Veterinary Services

Parasitic diseases

The relatively mild start to the month was associated with an increase in the number of outbreaks of parasitic gastroenteritis and fasciolosis. Five deaths were reported in a group of 100 ewes on a farm in Aberdeenshire. The group had been purchased from the west coast of Scotland, some two months earlier. While 300 ewes purchased from other sources were thriving this group was reported to be in very poor condition. When two carcasses were submitted for necropsy both ewes were found to be anaemic with extensive fibrosis of the bile ducts and large numbers of adult flukes present within the liver. Discussions with the owner revealed that these purchased sheep had not undergone a period of quarantine or a treatment programme on arrival at his farm.

Acute fasciolosis was recorded in a flock of hill Cheviot ewes in the Thurso area after six deaths occurred in a group of 180 over a period of ten days. The affected group had last received treatment for liver fluke in November.

A twenty-month-old Angora-cross doe was necropsied at the Inverness Centre following a period of malaise and bloating. This examination identified severe biliary hyperplasia, cholangitis and cholehepatitis, associated with the presence of large numbers of adult liver flukes. Evidence of a significant gut parasite burden was also recorded.

A Scottish Blackface wether lamb was presented for necropsy at the Dumfries Centre, as part of an ongoing investigation of ill-thrift and mortality. Parasitic gastroenteritis and cobalt deficiency had been confirmed in the group one month previously, but despite treatment with anthelmintic and a trace element supplement, losses had continued. The carcass submitted had a condition score of one and showed evidence of recent scouring. Although there was now no evidence of gut worm infection, the cobalt status as measured by liver vitamin B12 was poor at 0.17ug/g wet weight (reference range >0.19ug/g). Subsequent histopathology revealed large numbers of coccidial schizonts in the small intestine and huge numbers of sarcocysts within the muscle - the latter associated with inflammatory and degenerative changes. It was postulated that sarcocystosis may have been the underlying cause of ill-thrift and deaths, with the recent movement of the lambs from the hill onto better ground, resulting in their exposure to pastures contaminated with oocysts and sporocysts.

The Thurso Centre reported two outbreaks of nematodirosis due to Nematodirus battus infection in lambs aged six to eight months. The clinical history was of sudden onset scour, dehydration and depression - with two deaths recorded in one of the affected groups.

A live three-year-old Suffolk ewe was submitted to the St Boswells Centre with a history of wasting and a suspicion that Johne's disease was responsible. Examination revealed a condition score of one, anaemia and oedema of the muzzle. With the exception of a slight thickening of the small intestinal mucosa, no abnormality was detected on necropsy. However, 5,600 Haemonchus contortus adults were found in the abomasum and 1,000 Cooperia spp. in the small intestine. When Ziehl-Neelsen (ZN) stained smears and fixed sections of intestine were examined, no evidence of Johne's disease was apparent. It is estimated that each adult Haemonchus parasite can remove 0.05 ml of blood from a host over 24 hours - consistent with this ewe losing the equivalent of 280 ml of blood per day.

Generalised and systemic conditions

A total of 31 incidents of systemic pasteurellosis were recorded in Scotland during December. An outbreak in the Dumfries area resulted in the loss of ten out of 120 replacements. Losses halted after treatment of the group with systemic tetracycline, but recommenced two weeks later. The condition was also diagnosed at the Edinburgh Centre in a group of 270 Scottish Blackface ewe lambs in which there had been six deaths over a three-week period. On necropsy of one lamb, the caecal mucosa had multiple dark necrotic areas and haemorrhagic contents. Subsequent bacterial culture of the caecum confirmed the presence of Pasteurella trehalosi and Yersinia pseudotuberculosis. The latter organism is a recognised cause of enterocolitis in lambs, often associated with periods of stress such as weaning.

Alimentary tract disorders

A sharp increase in the number of diagnoses of paratuberculosis (Johne’s disease) was recorded this month. A three-year-old Suffolk ram on a croft on the Southern Isles was reported to be in poor condition and to be the only animal affected from the 30 sheep on the holding. When a faeces sample was submitted for examination, clumps of acid/alcohol-fast bodies resembling Mycobacterium avium subspecies paratuberculosis were detected on Ziehl Neelsen (ZN) stained smears confirming paratuberculosis (Johne’s disease) and a worm egg count of 2,050 trichostrongylid eggs per gram of faeces (epg) was also recorded.

A Scottish Blackface ewe and gimmer were submitted to the Edinburgh Centre alive for necropsy, with a history of chronic weight loss. There had been no evidence of diarrhoea in either animal and their appetite was reported to be good. The body condition score in each case was one and the gimmer exhibited marked oedema around the muzzle and submandibular area. Both sheep showed thickening and corrugation of the small intestinal and caecal mucosa, with a distinct yellow pigmentation. Smear examinations from the ileum of both sheep again proved positive for acid/alcohol fast organisms confirming the pigmented form of paratuberculosis (Johne’s disease).

A two-year-old Lleyn ewe was also submitted to the Edinburgh Centre with a history of chronic scour and weight loss, despite good appetite. This ewe had been treated twice with anthelmintic in the previous seven weeks and had also received a flukicide treatment. Body condition score was one and there was extensive faecal soiling of the perineum. Thickening of jejunum and ileum was noted, although on this occasion there was no mucosal pigmentation and no significant findings on examination of ZN-stained smears from the area. Further tests indicated a hypoalbuminaemia, but no evidence of a significant parasitic burden. Subsequent histopathology confirmed a granulomatous enteritis, likely to have had a parasitic aetiology and to have led to chronic protein loss from the gut.

Reproductive tract conditions

Abortion due to Salmonella Montevideo was diagnosed following culture of foetal stomach contents and placenta from an early lambing Suffolk ewe. The affected flock had suffered five abortions over a ten-day period, and one ewe had reportedly died during parturition. No other infectious cause of abortion was identified.

Toxoplasmosis was confirmed by foetal serology and brain histopathology in lambs submitted to the Ayr Centre from a flock experiencing weak newborn lambs and a small number of stillbirths.

Actinobacillus seminis was isolated in moderate growth from semen samples submitted from two rams. The rams were being used for artificial insemination and had undergone routine screening, including semen bacteriology, prior to use. Cytological examination of semen smears from the same rams showed many coccobacilli and significant numbers of neutrophils, consistent with a suppurative inflammatory process.

Nervous system disorders

A four-year-old Texel tup was reported to have shown progressive nervous signs for two weeks; starting with a drooped ear and progressing to lateral recumbency and vertical nystagmus. Antibiotic treatment had resulted in only temporary improvement. Necropsy revealed an abscess affecting the left brainstem and multiple small abscesses and necrotic foci scattered throughout the liver. Arcanobacterium pyogenes and Fusobacterium necrophorum were recovered from the lesions.

Renal diseases

Several deaths were reported to have occurred over the course of a few weeks in an outdoor group of 70, eight-month-old Texel rams. When one carcass was submitted to the St Boswells Centre it was found to be in good bodily condition. However crystals were noted around the preputial orifice and on extrusion of the penis the vermiform appendage was found to be blocked by calculus material. Internally there was bloody ascitic fluid and rupture of the bladder close to the neck. The death occurred during a period of freezing conditions, leading to speculation that this may have prevented the ram from drinking sufficient water, so predisposing the animal to urolithiasis. It was recommended that as a precaution, the mineral content of the ration the tups were receiving should also be reviewed.

Skin diseases

Seven outbreaks of sheep scab were diagnosed in Scotland during December, including cases recorded at the Perth, St Boswells and Thurso Centres.