Veterinary Services

Nutritional and metabolic disorders

Numerous submissions were examined at Centres during August in order to assess the trace element status of sheep flocks; this being carried out as part of the Animal Health and Welfare Management option under the Land Management Contract system sponsored by the Scottish Executive. For example, submissions from clinically normal lambs in Orkney and Shetland produced evidence of copper, cobalt and selenium deficiencies. These results will be used to improve the trace element status of these sheep by including appropriate measures in the animal health plans being developed by veterinary surgeons on behalf of flock masters.

Ayr reported the diagnosis of cobalt deficiency (pine) in a group of four-month-old Texel-cross lambs showing evidence of ill thrift. The vitamin B12 values of six out of ten affected animals were below the reference limit of 336 pmol/l. Two affected animals also showed elevated pepsinogen values indicating previous helminth challenge, although a bulk faecal sample collected from the group did not contain trichostrongyle eggs. Vitamin B12 deficiency is known to increase the pathogenicity of helminth infections in sheep by impairment of the immune system. Increased susceptibility to disease due to trace element deficiency was also suggested in the case of a lamb that died from pasteurellosis. Liver vitamin B12 content was less than 0.07 ug/g wet weight and liver selenium content was 0.5 umol/kg dry matter.

A four-month-old mule cross lamb was submitted to Dumfries for postmortem after six lambs died within one week. The findings at necropsy suggested a clostridial enterotoxaemia with haemorrhagic, friable kidneys and a chicken fat clot in the pericardium. However, clostridial toxin testing and brain histopathology did not support this diagnosis. Rather histopathological examination of the heart revealed extensive, ongoing, myocardial degeneration and necrosis with fibrosis and mineralisation. These changes were consistent with a nutritional myopathy.

Toxic conditions

Ayr diagnosed copper poisoning in a group of artificially reared lambs, which had been offered a proprietary calf mix. The diagnosis was made from viscera submitted by the attending veterinary surgeon when testing revealed a liver copper content of 21,000 µmol/kg (reference range 314 - 7,850 µmol/kg).

Parasitic diseases

Despite this August being the coldest recorded in Scotland since 1994, above average rainfall in July and August favoured the development of helminth larvae on pastures. Submissions of faecal samples from weaned lowground lambs confirmed parasitic gastro-enteritis on the basis of elevated worm egg counts on numerous occasions. This finding was consistent with the national trend from 2004 to 2007 illustrated in figure 2 (see top right-hand side) that shows a sharp seasonal increase in diagnoses of PGE during the month. SAC advice to veterinarians and farmers has highlighted the need to monitor faecal samples from growing lambs to ensure that strategic control measures are effective in maintaining lamb growth, whilst reducing selection for anthelmintic resistance.

Parasitic gastro-enteritis was confirmed in two flocks in Aberdeenshire following submission of faeces from four to six-month-old lambs, with a history of weight loss and scour. Recommendations were made to treat the groups with anthelmintic and to check faecal egg counts post-treatment at an interval appropriate to the type anthelmintic that was used.

Three May-born Cambridge-cross lambs that had grazed the same fields since birth died on the 30th of July and were submitted for postmortem at Dumfries. Each lamb showed evidence of recent scouring and small intestinal washes revealed burdens of 6,350, 9,500 and 10,500 Nematodirus battus worms respectively. A fatal N. battus challenge affecting May-born lambs at the end of July is unusual in southern Scotland. Another unusual factor was that part of the lamb’s pasture was cropped from 2004 to 2006 and the rest was employed only as a run-back for the weaned lambs grazing turnips in the autumn/winter. The SAC suggested that an autumn hatch of Nematodirus the previous year had lead to a build up of L3s on the pasture. In addition there may have been a later hatch of larvae, associated with rising temperatures in mid July.

Generalised and systemic conditions

Septicaemia due to infection with Streptococcus dysgalactiae subsp. dysgalactiae was confirmed in an adult ewe with a history of respiratory distress. A profuse growth of the organism was recovered from the udder, liver and lung. In addition abomasal parasitism due to Haemonchus contortus and Teladorsagia circumcincta was also confirmed.

Alimentary tract disorders

Serological examination confirmed Johne’s disease in two adult Merinos with a history of ill thrift. Johne’s disease has previously been confirmed in the goat herd on the same premises near Aberdeen.

A severe mycotic rumenitis was determined to be the cause of condition loss and lethargy, leading to recumbency in a four-month-old Suffolk-cross lamb. Necropsy revealed an extensive vegetative rumenitis involving most of the dorsal sac of the rumen, with inflammation extending through to the serosal surface. No fungal hyphae were seen in direct smears of the vegetative lesions, but histopathology revealed numerous fungal hyphae associated with necrosis and inflammation.

Musculo-Skeletal conditions

A flock in Sutherland reported chronic and unresponsive lameness problems in a small number of lambs. Gross postmortem examination and histopathology showed chronic septic arthritis and osteomyelitis. Bacterial cultures proved sterile, possibly due to chronic nature of the condition. Advice was given to the flock master on the welfare aspects of such cases and euthanasia of similar cases on welfare grounds was recommended.

Skin diseases

Numerous submissions of swabs from skin lesions were received by Thurso following recent concern over the emergence of caseous lymphadenitis (CLA) in the area. However, in no case was Corynebacterium pseudotuberculosis isolated. Other bacterial organisms including Fusobacterium necrophorum, Actinobacillus lignieresi, Staphylococcal species and Arcanobacterium pyogenes were identified. Serological evidence of CLA was obtained as a result of blood sampling animals from flocks where the disease had already been confirmed. In contrast, C. pseudotuberculosis was isolated from a swab taken from a pustular lesion in a Suffolk tup from the Scottish Borders.

Staphylococcus aureus was isolated from skin lesions on goats from two premises in northern Scotland. In one case there were crusty lesions over the back of the animal. In the second case there were purulent lesions on the nose, udder and neck.