Highlights report small ruminants-September 2024 by Royal GD

Numerous problems caused by haemonchose

In early June, GD received reports of haemonchosis in sheep. Post-mortem diagnostics frequently found haemonchosis as the cause of death during the summer months. The wet spring may well have played a role in the enormous disease burden. There were long periods when many plots were too wet for sheep to be grazed, making it difficult for grazing to keep them short and clean. Haemonchosis is caused by the barber’s pole worm, known scientifically as Haemonchus contortus. It is a subtropical gastrointestinal worm that presents an elevated risk for sheep and goats during the summer months. Humid conditions and high temperatures are ideal for the development of this worm. Where there is insufficient resistance or increased infection pressure, animals can become sick. The symptoms of illness are caused by adult worms ingesting blood in the abomasum. It manifests as

Staying alert for liver fluke

Liver fluke disease is caused by the liver fluke, a flatworm that affects the liver. The liver fluke’s eggs end up in the soil via the droppings of infected animals. Larvae emerge from these that develop in an intermediate host into tailed larvae. The intermediate host, a mud snail, thrives in particular on wet (low-lying) grassland and on the banks of ditches and trenches. After a while, the larvae are excreted by the snail and then attach themselves as infectious cysts to the grass. Grazing animals ingest these cysts and consequently get infected with the liver fluke.

pallid mucous membranes, accumulation of fluid between the parts of the jaw (oedema), emaciation and death. Diarrhoea is not generally a symptom of this disease. Lambs are more susceptible than adult sheep because they are still building up resistance during the first year of life. When adult animals’ resistance is lower, for example around lambing or because of disease, the barber’s pole worm can also cause clinical symptoms in adult sheep. Bluetongue resembles some of the symptoms of haemonchosis, including oedema, lethargy and mortality. Over recent months, concomitant barber’s pole worm infections were often seen in sheep that were infected with the bluetongue virus. GD recommends being alert for haemonchosis and monitoring infections properly, based on examinations of the droppings and on clinical symptoms.

In the autumn, acute liver fluke infections may be seen as a result of ingestion of infectious liver fluke cysts some weeks earlier. Mass migration of liver fluke larvae causes damage to the liver. Signs of anaemia such as pale mucous membranes, lethargy, growth retardation and sudden mortality are consistent with acute liver fluke infections. The Liver Fluke Forecasting Working Group used to issue provisional and definitive predictions annually (in mid-September and mid-November respectively), based on various findings and data, including snail counts and determination of the infectious stages of the liver fluke within the snails.

GD advises avoiding grazing as far as possible on high-risk wet plots, as well as monitoring any infections. Testing lambs for antibodies against liver flukes can show whether they have come into contact with liver fluke during their first year in the meadow. Antibodies remain present for a long time, so blood tests on adult sheep do not say anything about the moment when they came into contact with liver flukes. Examination of the droppings can show the presence of eggs and thereby of the adult stage of the liver fluke. In the event of losses, pathological examination can exclude an acute liver fluke infection as the cause.

Arthritis in kids

Pathological examinations were carried out on eight-week-old dairy kids with arthritis (or polyarthritis). Bacteriological investigations showed nonspecific bacteria as the cause, including Streptococcus dysgalactiae, subspecies dysgalactiae.

The bacterium Streptococcus dysgalactiae is part of the skin flora and can therefore be found in kids’ environments. This bacterium

Suspected

causes udder inflammation in cattle, as well as being known as a cause of joint inflammation in kids. There are many different pathogens for polyarthritis in kids. The bacteria involved are usually opportunists. A reduced immune response combined with elevated infection pressure are the main reasons why these bacteria may take hold. Preventive measures focus on keeping the mother animals healthy, clean

tuberculosis in a sheep in the abattoir

Contacts with the Netherlands Food and Consumer Products Safety Authority (NVWA) revealed that a sheep on the slaughter line had been suspected of having tuberculosis. Based on feedback from the NVWA, this sheep had presented with inflammation of the mesenteric lymph nodes that (on follow-up diagnostic testing) proved to be an infection with Mycobacterium avium complex. This result proved the suspicion of tuberculosis to have been incorrect.

Tuberculosis is a condition that is caused by the group of bacteria known as Mycobacterium tuberculosis complex. The bacterium causes caseous degeneration of the infected lymph nodes. Humans are also susceptible to developing tuberculosis. The group of bacteria known as Mycobacterium avium complex includes the subspecies paratuberculosis, a bacterium that causes chronic intestinal complaints in ruminants. It is suspected that the sheep in question

Copper deficiency in sheep and lambs

The Veekijker was contacted at the end of May about three Texel lambs a few weeks old that appeared weak in the hind legs. The clinical picture ranged from paresis to paralysis. One five-week-old lamb was submitted for pathological examination. A trace element determination carried out on the liver tissue showed a value for copper of 44 mg/kg dry matter. Liver values below 100 mg/kg dry matter are considered to be too low.

