Highlights report small ruminants-July 2024 by Royal GD

Chronic liver fluke infections in sheep

From February onwards, abnormal livers were detected in several sheep in the necropsy room caused by chronic liver fluke infections. Many of the case histories stated that the animals were in poor condition and had died suddenly. Detecting liver flukes in springtime means that liver fluke eggs are being excreted, which can infect the land and subsequently the liver fluke snail. A wet spring makes conditions favourable for the intermediate host of the liver fluke in many cases. Without the liver fluke snail Galba truncatula, liver fluke disease will not occur. This intermediate host lives in places where the soil is moist for most of the year, such as ditches, gullies, trampled ditch banks and

Indications were found in March for an infection with Leptospira spp., based on a specific microscopic staining of the liver in an aborted lamb. In the follow-up diagnostic testing, the placenta of a second aborted lamb from the same flock tested positive. In a third aborted lamb from the same flock, no indications of leptospirosis were seen. The farm was already known to have issues with abortions caused by Chlamydia abortus. Leptospira spp. are bacteria that can infiltrate the host through cuts, mucous membranes and macerated skin. The bacteria are secreted in the excreta, including urine. Some serogroups are known to cause host-specific illnesses, including several zoonoses. Only Leptospira interrogans strains are considered pathogenic. Mice and rats in particular are a

sites behind dykes where there is seepage. The liver fluke snail is barely affected by harsh winters but is susceptible to drought. When a liver fluke infection is suspected, it is essential to confirm this by pathological examination, blood tests or manure tests before treatment is started. Getting a clear picture of the presence of the liver fluke snail on plots of land helps to understand which plots are risky and better avoided at certain times of the year. More information about diagnostics and preventive measures can be found on https://www.gddiergezondheid.nl/ dapcontact/Dierziektes/Leverbot

Suspected abortions in sheep caused by leptospirosis

known reservoir of leptospira that can cause field fever (rat fever) and Weil’s disease in humans. Leptospira Hardjo can cause abortions in cattle, often without other symptoms, and is an occupational health risk for dairy farm workers.

The potential involvement of leptospira in sheep would be a new finding; this pathogen has not previously been detected in sheep in the Netherlands. Leptospira Hardjo is notifiable in the Netherlands among farm animals. The sheep farm’s veterinarian has been approached for follow-up diagnostic testing. Serological testing using an MAT test on the blood serum of the mother animal or others in the flock could settle the issue. Unfortunately, the livestock farmer stated that they do not want to cooperate with the follow-up diagnostic testing and it has therefore not been possible to follow up on the case.

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Salmonella types B and D on dairy goat farms

Pathological investigations detected salmonellosis in kids at two dairy goat farms. One case involved submission of aborted foetuses in which some kids showed indications of sepsis caused by Salmonella spp. type D. Typing the isolate further did not prove possible. Type D includes S. Dublin, a variant that often occurs among cattle. Further questioning revealed that the goats that aborted had been housed next to veal calves. The rearing of young goats for this farm is done at an external location, where salmonellosis was also detected a few weeks after the first abortion cases. Once again, Salmonella spp. type D was detected here. At the second farm, necrotising enteritis was seen in a kid a few days old caused by Salmonella spp. type B. Salmonella Typhimurium is a known serotype that is in group B. Previous outbreaks of salmonellosis on dairy goat farms have often been associated with S. Typhimurium. On this

particular farm, salmonellosis broke out at the end of the kidding period. The kids mostly had diarrhoea and did not grow well. Twenty of a group of a hundred kids died within seven days. The remaining kids responded well to the antibiotic treatment they were put on. Manure was delivered to this farm and stored there from cattle and pig farms. The occurrence of Salmonella spp. on dairy goat farms seems somewhat comparable to the occurrence on cattle farms. The severity of the clinical symptoms can vary greatly, from subclinical to high losses among the kids. Interventions to stop an outbreak are often associated with long-term use of antibiotics. In some cases, using antibiotics does not turn out to be sufficient. In very rare cases, salmonellosis is also seen in adult goats. Incoming animals and manure are seen as the key risk factor for introduction.

‘Weeping teat’ findings among milk goats

A milk goat was submitted in March for pathological examination because of unusual abnormalities of the base of the teat. The macroscopic picture was that several nodules 5 to 25 mm in width could be seen on both teats. Upon transection, these nodules had a cyst-like appearance and in some cases contained curdled milk. No macroscopic changes could be seen in the udder. Under the microscope, multiple cyst-like

structures of varying sizes could be seen, surrounded by ductal epithelium. These findings are consistent with the clinical picture known as ‘weeping teat’. In animals with this condition, milk-producing tissue can be present in the walls of the teats and milk can even filter out to the surface of the udder or teat through small pores in the skin without a visible opening being present. ‘Weeping teat’

In April, GD received two lambs for pathological examination because of an abnormal stance. The lambs came from a flock of Barbados Blackbelly sheep. They had been born in September 2023 and, over several months, they had both progressively developed an abnormal positioning of the legs.

The year before, a lamb aged three months had already been euthanised because of a severely abnormal stance. Based on the histological examination, a mild form of osteogenesis imperfecta was diagnosed in both lambs. In this condition, the accumulation of bone tissue is abnormal and compact bone is not produced as a result.

features milk cysts that are present in the teat and teat base. ‘Weeping teat’ is said to be associated above all with breeds of goat that have been selected for high milk production. Possible causes that have been mentioned are environmental factors and incorrect settings of the milking system.

Genetic abnormalities in Barbados Blackbelly sheep

Osteogenesis imperfecta has been described in various animal species and in humans. It is also known as brittle bone disease. The cause is not clear; it is suspected that it is genetic disorder, an autosomal recessive one.

From left to right: Karianne Peterson, Nienke Snijders-van de Burgwal, Eveline Dijkstra and René van den Brom

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.

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.

Detected very rarely in bats.

An outbreak of BTV-3 has been ongoing since September 2023. The impact of the outbreak on the affected farms is considerable, leading to excess deaths of over 55 thousand sheep. Clinical cases of BTV-3 have been reported in Belgium and Germany. Passive monitoring in the UK has detected BTV-3.

Overwintering of BTV-3 is seen as a realistic possibility. Several BTV-3 vaccines have been available since early May 2024.

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 is circulating. Mandatory vaccination is in place, aiming to restrict the outbreak.

B+D+E *

B+D+E

C+D+E *

Epididymitis in sheep (Brucella ovis)

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

Disease/disorder/ health characteristic

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

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. In February 2024, strong indications of Leptospira spp. were found in the liver tissues of aborted lambs. The serogroup involved is not known.

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 secreted into the milk for is not known.

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

*Further investigation into the types found in humans and animals would be desirable.

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 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 malformations in both lambs and kids in 2024. Excluding other possible causes of such congenital abnormalities 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 of 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

Abortion in small ruminants

Chronic liver fluke disease

Dermatitis caused by Staphylococcus aureus

Disbudding kids

Osteogenesis imperfecta

Brief description

During the early months of 2024, various infectious agents were detected that cause abortions in sheep and goats. Many causes of abortions are also zoonoses. The number of submissions remains low.

In the spring of 2024, several cases of chronic liver fluke disease were seen in sheep. Tracking down infections (including chronic ones) and treating them is important for combating this disease.

Dermatitis of the skin of the udder is regularly detected on dairy goat farms. S aureus can be transmitted between animals and humans

Multiple submissions of kids showing signs of meningitis after being disbudded.

Pathological examinations have found indications of osteogenesis imperfecta among Barbados Blackbelly lambs a few months old. It is thought likely that there is a genetic component to this.

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

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.