Veterinary Services

Nutritional and metabolic disorders

A six-month–old, Cheviot-cross lamb was submitted to Dumfries in order to investigate ill thrift in a group of organic lambs. Parasitic gastro-enteritis was confirmed on postmortem examination and 3,300 Teladorsagia worms were recovered from the abomasum and 7,700 trichostrongyle species worms from the small intestine. Subsequent trace element testing on the liver confirmed cobalt, copper and selenium deficiency.

Parasitic diseases

Acute liver fluke disease was diagnosed on six occasions this month compared with three in November 2006. Chronic liver fluke infection was diagnosed on eight occasions following the submission of faeces samples from the Isle of Skye as part of a routine parasite monitoring programme and on two occasions in the Outer Hebrides.

Aberdeen received a housed, one-year-old Dorset cross ewe for necropsy. In June Salmonella arizonae was isolated from its faeces. Since then, the animal was intermittently anorexic and pyrexic, and had suffered regular bouts of diarrhoea, despite being negative for salmonella on repeated faecal cultures. On necropsy the abomasal mucosal surface was covered with many pale nodules. The faeces were pelleted and the worm egg count was less than 50 eggs per gram. On histopathology changes in the abomasal mucosa were characterised as a lymphocytic infiltration. Similar findings were recorded in the small intestine where there was also distortion of the mucosa and thickening of the villi, as well as marked hyperplasia of gut associated lymphoid tissue. The findings were considered consistent with severe parasite challenge to the abomasum and small intestine. Since this was a housed animal the SAC VS suggested that it may have received unusual exposure to parasites and developed an exaggerated inflammatory response to a low level of parasitism.

Generalised and systemic conditions

November is usually the peak month for diagnosis of systemic pasteurellosis in Scotland. In last month’s report it was noted that only six outbreaks of the condition were recorded, compared with 30 incidents during October 2006. Similarly, November saw 27 recorded outbreaks, compared to the 42 seen in November last year. All SAC DSCs diagnosed the condition. Mortality rates ranged from two to 15 per cent. In several outbreaks there was a history of a move to improved grazing or kale in the previous 10 to14 days. A typical case was that of 13 lambs from Argyll which died at wintering on two farms on the Isle of Bute. The affected lambs were either found dead or had shown lethargy shortly before dying. Three animals submitted for necropsy showed classical lesions of systemic pasteurellosis, including necrotic oesophagitis, "ink-spot" pulmonary haemorrhages and widespread petechiation. Bibersteinia trehalosi (formerly Pasteurella trehalosi) was recovered in systemic distribution from all three lambs. In this case a full course of multivalent vaccine was administered earlier in the autumn. Two outbreaks in Ayrshire involved deaths in groups of store lambs. One group had received one injection of vaccine while the other was unvaccinated. Again B. trehalosi was recovered from affected viscera. Dumfries reported a case of systemic pasteurellosis in which one of the affected animals showed extensive miliary abscessation of the liver and spleen with a localised peritonitis.

Respiratory tract conditions

A seven-month-old, Texel ram lamb was submitted to Edinburgh with a history of sudden death. Necropsy revealed marked congestion and haemorrhage in the throat associated with laryngeal chondritis originating on the left side, with severe bruising of the left vocal fold and necrosis of the cartilage.

Skin diseases

Caseous lymphadenitis (CLA) was diagnosed in a five-year-old Suffolk ram. The animal had been in Shetland for four years, during which it had shown no clinical signs and had little contact with any other bought-in stock. The SAC noted that CLA infections are chronic in nature, and the internal or visceral form of condition common in sheep. Although this is an unusual case history, it is entirely possible for the disease in the ram to have remained clinically inapparent for years, before emerging in the external form later in the animal’s life.