Veterinary Services

 
Chronic copper toxicity was diagnosed by St Boswells as the cause of 18 sudden deaths in a group of 600 Lleyn ewes (3% mortality).   Postmortem examinations revealed typical jaundice, bronzed livers and gun metal coloured kidneys. The liver and kidney copper levels were grossly elevated above the reference range.  The ewes were at grass and had not received any copper supplementation.  Plant material from the grazing fields was analysed and in all cases the ratio of molybdenum to copper was between 1:17 and 1:20 (normal ratio ≤ 1:12).  This high ratio together with elevated pasture copper content ranging up to 14.3 mg/kg DM (normal range 5.0-8.0 mg/kg DM)  gave supportive evidence of copper availability well above normal requirements.  In addition the swards in the grazing fields contained a large proportion of clover.  Legumes grown under the same conditions as grass tend to have higher copper concentrations.  SAC C VS concluded that the main risk factors for copper toxicity in this group of animals were herbage with high copper and low molybdenum levels, access to clover and breed susceptibility.

Parasitic diseases

Acute fasciolosis was diagnosed by Edinburgh on an east coast farm that had never experienced this problem previously.  Six deaths occurred in the ewe flock within a week. Two carcases submitted for postmortem examination showed copious amounts of clotted blood and bloody fluid within the abdomen, associated with acute, severe parasitic hepatopathy.  Numerous immature liver fluke were identified as having recently invaded the livers, causing generalised tissue destruction.  No further losses occurred in the ewe flock after treatment with a flukicide, however a ewe lamb from an untreated group was found dead a week later.  At necropsy the liver had ruptured.

Alimentary tract disorders

The carcase of a Texel cross gimmer in good condition submitted to Perth for necropsy was the sixth of 80 animals in the group to be found dead.  Examination revealed severe, deep-seated necrosis of the tongue (Fig 3 - see top right-hand side) extending caudally towards the pharynx.  In addition there was a severe purulent pneumonia and pleurisy (Fig 4 - see top right-hand side) likely to have developed as the result of aspiration of necrotic debris.  No recent oral dosing of the group had taken place, suggesting that the tongue lesion was not a drenching gun injury.   The owners were advised to consider other possibilities, such as damage caused by feeding troughs or abrasive plants such as thistles.

Three Lleyn lambs were submitted to Dumfries from a farm where 10 had died over three days and others were ill.  Dosing gun injuries were confirmed in this case.  Circular holes through the pharyngeal wall were found dorsal to the larynx in all three carcases.  Cobalt/selenium boluses were administered ten days earlier.  In two of the lambs the boluses were found immediately behind the larynx, and in the third they were half way down the neck.  In each case infection had tracked down the tissues of the neck into the mediastinum, causing cellulitis and consolidation and necrosis of the anterior lung lobes. 

Nervous system disorders

An upland farm with around 1,200 April-born lambs experienced approximately 10 deaths spread over four groups.  Lambs were recently weaned and turned out on to permanent pasture.  Affected animals were found weak and recumbent, and died shortly afterwards.  One live lamb was submitted to Edinburgh for investigation.  This lamb was recumbent and, although attempting to rise, was unable to stand even with assistance.  Limbs were co-ordinated and no neurological deficits were apparent.  Opisthotonus was observed transiently. Neurohistopathology identified acute cerebrocortical necrosis, with thiamine deficiency and lead toxicosis among the suggested causes.  Liver lead concentration was low, and SAC C VS considered vitamin B1 deficiency to be the most probable cause.

Louping-ill was diagnosed in four flocks in Argyll in which lamb deaths were preceded by neurological signs in at least some of the animals affected.  On one farm 16 four-month-old lambs died from a group of 600 over a period of six days. Some presented as sudden deaths while others showed neurological signs with pyrexia prior to death.  Immunohistochemistry was carried out on fixed brain tissue confirming the involvement of louping-ill when two lamb carcases were submitted.  In this particular case the SAC C VS also suspected that tick-borne fever was also involved, increasing the susceptibility of the flock to secondary infections.

Skin diseases

 
Sheep scab due to infection with Psoroptes ovis was diagnosed twice.  In one case from Aberdeenshire approximately 50 per cent of a group of mule ewes were reported to have severe pruritis and crusting of the skin over the body and neck.