the entire body. The skin becomes sensitive and the hair pulls out leaving raw areas. Death in severe cases follows in few days.

Diagnosis;

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The condition is indicated by the presence of a wet eczema and confirmed by the presence of Bont-legged ticks usually under the tail or in the tail brush.

Treatment; The first line of treatment is to physically remove the offending ticks. The animal shld be kept in the shade as it is sensitive to sun. Antibiotics shld be given to protect against secondary bacterial infection and vitamin B12 acts as a useful tonic. b) Heel-Tick paralysis Definition; A paralytic condition of mainly calves caused by the toxin of ticks.

The condition is found in summer, particularly in Matabeleland.

Cause;

----------

The Brown-heel tick

Symptoms; The calf is initially weak and then unable to stand although it looks alert.

Diagnosis; The paralytic condition and discovery of Heel-ticks on the heels and betwn the claws indicates the condition.

Treatment; Physical removal of the ticks usually results in spontaneous recovery. c) Tick Toxicosis Definition; A toxic condition of cattle caused by a heavy infestation of ticks.

Cause; Mainly three-host ticks, especially the Brown ear tick.

Symptoms; The face and lymph nodes of the head swell dramatically and the animal’s immunity to other diseases such as Redwater and Gallsickness is reduced, rendering it susceptible to these diseases.

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Abscess formation below the ears can result, particularly in calves.

Diagnosis; This is based on the clinical signs and the overwhelming number of brownear ticks present on the animal.

Treatment; Immediate dipping.

2. INTERNAL PARASITES. (WORM INFESTATION). (Helminthiasis). a) ROUNDWORMS -Many kinds of roundworms occur in our domestic animals and they are very harmful.

Roundworms are elongated and round, like a piece of wire, some are as large as a lead pencil, while others are small and difficult to see in an animal.

Some are white or light yellow; those that suck blood are red or bluish-grey.

Roundworms lay a large numbers of eggs, which are passed in the feaces of the host. In some cases the eggs hatch in the intestines and larvae are found in the droppings. The presents of roundworms in the intestine or lungs can be diagnosed by the microscopic examination of the feaces for worm eggs. i. Parafilaria.

This parasite of cattle is widely distributed in warmer areas. Parafilaria inhabits the subcutaneous tissue and in the forequarters of the animal—the neck, shoulder, front ribs.

The female is about 50mm and the male about 30mm long. The worm causes a subcutaneous lesion up to 250mm in diameter of typical greenishyellow, dirt, slimy or dark red appearance. The lesions on the carcass look remarkably like those caused by bruising during handling and transport some time before slaughter. These lesions are the result of the reaction of the body to the irritation caused by the parasite. The live or dead partially encapsulated worm may be found in the lesion. The lesions are cut away at the abattoir, resulting in degrading and thus serious financial loss to the farmer. Parafilaria does not affect the health of the animal. The female worm makes a small puncture wound and the blood from the wound reveal, on microscopic examination, worm eggs. Flies ingest the blood from the puncture wound and transmit the young larval stage to other parts of the body or other cattle.

Control; 44

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No remedy is known that will kill this worm.

Fly control shld have a beneficial effect on the control of the infestation. ii. The wireworm.

Wireworm is the most harmful. It is often found in several kinds of wild antelopes and in shoats and cattle. Wireworm grows to about 25mm long and is fairy thin. The males are light red while the females have red and white spiral stripes like a barber’s pole. Young wireworms may be mistaken for brown stomach worms but the latter are dark in colour. Wireworms suck and spill much blood so that the contents of the abomasum, in which they live have a reddish-brown colour in heavily infested animals. Anaemia develops causing paleness of membranes of the eyes and mouth.

The blood becomes thin, and watery swellings often develop underneath the jaw (bottle jaw) while a watery fluid is found in the heart sac and the thoracic and abdominal cavities.

A female wireworm lays 10 000 eggs daily. The eggs are passed in the droppings of the animal and hatch in the pastures if it is sufficiently warm and moist. The young worms or larvae grow and moult twice before they are ready to continue their development in an animal.

