Veterinary Services

Toxic conditions

Edinburgh DSC reported copper poisoning in a three-year-old Texel ewe being used as an egg donor. The ewe had appeared slow when handled and had been found recumbent the previous afternoon, when clinical examination had indicated paleness, jaundice and tachycardia. At necropsy the liver was found to be friable and pale orange/brown and both kidneys were enlarged and very dark, with multi-focal haemorrhages on the surface. Liver copper was later confirmed as 27,300 umol/kgDM (reference range 314 – 7,850 umol/kgDM) and kidney copper was 1,700 umol/kgDM (reference range <787 umol/kgDM). Subsequent histology of the liver and kidney identified changes typical of copper poisoning.

Parasitic diseases

A shepherd in the Dumfries area purchased six ram lambs in September. Three weeks after arrival on the unit one Suffolk ram died after showing signs of colic and a second became ataxic, then recumbent, before dying soon after. At necropsy a scour was evident and 134,500 Nematodirus species worms were recovered from the small intestine. Questioning of the farmer revealed that lambs had grazed the same field as the rams earlier in the year. It was speculated that prolonged housing and repeated worming might have meant the young rams had not been exposed to significant numbers of gut worms and therefore had not developed immunity against Nematodirus as lambs.

Fasciolosis is a year-round problem in the islands off the West Coast of Scotland, meaning that flukicides are used at very frequent intervals as a result. Ten individual faecal samples were submitted from a flock on the island of North Uist in the Western Isles as a pre-dosing fluke egg check to assist in the investigation of possible resistance to triclabendazole. Liver fluke eggs were detected in nine out of the ten samples, with eggs numbers varying from small to large. These sheep were weighed and accurately dosed with triclabendazole. A repeat fluke egg count was then carried out just over three weeks later. On this occasion all ten faeces samples were positive for liver fluke eggs, with egg numbers again varying from small to very large, findings felt to be highly suggestive of triclabendazole resistance.

Haemonchus contortus was the cause of ill thrift and deaths on three farms in Caithness and Sutherland this month. One case was in homebred gimmers and the other two in homebred lambs born in May 2006. Additional faeces samples collected from one of these groups of lambs showed faecal worm egg counts in excess of 15,000 per gram, which is highly suggestive of haemonchosis.

Generalised and systemic conditions

Thirty outbreaks of systemic pasteurellosis due to Pasteurella trehalosi were confirmed at the eight SAC DSCs this month. In most cases the affected lambs were either unvaccinated or had not received a full vaccine course. Concomitant parasitic gastroenteritis was identified in the majority of cases.

Dumfries DSC reported a case in which 282 Scottish Blackface ewe lambs received their second dose of a multivalant vaccine before moving to wintering. The carcases of five of the 14 animals that died over the next four days were submitted for necropsy. No significant findings were recorded in two of the lambs, but in the other three there was a moderate to severe peritonitis. In each case this was apparently centred on an identical location on the right abdominal wall, immediately anterior to the stifle joint. It was suspected that intraperitoneal injection of the vaccine had occurred and that this had led to peritonitis and eventual death.

Alimentary tract disorders

A Texel ewe was submitted to the Edinburgh DSC with a history of dramatic weight loss and diarrhoea over a period of a week, despite a good appetite. At necropsy the body weight was only 37kg. The main finding of significance was marked thickening of the intestinal mucosa with yellowish pigmentation throughout the jejunum, ileum, caecum and parts of the proximal colon. Examination of these lesions confirmed a diagnosis of pigmented (chromogenic) Johne's disease.

A three-year-old goat was submitted to Dumfries with a history of death following prolonged weight loss, anorexia and scouring. The owner reported losing 6-7 goats with a similar history over several years, including the dam of this individual. On postmortem examination there were increased volumes of pleural, peritoneal and pericardial fluid consistent with hypoalbuminaemia, as well as evidence of anaemia. Chronic fasciolosis was confirmed and ZN-stained smears from the thickened small intestinal mucosa were positive for acid-fast organisms consistent with Johne’s disease.

Nervous system disorders

A total of 23 outbreaks of louping ill have so far been diagnosed in sheep in Scotland this year, compared to 21 in the whole of 2005 and 20 in 2004. This month approximately 30 deaths were reported in a group of 300 sheep on a unit in northern Aberdeenshire. Some of the deaths were attributed to pneumonia, pine and staggers, but many cases rapidly progressed to lateral recumbency, with no other specific clinical signs. One of a group of 12 calves introduced to the same park three weeks previously showed similar signs and a tick was noted on this animal. Tick borne fever was known to occur on the farm and louping ill was believed to occur in the locality. An adult female ewe in good body condition was submitted for a necropsy. The neuropathological examination was consistent with a diagnosis of louping ill. However, antibody to louping ill virus was not detected in an antemortem blood sample. Antibody to louping ill virus was detected in a blood sample from another similarly affected ewe in the same park, some of which was IgM, consistent with recent infection.

A group of 17 Scottish Blackface gimmers sold from the Black Isle to a farm in the west of Scotland were treated with a pour-on product for a heavy tick burden acquired at the new holding. However, three animals died in the week after purchase. The affected animals showed signs of tremor, salivation and tachypnoea, before dying within 24 hours. A high antibody titre to louping ill virus (>/=1/640) was detected in one gimmer which was submitted for postmortem examination. Neuropathology provided supporting evidence for this diagnosis, with an extensive, non-suppurative encephalitis reported.

A farmer in Dumfriesshire bought 50 cast Scottish Blackface ewes in September and mixed them with his homebred flock. One month later five of the purchased animals died, often after a short illness during which signs described as foot-stamping, tail-twitching and restlessness were noted. One of those ewes was submitted in lateral recumbency for necropsy. Histopathology carried out after an unremarkable gross necropsy revealed a non-suppurative encephalitis consistent with louping ill. Again high levels of louping ill antibody were detected, much of which was IgM, consistent with recent infection

Skin diseases

Psoroptes ovis mites were observed in a skin sample from a Suffolk ewe showing signs of pruritus and wool loss on an Aberdeenshire holding. The animal had been purchased some three months earlier, and other ewes in the flock were now also noted to be pruritic. Five percent of ewes in a flock of 100 on a holding in Skye were reported to be pruritic and one was noticed to have a crusty patch. Psoroptes ovis mites were detected on microscopy confirming the diagnosis of sheep scab. Sheep scab was confirmed at the Thurso DSC in a group of young sheep that had been injected with an avermectin in July 2006.