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July 2009 RVL Monthly Report

Cattle

Kilkenny examined a four-month old Belgian Blue calf with a history of poor thrive. The calf was considerably smaller in height at the withers than other calves of the same age on the farm. It had been treated for depression and inappetance two days previously. On post mortem examination the animal was emaciated and had lesions of diffuse pulmonary abscessation. No significant bacterial pathogens were isolated.

Kilkenny diagnosed systemic mycosis in a four-month old calf that had been treated for enteritis and had shown some improvement, but then had developed pneumonia and died. Post mortem showed jaundice and focal red areas in the liver, intestine, lung and reticulum. On histopathology these lesions were found to be associated with fungal infection. Tests for bovine viral diarrhoea (BVD) infection were negative.

A two-year old bullock was presented to Athlone. There were multifocal to coalescing cutaneous nodules one to ten centimetres in diameter on the face (figure 1), neck, forelimb, thorax, axilla, inguinal region, flank, ventrum and hindlimb.  The lesions were bilateral. On cut section the skin lesions were pale, firm and had pale striations arrayed perpendicular to the epidermal surface. Some of the lesions were ulcerated and associated with a purulent exudate. Post mortem examination did not reveal any masses in the respiratory, alimentary, urogenital or non-intracranial endocrine organs. Lymphadenomegaly of some of the superficial lymph nodes was noted.  Enzootic bovine leukosis serology (ELISA) was negative. Histopathology revealed lesions consistent with epitheliotrophic cutaenous lymphoma. Sections of enlarged superficial lymph nodes exhibited changes consistent with benign reactive lymphoid hyperplasia. A diagnosis of bovine cutaneous lymphoma was made.

Nodules associated with bovine cutaneous lymphoma

Figure 1: Nodules on the head and neck of a two-year old bullock associated with bovine cutaneous lymphoma (photo: Jim O'Donovan).

Kilkenny diagnosed cerebrocortical necrosis (CCN) in a cow with clinical signs of inco-ordination and blindness before recumbency and death. Two other cows in the group had similar signs and responded to thiamine therapy.

Sligo diagnosed fog fever in a thirty-month old cow at pasture.  There was severe pulmonary emphysema and oedema, mainly in the caudo-dorsal lobes of the lung. The affected areas were very heavy. Pulmonary oedema and emphysema were confirmed on histopathology.

A cow was presented to Kilkenny with a history of having been discovered in extremis- recumbent with cold extremities. Death occurred within hours. The only significant management change reported was the commencement of feeding of spoiled soya bean meal to the cows one week previously. Gross post mortem examination revealed enlargement of the liver with thickening and oedema of the wall of the gall bladder and oedema of the duodenal mesentery. On histopathology there was extensive necrosis of hepatocytes in the midzonal and periacinar areas. The findings were suggestive of a toxic cause of death.

Limerick isolated Salmonella Barranquilla from a faecal sample submitted from a Shorthorn cow. Three cows were affected with severe diarrhoea on the farm over a four-week period. All recovered fully following treatment. Straight citrus pulp was being fed to the cows at the time. It seems likely that a contaminated batch of pulp was imported, as this Salmonella strain is exotic to Ireland. Kilkenny isolated Salmonella typhimurium from an aged cow with profuse diarrhoea. On another farm which had reported cases of severe diarrhoea and milk drop in dairy cows, Salmonella Dublin was isolated from a bulked sample of cow faeces as well as from the faeces of one clinically affected cow.

Kilkenny isolated Pseudomonas aeruginosa from milk of two cows in the same herd. Both cows had a history of recurring mastitis and high bulk somatic cell count. It was reported that there had been a couple of cases of acute toxic coliform type mastitis on the farm during the spring. Pseudomonas spp. is reported as a less common cause of bovine mastitis but has been associated with both per-acute, toxic and chronic, persistent forms of mastitis.

Sheep

Three six-month old Texel lambs which were slightly icteric were submitted to Athlone. There was focally extensive haemorrhaging and oedema within the axillary muscles, and oedema of the lungs. Kidney copper concentrations to be five times the upper limit of the reference range (Kidney Copper 0.05 - 0.18 millimoles/ Kg wet matter). These results were consistent with a diagnosis of copper toxicity.

A six-year old ewe which had lambed two months previously was presented to Dublin for post mortem examination. This ewe, which was out on grass, became increasingly depressed and listless for three days before death, and anaemia was suspected. The main gross finding was of watery brown contents in both the small and large intestine. Parasitology revealed a strongyle egg count of 50,000 eggs per gram. Worm dosing of the remaining ewes in the group was advised.

Pigs

A large encapsulated tumour that had been removed from a five-month old finished pig at routine meat inspection was submitted to Dublin for examination. It weighed 6.5kg and had been situated in the dorsal aspect of the abdominal cavity at the level of the lumbar vertebrae. The external layers of the tumour capsule were closely adherent to the capsule of one of kidneys. When cut in cross section the mass appeared heterogeneous in nature, with large bony spicules interspersed with a soft tissue matrix. Histological examination revealed small hyperchromatic cells present that were forming tubules and primitive glomeruli in places. There was a loose stroma, with bone formation. The tumour was diagnosed as a nephroblastoma. Nephroblastomas are the most frequently occurring tumour in pigs and they tend to grow to a large size. They may contain muscle, bone, cartilage or adipose tissue.

Poultry

Kilkenny diagnosed caecal coccidiosis in a three-week old chicken from a backyard flock where some of the birds were passing blood-tinged droppings. The caeca were dilated with bloodstained faecal contents, and haemorrhages were seen in the caecal mucosa (figure 2).

Dilated caeca associated with coccidiosis

Figure 2: Caeca dilated with haemorrhagic faeces in a three-week chicken with coccidiosis (photo: Donal Toolan).

Limerick diagnosed histomoniasis (blackhead) in a bronze turkey, also from a backyard flock. The bird had been lethargic and had diarrhoea for a few days before death. Three other birds were showing similar signs. On gross examination there were lesions of necrotic enteritis involving the caeca and the characteristic focal necrotic lesions in the liver (figure 3).

Necrotic liver lesions associated with histomoniasis

Figure 3: Necrotic lesions in the liver of a turkey with histomoniasis (photo: Alan Johnson).

Other Species

In early July Cork became involved in investigating the cause of a large number of wild bird deaths on a lake in a public park in Cork city. Four carcasses (1 swan and 4 ducks) were submitted initially. There were some gross lesions in the lung of the swan but nothing of significance in the ducks. Subsequent submissions followed over the next two weeks. The total number of deaths recorded was 50 swans, 50 ducks (mainly mallards) and several fish (carp). The primary clinical presentation in the live birds submitted was muscular flaccidity. A tentative diagnosis of Clostridial poisoning was made. Subsequent laboratory results confirmed the presence of Clostridium botulinum type C toxin in gut contents of affected birds. Kilkenny also diagnosed botulism in a large group of mute swans (Cygnus olor). Clinical signs included inability to walk, flaccid paralysis of wings and of neck resulting in an inability to hold the head erect. The diagnosis was also confirmed by laboratory tests. The outbreak occurred at the same time as the Cork outbreak and resulted in the deaths of approximately fifty swans.