Veterinary Services

Nutritional and metabolic disorders

An investigation was carried out into the cause of ill thrift and diarrhoea in a group of 50 dairy cross yearling heifers in Aberdeenshire. They were treated twice over the summer with an avermectin wormer. Vitamin E levels were marginal in all five of the animals tested with a mean of 2.6 µmol/l (reference range 3.0 to 18.0 µmol/l). There was also evidence of selenium deficiency with four of the heifers having glutathione peroxidase (GSH-px) levels ranging from 13.6 to19.7 µ/ml red blood cells (RBC) (reference range ≥23 µ/ml RBC). Pepsinogen levels were elevated suggesting abomasal damage caused by parasites but only one of the heifers had a worm egg count considered to be of significance at 600 strongyle eggs per gram.  At this time of year parasitic burdens are normally pre-patent.

Parasitic diseases

The number of parasitic gastroenteritis cases was double that seen in October 2007.  In one case, the carcase of a six-month–old dairy heifer from an organic farm was submitted to Dumfries for postmortem examination.  The group were wormed with a levamisole product 12 days earlier due to scour problems.  The abomasal mucosa had a morocco leather appearance and histopathology confirmed significant parasitism affecting both the abomasum and small intestine.  The abomasal glands were dilated and distorted with larvae present within some of them.  This could have been due to reinfection or the fact that levamisole is not as effective at removing immature and inhibited larvae as other wormer groups.

A pooled faecal sample from four scouring dairy calves aged six weeks was submitted to Ayr. Very large numbers of pathogenic coccidial oocysts were detected and treatment with an anticoccidial drug was recommended. In addition a few eggs considered to be typical of Toxocara vitulorum were detected. A further two faecal samples were submitted from this group of calves but no further eggs were demonstrated. Monitoring will continue at this farm.

Generalised and systemic conditions

A nine-week-old dairy calf was submitted for postmortem examination from a calf rearer in Perthshire. Necropsy revealed a mild pleurisy with yellow fibrin tags present across the lung surface. The lungs were congested, with consolidation of the cranial lobes and a moderate volume of straw-coloured fluid was present in the abdomen. The liver was mottled throughout the entire parenchyma and had the appearance of a "nutmeg liver". Salmonella Dublin was isolated from the lung, spleen and kidney tissues.

A Charolais bullock aged twenty-one months was submitted to Ayr with a history of fever and inappetance with submandibular swelling. Gross pathology showed a proliferative endocarditis of the right atrio-ventricular valve (figure 1 - see top right-hand side) with right ventricular hypertrophy and excess pericardial fluid. The submandibular swelling was found to be oedema due to venous congestion. No significant bacteria were recovered from the heart valve and tissues, likely due to prior antibiotic treatment.

A six-year-old Friesian cow, the second to die in a week, was submitted to Edinburgh for postmortem examination. Death followed a period of non-specific malaise.  At necropsy a three centimetre wire was present in a tract between the reticulum and the liver with extensive adhesions throughout the anterior abdomen.  There was also anteroventral chronic suppurative pneumonia and pleurisy, with congestion and marked septal emphysema.  Four days later another cow was submitted from the same farm, having been seen with laboured breathing and milk drop before being found dead.  At necropsy fibrinous pericarditis was observed involving the entire heart, and there was vegetative endocarditis of mitral and tricuspid valves.  Metritis was also present.  No wire was found associated with the heart lesions, however three wires almost identical to that found in the first cow were discovered in the abomasum.  Further investigation identified the wires as having been incorporated in reinforced concrete laid on the approach to a silage face.  Mechanical scraping of the concrete had exposed the wires and caused some to be mixed with the silage.

Alimentary tract disorders

A four-month-old Aberdeen Angus suckled calf died after a two week history of scour and lethargy.  Postmortem examination at Dumfries revealed an anaemic and slightly jaundiced carcase. Five, one to two centimetre diameter ulcers were present in the abomasum and in addition there were erosions along the abomasal folds.  The mucosa surrounding the ulcers was discoloured being green/yellow and purple in colour.  Multiple 0.25 cm raised ulcers were found in the distal jejunum and ileum (figure 2 - see top right-hand side) and there was a grey scour.  Mucosal disease was suspected and histopathology supported this possibility. However, tests for Bovine Virus Diarrhoea (BVD) viral antigen and BVD immunohistochemistry were negative.   Histopathology confirmed that the mucosal ulceration was complicated by an invasive bacterial infection.  Escherichia fergusonii was isolated from the abomasal lesions. This organism was considered potentially significant.

