Black’s
Veterinary Dictionary 2 2 nd E DITION Edited by
Edward Boden
MBE, HonAssocRCVS, MRPharmS
And
Anthony Andrews BVetMed. PhD, DipECBHM, DipECSRHM, FBIAC, FRSM, MRCVS
Bloomsbury Information An imprint of Bloomsbury Publishing Plc LON DON • N E W DE L H I • N E W YOR K • SY DN EY
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Bloomsbury Information An imprint of Bloomsbury Publishing Plc 50 Bedford Square London WC1B 3DP UK
1385 Broadway New York NY 10018 USA
www.bloomsbury.com BLOOMSBURY and the Diana logo are trademarks of Bloomsbury Publishing Plc First published 2015 Š Edward Boden and Anthony Andrews, 2015 Edward Boden and Anthony Andrews have asserted their right under the Copyright, Designs and Patents Act, 1988, to be identified as Author of this work. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage or retrieval system, without prior permission in writing from the publishers. No responsibility for loss caused to any individual or organization acting on or refraining from action as a result of the material in this publication can be accepted by Bloomsbury or the author. British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. ISBN: HB: 978-1-4081-7572-9 ePDF: 978-1-4081-8128-7 ePub: 978-1-4081-4955-3 Typeset by RefineCatch Ltd, Bungay, Suffolk, NR35 1EF Printed and bound in Great Britain
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P R E FA C E
ofveterinary veterinarypractitioners, practitioners,students, students, farmers and and pet Generations of nurses, farmers owners have relied on Black’s Veterinary Dictionary as a primary pet owners have relied on Black’s Veterinary Dictionary as reference on on animal animal health health and and husbandry husbandry matters. matters.The The22nd 21st edition reference comprehensively revised updated; it covers the widest of has been comprehensively and expanded; it coversspectrum the widest veterinaryof data availabledata in a available single volume. The core of information spectrum veterinary in a single volume. Much new on animal health, husbandry and welfare topics, and signsand of information on animal health, husbandry and welfare topics, diseases and their is supplemented by many new and signs of diseases andtreatment, their treatment, has been added. Many entries amended These reflect thethat numerous developments reflect the entries. numerous developments have taken place sincethat the have edition taken place since the 20th edition wasadvances published; they range 21st was published; they range from in medication from advances in medication to descriptions of newly identified to descriptions of newly identified conditions; from the resurgence of conditions; resurgence of the old emergence scourges such as TB insuch cattle old scourgesfrom such the as TB in cattle to of diseases as to the emergingvirus. risk ofThe exotic imported following the Schmallenberg riskdiseases of exoticbeing diseases such as heartworm relaxation of travel arrangements for dogsofand cats.arrangements for being imported following the relaxation travel A major innovation is the inclusion of entries describing dogs and cats has been reflected by new entries. Popular breedsthe of popular dog and cat, conditions and the inheritable conditions to dog and breeds cat, andofthe inheritable to which they might be which they might be susceptible. susceptible, are described. Notes are included on many new species Some changes will be noticed in the spelling of certain medicines, being farmed or kept as companion animals. which have been amended to conform the recommended Dr G. R. Duncanson, BVSc, DProf,with MSc(VetGP), FRCVS, international non-proprietary namesMRCVS, for medicinal substances, in D. McK. Fraser BVM&S, CertWel. A.D. Malley FRCVS, accordance withS.EEC Directive 92/97. MVB, BA and Nicholas Clayton, BVSc, MRCVS, have all made Dr A.H.suggestions Andrews and BVetMed, PhD, MRCVS has colleagues again acted as extensive contributions; many more have assistant editor. Dr Andrews, D. McK. Fraser BVM&S, CertWel. given advice. We are very grateful for their input. MRCVS and A.D. Malley FRCVS, MVB, BA have all made extensive and contributions. I am grateful for their E.B., A.A. suggestions 2015 input.
Note: The use of small capitals, for instance, ANTIBODY, in the text, E.B. 2005 refers the reader to the entry of that name for additional information. Note: The use of small capitals, for instance, ANTIBODY, in the text, refers the reader to the entry of that name for additional information.
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A Ab
(See Antibody .)
Abamectin
An Avermectin used in cattle ectoparasiticide and endoparasiticide.
as
an
Abaxial
Away from the axis. Term often used in describing parts of bones. Opposite of Axial .
When only the wall of the abdomen has been damaged, there may be severe bruising, and haemorrhage into the tissues (See Haematoma ). If exposure of the abdominal contents has taken place, or if the organs have been themselves damaged, there is risk of Shock , haemorrhage, infection, and Peritonitis ; the latter may cause great pain and usually proves fatal. For this reason the injured animal should receive promptly the expert services of a veterinary surgeon or else be humanely destroyed. Simple Wounds or bruises of the abdominal walls are treated in the same way as ordinary wounds.
Aberdeen Angus Cattle
The part of the body in front of (below in quadrupeds) the spine between the thorax (see Chest ) and the Pelvis . (For a description of abdominal organs, see under appropriate headings.) As birds and reptiles have no demarcation between the thorax and abdomen (no diaphragm) it is inappropriate to use these terms in these Orders.
An old breed also called Angus. It was developed in Scotland and known since the 18th century with the herd book started in 1862. They were locally known as ‘doddies’ or ‘hummlies’. They are usually all black but can be all red. The cattle are naturally polled and occasionally have white udders. They are a relatively small animal but it means that the crosses have minimal Dystokia . They are hardy and able to fatten off pasture and are often sold as Aberdeen Angus beef which attracts a price premium. A few crosses with Friesian Cattle have shown Spastic calves.
Abdomen, Diseases of
Abiotrophy
Abdomen
(See under Stomach, Diseases of ; Intestines, Diseases of ; Diarrhoea ; Liver, Diseases of ; Pancreas, Diseases of ; Kidneys, Diseases of ; Bladder, Diseases of ; Peritonitis ; Bloat ; Colic ; Ascites ; Hernia .)
A degenerative condition of an organ or tissue leading to dysfunction or loss of function. Usually inherited and often involving brain or other nerve tissue. (See Lysosomes – Lysosomal storage disease.)
Abdomen, Injuries of
Abizzia spp.
These include injuries to the abdominal walls, to the alimentary tract and to the organs within the abdomen. Trauma may result in damage to the liver, spleen, kidneys, or urinary bladder. Apparently small external wounds of the abdominal wall may be far more serious than their appearance suggests. Radiographs and ultrasound can be useful in diagnosis.
