March 2006

Current Findings in the Regional Veterinary Laboratories
March 2006
Listeria moncytogenes was isolated from the stomach contents of an aborted bovine foetus
submitted to Dublin from a herd where Neospora caninum was also recently diagnosed as causing
abortion. This case illustrates that multiple infectious abortefacients can be present in a herd and
emphasises the need for continued investigation of all abortions in a herd.
Limerick isolated Yersinia enterocolitica from a day-old calf with lesions of polyserositis. The
appearance of the lesions suggested intra-uterine infection. Clostridium perfringens was isolated on
culture from an eight-day old calf with emphysematous abomasitis. Limerick and Athlone
diagnosed torsion of the abomasum in calves less than four weeks of age. A necrotic focus in the
basal ganglion region of the brain of a three-day-old calf submitted to Limerick was associated with
Escherichia coli endotoxemia (figure 1).
Calf faecal submissions typically reach a peak in March. Figure 2 illustrates the isolation rates for
the major enteric pathogens encountered.
Limerick diagnosed patent interventricular foramen in a ten-day old calf with a history suggestive
of cardiac failure. Two calves, one month and two months of age, from the same herd, that had died
within three days of each other were submitted to Cork. Each had cardiac dilatation, congested
and enlarged liver, moderate ascites and pulmonary interstitial oedema. In addition, one of calves
also showed severe pericardial fibrinous adhesions from which Listeria spp. was isolated.
Microscopic examination revealed changes in the heart consistent with cardiomyopathy and lesions
in the liver consistent with chronic passive congestion. The same bull sired the two calves, and a
congenital cardiomyopathy was suspected. The Listeria spp. was considered an oppertunistic
invader. Dual infection with Mycoplasma bovis and another respiratory pathogen was detected
by Dublin in pneumonic calves from two different herds. Mycoplasma bovis and Arcanobacterium
pyogenes were isolated from a three-month old Charolais calf, which had a bronchopneumonia of
cranial and cardiac lung lobes, and pleural adhesions. Five of thirty calves had died in this suckler
herd. Mycoplasma bovis and Mannheimia haemolytica were isolated from a three-week old,
Limousin bull calf, from another herd, which had a suppurative bronchopneumonia affecting all
lung lobes. Three recently purchased calves had died in this herd. Histophilus somnus was isolated
in Limerick from a five-week-old calf with lesions of chronic suppurative pneumonia.
A three-week old bought-in calf was submitted to Limerick from a herd where a number of deaths
had occurred linked with clinical signs of diarrhoea and septicaemia. Salmonella typhimurium was
isolated on culture. The herd owner was advised on the zoonotic risks associated with the disease.
Kilkenny also isolated S. typhimurium from a month-old calf with a history of scour and poor
thrive. Terminal dry gangrene was seen in a three-week old calf presented to Limerick. The herd
history and the lesions suggested salmonellosis. Bacterial cultures proved negative but this was
thought to relate to the stage of the infection. Athlone reported Salmonella Dublin in a number of
submissions. Faeces from a week-old calf with enteritis yielded S. Dublin. The bacterium was
also isolated from a two-week old calf with omphalitis, diffuse fibrinous peritonitis and
septicaemia. In this herd a salmonella vaccination programme was in place. In another herd, five
bought-in calves of five weeks of age all presented clinically with diarrhoea, dehydration and
septicaemia. Three of the calves died, one of which was examined by Athlone, where S. Dublin was
Athlone reported rumenal acidosis in a four-week old calf with no clinical history other than
sudden death. The diet consisted of whole milk from a group feeder and meal ad libitum.
Engorgement was suspected.
Athlone reported yew (Taxus baccata) poisoning in a seven-month old weanling. The animal was
found dead and was the third of the group to die. Pointed and flattened yew foliage was found in the
rumen. A follow-up investigation found that a tree on the rented farm where the animals were
grazing had fallen in a storm.
Post-mortem examination of a three-year old cow with a history of recumbency after calving was
found by Limerick to have fractures to the left and right ilial shafts of the pelvis. Blood samples
submitted to Limerick from a dairy herd with signs of post-parturient haemoglobinuria showed very
low serum inorganic phosphorus levels, and pronounced anaemia. The cows were on a diet
containing high levels of beet pulp. Wexford District Veterinary Office (DVO) referred a cow with
suspect tuberculous mastitis to Kilkenny for post-mortem examination. Gross lesions of
tuberculosis were found in lung, lymph nodes, pleura and udder. There was very extensive
involvement of udder tissue in all four quarters (figure 3). Suspect lesions of tuberculosis were also
seen in the uterus. Results of TB culture tests are awaited. Infectious bovine rhinotracheitis (IBR)
was diagnosed using a fluorescent antibody test (FAT) in two herds of dairy cows in which cows
after calving were showing high temperatures, pneumonia and coughing. At post-mortem
examination in Athlone, one cow from each herd showed severe catarrhal tracheitis (figure 4) and
lobar pneumonia. In one case Arcanobacter pyogenes was also isolated from affected lung tissue.
Athlone linked enterotoxigenic Escherichia coli (K99) infection with the deaths of a number of
three-day old lambs submitted from a 100-ewe flock where twenty deaths had been recorded to
date. All lambing had taken place indoors and the lambing season had been coming to an end when
the problems began.
Two seven-day old lambs were submitted to Kilkenny with a history of being unable to rise. There
had been no response to antibiotic treatment. Examination revealed yellow pus in multiple limb
joints, although the joints were not obviously swollen. Streptococcus agalactiae was isolated from
all joints cultured.
Other Species
During the month of March, Dublin alone examined 70 wild birds including, swans, ducks, gulls,
terns, gannets, geese, a guillemot, a cormorant, a moorhen, a ganser and a parrot, which were
submitted by veterinary inspectors from local DVOs following calls by the public to the avian
influenza help-line. All samples tested by virology division in Backweston were negative for the
virus. While the cause of death could not be diagnosed in all cases due to varying degrees of carcass
preservation, many birds had obvious signs of injury or predation. Athlone diagnosed myocarditis
of unknown aetiology in a swan that was submitted as part of the national avian flu surveillance.
Limerick carried out post-mortem examination on a twelve-year old mare that had a history of
unexplained weight loss over the previous twelve months. The immediate cause of death was
rupture of the bowel but this was associated with a large mesenteric tumour that Histopathological
examination revealed to be a fibroma.
Figure 1 “Necrotic focus in the brain of a three day old calf– photo Dave Kelly”
Figure 2 Major Calf Scour Pathogens Identified During March
Figure 3 “Tuberculous mastitis in a cow– photo Donal Toolan”
Figure 4 “Severe tracheitis in a cow associated with IBR infection- photo John Fagan”