Current Findings in the Regional Veterinary Laboratories
August 2007
Cattle
A dairy herd in which 33 cows aborted (25%) was investigated after a foetus
submitted to Cork showed histopathological lesions consistent with protozoan
encephalitis. Retrospective serology was carried out to provide evidence of an
association between these abortion episodes and Neospora caninum. Out of the total
number of pregnant females (n=132), 28% presented antibodies to Neospora. This
percentage was as high as 79% in the group of aborted cows and as low as 11% in the
group of cows with no history of abortion. 9% of the animals with Neospora
antibodies did not abort and 21% of the cows that did abort had no antibody titre.
Statistical analysis confirmed that Neospora caninum was likely to have contributed
substantially to the abortion outbreak of this herd. The average time in which abortion
occurred was at 179 days of pregnancy.
A four-month old calf was presented to Athlone for examination with a history of
non-responsive enteritis. Faeces proved positive for rotavirus and Cryptosporidium
spp.. Salmonella typhimurium was cultured from the liver. This was the twelfth
confirmed case of Salmonella typhimurium this year in Athlone, representing a
significant increase on the last number of years. Follow-up investigations have been
performed on each of the farms involved in an effort to identify common risk factors,
sample in-contact animals and to identify possible links between outbreaks. The
outbreaks have spanned cattle, sheep, horses and pigs but no in-contacts to date have
tested positive for the pathogen. Investigations have identified animal access to
watercourses and noticeably higher bird activity relative to other years, as two of the
most significant common findings to date. No links have been identified between the
outbreaks and the number of affected animals in outbreaks has been small, with three
losses the maximum number recorded. Practitioners should be aware of the increased
incidence of this pathogen this year in light of its zoonotic potential and should submit
samples to the RVL prior to treatment where the disease is suspected.
A ten-month-old weanling was presented to Athlone with a history of respiratory
distress before death. Gross examination revealed lesions of emphysema and
pneumonia mainly involving the caudal lung lobes. Lungworm larvae were evident in
the incised lung tissue but none were visible in the trachea or bronchi. Histopathology
showed severe epithelialisation of the alveoli with large numbers of lungworm larvae
present throughout the lung tissue. All laboratories have reported a dramatic increase
in the number of faecal samples positive for parasites (lungworm larvae, liver fluke
and strongyle eggs) this summer. In 2006 a total of 1,312 bovine faecal samples were
analysed for the presence of liver fluke eggs - an average of 5.3% of this samples
were positive. The wet summer of 2007 has already had a marked effect on the
number of positive samples received in the laboratories (figure 1). The mud snail
(Lymnaea truncatula), vital to the life cycle of the liver fluke, thrives in water and wet
mud. We expect to see a further rise in the number of positive samples this autumn
and winter.
A yearling Charolais heifer was presented to Sligo with a history of chronic ill-thrift,
cough and sub-mandibular oedema. Post mortem examination revealed a large
volume of fluid in the abdomen and thorax. The liver was enlarged and had a nutmeg
appearance. The heart was also enlarged and dissection revealed lesions of vegetative
endocarditis. (figure 2)
Dublin investigated a suspected outbreak of botulism involving 25 per cent of cows
in a ninety-cow dairy herd. The outbreak occurred over a three-week period. Affected
cows were found initially in sternal recumbency, but had normal heart rate,
respiratory rate, rumen movement, appetite, mucous membrane appearance and rectal
temperature. All cases failed to respond to calcium and magnesium therapy. Calcium,
magnesium and phosphorous levels were normal in blood samples taken from nine
affected cows. Post mortem examination of two cows revealed hyperemia of the
abomasum and intestines, with proteinuria and glucosuria in one of the cows. No
other significant lesions were observed. As is often the case in suspected botulism
outbreaks the source was not identified. However, the observation by the herdowner
of dead bird carcases near uncovered feed storage areas and the remains of one crow
seen in wagon-mixed supplementary feed, was considered as a possible source. Most
of the affected cows either died or required euthanasia but four cows did recover
following intensive supportive therapy.
