Veterinary Services

Generalised and systemic conditions

The risk of purchasing animals persistently infected with bovine viral diarrhoea virus (BVDV) was highlighted by the following two cases. Blood samples were submitted to the Perth Centre from a batch of eight heifers which had been purchased two years ago and had only managed to rear two calves to yearlings between them. Of their offspring, one calf was stillborn after a caesarean section, two calves died of scour and two died suddenly as stirks – one of which was identified as persistently infected (PI) with BVDV. When blood samples from the eight cows in question were checked serologically, two were found to be PI and the remaining six were serologically positive for BVD antibody.

In Aberdeenshire, mucosal disease was confirmed in a recently purchased, BVD vaccinated, three-year-old cow with a persistent scour. 

Alimentary tract disorders 

Impaired digestive tract function associated with ingestion of inappropriate feed led to the dehydration and death of a ten-day-old calf which was subsequently submitted to the Aberdeen Centre. The rumen was impacted with a large, dry, hard mass of yellow fibre and the abomasum contained material of a pasty meal consistency. No milk was present. There was no evidence of infectious disease, and managemental factors such as unpalatability of milk were suspected to be involved. 

Respiratory tract conditions 

Several cases of non-responsive downer cows were reported on a Perthshire dairy farm. In all cases blood mineral analysis proved satisfactory possibly due to treatment. Fluke eggs were detected in two of five faeces samples submitted and fluke serology proved positive in four of five blood samples with the fifth result inconclusive. One of the faeces samples was tested for lungworm larvae as the cow had started to cough, with a negative result.

An outbreak of coughing subsequently developed in the cows and three weeks later a cow was submitted for post mortem examination with extensive anteroventral consolidation of the lungs, interlobular oedema and emphysema. A small number of lungworm (Dictyocaulus viviparus)were present. Pasteurella multocida was isolated from lesions although histopathology was suggestive of infection with Histophilus somni. Fluorescent antibody tests (FAT) for respiratory viruses proved negative and histopathology did not indicate any viral involvement. The farmer was advised to treat for lungworm and also started antibiotic treatment.

Four days later a second cow was submitted for post mortem examination with a similar history, one of three cows to die that morning. The gross pathology was very similar to the first case and Histophilus somni was isolated from lung lesions and a small number of dead lungworms were detected. Again, no evidence of viral involvement was found and histopathology indicated an acute, fibrinous bronchopneumonia of bacterial aetiology. 

Reproductive tract disorders 

Abortion due to Salmonella Dublin was a common diagnosis in October. S Dublin abortion was initially confirmed at necropsy of a foetus from a dairy herd in Ayrshire and three further abortions due to S. dublin have now been confirmed in this 90 cow herd over a 16 day period. 

Musculoskeletal conditions 

Stiffness and leg swelling, mostly of hindlimbs, was reported in 15-month-old store cattle recently purchased from a hill herd and housed in a slatted shed in Perthshire. The first affected animal submitted for post mortem examination showed extensive lesions in the right hind leg with severe necrotic cellulitis extending from the hip to just above the hoof. The lesion also extended into the deep tissues of the leg and tracked in the fascia between the main muscle masses. A lesion deep in the muscle tissues on the lateral surface of the leg below the hip in which necrosis had removed all normal tissue to leave a void approximately 10 to 15 cm in diameter raised the suspicion of an injection site infection (figure 1). Necrotic changes were also extensive in the subcutaneous tissues overlying this area. Changes indicative of toxaemic/septicaemic change were evident extensively throughout the carcass. Direct microscopic examinations and cultures of the necrotic tissue revealed a large mixed population of bacteria.

A second animal was submitted 10 days later and the clinical presentation of this case was more typical of the group as a whole. Post mortem examination revealed severe septic and necrotic arthritis in the pedal joints of both hind feet. In each case the lesion was in one of the joints of each pair (lateral in one case and medial in another). In both cases an inflammatory tract could be found extending from the infected joint to the soft tissues of the coronary band. The soft tissues of both hind feet were swollen and inflamed. There was no evidence of the necrotic subcutaneous lesions described in the previous case. A necrotic focus (approximately 10 cms in diameter) was found in the right lung. The origin of the lesion appeared to be an infected embolism within a pulmonary blood vessel. A necrotic vegetative lesion (approximately two centimetres in diameter) was found on the left atrio-ventricular valve. Direct microscopic examinations and culture of the septic/necrotic tissue again revealed a mixed population of bacteria.