Veterinary Services

Nutritional and metabolic disorders

Two 18-month-old Cheviot rams were submitted to the Inverness DSC as part of an on-going welfare investigation. Both were cachectic and weighed respectively 31kg and 26kg. The liver selenium in the first ram was found to be 0.4mg/kg DM and in the second 0.23mg/kg DM (reference range 0.9 to 3.5mg/kg DM). In addition one animal showed evidence of chronic fasciolosis and the other of parasitic gastro-enteritis (PGE).

Parasitic diseases

The carcases of four ewe lambs were submitted to Edinburgh DSC from a farm with 40 Shetland and Icelandic sheep. These lambs had begun to scour some five days earlier. The animals were vaccinated and dosed with an avermectin in May and with diclazuril six days previously, with little effect. The lambs weighed from 11 to 17kg. Examination of all four lambs confirmed scouring and a moderate to severe verminous pneumonia. Meullerius capillaris and Dictyocaulus spp. worms were present in the respiratory tract and there was also evidence of severe enteric parasitism due principally to Trichostrongylid nematodes.

Nematodiriasis was diagnosed on seven occasions this month. St Boswells reported this condition in a five-month-old Romney cross lamb submitted for necropsy from a holding where several cases of diarrhoea and death had occurred in a group of 3,000. A total worm count of the small intestinal contents was attempted but the helminths present, of which Nematodirus species predominated, were too numerous to count.

Generalised and systemic conditions

A total of 42 separate incidents of systemic pasteurellosis due to Pasteurella trehalosi infection were recorded in Scotland in November, the month which traditionally sees most cases of this condition. This brings to 92 the number of outbreaks recorded in 2006, compared to the 50 diagnosed to the same point in 2005 of which 30 were in November (see graph - Related Documents at top right-hand side). All eight of the SAC VS Centres reported cases in monthly reports during the course of this month. In the great majority of cases the initial presenting sign was sudden death, with lambs in the age range of six to eight months most commonly affected. Reported mortality rates in November ranged from one per cent to as high as 25 per cent The pathology was typical with necrotic erosions in the pharynx and upper oesophagus (figure 1 - see Related Documents at top right-hand side) and swollen oedematous lungs with widespread focal haemorrhages (figure 2 - see Related Documents at top right-hand side). Concurrent PGE, trace element deficiencies and serological evidence of exposure to tick borne fever were identified in a number of the outbreaks reported by Centres.

The vaccination history of the affected groups was an important factor in history-taking, although farmers are often unsure of the exact vaccinal status of purchased lambs. It is clear however, that the use of a Pasteurella vaccine does not confer complete protection from systemic pasteurellosis. As an example, of the seven outbreaks investigated by staff at the St Boswells DSC during the month, the affected lambs had reportedly received a complete course of vaccination in six of those cases.

Risk factors suggested to be of importance in predisposing lambs to systemic pasteurellosis are folding on rape or kale, and movement to improved pasture. The association of outbreaks with periods of changeable weather, particularly prolonged wet weather, may be of greater significance this year. The weather in Scotland during November 2006 was particularly wet, albeit with temperatures that were significantly higher than average. It would be consistent with the theory of climatic stress as a risk factor that this spell of inclement weather coincided with a surge in diagnoses of systemic pasteurellosis.

Alimentary tract disorders

Twenty deaths were reported in a group of 1,000 recently houses lambs on an Aberdeenshire unit. The owner reported that these lambs had been offered hay and only a small amount of concentrate pellet. However, when two lamb carcases were submitted for examination there was a substantial amount of grain within the rumen and the ruminal pH of less than 5.0 was consistent with a diagnosis of acidosis.

The carcase of a seven-month-old Texel cross lamb which died suddenly, was submitted to the Dumfries DSC. On postmortem examination a large quantity of bloodstained ascitic fluid containing fibrin clots was found within the abdomen. In addition the caecal mucosa was thickened, inflamed and ulcerated, and the contents were bloody. Clostridium sordellii was isolated from the caecum in pure culture. Histopathology, which may have defined the significance of this bacteriological finding, was not possible in this case.

Two three-year-old Scottish blackface ewes were submitted alive to the Dumfries DSC. They had been in good bodily condition when put to the ram, but had wasted during the following six weeks and now weighed only 31 and 36kg respectively. Blood samples were taken ante mortem and albumin levels of 9 g/l and 13 g/l were measured (normal range 28 to 34 g/l). During postmortem examination lesions of the pigmented form of Johne’s disease were seen and ZN-stained smears of the ileum were positive for acid-fast bacteria.

A faecal sample was submitted from an eight-year-old castrated male goat that was reported to have suffered from scouring and pyrexia for three days. The other goat on the holding was unaffected. There was no evidence of underlying significant parasitism and both Salmonella and Campylobacter cultures were negative. However Yersinia pseudotuberculosis was isolated on culture of the faeces.

Reproductive tract conditions

In the first recorded abortions of the season Thurso DSC diagnosed Bacillus licheniformis infection in material submitted from a flock of 60 Suffolk ewes, in which six had lost lambs. A shepherd in the Scottish Borders reported that two Charolais ewes had aborted in a group of 40 due to start lambing in December. No significant lesions were evident in the placentae, but the foetal livers were friable and abdominal fluid was blood stained. Campylobacter fetus subspecies fetus was isolated from the foetal stomach contents.

Musculo-Skeletal conditions

A Scottish blackface ewe was reported to have literally dropped dead in front of the shepherd while being gathered from a hill near Edinburgh. At necropsy there was found to be tearing of the musculature of the left side of the neck adjacent to vertebrae C4 to C7, with extensive associated haemorrhage within the muscle, connective tissue and skin. The neck seemed unstable at C6/C7 and there was a large haemorrhage on the ventral side of the cervical spinal cord at C4 to C7 and on the underside of the brain stem. The findings indicated that the ewe had suffered severe trauma to the neck but had apparently been able to stand for a short period before spinal shock, collapse and death occurred.

Nervous system disorders

Two Scottish blackface ram lambs from the same group were both found recumbent within 24 hours on a holding near Edinburgh. Both remained bright and alert, and retained withdrawal reflexes in the hind legs, but neither was able to stand. Examination of the first lamb revealed a large abscess in association with vertebra L4 pressing on the spinal cord. In contrast, histopathological examination of the brain and spinal cord from the second lamb revealed a severe, widespread, non-suppurative meningomyeloencephalitis consistent with a protozoal aetiology, most likely sarcocystosis.

Skin diseases

Chorioptes ovis mites were detected in scrapings from the scabbed skin lesions over the fetlock and metacarpal area of a Scottish blackface hogg from an Inverness-shire flock that had died of pasteurellosis.