Diagnosis An exploratory
may be necessary to establish the internal effects of such wounds, and also the cause of internal haemorrhage, free intra-peritoneal gas, peritonitis, etc. Obtaining a sample by Paracentesis may be useful, although the hollow needle may be blocked by omentum. Use of a catheter and peritoneal lavage has been effective in detecting early intraabdominal traumatic lesions, rupture of internal organs, etc. in dogs and cats. When a stake or other pointed object has caused a large wound in the abdominal wall, the bowels may protrude through the opening, and if the incision be extensive, evisceration may take place.
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Laparotomy
A group of rapidly growing African trees being exploited as a forestry crop. The seed pods have caused poisoning in goats and cattle. Clinical signs include tachycardia, anorexia, ruminal stasis, anaemia, dyspnoea and recumbency. Affected animals always show methaemglobinaemia.
Ablation
Removal of an organ, or part of an organ, by surgery.
Ablepharia
The lack of eyelids – a normal condition in snakes.
Abnormalities, Inherited (See
Genetics, Heredity and Breeding Genetic defects .)
Abnormal Pigment Deposition in the Eye
An abnormal increase in the ocular pigment which eventually results in an impeding of the drainage of fluid in the eye and causes Glaucoma. It is recorded in a few breeds and mainly Cairn Terriers .
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2 Abomasum
Abomasum A Abomasum is the so-called 4th stomach of
ruminating animals; more correctly, the 4th compartment of the ruminant stomach. It is also called the ‘true’ or ‘rennet’ stomach, and the ‘reed’. It is an elongated, pear-shaped sac lying on the floor of the abdomen, on the right-hand side, and roughly between the 7th and 12th ribs.
Abomasum, Displacement of (See
Stomach, Diseases of ; Resonance in Cattle .)
Tympanitic
Abortifacient
A substance causing abortion.
Abortion
The premature expulsion of the fetus and fetal membranes. The termination of pregnancy. In farm animals it represents one important aspect of Infertility . Some of the causes of abortion in farm animals are shown in the tables below:
Cows
Infections Viruses BVD/MD (bovine virus diarrhoea/mucosal disease); bovine herpesvirus 1 (infectious bovine rhinotracheitis/infectious pustular vulvovaginitis) Chlamydophila C. abortus (Epizootic abortion) Rickettsiae Coxiella burnetii (Q fever) Ehrlichia phagocytophilia (tick-borne fever) Bacteria Arcanobacterium pyogenes (formerly Actinomyces pyogenes, previously Corynebacterium pyogenes) Salmonella dublin, S. typhimurium Bacillus licheniformis Brucella abortus; also B. melitensis Listeria ivanovii, L. monocytogenes Leptospira hardjo and other serovars Campylobacter fetus subspecies fetus Besnoitia Fungi Aspergillus fumigatus Mortierella wolfii Protozoa Neospora caninum Toxoplasma gondii Trichomonas fetus Non-infectious causes Claviceps purpurea (ergot in feed) Stress Recessive lethal gene Malnutrition Haemolytic disease Vitamin A deficiency Iodine deficiency
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Ewes (female Goats [does])
Infections Viruses Border disease/Thogoto virus Chlamydophila C. abortus (formerly Chlamydia ovis and Chlamydophila psittaci) (Enzootic abortion) Rickettsiae Ehrlichia phagocytophilia (tick-borne fever) Coxiella burnetii (Q fever) Bacteria Arcanobacterium pyogenes (formerly Actinomyces pyogenes previously Corynebacterium pyogenes) Brucella abortus, now called Taylorella equigenitalis; B. ovis; B. melitensis Campylobacter fetus subspecies fetus Campylobacter jejuni Bacillus licheniformis Salmonella dublin, typhimurium, montivideo, S. abortus ovis and others Listeria monocytogenes Arizona spp. Fungi Aspergillus fumigatus Protozoa Toxoplasma gondii Non-infectious causes Stress (e.g. chasing/savaging by dogs; transport) Near-starvation Pregnancy toxaemia Claviceps purpurea (ergot in feed) Iodine deficiency
Sows
Infections Viruses African swine fever virus Aujeszky’s disease Smedi Swine fever virus Bacteria Erysipelothrix rhusiopathiae (swine erysipelas) Brucella abortus suis (not in UK) Pasteurella multocida (occasionally) E. coli Leptospira pomona (not in UK) grippotyphosa, canicola, icterohaemorrhagiae Protozoa Toxoplasma gondii Non-infectious causes Malnutrition, e.g. vitamin A deficiency (See also Carbon Monoxide .)
Mares
Infections Viruses Equine herpesvirus 1 (Equine rhinopneumonitis) Equine viral arteritis
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Bacteria Aeromonas hydrophilia Salmonella abortus equi Brucella abortus (rarely) Haemophilus equigenitalis (contagious equine metritis) Leptospira spp. (sometimes in association with equine herpesvirus 1) Listeriosis Non-infectious causes Twin foals Plant poisoning (e.g. by Locoweed) In thoroughbred mares, following an abortion there was reduced reproductive efficiency but subsequent pregnancy and foaling outcomes could not be predicted.
Bitches
Infections Brucella canis (not UK) Canine herpes virus Neospora caninum Streptococcus spp. Toxoplasma gondii Non-infectious causes Hormonal imbalance Trauma
Queens
Infections Chlamydophila psittaci Feline herpesvirus Feline immunodeficiency virus Feline infectious peritonitis Feline leukaemia virus Feline panleukopenia virus Non-infectious causes Nutritional deficiencies Progesterone deficiency
Rabbits (does) Abortion is uncommon in rabbit does, but physiological resorption of fetuses can occur before 20th day of gestation. Expulsion of premature aborted fetuses occurs after 24th day of gestation. Prolonged gestation (more than 35 days) is usually due to a small litter of large fetuses which can be expelled or retained and mummified or macerated.
mouth from infected material. It can remain latent for long periods in non-pregnant sheep until they become pregnant again. (See Chlamydophila.)
Diagnosis Necrotic placentitis is indicative,
smears stained by Ziehl-Neelsen show many organisms. A competitive ELISA (cELISA) test is stated to be 100 per cent effective in testing for antibodies against abortion-causing strains of C. abortus. Paired serology of aborted ewes can assist, and Complement fixation test can be used.
Signs Abortion occurs during the last 6 weeks, and usually during the last 2 or 3 weeks, of the normal period of gestation. Stillbirths and the birth of weak full-term lambs also occur. The placenta is thickened and necrotic. Most infected ewes who do not become ill have a thick, infected vaginal discharge for a week or more. Infertility is temporary, since ewes usually lamb normally the following season. Enzootic abortion is a zoonosis (see Zoonoses ); pregnant women must avoid all contact with infected sheep. Prevention Replacement sheep should be
obtained from blood-tested disease-free flocks. Vaccines are available; antibiotics (oxytetracycline) given to the whole flock can reduce the level of abortions if given early in an outbreak. Vaccination should be administered to non-pregnant sheep; it is ineffective during an abortion outbreak.
