Veterinary Services

Toxic conditions

An unusual case of copper poisoning was confirmed in a one-month-old Lleyn lamb. The unit in Aberdeenshire reported three similar deaths in lambs of the same age. On necropsy there was a generalised jaundice of the carcase and the liver copper concentration was 17,000 umol/kg DM (reference ranges 314 to 7,850 umol/kg). Although this did not exceed the threshold to inform Food Standards Agency (Scotland), advice was given to help identify the source of copper and to prevent further cases of toxicity.

Parasitic diseases

A high worm egg count and Dictyocaulus filaria larvae identified in faeces samples submitted from an aged pygmy goat in very poor condition, both before and after administration of the anthelmintic fenbendazole. This product is not licenced for use in goats. Further information is currently being sought on the time of sampling post-dosing and whether the animal concerned was dosed at the appropriate rate for a goat.

The Thurso Centre reported severe parasitic damage to lungs, abomasum and small intestine following the necropsy of a four-year-old milking goat that had lost bodily condition and scoured. Analysis of samples of faeces from others in the herd indicated resistance to benzimidazoles and avermectin anthelmintics.

Generalised and systemic conditions

Dumfries reported an incident in which three lambs died suddenly from a group of 80. At necropsy unusual circular lesions were seen on the lungs, liver and kidneys (figure 2 - see top right-hand side) from which Staphylococcus aureus was subsequently isolated in pure culture. The farm involved had no history of ticks.

Respiratory tract conditions

A two-year-old Charollais ram that had failed to thrive since purchase as a lamb, developed dysphagia, a profuse frothy nasal and oral discharge and a swelling at the angle of the jaw. On postmortem examination the lungs were heavy and consolidated and histopathological examination of the tissues confirmed ovine pulmonary adenocarcinoma. In addition Corynebacterium pseudotuberculosis was isolated from a large retropharyngeal mass, confirming caseous lymphadenitis.

Pasteurellosis was diagnosed on the basis of postmortem examination and bacteriology in growing lambs from flocks in Ross-shire, Inverness-shire and Sutherland. In those flocks where the ewes were routinely vaccinated against pasteurellosis, the SAC considered that maternal immunity in the lambs had declined by the time the losses were incurred. Whilst vaccination of young lambs is possible following specific veterinary advice, the management and handling constraints are significant and careful consideration must be given before adopting this approach.

Reproductive tract conditions

This year the owners of 547 flocks submitted material to their local SAC Centres to assist in the investigation of abortion outbreaks. This compared to 466 flocks over the same period in 2006. Each year, 12 or more different infectious agents are recorded as the cause of such outbreaks. This season the two most common diagnoses in Scottish flocks remained Chlamydophila abortus infection and toxoplasmosis (diagram 1 - see top right-hand side ), which together accounted for almost two thirds of the diagnosed sheep abortion outbreaks in 2007 and rather more than the equivalent figure from 2006. Diagnoses of both conditions continued to be made during May, with ten incidents of EAE and 32 of toxoplasmosis recorded in Scotland. Most notables amongst these was the worst outbreak of toxoplasmosis recorded at the Thurso for many years, in which more that 240 ewes from a hill flock of 400, either aborted or produced non-viable lambs at full term. The affected ewes were maintained on five separate units, but had received the same supplementary food during pregnancy leading to speculation that this had been the source of the Toxoplasma gondii oocysts.

The bacterial organisms Campylobacter, Listeria and Salmonella were also common causes of abortion. The "Other" category, which was responsible for more than 20 per cent of outbreaks where a diagnosis was made, is composed of pathogens that are encountered more sporadically, including border disease virus and bacteria such as Arcanobacterium pyogenes, Bacillus licheniformis, Yersinia, Staphylococcus and Streptococcus species.

Fresh and fixed thyroid glands were submitted to Ayr from a farm where multiple lambs had been stillborn, some with large masses in the neck region (figure 3 - see top right-hand side). A thyroid gland from a 3.7 kg lamb weighed 419 g, an equivalent of 133 g/kg live weight (published normal < 0.4 g/kg live weight). Histopathology showed that the thyroid follicles were lined either with very flattened epithelium or with tall columnar epithelial cells thrown into papillae. No dark-staining colloid was present. Thyroid iodine value was 296 mg/kg (reference range 1200 to 2000 mg/kg), confirming the diagnosis of thyroid hyperplasia due to iodine deficiency.

Foetuses were submitted to Dumfries from a flock of 250 Scottish blackface ewes in which 30 were barren at scanning and 13 abortions were recorded subsequently. Blood samples from three of these aborted ewes were positive for antibody to tick borne fever (TBF) and histopathology of the brain of an aborted foetus showed leukomalacia of the corona radiata and the cerebellar white matter. Whilst these findings are not pathognomic for TBF, it was thought to be the most likely cause of the problem.

Mammary diseases

Mastitis due to Bibersteinia (Pasteurella) trehalosi and Streptococcus uberis was confirmed in a four-year-old Texel cross ewe from an Aberdeenshire unit. Five other ewes were reported to have died over the previous two weeks. St Boswells from the udder of a four-year-old ewe cultured Histophilus somni. Histopathology of the udder revealed a severe necrotising suppurative mastitis. Maedi-visna serology and mycoplasma cultures were both negative. No other abnormality was detected in this animal. The SAC is not aware of Histophilus somni being reported as a cause of mastitis in ewes.

Musculo-Skeletal conditions

Four diagnosis of infection with Streptococcus dysgalactiae subsp. dysgalactiae were made in Scotland May. This brought the total for 2007 to 20, compared to 12 over the same period last year. In the majority of cases the organism was associated with septic polyarthritis, although in some outbreaks the bacterium was also isolated from cases of meningitis and in one case pharyngitis.

Nervous system disorders

Ayr, Inverness and St Boswells diagnosed louping ill in young lambs. Ayr received fixed brain and spinal cord from a three-week-old Scottish blackface lamb that was found paralysed. Other cases of paralysis had also occurred in the flock. Histological examination revealed a severe non-suppurative meningo-encephalitis, with focal microgliosis, neuronal necrosis and lymphocytic perivascular cuffing, consistent with a diagnosis of louping ill. Inverness also diagnosed louping ill on the basis of histopathology in a Scottish blackface lamb from a flock on the Southern Isles. This lamb also had a significant Nematodirus battus and Trichostrongyle burden. St Boswells diagnosed louping ill a two-week-old lamb. It was bright but unable to rise and two other lambs were similarly affected in the flock. Histological examination revealed lesions consistent with a diagnosis of louping ill and suggested an in-utero infection. This was an unusual presentation for louping ill.