November 2007

Current Findings in the Regional Veterinary Laboratories
November 2007
The laboratories received a total of 255 bovine foetal submissions during the month.
Salmonella dublin was isolated from 47 (18%) of the submissions, making it the
most common bacterial pathogen isolated. Figure 1 gives a break down of the
results of culture for bacteria (only) from foeti for the month.
Septicaemia associated with Salmonella dublin was diagnosed by Dublin in calves
dying within the first week of life. Histopathological findings included vasculitis
with thrombosis, typhoid nodules in the liver, acute diffuse interstitial pneumonia,
fibrinous arthritis, suppurative meningitis and suppurative interstitial nephritis.
Salmonella Dublin was cultured from lung, liver, blood, brain, kidney, spleen and
faeces. The zinc sulphate turbidity (ZST) results in the two calves submitted indicated
that colostral immunoglobulin absorption was less than adequate.
A weanling bought three days previously at a mart, and with a short history of severe
respiratory distress, was presented to Athlone. Post mortem examination revealed
lesions of acute pneumonia with tracheal congestion and a fibrinous exudate in the
airways. Lesions were most severe in the ventral aspect of the cranial lobes but
oedema and congestion were seen throughout the lungs. Bovine respiratory
syncytial virus (BRSV) was detected and Mannheimia haemolytica was isolated
on routine culture. Another weanling, which had been treated for pneumonia a
number of times prior to death was presented to Athlone. Gross examination revealed
severely abscessed and emphysematous lungs with almost no area of unaffected lung.
The right lung was partially gangrenous and a localised fibrinous pericarditis was
present. Culture of the lung tissue yielded Pasteurella multocida and PCR was
positive for BRSV.
Malignant oedema was diagnosed in a heifer submitted to Athlone. A traumatic
injury several weeks previously may have provided the suitable conditions for entry
and growth of the anaerobic pathogen. Gross post mortem revealed gelatinous
oedema, haemorrhage and gassy change in the subcutaneous tissue and musculature
from the shoulder region to the thoraco-lumbar area. A fluorescent antibody test
(FAT) was positive for Clostridium novyi. Athlone also diagnosed blackleg in four
weanlings from four different herds. Clostridium chauvoei was detected (using an
FAT) in the affected muscle of two of the four animals.
Limerick suspected that hypomagnasemic tetany resulted in the sudden death of
a thirty-month old suckler heifer. It was the third death in a group of twelve that
were bought in September. Biochemical analysis of an aspirate of cerebrospinal fluid
gave a Magnesium reading of 0.67 mmol/l. This is at the bottom of the ‘normal’
reference range, but because of the length of time since death, the result was not
considered to be conclusive. Blood samples from five in-contact animals gave
magnesium readings as low as 0.4 mmol/l (normal range: 0.65-1.2 mmol/l). Athlone
also suspected that hypomagnesaemia was responsible for the death of a twelve-year
old cow. A sample of the aqueous humor of the eye was analysed and found to be low
in Magnesium in that case.
Carcass parts from a bullock were submitted to Athlone following a field post mortem
by the referring vet. A history of incoordination and ataxia was reported by the owner
following release of the animals onto a field of maize stubble. This animal was the
third loss. Histopathology revealed necrotising hepatitis, mild interstitial
pneumonia and globular thrombi (“shock bodies”) in the blood vessels of the
brain. These changes, when considered with the history, suggested a tentative
diagnosis of ruminal acidosis.
A heifer with a history of abortion, pyrexia, congested mucous membranes,
photophobia, ocular discharge and dermatitis was euthanased and submitted to Cork
for post mortem examination. Malignant Catarrhal Fever (MCF) was one of the
differential diagnoses considered but this was ruled out following a negative test
result. A test for BVD viral antigen was positive.
Athlone diagnosed acute fascioliasis that resulted in the death of two ewes.
Numerous mature liver fluke within hypertrophied bile ducts and associated with
localised peritonitis surrounding the liver were observed by Dublin in a ewe which
was one of 28 ewes that died within a 100-ewe flock. Twenty-seven of the 28 ewes
were found dead without any prior clinical signs observed and the ewe presented was
in very good body condition with normal faeces. The flockowner considered his land
as relatively dry and initially suspected clostridial disease but submitted a ewe for
post mortem when vaccination failed to halt the losses. Fascioliasis is being reported
on a frequent basis this year, probably due to the wet summer on some farms, where
the disease had not caused significant clinical problems in previous years.
Weaned pigs with a history of diarrhoea and high mortality were submitted to
Limerick. Post mortem examination showed lesions of necrotic typhilitis and
colitis. Salmonella typhimurium was isolated on culture. One of the four piglets
submitted also showed lesions of septicaemia. Fibrinonecrortic gastritis and typhilitis
was observed in a weaned pig submitted to Dublin. Salmonella typhimurium was also
isolated from that case.
Other Species
Salmonella typhimurium was isolated from the faeces of a foal submitted to
Athlone. The foal had a history of scour and depression. Salmonella typhimurium had
been isolated on the stud farm twice in the previous 15 months. At least thirty mares
had passed through the farm in 2007, many of which were kept on farm for a number
of weeks. The same paddock has been used for a number of those staying on the farm
so advice was given about how this could be better managed. Limerick diagnosed
acute suppurative pneumonia in a seven-month old donkey. Streptococcus equi
subspecies zooepidemicus was isolated on culture.
A five-month old farmed deer was presented to Athlone following a sudden death.
Large numbers of very small lungworm were evident on the cut surface of the
lungs. Treatment of other deer in the group was advised.
A red kite (Milvus milvus) was submitted to Dublin with a fractured wing, ruptured
proventriculus and liver and aspiration pneumonia. It was thought to have been hit by
a train while scavenging on a dead pheasant. Trace levels of alphachloralose were
found in tissue samples but it was considered that this poison did not play a role in the
bird's death.
Limerick was presented with a five-month old greyhound showing clinical signs of
hind limb ataxia that had worsened over a two-month period. The pup was one of
a litter of seven, the dam of which had been purchased in England after a leg injury
had prematurely ended a promising racing career. Two of the littermates had died
within a few days of birth and another two had been killed following an attack by
another dog. The two other surviving littermates appeared to be normal. Gross post
mortem examination did not reveal any significant lesions, but histopathological
examination of the brain revealed multifocal lesions of non-suppurative
encephalomyelitis. Scattered throughout the brain also were numerous tissue
cysts (figure 2) that were consistent with those seen in protozoan infection.
Immunohistochemical staining using Neospora caninum antibody was positive
(figure 3). Following this result the two surviving littermates were blood sampled and
were found to be serologically positive for Neospora caninum antibodies. The dam
(pregnant again) is now being tested.
Figure 1 <insert 0711foetalsummary>
Figure 2 <insert 0711limerick> “Tissue cyst containing bradyzoites in the brain of a
five-month old greyhound infected with Neospora caninum – photo Alan Johnson”
Figure 2 <insert 0711dublin> “'Immunohistochemistry positive staining Neospora
caninum tachyzoites in the cerebrum of a five-month old greyhound– photo Claire