After the second moult they are called infective larvae. The rate of development depends on the temp, in summer they take about six days to reach the infective stage and in winter it may take several weeks. The eggs and young larvae can’t resist dryness and will die as soon as they become dry. Wet places are breeding grounds for worms in all seasons.

The infective larvae crawl on to grass and shrubs. In cool weather they are able to live several months. They are very resistant to cold, but heat and dryness combined, kill them in a short time. In a dry summer many larvae die, but if it rains the infection accumulates rapidly, becoz a sheep with a hundred female wireworms passes one million eggs daily. During a dry winter most of the larvae in the pastures die so that at the end of winter the pastures are fairly clean.

The grazing animals swallow the infective larvae on the grass and shrubs.

The larvae develop into adults in a short period of time and the wireworms grow quickly and start laying eggs after about three weeks.

Prevention; In view of the above-mentioned particulars, wireworm shld be combated as follows; 1. The animals shld be treated at the beginning of winter so that they may 45

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2.

3.

4.

5.

start the difficult season without the worm burden.

They shld also be treated at the end of winter, in order to prevent them from re-infecting the pastures.

During summer animals shld be treated at intervals depending on the circumstances, especially the rainfall. Dose according to worm egg count.

Pasture rotation shld be practiced, three camps in each of which the animals graze a week in turn in summer. Overstocking shld be avoided.

Cattle can be used to graze ahead of sheep as they are not affected by wireworm infection to the extent that sheep are.

The animals shld be fed well and shld get mineral supplements in licks as required, as well as vitamins in winter, to maintain their resistance.

Treatment; Wireworm has developed resistance to most of the modern vermicides and the remedy usually chosen on advice from the local veterinarian will be one where resistance is not evident in that particular area. iii. The brown Stomach-worm.

The brown stomach-worm lives in the abomasum of shoats and cattle. It is partly embedded in the mucus membranes of the abomasum. It occurs especially in the cooler areas, such as the Eastern Highlands. The worm grows to 10 mm long, is very thin, but fairly well visible on account of its dark colour. The life cycle of this worm is similar to that of the wireworm and it also produces similar symptoms. iv. Bankrupt-worms.

The worms are very small and practically invisible to the uninitiated. There are various kinds of bankrupt worms that occur in shoats and cattle. They live in the small intestines, directly behind and in the abomasum. They are about 5 mm long and pale brown in colour. Their anterior parts are embedded in the mucus membrane. Their eggs are passed in the droppings of the host and their life cycle is in general like that of the wireworm.

Symptoms; 1. Bankrupt worms cause an inflammation of the intestines resulting in diarrhoea.

2. They produce a toxic substance that causes loss of appetite.

3. When the small intestine of an infected animal is examined, one sees that the front portion is reddened inside. The mucus membrane is thickened and the worms can be seen in a good light. It is best to scrape the inside 46

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of the gut with a knife and to mix the scrapings with a few drops of water on a glass slide, a second piece of glass is pressed slightly on to the first and the worms appear like small hairs. * Persian sheep and cross-breeds are very susceptible to bankrupt worms.

The eggs can survive on pastures right thru a dry winter. As soon as the larva is fully developed in the egg it will not hatch if the surroundings are too dry and remains in this state for over a year. As soon as it rains the eggs will hatch and the pasture teem with infective larvae. The infective larvae penetrate the skin especially of the lower leg, pass with the blood to the lungs breaking thru into the bronchi and then move up the trachea to be swallowed. The adult worms penetrate into the lining of the small intestine and cause a mild inflammation that may result in diarrhoea if the infestation is severe. The larvae during penetration of the skin may carry the necrosis bacillus that causes Footrot and the animals then acquire a massive infection all at once, they start purging and become paralysed in the hindquarter and die. *In cattle, the cattle bankrupt-worm, which is quite harmful, is frequently found. This worm is somewhat thicker than other bankrupt-worms and usually lies coiled up in the form of a ring in the small intestine, so that it is visible.

Treatment; Several of the modern worm remedies are effective against the white bankrupt worm. v. Hookworms.

