Current Findings in the Regional Veterinary Laboratories
APRIL 2006
Cattle
Cork diagnosed the neonatal form of infectious bovine rhinotracheitis (IBR) in a
pedigree suckler herd. The fourth loss of a calf one-week old was submitted and there
were lesions of necrotic pharyngitis, laryngitis and papillae on the epithelium of the
oesophagus. IBR was diagnosed using a polymerase chain reaction (PCR) test carried
out by virology division in Backweston. This neonatal form of IBR was seen first in a
pedigree Friesian herd in the Cork area in the spring of 1987, and was seen again in
the following two years in commercial dairy herds. No outbreak has been documented
since. All of the outbreaks have occurred in East Cork. The cause of death is usually
inhalation pneumonia. If that is avoided the calves will die of a viraemia, with
pneumonia and necrotic foci diffusely distributed throughout the liver. Kilkenny also
diagnosed IBR-associated pneumonia in a one-week old calf.
All laboratories examined a large number of neonatal calves, many with a history of
diarrhoea. Rotavirus and Cryptosporidium parvuum continued to be the most
frequently identified neonatal enteritis pathogens. Kilkenny diagnosed
colisepticaemia in calves under one-week old. Fibrin was found in the joints of many
of these calves, even though gross swelling of joints was not obvious. A common
finding in the calves was a low zinc sulphate turbidity (ZST) test, indicating poor
absorption of colostrum antibodies. Cryptosporidia infection was detected by Dublin
in a ten-day old dehydrated Friesian heifer calf with a history of diarrhoea. The calf
had come from a herd in which eleven of twenty calves had died.
Cork investigated the sudden death of six housed yearlings. Death by electrocution
was strongly suspected. A faulty underground cable was subsequently found to have
resulted in electric current being present in the rail of the automatic scraper. Athlone
diagnosed lymphosarcoma in a yearling with generalised lymph node enlargement.
Athlone reported a high incidence of uterine prolapse in first-calving Limousin
heifers from one herd. Five heifers out of a total of twelve had prolapsed after calving.
The results of blood biochemistry tests from animals in the herd were not conclusive,
with generally low serum copper values and one low serum calcium level.
Investigations are ongoing. Two cows were submitted from a dairy herd in west
Limerick where a number of cows had shown signs of depression, blindness,
incoordination and recumbency within weeks of calving. Examination of both cows
showed lesions of type 2 ostertagiasis, and one cow also had chronic localised
peritonitis associated with a foreign body. No significant bacterial pathogens were
isolated on routine culture but histopathological examination of brain tissue from both
cows showed changes strongly suggestive of listeriosis. At least seven deaths have
occurred in the herd to date. Psoroptes communis spp. was detected in skin scrapings
submitted to Limerick from cows with severe pruritis primarily affecting the shoulder
region. Limerick diagnosed chronic copper poisoning in a six year-old cow. The cow
had shown signs of inappetence and depression for two days. Gross post-mortem
examination showed lesions of anaemia, jaundice, haemoglobinuria, hepatitis.
Histopathology of the liver showed severe portal tract fibrosis, bile duct hyperplasia
with disruption of the limiting plate and scattered necrosis and apoptosis of
hepatocytes. Liver copper analysis gave a reading of 8.19mmol per kilogram wet
matter (normal range: 0.06-2.50mmol/Kg).
Sheep
Limerick diagnosed toxoplasmosis in aborted lambs submitted from one flock.
There were about 80 hoggets in the flock, about half of which had been purchased.
Ten of the eighty had aborted within four weeks of full-term. Necrotic foci were seen
in the placental cotyledons (figure 1) and serological examination of foetal thoracic
fluid samples using a latex agglutination test confirmed the diagnosis.
Dublin isolated Mannheimia haemolytica from the lungs of two six-week old
lambs submitted from a flock experiencing a large number of losses. At post-mortem
examination there was consolidation of approximately two-thirds of the lung tissue,
with a cranio-ventral distribution. A severe fibrinous pleurisy was seen in one of the
lambs. There was also evidence that the lambs had been suffering from diarrhoea and
further investigation revealed that there was a significant coccidial infection.
Kilkenny diagnosed urolithiasis in a ten-week old lamb from a flock where six
others had already died. According to the flock owner, the ‘hind legs go soft’ in
affected lambs. On post-mortem examination there was rupture of the urethra with
leakage of urine into the connective tissue of the ventral abdominal wall. There was
also some peri-renal haemorrhage and calculi were found in the bladder (figure 2).
Cork diagnosed chronic copper poisoning in a flock where 22 sheep had died over a
two-week period. Gross lesions, consisting of generalized jaundice, bronze kidneys
and haemoglobinuria were observed in the carcass submitted. An elevated liver
copper level of 4.31mmols per kilogram wet matter confirmed the diagnosis. The
sheep were being fed a beef ration and sheep are considered to be far more susceptible
to copper poisoning than cattle.
Poultry
Ascites caused by right ventricular failure was diagnosed in a broiler flock in
north Cork. A domestic free-range hen submitted to Limerick for avian influenza
testing was found to have died from peritonitis, the result of a nail penetrating the
gizzard wall.
Other Species
Multiple Herring Gull (Larus argentatus) deaths over one weekend were
investigated by Cork. Gross post-mortem examination revealed that the birds had no
evidence of disease, but had recently consumed grains of wheat and had died from
drowning. Following negative avian influenza results a representative sample of
stomach contents were analysed for the presence of alphachloralose by the
Department of Chemistry in the Cork Institute of Technology. Significant
concentrations of the poison were found to be present. Alfachloralose is legally sold
in Ireland as a ‘crow and pigeon poison’, but is banned in many other European
countries.
CAPTIONS FOR PHOTOS
Figure 1 “Placental lesions associated with ovine toxoplasmosis – photo Dave Kelly”
Figure 2 “Urinary calculi in the bladder of a ten-week old lamb – photo Donal
Toolan”