Veterinary Services

Cobalt deficiency was confirmed by Dumfries in two groups of lambs aged three to four months on farms where growth rates were reportedly poor and where there were problems with scour in the absence of parasitism.  The mean serum vitamin B12 activity in the two batches was 184 and 125 pmol/l respectively (marginal band for suckling lambs 230-350pmol/l).

Parasitic diseases

An Aberdeenshire farmer reported scour in a group of three-month-old lambs, already treated with diclazuril and benzimidazole.   Three deaths were reported from the group of 370 and the carcase of an 11-week-old lamb was submitted for necropsy.  Although there was a moderate oocyst count in gut contents, histopathological examination confirmed the presence of a necrotising typhlocolitis consistent with coccidiosis.  The unit in question has reported problems with coccidiosis in young calves and lambs as a perennial problem. 

Coccidiosis and Mannheimia haemolytica pneumonia were diagnosed on postmortem examination of another 13-week-old Texel-cross ewe lamb.  The history indicated that about 20 out of 1500 lambs developed scour and abdominal pain prior to death, and that nematodirosis was suspected.  The group were fully vaccinated against clostridial disease and dosed for worms and coccidia four days previously.  Necropsy revealed a severe diffuse haemorrhagic typhlitis but only 250 coccidial oocysts per gram of faeces were recorded.  However, histology of the caecum confirmed lesions consistent with severe coccidiosis, including marked mucosal damage.

Generalised and systemic conditions

In recent years Streptococcus dysgalactiae has emerged as a major cause of infectious polyarthiritis in neonatal lambs.  This year SAC recorded ten separate outbreaks in Scottish flocks.  Typically such outbreaks present as lameness in one or more limbs, affecting lambs between seven and 14 days of age.  One or more of the joints may be affected and S. dysgalactiae is normally isolated in pure growth from the synovial fluid.  This year morbidity rates of up to ten per cent of the lamb crop have been recorded in Scotland.   On occasions S. dysgalactiae infections may present in a slightly different way or affect older sheep.  This month two such cases were recorded. A three-week-old Scottish blackface lamb was submitted to Dumfries with a history of scour and joint ill.  On external examination the right carpus was swollen. At necropsy the right atrioventricular heart valve was affected by endocarditis and the adjacent myocardium was fibrosed.  The kidneys were pale and there were also areas of fibrosis within the liver.  Two abscesses were noted at the point where the umbilical artery enters the liver.  S. dysgalactiae was isolated from the viscera in septicaemic distribution.  Although at the time of necropsy the navel appeared to be grossly normal, the presence of abscesses within the liver suggested that this may have been the original point of entry for the infection.

In the second case the carcase of a three-year-old Scottish blackface ewe was submitted after the animal died suddenly while a group was being gathered.  At necropsy the ewe was found to be in good bodily condition.  However, the left atrioventricular valve was thick and nodular, and S. dysgalactiae was isolated in pure culture from there as well as the spleen, kidney and lung.

Four sudden deaths occurred over a period of two weeks in a group of 900 three-month-old Lleyn lambs on a Scottish Borders holding.  At necropsy there was pulmonary congestion and oedema, fibrinous pericardial effusion and multiple haemorrhages within the kidneys.  Epsilon toxin was detected in the intestinal contents allowing a diagnosis of Clostridium perfringens type D enterotoxaemia (pulpy kidney) to be made.  The flock in question was managed under organic principles and this batch of lambs had not received any vaccination against clostridial disease.

Respiratory tract conditions

Parasitic bronchitis due to Dictyocaulus filaria was diagnosed in a group of hoggs in an Argyllshire flock.  A total of 25 hoggs died from a group of 106, despite anthelmintic treatment. The diagnosis was made by histological demonstration of adult parasites, along with attendant alveolar and bronchial pathological changes.

Mammary diseases

Two ewes from different farms were submitted to Edinburgh as cases of sudden death.  On both occasions necropsy revealed severe mastitis with marked enlargement of one side of the udder.  M. haemolytica was isolated from both affected mammary glands and also from the lungs and livers, suggesting septicaemic spread of infection.  Additionally one ewe had multiple small abscesses scattered throughout the lungs and liver. 

Nervous system disorders

Louping ill was established as the cause of the death of a 15-month-old Texel-cross hogg from an Aberdeenshire holding, one of 40 animals reported dead.  This group of hoggs had been turned out onto the hill a month previously.  Only those animals grazing one particular area of hill, known to be tick affected, appeared to suffer disease.  In most years the replacement hoggs are vaccinated against louping ill virus. This was not possible in 2009 because of problems encountered with the availability of vaccine. 

Skin diseases

 
Formerly sheep scab due to infection with Psoroptes ovis mites was relatively uncommon in July.  However as the disease has become more prevalent in recent years, cases of scab have been recorded more regularly in the summer months.  In July the diagnosis was made on three different occasions.  P. ovis mites were identified in wool samples collected from pruritic shearlings submitted to Dumfries and in similar samples from pruritic sheep in Sutherland.