These are roundworms that live in the small intestine of their hosts and suck blood. The name hookworm is derived from the fact that the anterior end of the worm is slightly curved, like a hook. It has a large mouth cavity, into which it draws a bit of the mucus membrane, in which is then pierced by teeth enabling it to suck blood. Into the wound the worm injects a substance that prevents coagulation of the blood. When the worm has fed at one point for a while, it lets go and bites somewhere else. The old bite bleeds for a while and in this way much blood is lost. The worm does not digest the blood it sucks. It passes thru its intestine and absorbs only certain substances contained in the blood. The eggs of the worms are passed out in the feaces of their hosts and hatch if it is sufficiently warm. The larvae take about a week to reach the infective stage. They are able to live only in moist surroundings.

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They penetrate into the skin of any man or animal that they are able to reach and via the blood stream they reach the lungs, where they break out of the capillaries and enter the air spaces. They are coughed up and swallowed reaching the intestine where they grow to the adult stage provided they have entered the right kind of host.

Symptoms; The infected animal is poor in condition and anaemic.

In dead animals one finds much watery fluid in the heart sac. Many farmers have been misled by it, causing them to take measures against Heartwater while the calves die of hookworms. Hookworms practically bleed the animal to death.

Prevention; Animals become infected mainly at their watering points, where they stand about in mud and the larvae penetrate thru the skin of their feet.

Wet kraals are also dangerous.

NB. The larvae also introduce the bacteria that cause Footrot.

Animals shld be kept away from dams and water pans as far as possible and salt shld be applied around watering troughs to kill the larvae. vi. Nodular Worms The nodular worm of sheep is about 25mm long, white, and its front end is curved like the handle of a walking stick. The life cycle is similar to that of the wire-worm. The infective larvae are not resistant to dry weather. In winter sheep are not infected from a month after the last rain. After being swallowed the little worm forms a small abscess—the well known nodule in the large intestine. At first the nodule is soft, like an abscess, but after few months it becomes hard and slowly petrifies (frightens) he little worm therefore has about 3 months to escape or else it will die in the nodule. If no nodule is formed after 5 days, as happens in young lambs, the young worm returns to the inside of the intestine and proceed to the large intestine, where it grows to the adult stage. Five weeks later the female start laying 6 000-7 000 eggs per day. The worm feeds in a strange way; it does not attach itself to the intestine, but lies its head against the mucus membrane and applies a secretion from its large neck glands that result in the production of slime, which the worm swallows. The secretion from the worm is absorbed into the body of the sheep, it is very poisonous and Sheep grow thin and weak.

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Symptoms; *The nodular worm does not cause anaemia, but the sheep becomes emaciated and dies as if thru starvation.

Treatment; It is very difficult to treat animals effectively against these parasites, but it is desirable to treat animals after winter with a remedy that will kill other kinds of worms as well.

Treatment and Control of Roundworms in Shoats and Cattle Worm parasites cause more losses to the sheep farmer than all other sheep diseases together.

The sheep that die of worm infection represent only a small proportion of the losses. Much more important is the weakening caused by worms, which results in;  a smaller lamb crop  too little milk for the lambs  poor growth of young sheep  uneconomically use of food  susceptibility to diseases *If it were possible to calculate all this in figures, the result would be astounding.

We have only two ways to deal with Roundworm infestation: 1. To remove the parasites (worms) from the animals.

2. To remove the animals from the worms (heavily infested grazing) 1. Remove the worms from the animals On many occasions animals e.g. sheep are dosed when the worm burden does not warrant it. This is an expensive exercise in many ways. The more often we dose the sooner we are likely to run into parasite resistance to our drugs. By deworming your sheep you only remove 5% of the parasite population – 95% of the worms are still on the pasture.

2. Remove the animals from the worms

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We are far more likely to achieve results from this with this method. This method requires that we rotate our grazing as follows; During the hot wet months of the year change grazing areas every 4 days.

During the winter months especially after the first frost, but before the first summer rains a 7 day grazing cycle shld be reasonably safe. In both cases the longer the rest the better.

