Veterinary Services

The carcases of two north country Cheviot fattening lambs were submitted to Dumfries from a flock in which ten died over a ten day period. A barley-based concentrate ration was introduced recently. The rumen contents of the first lamb examined had large amounts of cereal grains and a pH of 4.0, confirming a diagnosis of acidosis.  In the second case the rumen had porridge-like contents, no barley was visible and rumen pH was 5.2.  Subsequent testing of small intestinal contents confirmed the presence of epsilon toxin of Clostridium perfringens. Since no clostridial vaccines were used in the group, SAC suggested that at least some of the deaths may have been due to clostridial enterotoxaemia.

Toxic conditions 

In another case dealt with by Dumfries, 450 Scottish blackface sheep on a local holding received injections of doramectin and nitroxynil solution. Within two hours of finishing, one animal had died and others were seen to be salivating, dyspnoeic and distressed.  The following morning a total of 15 gimmers and six ewes were found dead.  Four of the gimmers were submitted for postmortem examination. They weighed 38, 42, 44 and 48 kg respectively. Before treatment, a ewe was weighed and, based on a bodyweight of 75 kg, the gun used to inject the nitroxynil solution set at 2 ml.  At some point it was noticed that the setting had altered and a 4 ml dose was being administered. This represents almost four times the normal dose for the lightest gimmer examined.  This animal was injected subcutaneously in the neck. Multiple subcutaneous petechiae were noted over the thorax and there was an increased volume of bright yellow pericardial fluid. The cerebrospinal fluid was also bright yellow in colour.  In the other three cases the nitroxynil had been injected intramuscularly over the pelvis. Affected areas of muscle appeared dry and black in colour (figure 3 - see top right-hand side).  Clostridium sordellii was isolated in pure culture from affected muscle in all three gimmers.  Histopathology confirmed severe acute lung oedema and acute renal tubular degeneration in all four cases.  Nitroxynil uncouples cyclic phosphorylation thus increasing the metabolic rate.  This can lead to hyperthermia in cases of toxicity. SAC considered that the death of the lightest animal was a case of nitroxynil toxicity. The other three gimmers also had a severe necrotic hepatitis and an acute severe necrotising myopathy consistent with clostridial invasion.   SAC considered the cause of death to be clostridial myositis due to C. sordellii, with possible concurrent nitroxynil toxicity.

Parasitic diseases

A total of 31 outbreaks of chronic fasciolosis and 12 outbreaks of acute fasciolosis were confirmed. On one Ayrshire farm ten purchased Suffolk-cross lambs from a group of 300 died during a period of two weeks.  Classical lesions of acute fasciolosis were evident at postmortem examination, along with concurrent parasitic gastroenteritis. The group were treated with a flukicide seven weeks previously.  Further treatment was advised, followed by post-treatment monitoring for detection of possible flukicide resistance.

Lesions of chronic fasciolosis with parasitic bronchitis and secondary bronchopneumonia were also evident in a store lamb submitted for postmortem examination by Ayr Animal Health Office as part of an animal welfare investigation. Ten animals from a group of 150 died and it was reported that no fluke treatment had been given.

Faecal samples were examined at Dumfries from ten ewes before, and three weeks after, treatment with triclabendazole.  The average number of fluke eggs in the pre-treatment samples was 34. Three weeks later this number had increased to 43, suggesting treatment failure and possible resistance.

While most outbreaks of fasciolosis were recorded in the west of Scotland, outbreaks are becoming more frequent in the east of the country.  An Angus flock-owner reported 12 deaths amongst adult ewes over a period of three weeks. One affected animal submitted for necropsy was in poor condition and anaemic.  The liver was discoloured, friable and extensively fibrosed. Numerous immature and mature fluke were present. SAC recommended immediate treatment of the rest of the group with an appropriate flukicide.

A necropsy was requested on a five-year-old, Texel-cross ewe from a flock of 500 in the Edinburgh area. There were five sudden deaths in the previous five days.  The carcase was pale and there was a large amount of free blood and numerous clots in the abdominal cavity.   The liver capsule was detached in one area and appeared to be the source of the haemorrhage. No Fasciola hepatica  were seen on gross examination of the liver but an immature fluke was seen in an impression smear and a diagnosis of acute fasciolosis was made. 
Faeces submitted from llamas described as off colour and thin were positive for liver fluke eggs.

Alimentary tract disorders

Dumfries received 42 blood samples from a flock where a large number of ewes were ill thriven.  Eight of the samples were seropositive for Johne’s disease by ELISA, with a further two suspicious, indicating that Johne’s disease was playing a significant role in the problem.

A faecal sample was submitted from a four-year-old nanny goat with a history of weight loss and scour.  ZN smears were positive for acid fast bacteria confirming a diagnosis of Johnes disease.

Respiratory tract conditions

Ovine pulmonary adenocarcinoma (OPA) was confirmed at Aberdeen in two two-year-old Scottish blackface ewes found dead. The flock has a history of OPA and ten ewe deaths were reported since the start of the year.  In both submitted ewes there was a secondary bronchopneumonia. Mannheimia haemolytica and Pasteurella trehalosi were isolated from the lungs of each.
A diagnosis of OPA was also made when a nine-month-old ewe lamb was submitted to Perth with a history of dyspnoea and serous nasal discharge (figure 4 - see top right-hand side).  This was one of an over-wintering batch of 450, 130 of which were in poor bodily condition.  Due to the long period between infection with the jaagsiekte sheep retrovirus virus and development of the OPA lung tumour, it is unusual to diagnose the condition in animals under two years of age.  The owner reports a high incidence of ill-thrift and coughing amongst the ewe flock and further investigations are on-going to determine whether OPA is responsible for this.

Nervous system disorders

Dumfries reported that four of the five Suffolk ewes on a local small holding produced weak lambs. The lambs were recumbent or showed severe hind limb weakness.  Two were euthanased and submitted for necropsy. There were no abnormal gross findings, but subsequent histopathology revealed changes consistent with swayback.  Ewe serum copper results were low at between 2.6 umol/l and 4.6 umol/l, (Reference range 9 to 20 umol/l). The lamb liver copper results were less than 90 umol/kg DM (Reference range 314 – 7850 umol/kg DM). 

Skin diseases

 
Seven outbreaks of sheep scab due to Psoroptes ovis were confirmed. One outbreak affected a batch of store lambs from Aberdeenshire treated with doramectin at the beginning of December, but still pruritic at the end of January.  Scab was also diagnosed by demonstration of mites in a skin scraping from a hogg, euthanased as part of an animal welfare investigation by Ayr Animal Health Office.