Abortion, Epizootic
Chlamydial abortion in cattle.
Abrachiocephalus
Fetal anomaly without head or arms.
Abrachius
The absence of forelimbs (arms).
Abrasion
A superficial wound of skin or mucous membrane caused by trauma, chaffing, rubbing, etc.
Abscess
Abortion, Enzootic, of Ewes and Goats
Localised lesion comprising of pus, surrounded by inflamed tissue. A tiny abscess is known as a Pustule , and a diffused area that produces pus is spoken of as an area of Cellulitis . Abscesses in cats are usually of this type and may not always ‘point’ (see below)
Cause Chlamydophila abortus (formerly Chlamydia ovis and Chlamydia psittaci), which is ingested by
An acute abscess An acute abscess is the most common form in most species. It forms rapidly, comes to a head (points) and bursts, or else becomes reabsorbed and disappears.
Abortion, Contagious (See Brucellosis .)
This disease occurs in all parts of Britain, as well as overseas.
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A
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4 Abyssinian
Causes The direct cause of an acute abscess is A either infection with bacteria, or the presence of an
irritant in the tissues. The organisms that are most often associated with the formation of abscesses include staphylococci and streptococci Arcanobacterium pyogenes; Pasteurella pyocyanea and, in cats, Fusobacterium necrophorum (see Bacteria ). When bacteria have gained access they start to multiply, and their Toxins may damage surrounding tissue. White blood cells (leukocytes) – in particular, those called neutrophils – gather in the area invaded by the bacteria and engulf them. The area of invasion becomes congested with dead or dying bacteria, dead or dying leukocytes, dead tissue cells and debris all of which are converted into a liquefied mass (pus) by the action of LYSOZYMES .
Signs Inflammation, (redness, warmth, swelling,
and pain); and sometimes fever may occur. When abscesses are deep and so cannot be detected by palpation, measurement of body temperature, diagnostic imaging and blood tests (to identify changes of morphology and leukocyte proportions) may be required. An acute abscess is said to point when it has reached the stage when the skin covering it is dead, thin, generally glazed, and bulging. If slightly deeper, the skin over the area becomes swollen, is painful, and ‘pits’ on pressure. When the abscess bursts, or when it is evacuated by lancing (at the site of bulging or pitting), the pain disappears, the swelling subsides, and the temperature falls. If all the pus has been evacuated, the cavity rapidly heals; if, however, the abscess has burst internally into the chest or abdomen, then pleurisy or peritonitis may follow. When an abscess is deeply seated so as to be out of reach of diagnosis by manipulative measures, its presence can be confirmed by blood tests.
Treatment Lancing is the treatment of choice.
It is best to leave the opened abscess uncovered to encourage drainage. Hot fomentations, or application of a poultice, may afford relief. Antibiotics may be employed once drained or as the sole means of treating multiple or deep-seated abscesses. They may be injected into a cavity with or without following aspiration of the pus. A cold or chronic abscess takes a long time to develop, seldom bursts (unless near to the surface of the body), and becomes surrounded by large amounts of hard fibrous tissue. The pus can be solid (‘inspissated’) or semisolid (‘caseated’). Some can be lanced.
A cold or chronic abscess It takes a long time to develop, seldom bursts (unless near to the
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surface of the body), and becomes surrounded by large amounts of fibrous tissue.
Causes Abscesses due to
Tuberculosis , Staphylococci, and Caseous abscess formation in the lymph nodes of sheep, are the most common types of cold or chronic abscesses. They may arise when an acute abscess, instead of bursting in the usual way, becomes surrounded by dense fibrous tissue. The neutrophils of rabbits, birds, and reptiles do not contain many lysosymes (so are more properly described as heterophils) and the pus in their abscesses is less liquefied – caseated - and inspissated to such an extent that drainage is not achieved by lancing and total excision is the preferred form of treatment. Actinomycosis ,
Signs Swelling may be noticeable on the surface of the body (as in actinomycosis), or it may show no signs of its presence until the animal is slaughtered (as in the case of many tuberculous abscesses and in lymphadenitis of sheep). If it is present on the surface, it is found to be hard, cold, only very slightly painful, and does not rapidly increase in size. Treatment This may involve surgery to remove the abscess, and/or the use of antibiotics, depending upon the nature of the abscess and its location. Abyssinian
A breed of short-haired cat similar in appearance to those depicted in illustrations from ancient Egypt. It is favoured for its quiet vocalisation. Familial renal amyloidosis has been found in this breed and it is also prone to Myasthenia Gravis and Hip Dysplasia . DNA tests are available for Progressive Retinal Atrophy and Erythrocyte Pyruvate Kinase Deficiency . The breed was the first to have its genome sequenced.
Acacia Poisoning
Acacia poisoning has been recorded in cattle and goats. Signs include ataxia, excitation and prostration.
Acampsia
The inflexibility of a limb; rigidity, ankylosis.
Acanthosis Nigricans
A chronic condition of the skin, the primary form mainly found mainly in short-haired dogs, especially Dachshunds. The secondary form is seen in obesity, nutritional and endocrine disorders. The skin becomes thickened with loss of hair and excessive black pigmentation, and is velvety to the touch. The condition often starts in the axillae (armpits) but the abdomen has also been seen as the primary location. The primary disease cause is unknown and it is not usually curable. It and the
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Acephaly 5
secondary form may respond to corticosteroids (local and injection), after the removal of secondary infections.
A
Acapnia
Acapnia is a condition of diminished carbon dioxide in the blood.
Acardia
The congenital absence of the heart.
Acardiacus
A parasitic twin without a heart, utilising the circulation of its twin.
Acardius
A parasitic twin without a heart, utilising the circulation of its twin.
Acaricide
A parasiticide effective against mites and ticks.
Acarus
A forage mite only accidentally parasitic.
Acaudal, Acaudate The absence of a tail.
Accidental Self-Injection,
Needle Stick Injury
This has led to human infection with Brucellosis , Orf , Q Fever and Tuberculosis (TB). Accidental self-injection with an oil-based vaccine is painful and dangerous; it requires immediate medical attention. If the accident involves Immobilon , the effects can be reversed by an immediate self-injection of Revivon (diprenorphine hydrochloride). A veterinary surgeon who had no Revivon with him died within 15 minutes of accidental self-injection, when a colt made a sudden violent movement. Even a scratch with a used needle can cause collapse. All involved in a procedure with the drug should be aware of the location of the antidote and that of the product leaflet. (See Diprenorphine Hydrochloride ; Etorphine ; Immobilon/ Revivon .) Tuberculin testing can reactivate latent infection in humans. Certain other products such as tilmicosin can be dangerous if much is injected. Thus the ‘Warnings’ section on a data sheet or product marketing authorisation should always be read before using a new product. Prescribers and suppliers of veterinary medicines should at all times make sure that those using the products are suitably competent, and make them aware of the potential risk.
