Veterinary Services

Nutritional and metabolic disorders

A four-year-old cow was submitted for post mortem examination to the Edinburgh Centre from a herd reporting thin cows overwinter despite adequate feeding. Fasciolosis was suspected. The cows were at grass with concentrate fed in the parlour and buffer-fed two-year old silage and draff. The cow in question was one of four to show sudden onset inappetence, weight loss and decreased milk yield while passing dry, dark dung. At necropsy the carcass was thin and jaundiced and the abomasum contained a large blood clot due to two bleeding ulcers, 4 to 5 cms in diameter, in the abomasal mucosa.

Histopathology of the liver revealed fatty and hydropic change of metabolic aetiology and confirmed chronic ulceration of the abomasum with no underlying cause evident. However, bile pigment or excess haemosiderin was evident to explain the jaundice. A diagnosis of abomasal ulceration with haemorrhage was made and a previous episode of haemorrhage was proposed to explain the dark dung passed earlier in the week.

A dairy farm with a retained placenta problem submitted blood samples from two groups of six affected and non-affected cows for biochemistry. The only significant finding was the demonstration of hypocalcaemia in five of six affected and one of six non-affected cows. As far as was possible the two groups of cows sampled were at similar stages of lactation suggesting that the hypocalcaemia was not a stage of lactation effect.

 

Toxic conditions

 

Cases of lead poisoning were recorded from four Centres this month in cattle recently turned out to grass. In one example case in the Borders, three calves were submitted over a period of four days for post mortem examination. The first submission was a sudden death suspected to be vitamin E/selenium deficiency. Post mortem changes included forequarter congestion, pulmonary congestion and haemorrhage, epicardial and endocardial haemorrhages and pericardial effusion. A discarded car battery was found in the field and a further two calves were submitted. The calves had not shown typical signs of lead poisoning (acute respiratory distress in one, terminal circling and foaming at the mouth in the other), but tissues were collected to investigate the possibility of lead poisoning. Post mortem changes in the other cases were similar to the first. Lead poisoning was confirmed based on kidney lead estimation in all three calves. The incident was reported to the Food Standards Agency (Scotland) and the remaining 27 calves in the group blood sampled to check lead levels. Four calves with blood levels in excess of 1.21 umol/l were treated with sodium calcium edetate. The car battery had been removed on the day it was found and the ground covered with a door, but advice was given to remove soil from this area to limit further exposure to lead. In total five calves died and a further four were at risk with blood lead levels above the reference range.

A Holstein cow was submitted to the Dumfries Centre, one of three to have died after a short period of anorexia and milk drop. Post mortem examination revealed generalised congestion, emphysema and evidence of fibrosis and slight yellowing of the liver. No pathogens were identified from the case. Histopathology of the liver tissue confirmed fibrosis and biliary hyperplasia and revealed disorganisation of the hepatocytes with nuclear pleomorphism and eosinophilic bodies within the hepatocytes and sinusoids. These changes were considered suggestive of previous fluke damage and the possibility of either aflatoxicosis or copper toxicity was considered. Further blood and faecal sampling from the herd confirmed the presence of active fluke infection and was not suggestive of copper poisoning. A presumptive diagnosis of aflatoxicosis was made and further tests are being carried out on feed samples to investigate the problem further. The herd was being buffer-fed maize silage, considered to be a possible source.

 

Alimentary tract diseases

 

Severe coccidiosis and acute bovine virus diarrhoea virus (BVDV) infection was determined to be the cause of death of four, 9-month-old, dairy heifers submitted to the Edinburgh Centre. Examinations were compromised due to autolysis in two cases however in the other two, there was evidence of severe dehydration, scour and acute loss of condition. In one the intestinal content was watery and the intestinal mucosa congested and thickened from the jejunum caudally with diphtheresis of the caecum and colon. In the other, the lesions appeared to be more acute. The small intestine showed more intense congestion and necrotising enteritis was evident particularly over Peyer’s patches, which were covered with diphtheritic material. The caecum was empty but the colon contained large amounts of congealed blood and the colonic mucosa was thickened. The findings in both animals were considered to be consistent with coccidiosis, however coccidial oocyst counts (on content and mucosal scrapes) and Salmonella cultures proved negative. Histopathology of the intestines of both confirmed widespread gland damage in the large intestine consistent with coccidiosis but revealed widespread crypt damage in the small intestine and lymphoid depletion suggestive of BVDV infection. BVDV type 1 was detected in lymphoid tissues from both animals by reverse transcription polymerase chain reaction (RT-PCR) testing. The BVDV infection was considered to be acute and the presence of a persistently infected (PI) animal within the group was proposed. Screening and culling was advised. Treatment of the rest of the group for coccidiosis had already been undertaken.