Copper is an important trace element that has various functions in the body. Copper is involved in the immune defences, for instance, and in the absorption of iron from the intestines, wool growth, pigmentation of the wool and hair, bone development and formation of the myelin sheaths around nerve fibres. Underdevelopment of the myelin sheaths slows down the transmission of signals along the nerve fibres, leading to the typical weakness of the hindquarters known as swayback. This clinical picture often develops within a few weeks after birth.

surroundings, preventing overcrowding, appropriate umbilical disinfection, good colostrum management and minimum use of antibiotics. Arthritis (including polyarthritis) is occasionally associated with damage to the rumen. Culturing the agent can help understand the possible causes, the treatment and the preventive measures that can be put in place.

was infected with this bacterium. Paratuberculosis in sheep is occasionally diagnosed in the Netherlands. The bacteria M. bovis, M. caprae and M. tuberculosis –which all belong to the Mycobacterium tuberculosis complex – are notifiable. Suspected tuberculosis cases must be notified to the NVWA.

Once the symptoms of swayback have occurred, recovery is not possible; in the most favourable case, the symptoms may stabilize. It is much more important to prevent copper deficiency in the pregnant mother animals. However, the margin between deficiency and excess is narrow and copper deficiency should be diagnosed properly before any adjustments are made to the feed.

Monitoring animal health – small ruminants, 2024

Disease/disorder/ health characteristic

Brief description

Articles 2.1.a and 2.1.b of the Designation of Animal Diseases in the Rules for Animal Health/Implementing Regulation (EU) 2018/1882 of the Animal Health Law (EU) 2016/429 (Category A diseases)

Infectious pleuropneumonia in goats (CCPP)

(Mycoplasma capricolum subs . capripneumoniae)

Never detected in the Netherlands.

Foot-and-mouth disease (FMD) Not reported in the Netherlands since 2001.

Infection with goat plague (a.k.a. PPR, peste des petits ruminants)

Infection with Rift Valley Fever virus (RVF)

Never detected in the Netherlands. Outbreak ongoing since July 2024 in parts of Greece and Romania. Despite measures to restrict it, the number of infections is increasing.

Never detected in the Netherlands.

Sheep pox and goat pox (SGP) Never detected in the Netherlands.

Multiple outbreaks detected at sheep farms in Spain from September 2022 to the spring of 2023. The calculated risk of SGP being introduced into the Netherlands is deemed small. From October 2023 onwards, multiple outbreaks have been confirmed in Greece.

Articles 2.1.a and 2.1.b of the Designation of Animal Diseases in the Rules for Animal Health/Implementing Regulation (EU) 2018/1882 of the Animal Health Law (EU) 2016/429 (Categories B to E)

Infection with Brucella abortus, B. melitensis

Infection with the rabies virus

Infection with the bluetongue virus (serogroups 1-24)

The status of the Netherlands is ‘disease-free’. Monitoring is done annually on sheep and goat farms (a minimum of 1,475 farms) by taking blood samples. Additional efforts are required to obtain the requisite number of submissions because of the bluetongue outbreak.

Detected very rarely in bats.

Since September 2023, the Netherlands has been facing an outbreak of BTV-3. The impact on the sheep population was considerable, with 55,000 excess animal deaths in 2023. Three deactivated vaccines were licensed in the spring of 2024. Despite the vaccinations, the number of infected farms has been increasing rapidly since June 2024. The level of clinical symptoms varies widely.

BTV-3 has also been detected in Germany, Belgium, Denmark and Luxembourg.

There is an outbreak of BTV-8 in France leading to more clinical complaints than the outbreak that has been ongoing since 2015. The two BTV-8 serogroups detected are genetically different.

Active monitoring in Spain has shown that BTV-4 and BTV-8 are circulating.

B+D+E *

B+D+E

Disease/disorder/ health characteristic

Epididymitis in sheep (Brucella ovis)

Infection with Mycobacterium tuberculosis complex

(M. bovis, M. caprae, M. tuberculosis)

Anthrax (Bacillus anthracis)

Paratuberculosis (Mycobacterium avium subs. paratuberculosis)

Q fever (Coxiella burnetii )

Brief description

Examination of rams for export purposes. Not previously confirmed in NL.

The Netherlands has been officially free of bovine tuberculosis since 1999.

Last registered outbreak in cattle in 1993. No infections detected since then.

Regular cases, largely in goats (inc. dairy) and occasionally in sheep.

Q fever was detected in April in a bulk milk sample from a dairy sheep farm. The animals concerned were pregnant yearlings that had not been vaccinated against Q fever despite it being mandatory. The final dairy goat farm with C. burnetii was certified free from infection in 2016.

Echinococcosis An echinococcus cyst was detected during pathological examination of a sheep in April 2023. The specific type is not known.

Trichinellosis No known cases of trichinellosis in sheep or goats.