Accidents
Any part of the animal may be injured in an accident. Often the damage is obvious, such as a
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First-aid for owners: how to carry an injured cat with a suspected limb fracture. A dog may be carried similarly if not too large. An alternative for a bigger dog is to draw it gently on to a coat or rug, ready for lifting into the back of a car for transport to a veterinary surgeon. Photo, Marc Henrie / Pedigree Petfoods.
broken limb. Serious internal injury may not be immediately apparent. Road traffic accidents are the commonest cause of accidents to dogs and cats. Care must be taken in handling injured animals, as mishandling may make the injury worse. (See also Electric Shock, ‘Stray Voltage’ and Electrocution ; Fractures ; Bleeding ; Rabbits-Handling ; Internal Haemorrhage ; Burns and Scalds ; Shock ; Eye, Diseases and Injuries of .)
Accommodation (See Eye .)
Acemann
A potent anti-viral substance extracted from the fleshy leaves of aloe vera. It has the additional property of enhancing the immune system especially lymphocytic function.
Acephalobrachia
A development anomaly in which head and arms are absent, the same as Abrachiocephalus .
Acephaly
The absence of a head.
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R 3Rs
The term used to aid and improve the use of animals in scientific research where no alternatives exist. Reduction, replacement and refinement has been used as a concept in the UK since first described by W. M. S. Russell and R. L. Burch in 1959 in ‘The Principles of Humane Experimental Technique’, Methuen, London ISBN 0900767782. (See also Laboratory Animals .)
Rabbit Epizootic Enterocolitis (REE)
(See Epizootic Rabbit Enteritis .)
Rabbit Fur Mite
This may be picked up by dogs and rabbitkeepers, and cause intense irritation. (See Cheyletiellosis .)
Rabbit Haemorrhagic Disease,
Viral Haemorrhagic Disease
Rabbit haemorrhagic disease is widespread throughout the UK and the rest of Europe. The disease, caused by a calicivirus, originated in China and may have been imported into Europe in rabbit meat. Cases are not known in rabbits under four months, at which age liver metabolism changes. This makes it a serious problem for breeders when a doe dies, leaving an orphan litter. Clinical signs are often transient: difficulty in breathing, or a short squeal followed immediately by the rabbit falling over, is often accompanied by sudden death. Animals surviving the acute stage develop jaundice and die after a few weeks. Haemorrhage from the nostrils and/or anus may be seen. Prevention is by vaccination; a combined vaccine with Myxomatosis is available. Deliberate introduction of the disease has been tried as a means of limiting wild rabbit populations, e.g. in Australia.
Rabbit Rings
The British Rabbit Council issues 100,000 metal rings each year in the UK to members to use in identifying rabbits, but advises that the rings should be removed from rabbits sold or given away as pets. ‘Injury can occur if bedding material becomes trapped between ring and leg,’ or if the ring has become – with the rabbit’s growth – too tight, with the risk of causing necrosis. Should that occur, surgical intervention or euthanasia will be needed.
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Rabbits
These are members of the Order Lagomorpha, and are known as lagomorphs. Most domestic pets are the European rabbit (Oryctolagus cuniculus). Males are called bucks, females are does and the young are kittens or kits. Breeds of domesticated rabbits used for table purposes include the New Zealand white, the California, and the Dutch rabbit. (See also Pets, Children’s and Exotic .) Rabbits are Fibrevores and their feed should consist of good quality hay and grass given ad libitum, and small amounts of fresh greens and concentrated feed. Healthy treats like carrots and apples should be fed no more than twice a week. Rabbits can develop Obesity mainly from poor diet and lack of exercise as well as age, sex and neutered status. They practise Coprophagy . Overgrown claws, dental problems, diarrhoea and Urine Scald are common.
Handling Rabbits are flighty creatures tending to react to the slightest stimulus by attempting to escape. They may try and leap from a smooth surface (such as a table top) on which their claws cannot obtain purchase. They thus should be restrained on a rough surface such as secure sacking or carpet. When lifting a rabbit, a fold of skin over the shoulder should be grasped with one hand, while the palm of the other hand supports the rump. A rabbit should not be lifted by its ears. Struggling while being inexpertly handled can lead to fractures of limbs. A startled rabbit may leap and fracture the spine. Diseases include
Appendicitis ; Atrophic Rhinitis ; Coccidiosis ; Encephalitozoon Cuniculi ; Hydrometra (the accumulation of watery fluid in the uterus); Impaction of colon
or stomach (often the result of insufficient hay being provided); Johne’s Disease ; Listeriosis ; Maggots in Rabbits ; Mastitis ; Metritis ; Myxomatosis, Infectious ; Pasteurellosis in Rabbits ; Pneumonia ; Rabbit Haemorrhagic Disease ; ‘Rabbit Syphilis’ ; Salmonellosis ; Schmorl’s Disease ; ‘Sore Hocks’ (Pododermatitis ); Toxoplasmosis ; Tuberculosis ; Tyzzer’s Disease ; Yersiniosis . Pasteurella multocida causes a pneumonia which may be acute and fatal in rabbits under 12 weeks old. It may cause also middle-ear disease with a loss of balance, circling, and head held to one side, epiphora, and also ‘snuffles’ in which there is a discharge from eyes and nose and sneezing. Rabbits act as hosts of the liver-fluke of sheep, and of the cystic stages of some tapeworms, e.g. Taenia pisiformis, T. serialis. Rabbits have been used experimentally as incubators for sheep’s eggs.
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Rabies 723
A hermaphrodite rabbit served several females and sired more than 250 young of both sexes. In the next breeding season the rabbit, which was housed in isolation, became pregnant and delivered seven healthy young of both sexes.
Pregnancy diagnosis An ELISA test is available for this purpose. It can also differentiate between pseudo-pregnancy and pregnancy, and detect rabbits about to ovulate. Anaesthesia A wide range of anaesthetics is suitable for use in rabbits. Halothane and other inhalation anaesthetics are suitable and convenient to administer. Premedication with atropine (50 micrograms per kg by hypodermic or intramuscular injection) or acepromazine (1 mg per kg intramuscularly) is advisable half an hour earlier. Alfaxalone/alfadolone is one of several injectable anaesthetics recommended for surgery. Oxygen should be ready to hand. The Veterinary Formulary, published by the BVA/Royal Pharmaceutical Society, gives comprehensive details of anaesthetics and analgesics suitable for rabbits and small rodents.
