Current Findings in the Regional Veterinary Laboratories
March 2005
Leptospira hardjo titres in post abortion sera samples.
Dual infection with Mycoplasma bovis and Pasteurella multocida in two calves
Psoroptic mange in housed cattle.
Hypocalcaemia in blood samples from cows.
Post-parturient haemoglobinuria in a herd of dairy cows
A positive titre to Toxoplasma gondii and associated histopathological lesions in the brain of a
lamb
Screening tests on placentae were consistent with a diagnosis of Enzootic abortion
Deaths in lambs associated with administration of an anthelmintic
Sheep faecal samples found positive for coccidiosis,
Infectious Canine Hepatitis in a Grehound Pup
Bovine
Athlone found that 10.6% of the post-abortion maternal serum samples tested for Neospora
caninum antibodies were positive. 5.8 % of the serum samples tested for Salmonella dublin
antibodies had significant titres, and 47.3% of the samples tested for evidence of Leptospira hardjo
antibodies had positive titres, three quarters of which were classified as low positives.
Leptospira hardjo was identified on fluorescent antibody test of tissues from a foetus submitted to
Cork. The undersized fresh foetus was just two weeks short of full-term. It was the fourth abortion
in a group of unvaccinated dairy heifers. Arcanobacterium pyogenes was isolated by Dublin from
aborted foetuses from two herds. Histopathological examination revealed a suppurative
bronchopneumonia in both foetuses, indicating bacterial infection had occurred in-utero before the
death of the foetus. Cork isolated Streptobacillus moniliformis from an aborted dairy calf. This
organism is harboured by rats and is a zoonotic agent with potential to cause in humans rat bite
fever or fever from ingesting contaminated water of milk. There was one other abortion in the herd
but this was negative for bacteria, and no untoward symptoms in the household personnel were
reported. Limerick diagnosed septicaemia in a two-day old calf. Streptococcus dysgalactiae was
isolated in cultures from all viscera sampled, including the brain. Dublin diagnosed extensive
peritonitis, caused by Arcanobacterium pyogenes, arising from an ascending infection from a navel
abcess in a three-day old calf with a history of sudden death
Salmonella dublin was isolated by Athlone from the liver and intestinal contents of a six-day old
calf that died following a short period of intense muscular tremors. The umbilical vessels were
infected in this case and were the most likely route of entry.
Limerick diagnosed toxic tubular damage associated with eosinophilic granular material in the
kidneys of two two-week old calves from one herd. The history was of pining. The source of the
toxin could not be determined.
Dual infection with Mycoplasma bovis and Pasteurella multocida was detected by Dublin in two
four-week old calves submitted from the same herd. Both calves had bronchopneumonia with areas
of lung consolidation containing multifocal approximately one-inch diameter white foci of necrosis.
One of the calves in addition also had diffuse pleurisy and “bread and butter” like pericarditis. An
apparent ability to cause a synergistic pathogenic effect has been reported before for Mycoplasma
bovis when it occurs in combined infection with another respiratory pathogen.
The laboratory service accepted 746 calf faecal samples for analysis during the month. 261 (35.0%)
were positive for Rotavirus, 139 (18.6%) for Cryptosporidia, 30 (4.0%) for Salmonella spp., 13
(1.7%) for Coronavirus, 9 (1.2%) for Coccidia, and 5 (0.7%) for E. coli K99. It is important to note
that these samples were taken from calves varying in age from around one day to two months old
and that the age of the calf was used to determine which tests were carried out in each laboratory.
Sligo reported that a six-week old suckler calf, which had died of acute haemorrhage from a
bleeding abomasal ulcer, also had 3-4 small spherical caseous lesions (each 2-3 mm in diameter) in
the liver and one in the spleen. What appeared to be similar lesions, but flatter and confluent with
each other, were also noted under the diaphragmatic peritoneum, which was in contact with the
liver. These lesions were identified as tuberculous granulomas by histopathological examination.
Lead poisoning was diagnosed by Athlone in a six-week old calf, the second sudden death on the
farm.
Athlone reported TB in an eleven-month old weanling. The animal was presented for post-mortem
after a short illness and a history of ill-thrift. Acute pneumonia and pericarditis were evident on
gross examination. A mediastinal lymph node was enlarged. Histopathological examination
revealed granulomatous lesions, consistent with a diagnosis of TB which was probably incidental to
the pneumonia and pericarditis.
A ready-to-slaughter Simmental/Friesian cross bullock found dead, was necropsied by Cork. The
cartilage in the lower part of the trachea was incomplete and curled into the lumen with
invagination of the dorsal membranous tissue. This defect would appear to have compromised
breathing and asphyxiated the animal. The upper trachea was normal (Figure 1).
The large outbreak of Psoroptic mange in housed cattle from a sixty-cow suckler herd that was
reported by Sligo last month, has improved remarkably (Figure 2). Treatment with moxidectin
(Cydectin subcutaneous injections) and cypermethrin (topical washing with 'Ecofleece') appears to
have been effective.
Limerick noted hypocalcaemia in blood samples submitted from dairy cows in the peri-parturient
period. Some of the submissions were from cows with suspect or clinical milk fever signs. In other
cases blood samples were taken as part of investigations into stillbirth problems. Because of the
large number of stillbirths that are submitted to the RVLs and because of the poor return in
determining the aetiology from post-mortem examination alone, practitioners are being encouraged
to submit blood samples from cows in the peri-parturient period.
