Veterinary Services

Parasitic diseases

Two suckled calves found dead in a field where they had been outwintered since October were submitted for necropsy at Dumfries. Large numbers of worms were visible on the small intestinal mucosa. A total worm count was not possible because of the large numbers and clumping of the worms. These were identified as Nematodirus species, however speciation was not possible due to autolysis. The worm egg counts were negative in these cases, suggesting pre-patent infection. The exact cause of death in these cases was not established, however the parasite burden was considered potentially significant as a predisposing factor.

A holstein cow dropped dead in the milking parlour. It had calved eight months earlier without having a dry period. Five days previously her yield had dropped and she appeared ill. At postmortem examination fluke were seen within a pale and mottled liver. Several liver abscesses were present with adhesions to the body wall. Twin midterm foetuses were present in utero. Aqueous humour calcium was marginal (1.4 mmol/L, reference range > 1.5 mmol/L) and histopathology showed acute fatty change in the liver. It was suggested that the hypocalcaemia was secondary to the hepatopathy.

Alimentary tract disorders

A faecal sample was submitted to investigate the cause of diarrhoea in a small herd of cows in Uist. Salmonella bovis morbificans was isolated in culture.

A seven-day-old charolais cross bull calf, the third to die with a history of a few days scour was submitted to Dumfries for examination. The intestines were dilated with watery contents containing undigested milk. Circular 1.5 cm lesions on the rumen mucosa had coalesced to cover 80 per cent of the rumen and reticulum. Histopathology suggested that the severe enteritis was multifactorial involving bacteria and rotavirus. A mycotic infection in the rumen confirmed on histopathology was likely to be secondary to antibiotic treatment. Fungal hyphae were also seen within blood vessels suggesting systemic spread. No fungal species were isolated from the lesions.

Respiratory tract conditions

Submissions to investigate outbreaks of respiratory disease were common during the month across Scotland. Salmonella Dublin was isolated from a month-old calf by Ayr. The calf was one of a batch in which deaths from pneumonia had occurred between one and six weeks of age. Sloughing of the skin at the coronary band was also noted, possibly due to arteritis.

A three-month-old housed calf was submitted for necropsy at Perth. Other calves within the group of 30 had already been treated for pneumonia and had responded to antibiotic and anti-inflammatory treatment. In addition a calf persistently infected with bovine virus diarrhoea (BVD) virus had also recently been identified in the herd. Following postmortem examination a fluorescent antibody test (FAT) on lung tissues was positive for the presence of respiratory syncytial virus (RSV) antigen. Subsequent histopathology revealed acute interstitial pneumonia with necrosis of alveolar walls, congestion, oedema, fibrin exudation but only minimal inflammation. Such changes are not specific, but are most commonly caused by acute respiratory virus infections, thus supporting a diagnosis of RSV pneumonia.

Most outbreaks of pneumonia and upper respiratory disease investigated by Thurso were due to infectious bovine rhinotracheitis (IBR). Outbreaks in 12 herds in Caithness, Sutherland and Orkney were investigated. Affected cattle were from four months to two-years-old with mortality rates as high as five per cent in some units, especially with heavy cattle of 350 to 500 kg. The clinical presentation initially was of scour and pyrexia, then inappetence and finally respiratory distress. In only one outbreak were classical signs of conjunctivitis and coughing recorded. All cases showed a severe tracheitis and bronchitis with diphtheresis of the lining of the trachea. Emphysema was commonly found in the diaphragmatic lobes. Bovine herpesvirus type 1 was demonstrated by FAT.

IBR was diagnosed by FAT on ocular swabs from three farms in Dumfries and Galloway. Paired serology demonstrated seroconversion on three other farms. Five of the six outbreaks involved adult dairy cows. Respiratory signs were shown by some with two herds having only milk drop and poor production as clinical signs.

Parainfluenza type 3 virus was found to be the cause of one large outbreak of respiratory disease in heavy store cattle in northern Scotland with severe coughing, mild pyrexia, anorexia and deaths. No other significant agents were detected and the FAT examinations of bronchi and lung tissue were positive for the virus.

Reproductive tract conditions

Infection with BVD virus was implicated in abortions or stillbirths in three herds in Ayrshire. Antibodies to BVD were detected in the foetal fluids of two stillborn calves from a dairy herd. Six heifers had aborted or produced stillborn calves but the cows were unaffected. In the other two herds, BVD virus was isolated from the aborted calf of a bought-in limousin cow, and from the aborted calf of a three-year-old angus-cross heifer.