‘Rabbit Syphilis’
‘Rabbit syphilis’ is caused by a spirochaete, Treponema cuniculi (which does not affect humans). It is a venereal disease characterised by the appearance of nodules and superficial ulcers covered with thin, moist, scaly crusts and oedematous swellings of the surrounding tissues mainly in the region of the genitalia (hence the colloquial name, ‘vent disease’) and also sometimes in the region of the nose. The specific diagnostic is by the Silver Warthy Test, but generally response of the disease to parenteral Penicillin is regarded as diagnostic.
Rabbit Welfare Association and Fund
Address: PO Box 603, Horsham, West Sussex, RH13 SW1. Telephone: 0844 324 6090; helpline: 0870 046 5249; website: www.rabbitwelfare.co.uk
Rabies
The Latin word for madness (also known as Hydrophobia ), it is a specific inoculable Contagious disease of virtually all mammals, including man; and occasionally it occurs in birds, e.g. domestic poultry and vultures. It is characterised by nervous derangement, often by a change in temperament, with paralysis occurring in the final – and sometimes in the intermediate – stages. Foxes and cattle are both highly susceptible to infection. Rabies occurs in all continents with the exception of Australasia and Antarctica. In Turkey,
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dogs remain the principal vectors; in a few countries in Europe cats attack more people than do dogs. In Asia and South America dogs are still the most important vectors, but in many countries wild animals provide a reservoir of infection, and infect dogs and cats and farm animals – which in turn may infect man, who is an incidental host of the disease. (See table of vectors.) Rabies in wild animals – principal vectors in various regions Foxes, roe-deer, badgers, martens Wolves, jackals, bats, mongooses Foxes, skunks, coyotes, bats Bats
Europe Asia North America Central America South America and Trinidad
Public health Rabies is virtually always fatal in
the human being, and there is danger not only from being bitten by rabid animals, but also from contamination by their saliva of wounds, cut fingers, eyes, etc. Scratches may convey infection as well as bites. People have died from rabies following attacks by rabid dogs, cats, foxes, wolves, badgers, skunks, racoons, mongooses, bats, rodents, etc. Pet animals, such as rabbits, may be bitten by rabid animals and themselves become rabid; and it has sometimes happened that wild or exotic animals (originating in countries where rabies is endemic) were bought as pets while in the incubation stage of rabies, with unfortunate results. In the UK as in most other countries, rabies is a Notifiable Disease , and must be reported to DEFRA or to the police. Bitten persons should seek medical advice immediately.
R
Cause A Lyssa virus (one of the Rhabdovirus group). When it is injected into the tissues, either naturally (from a bite) or artificially, the virus passes along the nerves and reaches the central nervous system. The time elapsing between infection and onset of signs varies greatly with the location of the bite, its severity, and – no doubt – the quantity of virus in the saliva. In the most rapidly developing cases the signs may be shown as early as the ninth day after being bitten, and at the other extreme, cases have appeared several months after the incident. It is owing to this fact that the six-months period of quarantine insisted upon in Britain is something of a compromise. The average incubation periods in dogs, sheep, and swine are from 15 to 60 days; in horses and cattle, from 30
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724 Rabies
to 80 days. In young animals the period of incubation is shorter than in adults. In 2011, a new strain (a divergent novel Lyssa avirus) was found in an African civet (Civettictis civetta) in Tanzania, possibly originating from bats.
Signs Dog There are two distinct forms of rabies in the dog – the ‘furious’ and the ‘dumb’; but these are in reality two stages only. It is customary to consider three stages of typical signs.
R
1. Melancholy. The prodromal dull stage is often not noticed, or, if it is, only scant attention is paid to it. The habits of the dog change. It becomes morose and sulky, indifferent to authority, disregards its usual playthings or companions, shows a tendency to hide in dark corners, and may appear itchy or irritable as regards its skin. Noisy, boisterous animals become quiet and dull, while animals that are normally of a gentle, quiet disposition may become excitable. After two or three days of such behaviour the next stage is reached. 2. Excitement. The signs described above become exaggerated, and there is a tendency towards violence. The dog pays no attention to either cajoling or threatening. It becomes easily excited and very uncertain in its behaviour. Food is either disregarded completely or eaten with haste. Vomiting is a not uncommon sign. A fear of water is not a sign to expect in the rabid dog, which will often drink or attempt to do so even when partly paralysed. After a time the appetite becomes deranged. The dog refuses its ordinary food, but eats straw, stones, wood, coal, carpet, pieces of sacking, etc., with great avidity. If the animal is shut up in a kennel, it persists continually in its efforts to escape. Should it be released or should it escape, it almost invariably runs away from home. It may wander for long distances. In its travels it bites and snaps at objects which it encounters, real or imaginary, animate or inanimate. Some rabid dogs bite several people. The tone of voice is altered. The face has a vacant stare, the eyes are fixed and expressionless, and the pupils are dilated. This stage lasts from two to four days, unless the dog’s strength gives out sooner, and the next stage appears. 3. Paralysis. The characteristics of the last stage in the train of signs of rabies are those of paralysis, especially of the lower jaw and the hindquarters. The dog begins to stagger in its gait, and finally falls. It may manage to regain its feet when stimulated, but soon falls again. The lower jaw drops, the tongue lolls out of the mouth, and there is great salivation. The muscles of the
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throat and larynx are soon involved in the progressive paralysis. The dumb form of rabies consists of this paralytic stage – the stage of excitation having been omitted. The dumb form is the more common in the dog: barking ceases – hence the name. Vomiting may suggest merely a digestive upset. Protrusion of the nictitating membrane partly across the eye, together with a dropped jaw, i.e. partly opened mouth which can be closed by gently raising the lower jaw by means of a stick, are highly suggestive of rabies. In parts of Africa and Asia, the classical form of rabies in dogs (described above) is replaced by a form called (in Africa) ‘Oulou Fato’ .
Cat In this animal the furious form is more
common than in the dog. The aggressive stage is most marked, the cat attacking other animals and man with great vigour, and attempting to injure their faces with teeth or claws. Sometimes the rabid cat will at first show extra affection. The course of the disease is usually shorter than in the dog. Occasionally dogs and cats die from rabies without any observed signs. They may be found dead or dying. It is not unknown for a cat to be found lying in a field or garden unable to walk but still able to bite.
