Current Findings in the Regional Veterinary Laboratories
July 2005
Cattle
Kilkenny and Limerick diagnosed cerebro-cortical necrosis (CCN) in calves ranging from two to
four months of age. Kilkenny encountered three cases on one farm. Another outbreak involved a
two-month old calf found alive in a drain. It was treated and appeared to improve. However, the
animal deteriorated the following day, with blindness, teeth grinding and eventual death. Limerick
diagnosed the condition in two four-month old calves from two different herds. Both calves had
been seen staggering and appeared to be blind before becoming moribund and dying. In all cases
fluorescence was seen on examination of the brain with ultra-violet light. The diagnoses were
confirmed following histopathological examination of cerebral sections.
Athlone reported that hoose and parasitic gastroenteritis lead to mortality in a group of four-month old
calves. In another herd, hoose pneumonia was diagnosed in a four-month old calf that had presented
clinically as an acute pneumonia of suspected viral aetiology. Limerick also encountered hoose-associated
calf mortality during the month. Kilkenny identified respiratory syncithial virus (RSV) and Pasteurella
multocida in a one-month old calf with severe pneumonia and emphysema. Athlone also isolated Pasteurella
multocida from the pneumonic lungs of a two-month old calf. The calf had presented clinically with
recurring episodes of pneumonia. Kilkenny examined a three-week old calf that had been found dead. The
lungs were consolidated and there was a profuse fibrinous exudate on the pleura and pericardium as well as
on the surface of the liver and omentum. Mannheimia haemolytica was isolated from the lung tissue.
Listeria ivanovii was isolated from an aborted calf by Cork. This is a recognised bovine
abortefacient, although of infrequent occurrence (JAVMA (1992) 200 711-714).
Athlone reported segmental haemorrhagic enteritis in a ten-week old calf with a history of sudden death.
Clostridium sordelli was isolated from the lesion. Kilkenny dealt with a similar case involving an 18-month
old bullock. A three-month old calf with chronic scour and ill-thrift over a six-week period, was presented to
Kilkenny. Gross lesions included mild, localised pneumonia and pleuritis. Small ulcers were seen on the
mucosal surface of the abomasum and caecum. There was also some thickening of intestinal wall of the
ileum, caecum and colon. No significant bacterial or fungal pathogens were isolated on routine culture.
Histopathological examination showed lesions in the intestine and liver consistent with a systemic fungal
infection. Kilkenny examined a three-month old calf with a history of sudden death. Post-mortem
examination revealed a 360-degree torsion involving the small and large intestine (figure 1). Athlone
reported bacillary haemoglobinuria (BHU) in a five-month old calf and in a 14-month old bullock from
different herds.
Cork investigated a lameness problem involving all age groups of a suckler herd. Defective claw
horn growth (figure 2) was a feature of the condition. Frequent foot-paring was essential to try to
control the lameness. The herd was registered for organic production and feeding was almost
exclusively grass/clover based. Some of the yearling and two-year old animals had high serum
inorganic phosphorus and low serum calcium concentrations. Investigations, including soil and
herbage mineral analysis, are ongoing. Athlone reported babesiosis in a group of 15-month old
cattle. Three animals had died before the laboratory was consulted. A blood sample taken from one
clinically affected animal showed that a high percentage of the red blood cells contained Babesia
parasites. Kilkenny and Limerick also reported cases of babesiosis.
Sheep
Athlone diagnosed Clostridium sordellii-associated malignant oedema in a 15-week old lamb. The
mortality rate was high in the flock, with 15 lambs dead from the group of 50. Kilkenny diagnosed CCN in a
lamb that had presented clinically with opistotonus. Psoroptes ovis was identified in a wool sample
submitted to Kilkenny from a flock where sheep scab was suspected.
Horses
A foal that was bright and alert at birth but became dull and inappetant before dying at two days of
age, was examined by Limerick. Actinobacillus equuli was isolated from the liver, spleen, lung and
kidney and a diagnosis of sleepy foal disease was made. The history stated that this was the third
foal out of this mare to die from four full-term pregnancies. The literature suggests that the disease
may be enzootic on some farms, with successive foals frequently being affected.
Athlone reported strangles in an eight-week old filly foal with a discharging abscess.
A two-month old foal that died following clinical signs of pneumonia was submitted to Cork. There
were multiple firm nodules of varying sizes throughout the lungs (figure 3). The mediastinal lymph
nodes were enlarged, with caseous lesions present. Hepatomegaly was also a feature. Gross lesions
were consistent with Rhodococcus equi pneumonia and this bacterium was isolated from one of
the abscesses. Ulceration of the intestinal tract, which can be a feature of R. equi infections, was not
apparent in this case.
Kilkenny examined a pony with a history of asphyxia resulting from bilateral laryngeal paralysis.
Gross findings included cyanosis, pulmonary congestion, hepatic fibrosis and icterus.
Histopathologically there were lesions of hepatic fibrosis, hepatic cell megalocytosis, pulmonary
congestion, alveolar oedema, neuronal necrosis and satelitosis in the cervical ganglion. A diagnosis
of ragwort poisoning was made.
Poultry
Limerick examined a small number of hens from a free-range flock of approximately 4,000 birds.
There was a history of a slight drop in production, a reduction in egg size and an increase in
mortality. Post-mortem examination revealed lesions of haemorrhagic enteritis. Large numbers of
coccidial oocysts were found on microscopic examination of faecal smears.
Broiler breeders, 33 weeks old and submitted to Cork were found to have died from anaemia
resulting from Dermanyssus gallinae (red mite) infestation. Anecdotal reports indicated an
upsurge in infestations in other flocks, including layers. The hot humid weather was considered to
be a factor in this upsurge. The absence of a licensed product to treat infested birds in an obvious
impediment to red mite control.
Other Species
Seven premature greyhound pups delivered by caesarean section were submitted to Cork. Some of
the pups had been dead in-utero and the others died shortly after birth. Three pups were autolytic.
Pulmonary congestion was apparent grossly in one pup. Citrobacter youngae was isolated in pure
culture from the stomach contents of four of the pups. Severe diffuse hepatitis was observed in two
pups following Histopathological examination. Citrobacter spp. (gram-negative commensal
enterobacteria) are infrequent pathogens but local or systemic breaches of dam defences may have
facilitated the bacterial invasion of the foetuses.
Limerick investigated the sudden death of two dogs in county Tipperary. The owner had taken three
adult dogs (two Labradors and a Rottweiler) for a walk on the shore of Lough Derg. Two of the
three dogs swam in the lake. Within thirty minutes of retuning home, one of the dogs was seen to be
in a distressed state. The owner loaded the dog into the car and searched for the second dog. It was
found dead. The Rottweiler had not entered the lake and was unaffected. The sick dog was in
convulsions and frothing at the mouth on arrival at the local veterinary practice. Despite the use of
sedatives and supportive therapy, the dog died within a few hours. Post-mortem examination of the
first dog did not reveal any specific lesions. Based on the history, blue-green algae toxicity was
suspected. The local county council was informed and a section of the lake was closed to
swimmers. Toxicological analysis of a sample of stomach contents confirmed the diagnosis.
CAPTIONS FOR PHOTOS
Figure 1 “Intestinal torsion in a calf– photo Donal Toolan”
Figure 2 “Defective claw growth in a heifer – photo Eugene Power”
Figure 3 “Rhodococcus equi infection in a foal – photo Sorcha Spillane”