It would also help to rotate our overnight paddocks; larvae are definitely picked up at such places. Let your sheep out in the morning after the dew and/or rain is have dried off the grass and graze the flock later in the evening. The correct way of going about dosing is to have dung samples analysed regularly to determine the EpG (worm egg count per gram dung) and dose according to that information. *When sheep show visible signs of worm infestation it is already too late to obtain full benefit from dosing. Weight loss in your slaughter lambs that are dosed too late, is probably the greatest loss.

Rotational grazing and worm infestation.

The worm eggs passed in the sheep’s droppings hatch in the pasture, and the larvae develop there until they reach the infective stage after about 6 days, provided there is enough moisture.

The infective larvae then crawl up the grass and shrubs, and are swallowed by the grazing sheep. If it does not rain for a day or two and the sun is hot, the majority of the larvae die off soon. One week of dry, warm weather suffices to kill most of them.

If a camp is divided into three, we can allow sheep to graze one week in each camp. At the end of the week the first larvae will begin to migrate up the plants. Then the sheep are taken out for two weeks and during this time most of the larvae will die.

Pasture rotation forces the sheep to eat everything and the test have also shown that it leads to improvement of the pasture. If a fourth camp is added the grazing is improved even more by allowing one camp to rest each year when the grasses are in the seed stage and again in the spring when young plants grow from the seeds. b) TAPEWORMS All tapeworms go thru a cycle where their eggs are ingested, and become bladder worms in the intermediate host. The intermediate host is in turn eaten by the final host. Here the adult tapeworms produce egg-laden ripe

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segments which are released to pass out with feaces and thus recommence the cycle. i. Measles Cattle act as an intermediate host to various tapeworms of carnivores and humans. The best known is Beef measles where the bladder worms – only half the size of a pea, are found in the flesh betwn the muscle fibres. Their importance lies in their potential danger to human health. If it is people who eat it. At approved abattoirs certain muscle cuts are made during meat inspection to check for the presents of the measles.

Carcasses showing more than ten measles in these cuts are condemned as unfit for human consumption. Infected carcasses showing lesser numbers of parasites are detained and frozen long enough to kill the measles.

Prevention; a). Ensure that cattle do not have access to infected human excreta. b). On farms and ranches the labour force, including their families, can be treated for tapeworm. c). Ensuring that the labour force eat only inspected meat, and encouraging thorough cooking of all meat, this shld help to limit re-infection. d). Provision of latrine facilities near such sites as bus stops, stores, compounds and road camps shld also help. ii. Other bladder worms Bladder worms that are very much larger (up to tennis ball size) are sometimes found in the lungs, liver and other organs of cattle shoats, game animals and humans. They are the intermediate stage of tapeworms of dogs, cats, and wild carnivores. The presence of such bladder worms lead to condemnation of the affected organs. This condemnation is important since it prevents infected offals being sold as pet meat. Infected pets may infect humans.

Bladder worms in humans have on occasions caused serious problems especially when they occur in vital organs. *Pets should of course, be regularly treated for Tapeworms.

iii. Tapeworms in cattle Cattle are also final hosts to several different types of tapeworms. These are commonly called milk worms and shed ripe segments that look like white feaces. Various grass mites which act as intermediate hosts consume the eggs and minute bladder worms form in the mites. These are in turn ingested with the grass by grazing cattle and so the cycle is completed.

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Tapeworm infestations are virtually harmless in adult cattle, but heavy infestations sometimes occur, causing unthriftiness in calves and weaners. c) FLUKES The common Flukes that affect cattle in Zim are Liver Fluke (Fasciola gigantica), Conical Fluke (Paramphistoma spp) and Bilharzia (Schistosoma spp).