Cattle These animals are usually affected through
having been bitten by a rabid fox or dog. The stage of excitement is short and the dumb stage most evident. Affected cattle behave in an unusual manner; they may stamp or bellow, salivate from the mouth, break loose, and may do much damage. Rumination and milk production cease, muscular quiverings are seen, sexual excitement is noticed, and there is a great loss of condition. Exhaustion soon follows and paralysis sets in. Death occurs within two to six days or more after the commencement of the condition. Rabies may be mistaken for hypomagnesaemia, milk fever, botulism, anaplasmosis, listeriosis, lead poisoning, choking, etc. In Central and South America, cattle are infected with rabies by vampire bats, and may show long streaks of blood on their shoulders, necks and backs.
Sheep, goats and swine The sheep and the
goat are affected in a manner similar to cattle, but the stage of excitement is shorter or absent, and the dumb paralytic stage is more often noticed. Pigs become excitable; they may squeal and show muscular spasms before paralysis ensues.
Horse The furious form is common but the animal
may appear calm between bouts of aggressiveness. Dumb forms also occur and may be mistaken for colic, paresis or encephalitis from other causes. Signs
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may include a facial twitch, biting of woodwork or self-mutilation, head-tossing, frequent whinnying, abnormal posture, apparent lameness, ataxia and paralysis of hindquarters. The horse may continue to eat and drink until shortly before death. The tone of voice may be altered.
Diagnosis The routine examination for Negri bodies has now in most countries been superseded by the fluorescent antibody test, with confirmation by mouse inoculation if necessary. (If a dog which bit someone is still alive after 10 days, it cannot be assumed that the dog is not rabid.) Differentiation between laboratory and street rabies virus, between rabies vaccine virus and street virus, and between rabies virus and rabies-like viruses (e.g. Mokola, Lagos bat, and Duvenhage viruses) is possible by laboratory tests based on differentiation of monoclonal antibodies. Prevention Prevention of the disease in man
and animals stems from the research of Louis Pasteur in the 1880s. He discovered the process of attenuation, by which the virulence of a microorganism is reduced but not its ability to produce antibodies against disease. Pasteur achieved this by infecting rabbits with rabies from a dog. Although this was fatal to the rabbits, dogs survived infection with the rabbit virus. Tissue from the spinal cord of an infected rabbit was then used to prepare a vaccine. His triumph came in 1885 when the vaccine saved the lives of two badly bitten boys. In the intervening years many modifications have been made, and new techniques developed, to make rabies vaccines which would be safe and free from dangerous side-effects, and so could be used to immunise people and animals against rabies (‘preexposure’ – vaccination), as well as provide ‘postexposure’ treatment of those bitten by rabid animals. The table shows examples of vaccines prepared from tissue culture cells. The last one, the Merieux, was developed by the Merieux Institute of France using a technique pioneered at the Wistar Institute of Philadelphia. Only 1 ml doses are required, and two injections (apart from any booster doses). (See also Vero Cells .) In the UK, two vaccines approved for use in dogs and cats: Rabisin rabies vaccine (Merial)
containing inactivated GS-57 Wistar virus strain; and Nobivac Rabies (Intervet) prepared from virus grown on cell-line tissue culture. Mass vaccination of dogs is carried out in many countries as a control measure; and in Central and South America, cattle on ranches are vaccinated against vampire-bat-transmitted rabies. In France and other countries of Europe, hundreds of thousands of cattle are vaccinated against rabies (often a combined rabies/foot-and-mouth disease inoculation). It must be remembered, however, that no vaccines are 100 per cent effective, that certificates of vaccination can be forged, and that consequently it is still essential to control the import of animals, whether vaccinated or not, and to enforce quarantine measures where appropriate.
Control of rabies in Britain The last case acquired by a dog living in Britain was in 1902. From 1902 until 1918, no cases occurred in the British Isles; but in that year infected dogs were smuggled from the Continent, and the disease obtained a fresh hold for a period of little more than three years. The last case in Northern Ireland was in 1920. Britain had been free since then, but in 1969 a dog released from quarantine 10 days earlier showed signs of rabies and bit two people at Camberley, Surrey; a second case occurred in 1970. In 1965 there was a case in a recently imported leopard in quarantine at Edinburgh Zoo. In Britain, in 1969, the danger of allowing the importation of rabies-susceptible exotic animals, for sale as pets or for research, was officially recognised, and the quarantine regulations amended to include monkeys, mongooses, etc. Following strong pressure to replace quarantine for pet dogs with a vaccination/identification policy, a government committee was set up in 1997 to examine the issue. The committee recommended that a strict scheme of medical examination, rabies vaccination and veterinary certification should replace the compulsory quarantine regulations for dogs and cats. The recommendation was accepted and an arrangement introduced in 2000 under which dogs and cats may travel to and from the UK and specified countries without quarantine under the Pet Travel Scheme . (See also Importing/ Exporting Animals .)
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Examples of rabies vaccines prepared from tissue culture cells Live virus: ERA HEP-Flury Inactivated: Fixed
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Cells used: Pig kidney Dog kidney Hamster kidney Hamster embryo
Cats, dogs, cattle and other animals Cats, dogs, and cattle Cats, dogs, cattle and other animals Cats, dogs, horses, cattle and sheep
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V Vaccination
A method of producing active immunity against a specific infection by means of inoculation with a vaccine, i.e. a preparation of the necessary antigen(s). (See Immunity ; Immunisation ; Immune Response ; Vaccine .) Vaccination in mammals is normally carried out by inoculating individual animals. The method of administration depends on the type of vaccine. Most inactivated vaccines are injected intramuscularly or subcutaneously; temperature-sensitive live vaccines may be administered as drops into the nasal passages; vaccines against Parasitic Bronchitis are given orally. Mass vaccination of poultry against Newcastle Disease may be achieved by dispersing aerosols of vaccine over the heads of the birds with fine spray pumps or adding vaccine to the drinking water. Some fish are vaccinated by dipping the fish in a solution of the vaccine. Fox populations in Europe have been vaccinated against Rabies by impregnating chicken heads or other baits and spreading them in known fox runs. Multiple-component vaccines containing antigens against a number of diseases are available. For example, sheep can be simultaneously immunised against Pulpy Kidney Disease , Lamb Dysentery , Braxy , BlackLeg , Black Disease , Clostridium haemolyticum infection and Tetanus by a single 8-in-1 vaccine. There are also 10-in-1 vaccines which include Cl. sordellii. (In connection with foot-and-mouth disease, see also Ring Vaccination .)
