Current Findings in the Regional Veterinary Laboratories

Current Findings in the Regional Veterinary Laboratories January 2007 Cattle Sligo investigated an outbreak of abortion in a 45-cow dairy herd. There was a history of cows being scanned in calf, but subsequently returning to oestrus. Five foetuses were presented for postmortem examination. Bovine viral diarrhoea (BVD) virus was detected in one of these foetuses, while there was histological evidence of BVD infection in the brain of another foetus. Serology revealed widespread seroconversionl to the virus. The owner of a herd from which an eighth-month foetus was submitted to Cork, had developed pinhead sized pustules on a forearm. Although wearing gloves when assisting the cow in the delivery, the teeth of the calf tore the glove on that arm. The description of the arm lesions fitted those described for dermatitis in humans caused, in similar circumstances, by both Salmonella dublin and Listeria monocytogenes (Williams, 1980). However, neither of these bacteria was detected in the foetus. Staphlococcus aureus was isolated. Salmonella enteriditis was isolated by Dublin from the stomach contents of a foetus submitted from a farm where five heifers had aborted. Three faecal samples submitted from the same heifer group also cultured positive for the pathogen. Faecal cultures from poultry on the farm were negative for Salmonella spp.

Joint ill associated with colisepticaemia was diagnosed by Kilkenny in a five-day old calf. Fibrin tags were found in many joints, but no joint swelling was obvious. Escherichia coli was isolated from the liver and spleen but not from the joints. A zinc sulphate turbidity (ZST) test result of 7 units was considered to be very low, an indication of poor absorption of colostrum antibodies. A ten-day old calf presented to Athlone following an acute illness also had a low ZST reading of 15 units. Salmonella typhimurium (a zoonotic agent) was isolated from multiple organs.

Listeriosis was diagnosed by Sligo in an eight-month old weanling heifer. The animal was the second of the group to die with a history of neurological signs. A ten-month old weanling was submitted to Limerick with a similar history. The animal had been diagnosed with meningitis as a calf. It had responded to treatment but had lost the sight in one eye. Recently the animal had shown stiffness, which progressed to ataxia and eventual recumbency. The animal was euthanased and postmortem examination revealed a large abscess in the cerebrum (figure 1).

Twenty-month old heifers slaughtered for the local trade in West Cork were found on routine veterinary inspection to have heavy burdens of the rumen fluke, Paramphistomum cervi (figure 2). The heifers were from one farm, but not all animals from that farm had a heavy infection. The parasites are usually considered to be of little veterinary significance in temperate climates, but can cause disease in the tropics and subtropics, with diarrhoea being the most common clinical presentation. In this case the herd owner was adamant that the animals with heavy burdens were not in as good a condition as the others.

Athlone reported warfarin poisoning in a dairy herd where three pregnant dry cows on an out farm were found dead. One animal was submitted for postmortem examination and this showed diffuse haemorrhage. Bracken poisoning was initially suspected but the owner ruled this out as the cows were housed and being fed whole- crop maize silage. Further investigation revealed that the owner had placed rat poison in top of the silage pit to try to control a rat problem. It is likely that this fell into the silage face and was inadvertently fed to the cows. No further deaths occurred.

Sheep Athlone diagnosed Campylobacter (Vibrio) abortion in a flock of ewes. The organism was cultured from one foetus but the pathognomonic liver lesions were not seen at gross examination.

Limerick investigated high mortality in two-day old lambs. The lambs were housed, were healthy at birth and suckled well. Postmortem examination showed lesions of acute enteritis and dehydration. Enterotoxigenic Escherichia coli (K99 positive) was isolated on culture. ZST tests showed that adequate immunoglobulins had been absorbed.

Urolithiasis with urethral obstruction at the vermiform appendage leading to bladder rupture and intra-abdominal haemorrhage was the finding in two ram lambs presented to Sligo. Cork examined a nine-month old lamb, unable to stand for a week. The lamb had a severe parasitic infestation of strongyles, coccidial oocysts and tapeworms. Many cysts (presumably Toxoplasma gondii) along with lesions of non- suppurative encephalitis and vasculitis were observed histologically in several brain sections.

Kilkenny diagnosed listeriosis in two hoggets that had a history of circling, drooling, and eventual recumbency. Ten of 1,500 animals had died with similar signs over a 24- hour period. Listeria monocytogenes was isolated from one but both showed the characteristic histopathological brain lesions. The second hogget also had lesions of pneumonia from which Mannheimia haemolytica was isolated.