Life cycle The Flukes each require specific species of water snails as intermediate hosts. Fluke eggs pass out with the feaces of the cattle host. If they are deposited in water, the eggs hatch and from each egg the emerging miracidium swims around in the water in search of a host snail which it penetrates. Some developments take place in the snail over a period of two months or longer before the parasites emerge as cercariae. In the case of Bilharzia, these cercariae swim around the water in search of the final host (cattle, sheep or man) which they must find within two days or perish. They penetrate the skin and so enter the blood stream. In the case of Liver Fluke and Conical fluke, the cercariae attach themselves to the vegetation at the water edges. Here they develop a shell or capsule and may be seen on the grass or reeds as small pin-point spots. They remain viable for up to a year in this resistant state (as metacercariae). Livestock become infected if they eat this vegetation when the water recedes. i. Liver Fluke (Fasciola gigantica) When ingested together with, the young flukes emerge after the small shells or capsules around them have been dissolved. These flukes then penetrate the tissue with the general objective of reaching the Liver. They spend up to two months growing in the tissues of this organ and leave behind them a trail of damage. The healing process produces minute scars; fibrosis of the whole liver may follow severe infestations. Once the flukes are mature they enter the bile ducts of the liver where they leave for several years – possibly for the rest of the host’s life. Their presence causes considerable thickening of the walls of the bile ducts. These become externally visible during postmortem examination as white fibrous cords under the liver capsule. Adults liver flukes are easily recognized as they emerge from the bile ducts when the liver is cut open. They are up to 30 mm long and 10 mm broad, and flat and shiny. Becoz of the longevity if this parasite, undosed cattle accumulate infection over the years and older animals are usually worst affected. On fluke-infected farms, priority shld be given to dosing the breeding herd

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becoz they remain longer on the property and therefore accumulate the biggest infestations.

It is sometimes practicable to use paddocks that are less fluke-infested for the breeding herd. Sometimes it is worth fencing off marshy areas, especially dams, and piping the water for cattle. Alternatively, removal of vegetation at the water’s edge or limiting drinking to short stretch of water frontage shld help. ii. Conical Fluke (Paramphistoma spp) These are red, stout, conically shaped parasites up to 10 mm long. The adults are found attached to the wall of the rumen usually congregated in one patch. Conical infestations are very common, but are considered to be relatively harmless and self limiting. The shell or capsule of the ingested metacercaria is only dissolved towards the end of the small intestine, thus liberating the baby conical fluke. From this position immature flukes make their way forward until they reach the rumen. During this migration they cause an irritation to the bowel wall. Occasionally a massive infestation of immature conical fluke occurs, causing severe persistent diarrhoea, bottle jaw and sometimes even death. This has occasionally occurred in Zim where cattle grazed vegetation around dams, but is most unusual and is more commonly a problem of sheep.

Treatment; Any serious outbreak of diarrhoea shld be investigated by a veterinarian who will prescribe treatment.

Some anthelmintics are effective against immature stages of conical fluke.

Removal of animals from the source of infection will result in termination of the symptoms after a few weeks. iii. Bilharzia (Schistosoma matthei) Over 50% of the cattle in Zim are infested with Bilharzia. The parasite can be seen in the blood vessels of the mesentery (the membrane supporting the intestines) when held against the light. They appear as white worms about 20 mm long, with a thin black line down the centre. Often what appears to be one worm is in fact a pair, the more slender male being enveloped by the longitudinal folds of the female. Sheep are more susceptible to all the illeffects of Bilharzia infection, but cattle more easily develop a resistance which limits the number of surviving parasites. A very high challenge occasionally builds up where cattle concentrations coincide with high snail populations in rivers, dams and even drinking troughs. This may result in 53

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unusually high Bilharzia infections, causing lowered productivity, unthriftiness and even mortality---especially in cases where stress factors like malnutrition are also involved. Sharp points on Bilharzia eggs enable them to break thru the intestinal wall and be passed out with the feaces. This causes small injuries, often with some haemorrhage. Occasionally, haemorrhagic diarrhoea cases occur which appear to be associated with the passing of these eggs. Bilharzia eggs may also end up in various organs of the body, especially the lungs where they cause injuries resulting in formation of scar tissue.

Treatment; Treatment of animals for Bilharzia is still fairly expensive and rather complicated. Veterinary advice shld be sought regarding the choice of drug and dosage.

An increased level of nutrition greatly assists recovery.

Prevention; Preventative measures are most important on properties which have a Bilharzia problem.

These include avoiding infectious concentrations and taking action against water snails.

THE END

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