Current Findings in the Regional Veterinary Laboratories
June 2007
Cattle
Salmonella typhimurium (DT104) was isolated from the stomach contents of a
bovine foetus submitted to Athlone. Appropriate advice was given regarding the
zoonotic nature of this pathogen. Kilkenny isolated S. typhimurium DT 104 from
calves that were scouring. A vaccination programme against Escherichia coli K99,
rotavirus and coronavirus was in place on the farm.
All centres reported cases of cerebrocortical necrosis (CCN) during the month.
Apple green florescence on examination of the brain with an ultraviolet lamp was
used to provide interim diagnoses in all cases, with confirmation by brain
histopathology. An example of one case was a four-month old calf presented to
Athlone, one of four calves affected in a group of eight. The calves had been housed
for the previous two months. The clinical signs reported included blindness and head
pressing. The other calves responded well to B-vitamin and anti-inflammatory
treatment.
Athlone diagnosed valvular endocarditis in a yearling bull, which had presented
with acute respiratory distress and pyrexia. In addition to the vegetative lesions in the
valve and wall of the left ventricle, there was severe pulmonary oedema and
congestion. Histopathological examination of the lung showed some evidence of
concurrent lungworm infection, but this was considered to be an incidental finding.
Parasitic pneumonia (hoose) was confirmed by Athlone to have caused the deaths of
two 16-month old heifers submitted with a history of dyspnoea.
Sligo recorded five separate outbreaks of lead poisoning in young cattle during the
month. On four of the farms the source was found to be the usual accumulator battery.
On one premises the source was not located. Athlone confirmed lead poisoning on
two farms during the month. A yearling bullock found dead in the field was presented
to Dublin. The findings included generalised petechial and ecchymotic haemorrhages
throughout the body (figure 1), most likely due to disseminated intravascular
coagulation (DIC). Acute periacinar necrosis, usually seen in toxic or anoxic
conditions, was seen on histopathological examination of the liver. Although the liver
copper was within normal limits, the level of copper in the kidney (0.52mmol/kg) was
almost three times the normal level (0.06-0.18mmol/kg). The bullock had been put
through a copper sulphate footbath the day before it died and it is assumed that the
animal drank some of the foot dip. A presumptive diagnosis of acute copper
toxicity was made. Cork received liver tissue taken from a cow, the fifth to die from a
herd of ten. The clinical signs that preceded death featured depression, inappetance,
tenesmus and blindness. Histopathology showed lesions consistent with ragwort
poisoning.
Kilkenny isolated Pasteurella multocida from a milk sample of a cow described as
showing curds in milk at start of milking but with no palpable firmness of the udder.
The bulk somatic cell count (BSCC) was normal. Sligo carried out investigations on
two dairy farms with BSCC problems. In the first herd (a 160 cow herd in the process
of expansion) foremilking as an aid to early mastitis detection was not practiced,
and chronically infected cows were being retained. At the time of the visit, up to 25
cows had elevated SCCs. Identifying and culling chronically infected cows,
foremilking, and early treatment of clinical cases were amongst the main
recommendations. The second herd consisted of 50 cows. There had been a sudden
rise in BSCC. Five or six cows appeared to account for over 60% of the BSCC. The
main finding in this herd was over-milking resulting in teat end damage and
hyperkeratosis. This damage can lead to the teat seal becoming more permeable to
bacteria.
Sheep
Athlone diagnosed pulpy kidney disease in two thirteen-week old lambs. In another
case, Athlone examined a six-month old lamb with a history of sudden death. Gross
findings included congested lungs with consolidated apical lobes. Culture of the lung
yielded Mannheimia haemolytica.
Athlone examined a ewe with a history of sudden death. Postmortem examination
revealed pulmonary congestion and very watery intestinal contents. Culture of lung,
liver and faeces yielded Salmonella typhimurium. Appropriate advice was given
regarding the zoonotic nature of this pathogen. Sligo has observed high faecal egg
counts in a number of adult sheep presented for examination. Questions were raised
over worming protocols and possible anthelmintic resistance.
Poultry
Cork investigated a high mortality problem in a batch of five-week old broiler breeder
chicks. Lesions found included haemorrhagic-mucoid enteritis involving the mid
small intestine, and haemorrhage in the caecal tubes. Both of these lesions are
associated with the early stages of coccidial infection. The chicks had been given an
oral coccidial vaccine in the second week of life, but this coincided with a
management mishap during which the water supply had been interrupted, leading to
dehydrated birds. It was postulated that this event might have compromised the
efficacy of the vaccine.
Peritonitis in broiler breeders just after the commencement of lay was attributed by
Cork to be largely due to vent-pecking.
Other Species
A strangulating umbilical hernia involving the caecum was diagnosed in a two-week
old foal submitted to Sligo. Gross postmortem examination of a one-month old foal
examined by Athlone showed diffuse enteritis with multiple small white spots on the
mucosa of the large intestine. Salmonella typhimurium was isolated from the liver
and faeces. Appropriate advice was given regarding the zoonotic nature of this
pathogen. Limerick diagnosed impaction of the colon in a six-week old foal that had
just returned from stud. The foal had been away for three weeks and was noticed to
have lost condition and was teeth-grinding on arrival back at the home farm. The
faeces were dry and chalky but the temperature was normal and the foal seemed
bright and alert. Treatment for gastric ulceration was given, but the foal deteriorated
over night and died the following day. The impaction was at the pelvic flexure and the
contents had a sandy texture (figure 2).
Kilkenny suspected that listeriosis caused the death of a three-month old cat based on
the histopathological lesions seen in the brain. The cat was presented to the
practitioner in right lateral recumbency with its head bent back.
Kilkenny examined a seven-month old rabbit, the second death within a week.
Numerous small haemorrhages were seen on the lung (figure 3), and
histopathological examination showed extensive liver necrosis suggestive of rabbit
haemorrhagic disease (RHD).
CAPTIONS FOR PHOTOS
Figure 1 <insert 0706dublin> “Subcutaneous ecchymotic and petechial haemorrhage
over the ribcage of a bullock with suspected copper toxicity – photo Ann Sharpe”
Figure 2 <insert 0706limerick> “Colonic impaction in a six-week old foal – photo
Dave Kelly”
Figure 3 <insert 0706kilkenny> “Haemorrhage in the lungs of a rabbit with rabbit
haemorrhagic disease – photo Donal Toolan”