Article 2.1.c Designation of animal diseases in the Rules for Animal Health of the Dutch Animals Act

Transferable TSEs (scrapie, BSE) No cases have been seen in sheep in the last ten years. In goats, the first case of scrapie was in 2000 and the last in 2001.

Article 3a.1 Notification of zoonoses under the Rules for Animal Husbandry of the Dutch Animals Act Campylobacteriosis (Campylobacter spp.)

Leptospirosis (Leptospia Hardjo)

Listeriosis (Listeria spp.)

A few cases per year. Particularly known as a cause of abortion in small ruminants.

Not previously confirmed in NL. Indications of Leptospira spp. were found in February 2024 in the liver tissues of aborted lambs. The diagnosis could not be confirmed because the livestock farmer did not want to cooperate with the follow-up diagnostic testing.

Encephalitis caused by Listeria monocytogenes is regularly found in sheep and especially in dairy goats. Problems caused by listeriosis are reported at a few dairy goat farms each year. How long listeria bacteria are excreted into the milk for is not known.

Both L. monocytogenes and L. ivanovii can cause abortion in sheep and goats.

Because of green silage use in the spring and the associated difficulties with preservation and contamination, additional awareness of the possibility of listeriosis is recommended.

Disease/disorder/ health characteristic

Salmonellosis (Salmonella spp.)

Yersiniosis (Yersinia spp.)

Toxoplasmosis (Toxoplasma gondii )

Other OIE list diseases

Enzootic abortion (Chlamydia abortus)

Caprine arthritis encephalitis (CAE)

Maedi-visna virus (MVV)

Tularaemia (Francisella tularensis)

Mycoplasma agalactiae

Nairobi sheep disease

Heartwater (Ehrlichia ruminantium)

Infections with Schmallenberg virus (SBV)

Brief description

Since 2016, there have been recurrent and large-scale losses of kids at dairy goat farms, caused by a multiresistant S. Typhimurium. There also were multiple cases of illness in humans caused by the same MLVA strain of the bacterium.

In March 2024, salmonellosis was detected at two dairy goat farms. These were infections with Salmonella spp. from groups B and D. Effects such as abortions, severe diarrhoea and elevated mortality rates were observed.

A few cases per year. Identified as a cause of diarrhoea, mortality and abortion.

Only a few confirmed cases per year but probably one of the most commonly occurring causes of abortion. High seroprevalence has previously been demonstrated in sheep and goats.

One of the main causes of abortion in goats and sheep for many years. Distribution from farm to farm is through contaminated female breeding stock. Very difficult to tackle once introduced to a flock.

Commonly occurring disease in which the pathogenic virus sometimes behaves differently depending on the size of the farm. Source of introduction not always clear.

A significant infectious disease (or indeed the most significant) at sheep farms, larger ones in particular.

Since 2011, infected hares have regularly been found in the Netherlands, as well as a small number of human tularaemia patients.

Never detected in the Netherlands.

Has been detected virtually every year since 2011 as a cause of congenital abnormalities in lambs. It has been detected as the cause of congenital abnormalities in both lambs and kids in 2024. Excluding other possible causes in lambs remains important for early detection of the introduction of other viruses from the Bunyaviridae group, which can lead to the same external clinical deformations. The UK reported elevated incidences of SBV early in 2024.

further study

dairy goats is underway within the framework of public-private partnership, looking at increased sustainability of dairy goat farming.

Disease/disorder/ health characteristic

From monitoring

Haemonchosis (Haemonchus contortus)

Liver fluke (Fasciola hepatica)

T. +31 (0)88 20 25 575 info@gdanimalhealth.com www.gdanimalhealth.com

Brief description

Very serious infections due to haemonchosis were seen in sheep during the summer months of 2024. This gastrointestinal worm infection caused acute mortality on several farms. In addition, numerous concomitant infections with bluetongue were detected.

In the spring, several animals were observed upon necropsy to have chronic liver fluke infections. The wet spring led to favourable conditions for liver fluke disease. Livestock farmers should remain alert in the autumn. Antibody testing in lambs will provide a clear picture of the infection in good time.

1 Quiet: no action required or action is not expected to result in a clear improvement.

2 Increased attention: alert to an anomaly.

3 Further investigation: further investigation is ongoing or required.

Continuation of

Animal health monitoring

Royal GD has been responsible for animal health monitoring in the Netherlands since 2002, in close collaboration with the veterinary sectors, the business community, the Ministry of Agriculture, Fisheries, Food Security and Nature, veterinarians and farmers. The information used for the surveillance programme is gathered in various ways, whereby the initiative comes in part from vets and farmers, and partly from Royal GD. This information is fully interpreted to achieve the objectives of the surveillance programme – rapid identification of health issues on the one hand and monitoring trends and developments on the other. Together, we team up for animal health, in the interests of animals, their owners and society at large.