On an Ayrshire dairy farm, four deaths occurred in a group of twelve scouring steers. They were treated with a macrocyclic lactone anthelmintic at turnout in May and again in July and September (three weeks prior to death). One of the steers submitted for postmortem examination was in very poor condition and showed signs of dehydration. Severe abomasitis and enteritis were noted on gross pathology and abomasal pH was found to be elevated at 6.7 (reference value < 4.5). No nematode eggs, fluke eggs or coccidial oocysts were detected in caecal contents and no worms were detected in the abomasum or small intestine. Histopathology however confirmed a severe, acute, focally extensive, necro-haemorrhagic abomasitis with intra lesional fungi and severe, chronic, lymphocytic and eosinophilic enteritis. A reactive lymphoid hyperplasia was also present. Although there was no direct evidence of abomasal parasites, the eosinophilic infiltrate and glandular hyperplasia were suggestive of a previous helminth challenge.

Respiratory tract diseases

A severe outbreak of bovine herpes virus type 1 (BHV1) infection occurred in a finishing herd in Aberdeenshire while at grass. Two 16-month-old animals were submitted for postmortem examination by which point five animals died over a ten day period. One bullock had a severe necrotic laryngitis and tracheitis with a thick diphtheritic layer affecting the whole length of the tracheal mucosa (figure 3 - see top right-hand side). Both animals had severe bronchopneumonia and one animal also had a hepatic abscess and rumen acidosis. BHV1 infection was confirmed by fluorescent antibody testing (FAT) and isolation in cell culture. Arcanobacterium pyogenes was isolated from the lungs of both animals, Pasteurella multocida was also isolated from one and Mycoplasma bovis from the other. The group was vaccinated against BHV1 but two weeks later seven animals died over a weekend and animals were still requiring treatment for respiratory disease.

Ayr received samples from a dairy herd experiencing poor milk yields and malaise following a change in feed. Many affected cows were also swishing their tails. Two years previously the herd had an outbreak of infectious bovine rhinotracheitis (IBR) but no vaccination policy was currently in place.  First and second lactation cattle were most markedly affected in the current incident with many pyrexic and some seen salivating excessively. Initially no ocular or nasal discharge was evident although some were seen to have vaginal ulceration. Three days later a few animals were noted to have a nasal discharge. Acute serology of five animals showed all to be seronegative for BHV1. Four nasopharyngeal swabs were also negative for BHV1 on FAT. BHV 1 was however isolated in cell culture from one of the submitted swabs. On farm rumenocentesis was performed on three cows and all had pH values less than 5.5 suggestive of concurrent subacute ruminal acidosis. It was postulated that a dietary upset had caused older cattle latently infected with IBR to start shedding the virus.

Musculo-Skeletal Conditions

Two 18-month-old Limousin cross cattle were euthanased and submitted for postmortem examination.  This was to investigate the cause of lameness affecting cattle on slats. One of the animals fell through the slats two weeks previously and had a large, open, infected wound on the medial aspect of the right hind leg, exposing 10 to 12 centimetres of the tibial shaft. There was extensive under-running of the skin away from the wound due to tracking of infection. There were a number of other smaller infected wounds on the skin. There was also foul-smelling, greyish-brown, opaque, purulent fluid in the left stifle. Advice was given relating to animal welfare. The other animal had a large area of necrotic, infected tissue in the brisket region. This extended subcutaneously up the neck and in towards the sternum. Arcanobacterium pyogenes and Bacteroides melaninogenicus were isolated in culture from the affected region. There was also excess cloudy fluid with some fibrin in the right stifle and excess cloudy yellow fluid in the right carpus. No significant organisms were isolated in culture from the joints.