Veterinary Services

Toxic conditions

North Ronaldsay sheep are highly susceptible to copper poisoning because of their adaption to the copper deficient environment in North Ronaldsay. Further deaths occurred in a small flock of North Ronaldsay sheep near Edinburgh where copper poisoning was described in the October SAC VS report. Analysis of the liver from a three-year-old ewe revealed copper levels of 39,000 umol/kg (reference range 314 to 7850). Blood samples were submitted from a further four ewes showed elevated liver enzyme values. Three of these animals also had elevated plasma copper levels of up to 27.1 umol/l (reference range 9.0 to 20.0).

The presence of rhododendron leaves in the rumen and a typical clinical history led to a diagnosis of rhododendron poisoning in a lamb at St Boswells. Several other lambs from the group of 530 presented with signs of depression and ataxia, and four of these animals had died.

Parasitic diseases

Four incidents of acute fasciolosis and 41 of chronic fasciolosis were diagnosed in sheep flocks this month. Deaths due to fasciolosis were recorded on three farms in the Dumfries area. The postmortem findings were similar in all cases, with evidence of anaemia, hypoalbuminaemia and severe damage to the liver. The affected ewes on two farms were dosed with triclabendazole pre-tupping and were due to be treated again during January. The history and necropsy findings suggested that there was re-infection with large numbers of immature fluke soon after the October treatment. The SAC VS considered that this heavy challenge was sufficient to cause deaths before the next routine dose was due.

Inverness reported demonstrating Fasciola hepatica eggs in 12 pooled faecal samples submitted from the Uists and Barra where an active fluke-monitoring programme is in place. While the majority of these submissions were pre-dosing samples, on four occasions fluke eggs were demonstrated in faeces three to four weeks after treatments with triclabendazole (three occasions) or closantel (once). Further investigation of these cases will be undertaken.

Generalised and systemic conditions

Edinburgh reported an unusual presentation of caseous lymphadenitis in a four-year-old, Texel ram submitted from a flock with no history of the disease. The ram showed chronic intermittent dullness that responded temporarily to antibiotic treatment. Corynebacterium pseudotuberculosis was isolated from one of many subcutaneous abscesses over the face and from large abscess at the pituitary gland. The location of the subcutaneous lesions suggested that they were a consequence of fighting.

Over a three-week period a total of 26 hoggs died from a group of 200 that was housed in November and fed bale silage. Five carcases presented to Thurso for necropsy showed evidence of septicaemia. Listeria monocytogenes was isolated from the viscera.

Alimentary tract disorders

Impaction of the oesophagus with dry beet pulp was found on necropsy of a pedigree Suffolk gimmer from a farm in Ross-shire. The group was fed a diet of hay, oats, beet pulp and straw. Some of these animals were observed to froth from the mouth when eating, but had all recovered. This animal was said to have died after exhibiting similar symptoms.

An ill-thriven and recumbent four-year-old Scottish blackface ewe submitted to Edinburgh DSC for examination showed evidence of ascites and tissue oedema, along with thickening of walls of the ileum. Johne’s disease was suspected but acid-alcohol fast organisms were not demonstrated in mucosal smears. Subsequent histology revealed varying degrees of mucosal hyperplasia and distortion, and cellular infiltration in the small and large intestines. The mesenteric lymph nodes contained sheets of macrophages and occasional multinucleate cells. Once again no acid-fast organisms were seen in Ziehl Neelsen (ZN) stained sections, although Johne’s disease was still considered to be the most likely cause of the intestinal pathology. To this end mycobacterial culture was undertaken and this proved positive for Mycobacterium avium subsp. paratuberculosis after 35 days, confirming a diagnosis of paucibacillary Johne’s disease.

In a more typical case of Johne’s disease, acid-fast bacterial were demonstrated on examination of ZN-stained smear of the gut mucosa of a Texel cross ewe from a flock where one per cent of the flock was lost each year due to wasting. The distal jejunum and ileum were corrugated and yellow in colour.

A three-year-old castrated male pygmy goat that died suddenly showed evidence of acute enteritis with secondary intussusception of the ileum. A clostridial toxin ELISA was positive for alpha and epsilon toxin and negative for beta toxin, consistent with Clostridium perfringens type D enterotoxaemia. The gross findings of enterotyphlocolitis and lack of kidney lesions as in this case were considered typical of the acute syndrome seen in adult goats. Goats do not respond well to clostridial vaccination and need to be vaccinated every six months to maintain immunity.

Reproductive tract conditions

The benefit of seeking a specific diagnosis was well illustrated by the investigation of five abortions in an early lambing Suffolk flock in the south of Scotland. The placental pathology was typical of Chlamydophila abortus infection and this was confirmed on microscopic examination. The rest of the flock was not due to lamb for three months. It was immediately vaccinated with the killed vaccine because of the threat of infection transfer from the early lambing ewes. Listeria ivanovii was isolated from the placenta and stomach contents of a foetus that was aborted ten days early. This was the first abortion in a small flock of Suffolk ewes.

Renal diseases

Bilateral pyelonephritis due to infection with Arcanobacterium pyogenes and Pasteurella multocida was confirmed in a ewe submitted to Aberdeen (Figure 1 see top right-hand side). At the same Centre, urolithiasis was confirmed in a nine-month-old Texel hogg that died following a period of blindness and depression. Similar clinical signs were observed in three feeding hoggs in a group of 130. These lambs were on self-feed rape and ad lib concentrate for the preceding six weeks. The rumen contents were noted to be very dry and the owner was advised to check that there was access to water.

Skin diseases

Sheep scab was diagnosed in nine flocks this month compared to ten flocks over the same period in 2007. The efficacy of treatment with an injectible avermectin was questioned when sheep scab was confirmed in a group of sheep near Thurso that was treated with injectible avermectin only four weeks previously.