Vaccine
When an animal is inoculated with a vaccine as protection against a specific disease, e.g. blackleg, this is carried out with the object of stimulating production of antibodies in its system, which will confer active immunity against blackleg organisms. Vaccines may be prepared from live microorganisms; from inactivated (killed) microorganisms; from genetically engineered subunits of the pathogenic fraction of the organism; or from toxoids – heat- or chemically-treated microorganisms that have lost their virulence but retain their antigenicity, i.e. ability to create resistance to disease. Live vaccines are vaccines prepared from bacteria or viruses whose virulence is reduced by heat, chemicals or passage through an animal other than the normal host species. For example, cattle
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plague vaccine may be prepared from the virus passaged through (i.e. grown in) chick embryos. Occasionally the live viruses used are related but non-pathogenic strains, useful because they will stimulate antibody production but will not produce the disease. Viruses may be inactivated by phenol or ultraviolet rays, for example; or they may be modified in some way, such as by artificially induced mutation, to produce a temperature-sensitive virus which will replicate in the nose but not in the lungs. Such a virus vaccine can be administered by nasal spray. Tissue culture vaccines – live vaccines grown on cell cultures – are used in the prevention of canine distemper, rabies, etc., and in treatment of benign skin papillomata (warts) of cattle. Vaccines are sometimes used for treatment as well as for prevention of a particular disease. X-irradiated worm larvae vaccine is used in the prevention of Parasitic Bronchitis . It is important that, in the commercial production of live vaccines involving the use of chicken embryos (or of tissue cultures derived from them), contaminant viruses are eliminated. For example, the Avian Lymphoid Leukosis virus has contaminated distemper vaccine and would represent a risk to vaccinated poultry if contaminating vaccines for them. Scrapie was accidentally spread by an early Louping-Ill virus contaminated by the scrapie agent. In Europe, Bovine Viral Diarrhoea virus contaminated marker Infectious Bovine Rhinotracheitis vaccine. It is essential that vaccines are stored under suitable conditions of temperature, etc.; that they are not used after the expiry date shown on the package; that where two doses are stated to be necessary, both are given – and at the correct interval. Failure to observe these rules can mean that the vaccinated animal does not become immunised; it has led to dogs presumed properly vaccinated against rabies becoming rabid after exposure to a natural infection. Another problem that can be encountered when using improperly stored vaccine can result in hyper-immunisation and anaphylactic shock. (See also Injections ; Genetic Engineering .) Inactivated vaccines are prepared from killed micro-organisms that retain sufficient antigenic activity to promote immunity. They are not as potent as live vaccines, and two doses at specified intervals are usually necessary to produce effective immunity. Inactivated vaccines often contain an adjuvant, usually an aluminium salt such as aluminium hydroxide, which enhances the immune reaction. Some are water-based, others formulated in an oily medium. Oil-based vaccines can cause serious reactions if accidentally self-injected into the
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operator. It is essential that the person injected receives immediate medical attention and the product data sheet or specification of product characteristics accompanies the person. Subunit vaccines are genetically engineered so that only the antigenic fraction of a pathogen is utilised. The vaccine does not cause infection but does stimulate immunity. Feline Leukaemia vaccine and Aujeszky’s Disease vaccine are examples. The virus component of the subunit vaccine has difficulty in penetrating the cells of the vaccinated animal; it does not multiply well within the cells and the animal does not shed the virus. By testing for the fraction missing from the vaccinial strain of virus, a vaccinated animal can be determined from one carrying the infection. Toxoid vaccines are produced by treating toxins from micro-organisms so that their harmful effects are removed but the antigenic properties remain. Tetanus vaccine is an example.
Marker Vaccines Vaccination can cause a problem when making a diagnosis of disease due to the same organism, as usually it is not possible to distinguish between antibodies produced by infection and those from vaccination. This has been overcome in a few vaccines by making them ‘marker’ vaccines. Marker vaccines have either a gene deletion which can then be detected, such as with Infectious Bovine Rhinotracheitis marker vaccine, or they can be produced by adding one or more genes.
Vaccinia Virus
This term may refer to the virus of naturally occurring cow-pox, or to a strain which has undergone mutation and was used for vaccination against smallpox. The virus was also used as the carrier for the antigen of rabies virus in the live vaccine that has been used to eliminate rabies from wildlife in Western Europe and the USA. (See Pox .)
Vacuole
A cavity within a cell.
Vacuum-Dipping of Eggs
A technique used in assisting the eradication of Mycoplasma spp. in poultry. Fertile eggs are dipped in a concentrated solution of antibiotic (usually Tylosin ) and subjected to a negative pressure. Some of the air in the egg’s air pocket is thus extracted and about 0.5 ml of antibiotic drawn through the shell into the egg and absorbed. This process is more effective in helping to eliminate M. gallisepticum than other mycoplasmas.
Vagina
The vagina extends from the cervix of the uterus to the vulva. Vaginal mucus is altered in character
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during pregnancy, a fact which can be made use of in pregnancy diagnosis. (For inflammation of the vagina, see Vaginitis .) An artificial vagina is used at AI centres for the collection of semen.
Vaginal prolapse in ewes This may precede lambing by up to 55 days, but most cases occur within the last 21 days of pregnancy. Rupture of the vagina, with protrusion of the
intestine and rapid death, occurs not uncommonly in ewes of a large breed, of mature age, carrying a twin – a week or two before lambing is due. Bulky foods – swedes, turnips, kale – are often involved.
Vaginoureteral fistula This has been recorded in dogs and cats, as a complication of ovario-hysterectomy or a caesarean operation, and leads to urinary incontinence. It has been suggested that the fistula may occur following accidental ligation of the ureter during surgery, or because the ureter becomes involved in an inflammatory adhesion originating in the vaginal stump. Intermittent haemorrhage occasionally occurs in mares having very prominent varicose veins at the dorsal aspect of the vulvo-vaginal area; it does not appear to affect health or fertility. Persistent vulval haemorrhage from varicose veins of the dorsal wall of the vagina has also been described. It yields to local haemostatic treatment.
Vaginitis
Inflammation of the vagina. (See under Infertility – Diseases of the genital organs in female; also ‘Whites’; Epididymitis – Epivag; Vulvovaginitis, Granular ; Prolapse .)
Vaginoscope, Vaginoscopy
An instrument used to examine the vaginal lining and is introduced via the Vulva .
Vagotomy
Severing of the vagus nerve. (See Osteopathy .)
Hypertrophic
Vagus, Pneumogastric Nerve
The vagus (pneumogastric nerve) is the 10th cranial nerve. This nerve is remarkable for its great length, and for the attachments which it forms with other nerves and with the sympathetic trunks. It arises from the side of the medulla, passes out of the skull, and runs down to the jugular furrow of the neck, where, along with the sympathetic, it accompanies the carotid artery to the entrance to the chest. From this point the right and left vagi differ from each other in their course. They both
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920 Valerian
pass through the chest cavity, giving branches to the pharynx (which run up the neck again), to the heart, bronchi, oesophagus, etc. Each nerve then splits into two parts and the two upper branches fuse with each other to form the dorsal trunk, the lower branches behaving similarly to form the ventral trunk. These two branches now pass through the diaphragm, with the oesophagus, into the abdominal cavity, and end by giving branches to the stomach, duodenum, liver, and various ganglia nearby. (See Parasympathetic Nervous System; also Brain .) (See Guttural Pouch Disease .)