Pigs Kilkenny found gross lesions of necrotic enteritis and pneumonia in 12 to 40 day old pigs from one piggery. The history was of poor thrive in approximately 10 per cent of post-weaning pigs. Salmonella typhimurium was isolated and porcine circovirus 2 (PCV2) was demonstrated using tissue immunohistochemistry. Histopathological findings included interstitial pneumonia, interstitial nephritis and granulomatous enteritis.

Poultry Colibacillosis was diagnosed by Sligo in two batches of day-old chicks from separate flocks in east Mayo. The chicks had originated from the same hatchery.

Other Species Limerick diagnosed tuberculosis (TB) in a four-year old lactating goat. The goat had died after a short illness, with signs of acute diarrhoea and colic. Death was linked to ruminal acidosis (rumen pH 4.5), the result of grain engorgement. Lesions of chronic necrotic pneumonia, with pleurisy and pericardial adhesions were also seen. Culture yielded a growth of Mycobacterium bovis. The local district veterinary office was notified and the herd, which included cattle, was restricted. Limerick diagnosed leptospirosis in an eight-week old pup that died after a short period of convulsions and collapse. The principal lesions noted were anaemia, jaundice and widespread petechiation. The diagnosis was made on histopathology. A skin scraping from three-year old pruritic dog with suspected ringworm was found by Kilkenny to contain large numbers of adult Demodex mites.

References Williams, E. (1980). British Medical Journal. 280: 815-818.

CAPTIONS FOR PHOTOS Figure 1

“An abscess in the cerebrum of a ten-month old bovine weanling – photo Alan Johnson” Figure2

“Adult paramphistomes in the rumen of a 20-month old heifer – photo Pat Sheehan”

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Athlone examined a two-week old calf presented with a history of respiratory distress that initially responded to treatment, but relapsed. Postmortem examination revealed a laryngeal abscess that had caused occlusion of the airway. Kilkenny isolated Mannheimia haemolytica and Haemophilus somnus from a seven-week old calf with a history of pneumonia. Three two-month old calves were presented to Sligo from a 50- cow suckler herd with a history of high calf mortality. The calves were born outside in November, but were housed in a creep area beside the dams at the time of death. The ventilation in the creep area was considered insufficient, due to the wide span of the shed and the lack of sufficient air outlets. An additional four calves died on the farm over the following week. Mannheimia haemolytica was isolated from two of the calves, and Salmonella Dublin was isolated from the third animal. Two of the calves had histological evidence of haemorrhagic enteritis. No respiratory virus was detected using tissue polymerase chain reaction (PCR) tests. Kilkenny isolated Mycoplasma bovis from the joint of a six-month old calf with swollen joints and abscessation of the lung.

Athlone reported mucosal disease in a group of four-month old weanlings from a dairy herd. There was a clinical history of pyrexia, diarrhoea and buccal ulceration. Postmortem examination on one animal showed more extensive ulceration along the alimentary tract. A BVD virus isolation test was positive.

Kilkenny examined an eleven-month old heifer that had developed submandibular and brisket oedema, and had stopped eating. A large (seven centimetre diameter) lesion, from which Staphylococcus aureus was isolated, was found on the right atrio- ventricular heart valve. There was also hydrothorax, ascites and passive congestion of the liver. A yearling bull was submitted to Athlone with a history of lameness in the hind limbs, which progressed to a forelimb before death. Gross post mortem examination revealed an abscess involving the right ventricular wall of the heart and the pericardium. There were also multiple micro abscesses in the lungs, necrotic infarcts in the kidney and extensive purulent lesions between the large muscle bundles of the two hind limbs. An eighteen-month-old heifer from a feedlot unit was presented to Athlone following sudden death. Post mortem examination revealed abscessation of the posterior vena cava and liver. This was the second such diagnosis from this farm. Other animals submitted from the same feedlot have presented with diverse intestinal problems and low pH readings for the ruminal contents, suggesting a herd sub-clinical acidosis problem.

Athlone also diagnosed listeriosis in hoggets during the month. Dublin diagnosed listeriosis in two ewes that had presented with nervous signs in late pregnancy. Both ewes were carrying twin lambs and were in good body condition. Gross postmortem findings were unremarkable. Histopathology confirmed the presence of peri-vascular lymphocytic cuffing and micro-abscessation in the cerebellum and brain-stem. Listeria monocytogenes was isolated on culture of spinal cord from one of the cases.

The sudden death of an eleven-month old greyhound examined by Cork was due to cardiac tamponade following rupture and haemorrhage from an aneurysm at the base of the aorta.