Veterinary Services

Parasitic diseases

Three Swaledale ewes were submitted live to the St Boswells DSC from a flock with a recent history of ewes in poor bodily condition. All three ewes were found to have nodular thickening of the abomasal folds. Although an intestinal worm count conducted on one of the submitted sheep revealed a relatively modest abomasal parasite burden of 1,200 Teladorsagia circumcincta, subsequent histology of the abomasal mucosa revealed changes consistent with abomasal parasitism; namely intense diffuse mucosal infiltrate of lymphocytes, plasma cells, eosinophils and globule leukocytes. Abomasal parasitism was diagnosed as the main cause of the poor condition.

Thurso Disease Surveillance Centre (DSC) reported acute fasciolosis as the cause of death in the case of a Texel ram from a local flock and in that of two gimmers in another Cheviot flock. The postmortem findings in these cases were of free blood in the abdominal cavity and severe damage to livers. In the case of the Texel ram there was also evidence of concurrent black disease due to Clostridium novyi type B.

Generalised and systemic conditions

A further 18 incidents of systemic pasteurellosis due to Pasteurella trehalosi were recorded in Scotland in December, bringing the total for the year to 110. As described in the SAC VS November report, the incidence of this condition is significantly higher than last year, when the total number of recorded diagnoses was 65. In one typical outbreak in December, 11 ewe hoggs from a group of 270 homebred animals were found dead on a unit in Perthshire. This group had received a full course of vaccination with a multivalent product and had a history of recent prophylactic anthelmintic treatment. Necropsy of two submitted carcases revealed marked subcutaneous haemorrhage over the neck and chest, necrotic ulceration of the larynx and oesophagus, and intense pulmonary congestion and petechiation. The diagnosis of systemic pasteurellosis was confirmed following the isolation of P. trehalosi in pure growth from the lung, liver and spleen of the affected animals.

The owner of a Fife farm reported the sudden death of a number of lambs that were being finished inside on a grain based diet. When four carcases were submitted for examination there was clear evidence of ruminal acidosis in one animal. However findings suggesting a clostridial enterotoxaemia were noted in the other three. On neurohistopathology two brains showed swelling, perivascular serum leakage and congestion, consistent with pulpy kidney disease and the action of the epsilon toxin of Cl. perfringens type D. The brain from the third lamb showed lesions characteristic of focal symmetrical encephalomalacia, prompting a similar diagnosis. Questioning of the owner indicated that none of the 500 lambs that he finished in this system each year received any vaccination against clostridial disease.

Alimentary tract disorders

Barley overload and consequent rumen acidosis were confirmed in two, eight-month-old Mule lambs on an Aberdeenshire farm. A group of 70 homebred lambs had been housed three weeks previously and introduced to a crushed barley based diet. Seventeen deaths had been reported over a 36 hour period. Initially lambs were found dead, but more latterly the affected animals were seen alive but dull, listless and scouring.

Respiratory tract conditions

A postmortem examination confirmed the presence of a very large retropharyngeal abscess in a six-month-old lamb with a short clinical history of vague malaise. A pure growth of Arcanobacterium pyogenes was isolated from the lesion. A dosing-gun injury was suspected with death the result of a toxaemia/septicaemia.

Ovine pulmonary adenocarcinoma (OPA) was diagnosed in three Scottish blackface ewes from a flock near Edinburgh with a history of numerous deaths amongst older ewes. The ewes were submitted alive and on arrival were found to be in generally good bodily condition, bright and alert, although they each showed marked respiratory effort. Following euthanasia copious fluid flowed from the nose of one ewe. Examination of all three revealed heavy, oedematous lungs that did not collapse when the chest was opened and multiple pale, firm nodules throughout the lung parenchyma. The gross findings were consistent with OPA and this diagnosis was confirmed by histology.

Reproductive tract conditions

Outbreaks of abortion were investigated in early-lambing flocks around the country. Diagnoses of toxoplasmosis, Campylobacter fetus and Bacillus licheniformis abortion were reached in three of these outbreaks.

Nervous system disorders

St Boswells DSC reported that a Branhamella species (most probably B. ovis) and Mycoplasma conjunctivae were isolated from conjunctival swabs submitted from two lambs. These animals were part of a group that had a history of recurrent keratoconjunctivitis throughout the summer.

Skin diseases

Five outbreaks of sheep scab were recorded in December. In one case in an upland area of Angus, there was evidence that infection had spread from one flock to a number of other holdings in the vicinity, emphasising the importance of a common and concerted approach to parasite control.