Veterinary Services

A group of 630 seven-month-old meatlinc-cross finishing lambs was recorded as having very poor growth rates. Several carcases were rejected at meat inspection due to pleurisy. The farm was known to be deficient in selenium but only replacement breeding stock received specific selenium supplementation. All lambs were fully vaccinated against clostridial disease and pasteurellosis.  Initially, four live lambs were submitted for postmortem examination.  Chronic fasciolosis was present in one. A second had pneumonic change in the right cardiac lobe from which Mannheimia haemolytica and Mycoplasma ovipneumoniae were isolated.  Liver selenium content varied between 0.62 and 0.89 mg/kg DM (reference range 0.90 to 3.50).  The farmer was advised that selenium deficiency was likely to be an underlying factor in the reported problems.  Although improved growth rates and demeanour were initially reported after the animals were moved to rape and treated with oxytetracycline, this was not sustained.  Eleven lambs died the following week, with two being submitted for postmortem examination. Systemic pasteurellosis due to Bibersteinia trehalosi was diagnosed. 

Parasitic diseases

Ten lambs from a group of 90 died suddenly over a two week period in a 400 ewe flock in the Scottish Borders.  The lambs were treated with a long-acting anthelmintic at the end of August and were fully vaccinated.  Postmortem examination of one lamb revealed a large blood clot adherent to the capsule of the liver and bloody fluid in the abdomen.  There was a degree of liver fibrosis and atrophy with numerous immature Fasciola hepatica detected in the liver parenchyma. These were measured at between five and seven mm in length, suggesting that ingestion of the metacercariae took place approximately eight to ten weeks before.

Acute fasciolosis was also diagnosed in Ayrshire and Lanarkshire flocks. In one affected flock four eight-month-old Texel tup lambs died over a period of ten days despite flukicide treatment in September.  Postmortem examination revealed haemorrhagic tracts in the liver parenchyma and the presence of immature liver flukes. The size of the immature flukes recovered indicated that deaths may have been due to re-infection rather than flukicide inefficacy and further monitoring was suggested.

Chronic fasciolosis was the most common diagnosis recorded at Ayr, affecting flocks in Renfrewshire, Dunbartonshire and Argyllshire.  On one Argyllshire farm post-treatment efficacy testing revealed evidence of inefficacy associated with the use of triclabendazole in Scottish blackface ewes.  Treatment with an alternative flukicide was recommended and the manufacturer informed.  Further monitoring of the flock by examination of faecal and blood samples was suggested.  On another farm post-treatment efficacy testing gave an equivocal result and further assessment was advised.

Very high worm egg counts were recorded in two faeces samples submitted to Aberdeen from five-month-old Suffolk cross mule lambs with persistent scour. The flock was treated with doramectin six weeks previously. Given that doramectin does not have persistent action in sheep, SAC C VS considered it likely that the worm egg counts represented reinfection from heavily contaminated pasture. There were two lamb deaths and further investigation confirmed the worm burden was predominantly of trichostrongylid worms, plus low levels of Nematodirus and Haemonchus species.  Further sampling was recommended and the presence of significant numbers of strongyle worm eggs was confirmed following examination of a bulk faeces sample from ten lambs.

Coccidiosis was diagnosed in farms in Argyllshire and Renfrewshire.  Speciation of the coccidial oocysts recovered from faecal samples from scouring hoggs and ewes confirmed a preponderance of Eimeria ovinoidalis and E. crandallis.  Treatment with a coccidiostat was recommended.  On a further Ayrshire holding, histopathology carried out on viscera received from a casualty Lleyn hogg revealed mild enteric coccidial damage, on which was superimposed a more extensive bacterial-type enteritis, typical of that seen in yersiniosis.  SAC C VS considered that coccidial damage may have predisposed to this bacterial invasion.

Generalised and systemic conditions

A total of 11 outbreaks of systemic pasteurellosis due to Bibersteinia trehalosi were recorded. SAC C VS considered this rather low compared to the mean for the previous four years of 26 outbreaks for the month.   

Systemic disease due to infection with Pasteurella multocida and concomitant infection with Arcanobacterium pyogenes were confirmed in two seven-month-old lambs found dead.  A total of 28 deaths were reported on this Aberdeenshire holding amongst a group of 350 lambs purchased four to six weeks previously. 

Pulpy kidney was confirmed in an eight-month-old crossbred lamb. Six sudden deaths had been recorded in this group of 230 lambs over the preceding four weeks. The group received only their first dose of clostridial vaccine; a relatively common practice where farmers wish to make savings on their drug bills.  

Alimentary tract disorders

 The carcases of two ewes were submitted for necropsy as cases of sudden death.  Cellulitis was found within the tissues of the neck of one ewe.  A trace element bolus had ruptured the oesophagus and was found within the area of reaction.  In the other ewe large blood clots were found within the rumen and there was an area of necrosis and haemorrhage lateral to the mandible also believed to be due to a dosing gun injury.

Johne’s disease was diagnosed in Scottish blackface ewes from two different farms in south-west Scotland.  In the first case submitted carcases showed marked ascites, with a corrugated and yellow small intestinal mucosa, and Zeil-Neilsen (ZN) stained mucosal scrapings were positive for acid-fast bacteria.  With a ewe from the second farm the thickening of the intestinal mucosa was much less severe and ZN stained scrapings showed only occasional acid-fast bacilli.  Although an ELISA test on serum also proved negative for Johne’s disease, the condition was subsequently confirmed in this animal on histopathology.

Musculo-Skeletal conditions

Six eight-month-old cross lambs were discovered to be dragging their right fore legs, with no evidence of disease in the foot.  One lamb died and was submitted to Dumfries for necropsy. A severe cellulitis was found on the right side of the neck extending to the axilla and over the thorax, with swelling and oedema.  No clostridial involvement could be identified and Arcanobacterium pyogenes was isolated.  The lambs were vaccinated one week earlier on a wet day, and SAC C VS suspected that bacteria introduced at that time was the likely source of the problem.

A diagnosis of contagious ovine digital dermatitis (CODD) was made in flock of 950 hill ewes in the Borders after some ten percent of the animals fell lame.