Veterinary Services

Nutritional and metabolic disorders

Hypomagnesaemia was diagnosed as the cause of sudden death of three cows in a group of out-wintered autumn calving beef cows in the Borders. The diagnosis was based on low vitreous humour magnesium levels in two of the cows of 0.5mmol/l (values <0.55mmol/l consistent with hypomagnesaemia). The outbreak was notable for the fact that no sign of clinical disease was detected. With the provision of magnesium cobs and straw bales no further incident occurred.

Rumen acidosis was diagnosed as the cause of sudden death of a recently weaned beef calf that had been on concentrates rising to 3kg/head/day. Some of the contemporary calves in the group had shown signs of vague ill health. At necopsy the rumen pH was 4.6.

Parasitic conditions

Faecal samples were submitted from three, three-month-old dairy calves with suspected coccidiosis. Coccidial oocysts were detected in two of the three in fairly low numbers (700 and 2,400opg). No salmonella or worm eggs were detected. A presumptive diagnosis was made of early coccidiosis. The SAC considered that relatively low coccidial oocyst counts are significant in dairy calves with chronic scour and ill thrift.

Generalised and systemic conditions

A five-year-old, Holstein cow had been losing weight over a number of weeks. She was treated for liver fluke but failed to improve and was tested serologically negative for Johne's disease. Subsequently she was treated for pneumonia and showed some improvement initially but continued to decline thereafter. The cow was euthanased and submitted for postmortem examination at the Edinburgh centre. Extensive chronic peritoneal adhesions lay between the liver and the diaphragm, some adjacent small intestinal loops and the mesentery. There were multiple abscesses within the mesentery. Examination revealed a massively enlarged liver with multiple large abscesses throughout the organ, leaving little recognisable liver tissue. The lungs showed chronic bacterial pneumonia affecting the entire cranial and middle lobes bilaterally. Tissue was consolidated with numerous abscesses throughout. There was generalised lymphadenopathy. Arcanobacterium pyogenes was isolated from all liver abscess and pneumonic lung samples.

Antibodies to the virus of Malignant Catarrhal Fever were detected in a six-year-old Charolais bull. The animal had been ill for three to four days with an increased respiratory rate, scabs at the nostrils and a temperature of 39.5° C. No in-contact animals were showing similar signs.

Two one-year-old Limousin cross bullocks were submitted for postmortem examination from a herd in Ross-shire with a history of mucosal disease. At postmortem the ileum in both animals had multiple bleeding erosions and the Peyer’s patches were hyperaemic with necrotic mucosal surfaces (Figure 1; see Related Documents at top right-hand side). Further questioning revealed that six weeks previously, the 88 yearlings had been split into two groups. Thirty-six poorer-thriving cattle were brought inside and the better animals were left outside. The problems started about four weeks after housing shortly after a hopper was introduced to feed barley, though they had been receiving barley before this. The affected animals were all in the housed group. Bovine virus diarrhoea (BVD) virus was isolated from both animals. Histopathology demonstrated extensive areas where haemorrhage and oedema dramatically distorted the intestinal mucosa and denuded villi appear carpeted by bacteria. There was a lymphocytic infiltrate in the submucosa. The mucosa had collapsed into the Peyer’s patches. There was also mucosal damage in the large intestine consistent with BVD virus infection. There was no evidence of widespread crypt damage in the small intestine, which is usually a feature of BVD virus infection. Two more animals were submitted for postmortem examination seven days later. By this stage seven yearlings had died and a further four or five were affected with clinical signs of foul-smelling diarrhoea with tenesmus, dullness, anorexia and severe dehydration. Classic signs of mucosal disease were seen at post-mortem examination in these two animals. Both were antibody negative and antigen positive for BVD virus and BVD virus was isolated from both cases. BVD virus was introduced into the naïve herd approximately two years ago when 25 in-calf BVD antibody positive heifers were purchased to increase the size of the breeding herd. Three persistently infected calves were born and although the bought-in group had been kept isolated from the main herd it is suspected that the bulls introduced infection from the heifer group to the main herd.