Sheep
A four-month old lamb was presented to Athlone, as one of a number that had died
with clinical signs of diarrhoea over a two-week period. Gross examination
revealed watery green large intestinal contents, but no other significant lesions. The
owner had mentioned having previous problems with mineral deficiencies and that
supplementation had been given to these lambs. Liver analysis for cobalt gave a
reading of 26 micromols per kilogram wet matter, a level considered to be toxic (the
normal range for cobalt is 0.7 - 5.0 micromols per kg).
Two five-month old lambs were presented to Athlone after being found dead with
froth at the mouth. Both were in good condition. Gross examination revealed
congestion of the lungs, friable kidneys and glucosuria. Anaerobic culture of the
kidneys lead to the isolation of Clostridium spp. A diagnosis of pulpy kidney disease
was made. Sligo also diagnosed pulpy kidney disease in three lambs from a flock
where routine clostridial vaccination was not being practiced.
Sligo investigated two outbreaks of orf in lambs. In both cases the lesions were very
severe. In one flock marked facial oedema was a prominent feature of the syndrome
presented (figure 3), and in both cases it was felt that a heavy crop of thistles on the
pasture being grazed by the lambs was a significant factor in the epidemiology. With
the continuing presence of Bluetongue in northern Europe and now in the U.K., it is
important that cases of orf are examined, as it is an important differential for
bluetongue.
Sligo reported an unusual cause of myiasis (fly strike) in a ram, which died of
clostridial enterotoxaemia. The strike had occurred in the areas chafed by the crayon
marker harness, a timely reminder that these harnesses need to be properly adjusted
and regularly checked.
Pigs
Streptococcus suis type II bacteraemia was diagnosed in a five-week old bonham
presented to Limerick.
Poultry
Sligo diagnosed amidostomiasis in a three-month old gosling. The gosling was in
poor condition and came from a flock where several deaths had been recorded.
Amidostomum anseris is a parasite of the upper alimentary tract, in its adult stage is
bright red in colour and is typically found in the horny lining of the gizzard.
Other Species
A two-month old foal with a history of sudden and severe respiratory distress was
examined by Cork. Multifocal pulmonary abscessation was the primary finding. The
abscesses ranged from grape to plum size and appeared as purulent fluid material
encapsulated within a membrane. The lymph nodes were enlarged and there was also
slight enlargement of the liver. Ulcerative enterocolitis was not seen. Rhodococcus
equi and Streptoccocus equi subspecies zooepidemicus were isolated from the lungs.
Salmonella typhimurium was isolated by Limerick from a three month-old foal
that was found dead in the field. There were a number of deaths in the group before
this but this was the first one submitted for post-mortem examination. Necropsy
showed lesions of peracute enterocolitis. There was also a heavy intestinal parasitic
burden.
Limerick examined a three-year old filly that was euthanased two days after
presenting with signs of incoordination and nystagamus before becoming
recumbent.
Post-mortem examination showed pulmonary congestion and
haemorrhage, fracture of one wing of the atlas and epidural haemorrhage around the
spinal cord in the anterior cervical vertebrae. Six horses in a nearby field died from
lightning strike at the same time and it is believed that the injuries seen in this case
could be associated directly or indirectly with the same event.
Acute myopathy was diagnosed in a four-month old kid goat that was found dead
and was submitted to Limerick. Kidney selenium levels were found to be normal and
other toxic causes were considered to be unlikely. Exertional rhabdomyolysis, the
result of being chased by dogs, is believed to have been the most likely cause as there
were some facial skin wounds evident on the animal.
A three-month old home reared fallow deer (Dama dama) was presented to Sligo. It
was the twelfth animal in the group to die. Salmonella dublin was cultured from the
spleen, liver and faeces. A diagnosis of mismothering was made on a second fallow
deer, from a separate herd. There was no evidence of milk in the digestive tract and
fat depots had been depleted.
CAPTIONS FOR PHOTOS
Figure2
“Vegetative endocarditis in a yearling Charolais heifer – photo Damien Barrett”
Figure3
“Orf in a lamb– photo Michéal Casey”