Cork diagnosed post-parturient haemoglobinuria in a herd of dairy cows. The
hypophosphataemia found in the cows was considered to have been due to the selective
consumption of large quantities of pressed beet pulp that had been available ad lib along with
silage. Bloods submitted to Limerick from a separate outbreak of post-parturient haemoglobinuria
did not confirm a hypophosphataemia. Beet pulp was also a major component of the diet in this
case.
Bacillus cereus was isolated in Sligo from five cows in a 45-cow dairy herd with persistent high
somatic cell counts. There were no cases of clinical mastitis. This zoonotic bacterium can cause
diarrhoea or vomiting in humans, if ingested. The symptoms caused by Bacillus cereus can mimic
the so called "winter vomiting bug", with nausea and diarrhoea starting from a half hour to six hours
after ingestion, and rarely lasting more than a day. The herd owner was reminded not to consume
unpasteurised milk.
Athlone reported that a thirty-month old cow that died five days after calving and was the fifth such
death this year, showed lesions consistent with malignant oedema. There was also a very severe
metritis in the cow.
Ovine
Salmonella dublin was isolated from two aborted lambs submitted to Kilkenny from the same flock.
One of the lambs had a positive titre to Toxoplasma gondii and associated histopathological
lesions in the brain. High titres to Toxoplasma gondii were found in blood samples examined in
Limerick from ewes in a flock with a high percentage of late abortions and stillbirths. Dublin
investigated an abortion outbreak in a sheep flock with an abortion rate in excess of 5%. The
incidence of abortion had reduced after the administration of long-acting oxytetracycline. Initial
screening tests on placentae were consistent with a diagnosis of Enzootic abortion
(Chlamydophila abortus). As available tests are not completely specific for Chlamydophila abortus
it has been recommended that serological testing of the flock be undertaken to confirm the
diagnosis. Campylobacter species were isolated by Dublin from the stomach contents and placentas
of four lambs from another sheep flock with a high incidence of abortion. Further testing is being
undertaken to identify the species..
Sligo is investigating the death of thirty lambs on a farm in Co. Mayo. The deaths occurred within
five days of the administration of an anthelmintic (containing albendazole, selenium, and
cobalt). This farm routinely doses and moves ewes and lambs to fresh pasture on an out-farm in
June. All animals would get the same volume of anthelmintic. The move was made much earlier
this year. The same volume of drench was given, despite the fact that the lambs were much lighter
in weight. The drench was also changed from a fenbendazole-based product to an albendazolebased one. Albendazole has a narrower margin of safety than most other benzimidazoles ('white
drenches') and accidental poisoning with this product has occurred in the past. Preliminary findings
suggest that the youngest lambs received a dose that was about ten times the recommended dose
rate. Sligo isolated Erysipelothrix rhusopathiae from the liver and spleen of a lamb that showed
gross lesions of septicaemia at post-mortem examination.
Athlone detected liver fluke eggs in one out of 21 ovine faecal samples examined during the month.
Seventy per cent of faecal samples examined were found to be positive for coccidiosis, with
infections varying from mild to severe. Kilkenny diagnosed twin lamb disease in a three-year old
pregnant ewe that had a history of inappetance and isolation from the rest of the flock. The ewe was
found to be carrying two large lambs, had a pale liver and a ketonuria. A four-year old ewe was
presented to Sligo with a history of blindness and circling with short clinical course. Only a
moderate ketosis was detected on post-mortem examination (possibly due to inappetence).
Histopathologically in the brain there were multifocal small abscesses, containing bacteria. These
were mainly confined to the frontal lobes. Gram stains of the lesions identified gram-positive cocci
(probably Staphs).
Equine
Equine herpes virus 1 was detected in an aborted foal submitted to Cork. Post-mortem examination
by Limerick of a one-day old foal that showed ‘Dummy foal’ like symptoms was found to have a
ruptured liver with haemorrhage into the peritoneal cavity.
Porcine
Sligo reported that Pasteurella multocida was isolated from the lungs of a weaner pig with an acute
necrotising bronchopneumonia. Gross and bacteriological examination of weaners from one herd by
Cork also established a diagnosis of bronchopneumonia. Pasteurella multocida was isolated.
Further tests showed lymphoid depletion in this case and when circovirus (PCV2) was
demonstrated by immunostaining, post weaning multisystemic wasting syndrome (PMSWS) was
diagnosed.
Avian
Sligo examined four adult free-range hens in a mixed species flock that died acutely after a chronic
wasting illness. On post-mortem examination three of the four birds had ruptured livers and
intraperitoneal haemorrhage. Histopathologically lesions were consistent with diffuse hepatic
tuberculosis. The history given could not explain the presence of high titres to infectious bursitis in
these birds, which were said to have been unvaccinated.
Other Species
A greyhound pup aged ten weeks examined by Cork was jaundiced on gross examination.
Histopathology revealed lesions of infectious canine hepatitis. Sligo diagnosed paraquat/diquat
poisoning in a seven-year-old greyhound bitch, which had been submitted with a history of acute
respiratory distress and haemoptysis.
CAPTIONS FOR PHOTOS
Figure 1 “Sections of upper and lower trachea of a bullock – photo Pat Sheehan”
Figure 2 “Psoroptic mange in a suckler cow – photo Michéal Casey”