Veterinary Services

SAC C VS consider that ruminal acidosis is a common hazard in the autumn. Sheep are often introduced to a high carbohydrate concentrate ration for the first time. In one case from the Scottish Borders, three deaths were recorded in a group of 320 easycare gimmers.  When one of these carcases was submitted to St Boswells for postmortem examination there was a large amount of whole grains within the rumen and the contents had a ‘sharp’ smell.  The ruminal pH was 4.4, indicative of acidosis. Other instances of acidosis were diagnosed on postmortem examination in finishing lambs from two flocks in Caithness.  On both occasions lambs were recently introduced to concentrate feed.

Generalised and systemic conditions

Fourteen outbreaks of systemic pasteurellosis due to Bibersteinia trehalosi were confirmed at the eight SAC C VS Disease Surveillance Centres.  In the majority of cases the condition affected unvaccinated lambs or lambs that had not received a full vaccine course. Concomitant parasitic gastroenteritis (PGE) was identified in a number of these cases.

In the course of a week five deaths occurred in a group of 100 gimmers from a flock of 1,500 Cheviot mule cross ewes in the Borders.  Clinical signs of stiffness, lethargy and pyrexia were observed prior to death.  Postmortem examination of one carcase revealed lesions consistent with a diagnosis of systemic pasteurellosis. There was also evidence of chronic fasciolosis and a moderate burden of Teladorsagia species worms in the abomasum.  Bibersteinia trehalosi was isolated on culture from multiple tissues, including the brain.  Systemic pasteurellosis is an unusual diagnosis in this age of sheep. Since the group were grazing a hill field known to be tick affected, SAC C VS suspected that tick borne fever (TBF) could be a predisposing factor.  Intracellular bodies typical of Anaplasma phagocytophilum were observed on examination of smears from a peripheral lymph node.  The significance of these bodies was unclear since A. phagocytophilum is reported to have tropism for neutrophils, but whether they can be released and taken up by sinus histiocytes is not documented.

In other outbreaks of systemic pasteurellosis 11 deaths of Scottish blackface lambs were reported on one Aberdeenshire unit. A single death in a group of six seven-month-old ryeland lambs was reported on another unit. In these cases there was evidence of underlying PGE and no recent anthelmintic treatment.

Eight deaths occurred in a group of five-month-old Texel cross lambs over a period of three weeks. These unvaccinated lambs remained at grass, but had access to a cereal based concentrate ration on an ad lib basis.  Following necropsy the epsilon toxin of Clostridium perfringens was detected and neuropathology revealed changes consistent with focal symmetrical encephalomalacia (FSE). 

Alimentary tract disorders

Two Scottish blackface ewes were submitted alive for postmortem examination.  The Ayrshire farm of origin experienced problems with ewes scouring and losing condition. Johne’s disease (paratuberculosis) was diagnosed previously in the flock.  Postmortem examination of one affected ewe revealed gross thickening, corrugation and yellow pigmentation of a large portion of the jejunum and ileum. The pigmented form of paratuberculosis was confirmed by demonstration of large numbers of acid/alcohol fast organisms typical of Mycobacterium avium subspecies paratuberculosis in small intestinal lesions. Enteric lesions evident in the second ewe were associated with a severe lympho-plasmacytic enteritis with eosinophils, consistent with parasitism, and a mild, chronic interstitial pneumonia. 

Deaths caused as the result of injury during drenching or bolus treatment were recorded in five flocks.  In Dumfriesshire three ewes died with a history of oral haemorrhage and sub-mandibular swelling and one was submitted for postmortem examination.  Damage due to a dosing gun injury suffered some three weeks earlier was identified on the left side behind the last lower molar tooth.  A necrotic tract containing purulent material could be followed from here to the angle of the mandibular ramus.  A large amount of clotted blood was found in the rumen.   On another holding two seven-month-old lambs were seen to be lethargic and losing condition.  Both lambs had lesions consistent with dosing or drenching injuries, with chronic abscessation involving the larynx, jaw bone, soft palate and nasal cavity.  Arcanobacterium pyogenes was isolated from the sites of the dosing injuries in both lambs. The lambs were given a worming drench five weeks before.

Nervous system disorders

The carcase of a Scottish blackface ewe was submitted to Dumfries for postmortem examination after four of 200 ewes died within three days.  Some were found dead and others were in lateral recumbency and paddling.  There were no gross findings of significance, but histopathology revealed a severe meningoencephalitis and immunohistochemistry confirmed louping-ill virus involvement.  Serology supported this diagnosis with an immunoglobulin M (IgM) titre of 1/10240 and an immunoglobulin G (IgG) titre of 1/80, consistent with recent infection.