Valerian
A herb long used in human medicines that help in relieving anxiety and tension; its mode of action is unknown. It is found in herbal preparations for dogs and cats, as a sedative, for travel sickness, and as adjunct in treating Epilepsy . Tincture of valerian produces an odour that is attractive to male cats.
Valgus
A bone growth-plate defect. (See under Bone, Diseases of .) This results in a bending outwards usually of a limb or the pelvis, with angulation away from the midline. The opposite also occurs and is known as Varus .
Valnemulin
An antibiotic licensed for treating respiratory and intestinal infectious diseases of pigs. It is toxic to rabbits and it reacts with ionophores, resulting in a syndrome like ionophore poisoning. (See Monensin Sodium .) In Scandinavian countries there have been adverse reactions reported in Landrace breeds and so care should be taken when using in these breeds.
Valves
Valves are found in the heart, veins, lymph vessels, etc., and serve the purpose of ensuring that the fluids will only circulate in one direction. (See Heart ; Veins ; Ileocaecal .)
Valvular Disease (See Heart Diseases .)
Vampire Bats
Vampire bats are important transmitters of rabies in parts of South and Central America, the West Indies, etc. The bat laps blood from the wounds inflicted with its upper incisor teeth on cattle, horses, etc. In Mexico infected vampires have made necessary the preventive inoculation of 800,000 cattle a year. Trypanosomiasis can also be transmitted by vampire bats. Vampire bats imported into the UK remain in quarantine for the rest of their life.
Vanadium
A trace element essential in minute quantities for the growth of chicks; as little as 10 mg/kg of diet is an overdose that will suppress growth. It works with insulin to increase the amount of glucose and amino acids taken up by muscle.
Vane
The outer part of a contour feather composed of tightly-held barbs. (See Skin - Appendages of the skin .)
Varicose Veins (See under Veins .)
Varied Diet, Need for (See
Diet and Dietetics ; Amino Acids ; Cat Foods ; Dogs’ Diet .)
V One-month-old foal with bilateral carpal valgus. (With acknowledgements to Professor L. C. Vaughan and the Royal Veterinary College.)
Variocele
Valine
Variola, Pox
One of the essential amino acids which must be supplied in a well-balanced proportion with leucine and isoleucine. It is glycogenic and is metabolised in the muscles.
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Variocele is a condition in which the veins of one or both testicles are greatly distended. Variola (pox) is the inclusive term for fevers of animals and man, in which a skin eruption takes the form of a ‘pock’, caused by a Pox virus.
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Varroasis
Varroasis is a parasitic disease of honey bees, Apis melifera, caused by the mite Varroa jacobsoni. The mite feeds on the developing larvae and on the adult bees. The result is weak bees and sometimes the death of the queen. Whole hives can be wiped out, causing great economic loss not only to the apiculturalist but also to fruit and arable farmers; beekeepers often supply hives to fruit growers and to fields of rape and Linseed . Varroasis is prevalent in the UK and is a Notifiable Disease . As both parasite and host are arthropods, products used for control of the disease must have a fine division between toxicity to the mite and toxicity to the bee. Suspending strips impregnated with flumethrin or fluvalinate in the hive can be effective. Other treatments include tobacco smoke or a vaporising block containing thymol and aromatic oils. Eradication, however, is difficult. The disease came from Asia, where it does less harm because Asiatic bees groom each other, thus removing the mites. Long term, it has been suggested that European and Asian bees may be cross-bred to try to introduce the grooming habit into the European bee population. A variant bee has been found in the English Midlands that will groom other bees and destroy the mites by biting them. A leaflet available from DEFRA gives more details of the disease and its control.
Varus
A bending inwards towards the midline usually of a limb or the pelvis. The opposite is Valgus .
Vascular
Pertaining to, consisting of, or containing (a high proportion of ) blood vessels.
Vascularisation
The establishment of blood vessels within an organ or body part.
Vascular Rings
A congenital condition found in dogs; it involves the great vessels in the thorax. Often there is aortic transposition from left to right side of the heart. The signs are vomiting in a newly-weaned puppy. Diagnosis is to eliminate Megaoesophagus . Surgery should be performed as soon as possible. (See Heart Diseases .)
Vasculitis
retains its libido and may be used for the detection of oestrus (e.g. in cattle). In breeding catteries one or two toms are sometimes vasectomised for the sake of peace, quiet and contentment of queens not being bred from until a later oestrus. In sheep they are often used to initiate oestrus before or at the start of the breeding season. Sterility does not immediately follow vasectomy (or castration), as some sperms will be in the seminal vesicles and can lead to conception after mating. It may be three weeks or more before the animal is sterile.
Vasoconstriction
Decreased diameter of blood vessels.
Vasoconstrictor
Anything which reduces the size of blood vessels.
Vasodilation, Vasodilatation Increased diameter of blood vessels.
Vasodilator
Anything which causes dilation of blood vessels. A drug used for this purpose is Isoxsuprine hydrochloride. (See Navicular Disease .)
Vasomotor Nerves
Vasomotor nerves are the small nerve fibres that lie in or upon the walls of the blood vessels and connect the muscle fibres of the middle coat with the nervous system. By the continuous action of the nerves the muscular walls of the vessels are maintained in a moderate state of contraction. Any continuous and generalised increase in this action results in a raising of the blood pressure of the body, while a diminution produces a lowering of the pressure. Such vasomotor nerves are called vasoconstrictors, but there are vasodilators as well. The latter are able to dilate the vessels, and cause either a general or a local fall in the blood pressure, along with an increased supply of blood to the part.
Vasopressin
A hormone secreted by the posterior lobe of the pituitary gland. It is also called Antidiuretic Hormone (ADH). (See Pituitary Gland .)
Vasotocin
(See under Testicle .)
A hormone found in non-mammalian vertebrates such as birds, amphibians, fish and foetal mammals. It is secreted by the Pituitary Gland and has the biological properties of both Oxytocin and Vasopressin .
Vasectomy
Vector
Inflammation of a blood vessel.
Vas Deferens
An operation in the male animal in which the vas deferens is cut. Such an animal is sterile though it
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The carrier which transmits a disease from one animal to another. For example, the mosquito
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