Veterinary Services

Parasitic conditions

Parasitic gastroenteritis was reported as a significant problem in cattle recently turned out in the North of Scotland. Both adult cattle and young stock from six weeks of age were affected. Faecal worm egg counts were as high as 8,000 trichostrongylid eggs per gram (epg) in one case. It was assumed that considerable numbers of infective larvae (L3s) had overwintered on affected pastures. A number of cases occurred in outwintered cattle, which had been treated with avermectin in late 2004.

Generalised and systemic conditions

An increased mortality rate in young suckled calves at pasture was recorded this month and it was assumed that a period of colder wet weather was a predisposing factor. Numerous common diagnoses were recorded as illustrated below:

Post mortem examination of a three-day-old, Limousin-cross calf by the Edinburgh Centre revealed diffuse fibrinous peritonitis secondary to navel ill with necrosis, haemorrhage and inflammation of the umbilical vessels. The calf was reported to have been sucking well but the zinc sulphate turbidity (ZST) level was only 1 turbidity unit (reference range >14) indicating hypogammaglobulinaemia.

Death due to enterotoxaemia was diagnosed in a one month old, Charolais-cross bull calf at the Inverness Centre. The affected group of 35 cows and calves had been moved from bare to lush pasture the day prior to the calf’s death. At necropsy patchy haemorrhagic enteritis with fluid contents was evident and the rumen contained lush, green material. Analysis of a sample of thoracic fluid revealed Clostridium perfringens alpha toxin consistent with type A or type E enterotoxaemia. The enterotoxaemia was considered to have been precipitated by the consumption of excess fermentable carbohydrates from the lush pasture.

A five-day-old calf from Perthshire, which had been apparently normal, collapsed and died shortly afterwards. At post mortem examination the navel was thickened but not visibly infected. Polyarthritis was evident and excess cerebrospinal fluid was present. E.coli was isolated from all culture sites and a diagnosis of colisepticaemia was made.

An 18-month-old calf from Perthshire with respiratory distress tested positive for bovine virus diarrhoea (BVD) antigen.

Following an outbreak of Border disease, two cases of mucosal disease occurred in twenty-two-month-old stirks. The sheep and cattle had been mixed in the same field. Border Disease Virus (BDV) was not isolated from the sheep to compare the viruses although approximately 20% of BDV cases are of BVD origin (Nettleton et al, J Virol. Methods, In Press, 2005)

Respiratory tract diseases

Outbreaks of pneumonia in suckled calves at grass were recorded commonly with inclement weather again being a significant factor. Fibrinous pleurisy, peritonitis and pneumonia due to infection with Mannheimia haemolytica was confirmed in an eight-week-old calf in Aberdeenshire. Eight deaths were reported in the group of 80 calves at pasture.

Respiratory Syncytial Virus (RSV) was diagnosed as the cause of pneumonia in young cattle aged four to twelve weeks on five farms in northern Scotland. All the animals found dead unexpectedly, were in good condition and had been thriving. RSV infection was confirmed on the basis of fluorescent antibody testing (FAT) of lung tissue. In some cases secondary Pasteurella or Histophilus infection was present. This is the first year that significant numbers of RSV associated deaths have been recorded in young cattle at grass in this area.

Two yearlings were submitted for post mortem examination from a small-holding in northern Aberdeenshire. Six deaths were reported in a group of 40 cattle within a two week period. The animals were outside in two separate but adjoining fields and deaths were reported in both fields. Affected animals presented with acute onset pyrexia and upper respiratory tract signs followed by neurological signs. The respiratory tract signs apparently resolved prior to euthanasia and submission of the first animal, but the second animal submitted showed keratitis, conjunctivitis and ocular and nasal discharges. Histopathological examination of the brains and lymph nodes was consistent with malignant catarrh fever (MCF) and MCF antibody was subsequently detected in plasma from two further cases. Initial enquiries did not suggest that close association with sheep had taken place. However, subsequently it was revealed that a sheep flock had lambed in the same building as the cattle prior to turnout. To date 13 deaths have occurred in the group.

Diseases of the reproductive tract

An abortion storm was investigated in a dairy herd in Dumfries and Galloway. The herd, which vaccinated for BVD, Leptospira hardjo and Salmonella, experienced a total of 14 abortions, nine occurring in three days. Foetuses were of approximately 200 days gestation.

Foetal material was examined from the herd and in all cases a diagnosis of abortion due to Neospora caninum was made. In all cases foetal fluids proved seronegative for Neospora and the diagnosis was based on the demonstration of classical neuropathological lesions and labelling of N. caninum antigen by immunohistochemistry. Seven aborted cows were seropositive for N caninum confirming exposure. These results were interpreted as an acute outbreak of neosporosis due to horizontal rather than vertical transmission, although the source of any such infection could not be identified. The herd was being buffer fed a total mixed ration and this was one possible source of infection.

Neospora caninum was also confirmed as the cause of late abortion in another dairy herd in Dumfries and Galloway on the basis of neuropathology and immunohistochemistry. The herd was experiencing problems with embryo loss following positive pregnancy diagnosis and although this abortion occurred later in pregnancy, blood sampling a group of aborted and pregnant cows showed a higher seroprevalence in aborted cows. Although not conclusive this finding with did suggest that early infection with Neospora caninum may have been associated with the embryo loss problem.

Musculoskeletal conditions

Chondrodystrophy of suckled calves associated with silage feeding of dams during gestation was suspected on a beef unit in Aberdeenshire. Six calves had been affected with two considered non-viable and euthanased. Shortening of the limbs and hyperextension of the metacarpophalangeal and metatarsophalangeal joints were reported with severely affected calves unable to rise. Dams of affected calves had all received pit silage. Calves of dams fed big bale silage were unaffected.

Stiffness progressing to sternal recumbency with inability to rise on fore or hind-limbs in Holstein bulls in straw-bedded courts was reported from another unit in northern Aberdeenshire. Two entire bulls were euthanased for examination. In addition to subcutaneous and periarticular oedema and haemorrhage associated with prolonged recumbency, the first animal examined had a transverse fracture of the neck of the left femur. The second animal had an oblique displaced fracture of the shaft of the right radius. Nutritional osteodystrophy was suspected but as clinical chemistry, histopathology and bone ash analysis are usually unrewarding in confirming the diagnosis, dietary evaluation was recommended. Intensive beef minerals were reported to have been included in the feed but the owner suspected they had been improperly mixed.

Diseases of the circulatory system

A three-week-old Blonde d’Aquitaine calf was submitted for necropsy at the St Boswells Centre after failing to respond to treatment for an apparent pneumonic condition. A course of antibiotics had been administered after the animal was seen to be lethargic and dyspnoeic. At necropsy the calf was found to be in good bodily condition, but the heart was grossly enlarged and surrounded by a clear pericardial effusion. Bilateral ventricular hypertrophy and a ventricular septal defect of some 3-cm diameter were evident. The liver was subsequently found to be markedly enlarged and to show a "nutmeg" pattern of fatty degeneration. Other changes in the carcass were also consistent with a diagnosis of congestive heart failure.