September 2005

Current Findings in the Regional Veterinary Laboratories
September 2005
Salmonella Dublin was isolated from placental tissue and stomach contents of an aborted foetus
submitted to Dublin. Four abortions had occurred in a group of twenty heifers from a 100-cow
suckler herd.
Kilkenny examined a five-week old calf that had been born prematurely. There was obvious
abscessation of the umbilical veins with involvement of the liver. No thickening of the navel was
palpable externally. A smear taken at the lesion site showed large numbers of gram-negative coccobacilli. Pasteurella multocida was isolated from liver and lung.
Athlone carried out histopathological examination of the lung of a three-month old calf that had
died with signs of pneumonia. Lesions of post-patent hoose were seen, with a superimposed
suppurative infection. Suppurative emboli were found on gross examination of the liver and kidney.
Cork received a skin biopsy from a six-month old Friesian heifer calf with discrete cutaneous
plaques affecting all of the body except the head (Figure 1). No lymph node enlargement was seen.
Histopathology revealed dermal, densely cellular, non-demarcated, infiltrative sheets of round cells
that resembled lymphocytes/lymphoblasts. The epidermis showed characteristic multifocal clusters
of lymphocytes (Pautrier's microabscesses). A diagnosis of lymphoma was made (cutaneous bovine
sporadic lymphoma). A blood sample tested for Enzootic Bovine Leucosis (EBL) was negative.
Athlone reported yew tree (Taxus baccata) poisoning in a group of weanling heifers. Post-mortem
examination did not reveal any specific lesions, but twigs and leaves of the tree were found in the
rumen contents. Two animals died out of a group of 43. Kilkenny diagnosed ragwort (Senecio
jacobea) poisoning in a yearling heifer that had poor-thrive for some time. Oedema and ascites
were not seen in this case. The diagnosis was made on histopathological examination of the liver.
A thirty-month old heifer showing signs of goose stepping, depression, loss of balance, inapettance,
lack of bowel motility and normal temperature, was identified on active surveillance as a BSE
suspect. The animal was euthanased and the brain was removed in Athlone. Histopathological
examination revealed a choroid plexus carcinoma. This is a rare type of tumour that can lead to
acquired hydrocephalus as a result of the obstruction of the flow of cerebro-spinal fluid. The animal
tested negative for BSE.
Athlone examined a blood sample taken of a five-year old cow that had been pining and inappetant
for a number of weeks. Routine haematological examination revealed anaemia and leucocytosis.
The cow did not respond to treatment and died. Gross post-mortem examination revealed a
vegetative endocarditis involving the tricuspid and bicuspid valves. In addition, small abscesses
were seen in the heart muscle and lungs. Limerick also diagnosed vegetative valvular endocarditis
and pulmonary thrombo-embolism in an 18-month old bullock that collapsed and died as it was
being yarded for routine preventative anthelmintic dosing.
Cork encountered a case of suspect silage gas poisoning in cattle. The case involved a single
wrapped silage bale that had been made in June 2005. The bale was opened while poised on the lift
on the back of a tractor. The group of eighteen-month old cattle were hungry and were nosing the
silage as the plastic was being cut. Four of the cattle nearest to the bale collapsed gasping and
frothing from the mouth. Three animals recovered within minutes, but one died. The practitioner
arrived 20 to 30 minutes after the first clinical signs. The three recovering animals were considered
not in need of therapy. The dead animal was removed to a licensed knackery before a post-mortem
examination could be undertaken. The danger of silage gas poisoning to humans and animals is
well documented. O’Kiely, Turley and Rogers published a paper on the matter in the Veterinary
Record ((1999) 144: 352-353). In this case the livestock owner was unaffected and did not observe
any coloured gas or unusual smells when opening the bale. However, this is not surprising as many
of the gases produced from silage are heavier than air. Many livestock owners follow the
convention of opening silage bales the day before feeding to reduce the risk of ocular listeriosis.
While this procedure removes the potential danger of noxious gases in the bale from the livestock,
the operative would still be vulnerable. Cork encountered a similar condition in pigs that were in
close proximity to a silage pit in June 2000. Nitrogen dioxide poisoning was suspected in that case.
Another case, involving poultry occurred in June 2001. These two cases related to pit silage
enclamped within the previous two days.
Kilkenny diagnosed pneumonia and pyothorax in a two-week old lamb. Arcanobacterium pyogenes was
isolated on routine culture. Mannheimia haemolytica (formerly Pasturella haemolytica) was isolated
by Dublin from multiple tissues taken from two lambs submitted from the same flock, with a
history of sudden death. Histopathological examination of a section of lung confirmed the presence
of an interstitial pneumonia, a finding consistent with a diagnosis of septicaemia caused by
Mannheimia haemolytica.
Parasitic gastro-enteritis was diagnosed by Limerick in a flock of lambs. The lambs had chronic
diarrhoea but were being treated for coccidiosis. Two five-month old lambs with a history of illthrift were submitted to Kilkenny. Both had high parasitic egg counts (>5000 eggs per gram of
faeces). Mannheimia haemolytica isolated from the lungs of one of the lambs.
Cork dealt with two flocks - one free-range layers, the other broiler breeders- in which the majority
of post-mortem findings were of peritonitis. The lesions were considered to have originated in the
cloacal region and to have resulted from vent-pecking injuries. This type of peritonitis was
described previously in the monthly report of April 2004 (Irish Veterinary Journal (2004) 57: 404).
On that occasion the high proportion of extra large eggs being produced was considered to be a
contributory factor. In this occasion the contributory factor in the layers was considered to be poor
feathering while in the broiler breeders the vice had developed in the flock at the restricted-feeding
stage of rearing.
Other Species
Kilkenny examined a six-day old greyhound pup that had been born a few days prematurely. All
eight of its littermates had been stillborn. Gross lesions of pneumonia and hepatitis were seen in the
pup. Staphylococcus intermedius was isolated from these organs. The three-year old dam of these
pups was whelping for the first time; her dam also had a history of litters of pups dying at a few
days old.
A six-month old greyhound examined by Kilkenny was found to have a massive abdominal
haemorrhage. Lesions consistent with canine adenovirus type 1 (CAV-1) were seen on
histopathological examination of the liver.
Limerick investigated high mortality in a group of pet rabbits. Ten rabbits were found dead out of a
group of twenty. Histopathological examination of liver sections showed a diffuse coagulative
necrosis with hyalinisation and individualisation of hepatocytes, marked karyorrhexis and pyknosis.
There was haemorrhage and a low-grade infiltration of neutrophils and lymphocytes into the
sinusoids. The kidneys showed lesions of disseminated intravascular coagulation (DIC). The
changes were consistent with a diagnosis of rabbit haemorrhagic disease (RHD). Kilkenny and
Athlone also diagnosed this disease during the month.
Salmonella typhimurium was isolated from pigeons that were experiencing high mortality in a loft
in the Limerick area. The owner was warned about the zoonotic risks associated with the disease.
Figure 1 “Sporadic cutaneous lymphoma in a six-month old calf – photo WilliamBuckley,
Riverview Veterinary Clinic, Bandon”
Figure 2 “Megaoesophagus in an unweaned greyhound pup– photo Donal Toolan”