An aborted foetus was submitted to the Perth centre from a suckler herd that had been suffering problems of infertility for some time. The foetal dimensions were consistent with seven months gestation. No significant lesions were recorded on examination of the carcase but Campylobacter fetus fetus was isolated from foetal tissues and stomach contents. Histopathology revealed changes consistent with diagnosis of campylobacter abortion.

Musculo-skeletal conditions

Aberdeen continued to investigate an outbreak of rickets in dairy calves. Animals were affected pre- and post-weaning. They showed evidence of hindleg stiffness and recumbency. Gross pathology included poor mineralisation of bones and abnormal articular cartilage formation. Histopathology confirmed a diagnosis of rickets with the growth plates noted to be irregular with retained cartilage. The calves were fed whole milk and a commercial mix of wheat, barley, soya and beans pre-weaning. After weaning they also received baled silage in addition to the above mix. Further assessment of the ration is in progress.

An eight-month-old, purchased limousin-cross heifer was submitted to Edinburgh. This was one of three which were stiff on arrival, had a reduced food intake and then died. Necropsy revealed extensive oedema of the right abdominal wall, an area of acute haemorrhage over the right thoracic wall and around the larynx and a fracture of the pelvis involving the right ilium. There were numerous pieces of necrotic bone and extensive necrosis of the surrounding muscle and connective tissue. The necrosis and inflammation had tracked forward to produce the changes in the abdominal wall and into the caudal abdomen to produce a fibrinous peritonitis. This in turn had tracked through the diaphragm so there were fibrinous adhesions between the diaphragm and haemorrhagic caudal lung lobes. The age of the lesion was consistent with trauma having occurred at the market or in transit. Streptococcus dysgalactiae and Arcanobacterium pyogenes were isolated from both the necrotic muscle and the spleen confirming systemic spread of the infection from the site of trauma. As the severity of the damage was clearly not suspected clinically, it was advised that the other two stiff animals be examined to assess their injuries.

A 62 kg belgian blue heifer calf born by caesarian section died two days later without ever having gained its feet. Necropsy at Dumfries revealed subcutaneous oedema over the hindquarters (See Figure 1 at top right-hand side). The limb muscles were mottled and white as were the muscles of the abdominal wall. Histopathology showed acute myofibre degeneration and myoglobin within the kidneys. The pathology in the skeletal muscles was extensive suggesting white muscle disease although unusually there were few changes in the diagphragm or intercostal muscles. Liver vitamin E and selenium status was normal at the time of death.

Diseases of the nervous system

A nine-year-old, simmental-cross suckler cow was submitted to Edinburgh for necropsy. The cow presented with repeated bouts of collapse to one side, going down on her front legs and twitching. It was treated for staggers and given non-steroidal anti-inflammatory treatment. It was euthanased the next day as there was no clinical improvement and the right fore appeared to knuckle over. Nerve damage was suspected. No significant abnormalities were found on detailed dissection of the forelimbs, axillae and cervical spine. The meninges appeared thickened and opaque but this was likely to be an age effect. Brain cultures were sterile. Histopathological examination of the brain and cervical spinal cord was carried out once a negative BSE result was received. This revealed degeneration of large motor neurones in the red nucleus and in the medulla adjacent to the median raphe. In addition, a very few neurones in the spinal cord were similarly affected. In the cord, there were also isolated vacuoles in the ventral white matter columns, some of which contained swollen axons and others contained membrane "figures". Nothing of significance was found in either the left or the right brachial plexi. The cause of the neuropathology could not be determined but it was consistent with the clinical signs described. A diagnosis of central nervous system degeneration of unknown aetiology was made.

Renal diseases

A six-year-old dairy cow that died after a history of recumbency, anorexia and thirst was submitted for postmortem examination. Both kidneys were markedly enlarged, pale and firm with scattered areas of fibrosis and a strong uraemiac smell. There was massive oedema of the abomasal folds and the gastrointestinal content was fluid throughout. Histopathology of the kidneys revealed that the glomerular loops were thickened and hypocellular and the tubules were distended by protein-rich fluid confirming renal amyloidosis. There was also a mild chronic interstitial nephritis, the cause of the areas of fibrosis.