Two three-week-old heifers were submitted to the Dumfries centre from a dairy herd where there was a problem with calves wasting. Several had died in the previous 10 days. Both calves had anteroventral lung consolidation and no evidence of milk in their abomasums. Mannheimia haemolytica was isolated but no enteric pathogens were isolated. BVD virus was isolated from both calves. The SAC advised screening the survivors to check for further persistently infected calves.

Diseases of the respiratory system

A six-month-old, Shorthorn-cross heifer from a pen of 21 cows and single suckled calves was submitted to the Edinburgh centre for postmortem examination. The group had been housed one month ago and was given an avermectin three weeks ago. They were not vaccinated against respiratory disease. Three were found dead one morning, one of these was submitted. Examination of the lungs revealed anterioventral collapse with and without consolidation and emphysema. This affected 60 percent of the right lung and 30 percent of the left lung. The dorsal lungs were emphysematous. There was a plug of clotted blood and debris at the tracheal bifurcation. The gross findings indicated severe, acute pneumonia and a combination of viral and bacterial pneumonia was suspected because of the consolidation and emphysema present. Fluorescent antibody tests (FAT) for respiratory syncitial virus (RSV) and parainfluenza type 3 virus (PI3) were both negative and cultures were overgrown by Proteus species and had to be abandoned. Histopathological examination of four sections of lung revealed advanced autolysis. However, severe, acute broncho to lobar pneumonia was still evident. There was no evidence of underlying viral challenge. The diagnosis was revised to acute bacterial pneumonia with no viral involvement.

In another outbreak of pneumonia in recently housed, spring-born, Limousin-cross calves, BVD virus was isolated incidentally from pneumonic lung tissues from one calf submitted for examination. Other laboratory tests confirmed that death was due to bacterial pneumonia with pleuritis. Although BVD is not a respiratory pathogen as such, acute infection with BVD infection will cause a significant transient reduction in neutrophil numbers. The resultant immunosuppression may be a factor in the development of bacterial pneumonia.

A severe respiratory problem developed in heavy fattening cattle of 500 to 550kg in weight in Orkney. The problem started in pens of heifers with scour, anorexia and dullness. A rhinitis then developed followed by severe pneumonia especially of the diaphragmatic lobes. All the affected animals had pyrexia of 41 to 42°C. Some animals developed breathing difficulties and over one week four died. All had emphysema of the diaphragmatic lobes of the lungs, massive rhinitis and diphtheresis of the trachea and bronchi and hyperaemia of the nasal passages. FAT examination of the trachea and bronchi was positive for bovine herpes virus type 1 (BHV1). Paired serology showed there to be seroconversion to BHV1 and RSV.

Two bulls of seven and 19 months of age died after a four-day history of pneumonia. In both cases there was a necrotic tracheitis and anteroventral consolidation. One animal had an associated pleurisy and pericarditis while the other had lung emphysema. There were no significant findings on bacteriology probably due to antibiotic treatment. FATs for BHV1 were negative however histopathology of the trachea was consistent with infectious bovine rhinotracheitis in the reparative phase.

Diseases of the locomotion system

The owner of a herd of 90 farmed buffalo cows reported that three cows had developed hind limb lameness and swelling of the lower leg and foot. This then progressed to the formation of a distinct indentation around the circumference of the limb proximal to the fetlock joint, below which the hair was lost and the skin became hard and necrotic (Figure 2; see Related Documents at top right-hand side). In turn this led to the eventual sloughing of digits in two of the affected animals, which were euthanased on humane grounds. The third cow made a recovery following the daily use of a proprietary "heat" spray containing glycol monosalicylate and methyl nicotinate; active ingredients which respectively block the production of prostaglandin and trigger local vasodilation. In this case a tentative diagnosis of ergotism or the similar condition fescue foot (caused by toxic substances in tall fescue) was made. However neither diagnosis could be confirmed since the likely exposure to the toxic agent would have occurred while the animals were grazing in the late autumn. The field was now bare.

Cardiovascular disease

An eight-year-old Friesian cow died suddenly whilst dry. The apex of the heart was adhered to the pericardium. A tennis ball sized abscess was present within the wall of the left ventricle. There was no evidence of a wire or reticular involvement. Arcanobacterium pyogenes and Fusiformis necrophorum were isolated. Multiple abscesses were also found within the right fore quarter and may have been the source of the problem.