A 29-month-old dairy heifer was submitted for necropsy to the Ayr Centre with a history of dysphagia followed by collapse. A piece of wire, possibly from a car tyre, was found in an abscess of a retropharyngeal lymph node from which cellulitis extended to the foramen magnum.

Cases of necrotic enteritis were diagnosed commonly this month, particularly in southern Scotland. In one case a two-month-old Aberdeen Angus bull calf was submitted for necropsy, after being found dead at grass on a Berwickshire farm. It had been observed coughing the day before, but had received no treatment at that time. Bodily condition was found to be good, but there was evidence of black faecal material at the perineum. Internal examination identified mucosal erosions deep within the nasal cavity and at the larynx. Subacute to chronic pneumonia within the cardiac lobe of the lungs was also present. Limited mucosal ulceration was noted in the abomasum, but the most dramatic changes were seen within the ileum, with widespread diptheresis over Peyer's patches, and similar diptheritic lesions extended distally into the caecum and colon. Mannheimia haemolytica was isolated from the area of pneumonic lung, but cultures for Salmonella and tests for BVD viral antigen proved negative. The typical gross findings and negative results for enteric pathogens met the criteria for a diagnosis of necrotising enteritis.

 

Respiratory tract diseases

 

Bacterial pneumonia due to Pasteurella multocida was diagnosed in a two- month-old, dairy heifer, which had died despite antibiotic treatment. The farm had a problem with pneumonia in calves at weaning which was worsening with three recent deaths. The calves were housed in groups of eight and all deaths were confined to one shed, even though ventilation is considered to be good. At necropsy 60% of the lung field was consolidated with fibrinous pleurisy and mucopus present in the airways. Fluorescent antibody tests (FATs) for respiratory syncytial virus (RSV) and parainfluenza type 3 (PI3) virus proved negative and a scant growth of Pasteurella multocida was obtained despite treatment.

 

Reproductive tract conditions

 

An increased incidence of thyroid hyperplasia and iodine deficiency was noted in the south-west of Scotland. In all cases the clinical presentation was of stillbirths and weak calves in spring calving suckler herds with the diagnosis confirmed either by plasma inorganic iodine testing of cows or foetal thyroid histopathology and iodine content.

In one spring calving suckler herd the problem was first diagnosed in March 2005 and iodine supplementation was provided through use of high iodine free access minerals. Problems continued throughout the calving season with 10-15 cases in total and further cases were submitted to the Dumfries Centre. The diagnosis of thyroid hyperplasia was made with histopathological evidence of thyroid follicles devoid of colloid. The thyroid iodine content was 605mg/kgDM (reference range 1200-2000) confirming a diagnosis of thyroid hyperplasia and goitre and no other deficiency or infectious process was identified. Further supplementation of the cows was then advised and it was assumed that the initial levels of supplementation were not sufficient in some cases.

 

Diseases of the circulatory system

 

Acute myocardial infarction was found to be the cause of death in a twelve-month-old, Limousin-cross heifer submitted to the Edinburgh Centre which was clinically hypothermic and bradycardic but did not show neurological signs. The remaining 89 animals in the field were fit and well. At necropsy oedema of the subcutaneous tissues of the brisket and lung and congestion of the cervical tissues was present. The pericardial sac contained a small volume of free fluid and fibrin. The caecal mucosa was congested with an area of fibrous adhesion to a thickened, fibrosed semi-annular lesion of the descending colon. This fibrosed lesion was roughly the size of a grapefruit. The intestinal mucosa was not ulcerated and the colon was not obstructed. A provisional diagnosis of fibrinous pericarditis and chronic peritonitis with fibrosis was made. Histopathological examination of the heart revealed focally extensive coagulative necrosis of the myocardium centred on inflamed and thrombosed blood vessels with inflammation throughout the oedematous perivascular connective tissue. An acute inflammatory infiltrate with congestion, haemorrhage and oedema was evident within the epicardium tracking into the perivascular connective tissue below. Examination of the colonic mass revealed a dramatic, acute peritonitis with extensive adhesions involving the pancreas. The mucosa was unaffected. Although no cause for the peritonitis could be found it was considered to be the source of septic thromboemboli leading to myocardial infarction and death.

 

Nervous system disorders

 

Neuropathological examination revealed changes consistent with louping ill in an eight-year-old suckler cow and a three-four month old calf from the same premises in Perthshire. The disease was suspected clinically in both cases and had already been considered in sheep from the same farm.