Current Findings in the Regional Veterinary Laboratories
March 2008
Cattle
Diffuse mutifocal non-suppurative encephalitis consistent with a diagnosis of
Neospora caninum infection was seen in an aborted bovine foetus submitted to
Dublin. Multifocal hepatic necrosis was observed by Dublin in a bovine foetus,
associated with Bovine Herpes Virus 1 infection. The antigen was detected in a
sample of pleural fluid, using a polymerase chain reaction (PCR) test. The pleural
fluid was negative for BHV-1 antibody. In BHV-1 abortions, the foetus usually dies
so quickly that there is no evidence of foetal antibody production.
A ten-day old calf that died suddenly and was submitted to Kilkenny had an
enlarged, rounded heart with complex congenital malformations. Two fingers could
be put through a defect in the atrial septum. The left ventricle was small and was not
connected to the aorta. The aorta was narrow and arose from the right side of the
heart. The aorta widened after it was joined by the ductus arteriosus. The main
systemic blood flow came from the right side of the heart, through the pulmonary
artery, patent ductus arteriosus and aorta.
A four-week old calf with bilateral segmental necrosis (dry gangrene) distal to the
metatarsal joint was euthanased on humane grounds and submitted to Cork for
examination. Salmonella dublin was isolated from all organs. Sligo diagnosed severe
peritonitis as a result of a perforated abomasal ulcer in a calf with a history of sudden
death. Coccidiosis was diagnosed by Dublin in four-week old dairy calves with
bloody diarrhoea and straining. They were housed on straw. Large brown casts and
haemorrhage filled the spiral colon, the mucosal surface of which was ulcerated,
hyperaemic, covered by thick layers of necrotic cellular debris and contained scattered
clusters of coccidia. Low numbers of coccidial oocysts were observed in the faeces.
Kilkenny investigated a large outbreak of lead poisoning in weanlings. 53 animals
from a group of 60 died over a five-day period. The source of lead was a car
battery, which had contaminated a single round silage bale. This bale was chopped in
a diet feeder and its contents were distributed to all animals at feeding. One animal
was submitted for post mortem, this animal had classical paleness of the musculature
and ecchymotic haemorrhages in the thymus. Tiny lead particles were found in the
reticulum. Thirteen animals were examined in a knackery, and in most cases, the
rumen contents were heavily peppered with cruciate lead particles (consistent with
lead grill plates from a battery being shattered by both the silage making and diet
feeder machines). All animals exhibited signs consistent with lead toxicity. Kidney,
liver and rumen juice lead concentrations ranged up to 810, 452 and 410 umol/kg
respectively, indicating significant exposure.
Sligo investigated an outbreak of milk fever, slow calving, stillbirths and retained
afterbirths in a 40-cow dairy herd. The herd was relatively high yielding. The dry
cow diet consisted of grass silage with a pre-calver mineral spread on top. There were
no significant findings on the biochemistry tests carried out on blood samples
collected during the farm visit. However, it emerged that there was a large amount of
potassium being spread on the silage ground (both slurry and chemical
fertiliser). High potassium is known to interfere with magnesium uptake. In the short
term the farmer was advised to dose the cows with magnesium chloride as they
approached calving. In the longer term, a reduction in potassium usage was
recommended.
An emaciated three-year old heifer with a history of chronic scour was submitted to
Athlone for post mortem examination. The jejunum and ileum had a corrugated
appearance, with mucoid exudate on the mucosal surface (figure 1). The mesenteric
lymph nodes were not enlarged. A dark viscous scour was evident in the large
intestine. Histopathology revealed a granulomatous enetritis present with giant cells in
both the mesenteric lymph nodes and the peyers patches. Culture for Mycobacterium
avium subspecies paratuberculosis was positive.
Sligo reported that Salmonella typhimurium was isolated from six faecal samples
submitted from a dairy herd. This herd had an epidemic of scour and milk drop in
adult cows. A member of the farm family was also severely affected with vomiting
and diarrhoea. The farm is situated in close proximity to a licensed landfill site and to
an abattoir. Investigations into the source of the infection and into the serotype of the
isolate are continuing.
Sligo diagnosed necrotising tracheitis with secondary bacterial pneumonia
(Arcanobacter pyogenes isolated) as the cause of death of a feedlot cow. One other
cow had already died and the other cows in the pen were showing clinical disease.
Infectious bovine rhinotracheitis (IBR) virus was identified using a PCR test.
Sheep
Four lambs were submitted to Dublin from a farm experiencing poor, weak lambs at
birth. The perinatal mortality rate was significantly higher than expected.
Imperforate urethra with secondary hydronephrosis (figure 2) was diagnosed in one
animal; another had severe abomasal distension and multifocal abscessation in the
liver and spleen, indicative of gram-negative septicaemia. The remaining two lambs
had low zinc sulphate turbidity (ZST) test results indicating inadequate absorbtion of
colostrums antibodies; one of these had evidence of aspiration pneumonia while the
other had an empty abomasum and depleted fat reserves. Three of the lambs also had
low liver cobalt levels (0.24, 0.49 and 0.65 mol/kg, normal range 0.7 – 5.0). Cobalt
deficiency in ewes has been associated with reduction in the viability of offspring.
Three lambs were submitted to Athlone with a history of severe arthritis.
Streptococcus dysgalactiae was isolated from the joints. ZST test results were normal.
Kilkenny isolated Streptococcus agalactiae from the liver, lung and heart valve of
a five-week old lamb with gross lesions of endocarditis involving the right
atrioventricular valve. Athlone examined a two-week old lamb, which was found
dead. Pinpoint abscesses were seen on the surface of the liver and Listeria
monocytogenes was isolated from multiple organs.
Three adult sheep were submitted to Cork from a flock where 32 out of 70 had died
after showing symptoms of weakness and haemoglobinuria. Gross lesions consistent
with chronic copper toxicosis were observed (icterus, gun-metal colored kidneys,
enlarged yellow friable liver) in all three. Liver copper concentrations were elevated
in all three animals, with one as high as 12.76mmol/kg wet matter (normal range 0.06
to 2.5 mmol/kg). Selenium and Cobalt concentration were also elevated.
Other Species
Sligo reported that Salmonella typhimurium was isolated from a Greenfinch
(Carduelis chloris) and a Siskin (Carduelis spinus) found dead at a bird feeder in an
urban garden. The garden owner was advised on the need to clean and disinfect wild
bird feeders regularly, to move the feeding area periodically, and to practice
scrupulous personal hygiene after handling the feeders and before eating or drinking.
Kilkenny examined a twenty-eight-year old donkey with a history of rapid weight
loss, anorexia and azotaemia. A single spherical mass, about 1cm in diameter, was
found in one kidney. This was diagnosed as a focal renal adenoma. There was also
extensive chronic interstitial nephritis, which was considered to be the important
lesion.
CAPTIONS FOR PHOTOS
Figure 1 “Corrugated appearance of the ileum associated with Johnes disease in a
three-year old heifer – photo Gerard Murray”
Figure 2 “Hydronephrosis in a lamb – photo Ann Sharpe”