Current Findings in the Regional Veterinary Laboratories
June 2005
Cattle
Sligo reported that a four-day old calf had died of congestive heart failure secondary to an unusual
combination of cardiac defects. There was a large ventricular septal defect and transposition of the
great vessels (the aorta leaving the right side of the heart and the pulmonary artery entering the
right). Athlone reported on a two-month old calf that presented clinically with ill-thrift, chronic
cough and irregular heart sounds. Post-mortem examination revealed a large abscess in the septum
between the ventricles of the heart. Kilkenny found a cardiac septal defect in three-month old calf
that had been found dead in a drain.
Post-mortem examination by Limerick on a ten-week old calf showed lesions of caudal vena caval
thrombosis and fulminating pulmonary thrombo-embolism, the result of long-standing liver
abscessation. It is thought that the liver lesions were likely to have arisen from an ascending navel
infection. The calf had died suddenly without showing any signs of illness. Athlone examined a
three-month old calf that had been euthanased following a period of posterior paralysis. Postmortem examination showed osteomyelitis of a lumbar vertebra with spinal cord involvement.
Salmonella dublin was isolated from the lesion.
Kilkenny, Limerick and Sligo encountered patent parasitic bronchitis (hoose) in calves at grass.
The outbreaks underline the outstanding epidemiological feature of parasitic bronchitis in Irish
cattle, i.e. disease can occur at any time of the year where pasture is heavily contaminated and the
temperature and humidity are suitable for the growth of the Pilobolus fungus that plays a critical
role in dispersing infective larvae onto pasture.
Athlone reported hypo-magnesaemic tetany in a pen of 20 three-month old calves. The calves
were on a whole milk diet, with access to concentrates. They presented clinically with excitability,
salivating, shivering, bellowing and running. No deaths had occurred. The episodes were short and
separated by periods of normal behaviour. Comrade animals in two separate pens were not affected.
It was recommended, following blood sample analyses, that the calves be treated with magnesium
by subcutaneous injection. The response was rapid and no recurrence of the symptoms has been
seen. Limerick encountered outbreaks of cerebrocortical necrosis (CCN) in weaned calves at
grass. Kilkenny suspected levamisole poisoning as the cause of death of two calves that showed
clinical signs within an hour of treatment. They became agitated and this progressed to recumbency
and death within five hours. Both calves were only half the size of the thirty-five comrade calves
treated at the same time, but were given the same volume of the anthelmintic. No diagnostic lesions
were seen at post-mortem examination. Sligo reported that hepatic encephalopathy (secondary to
ragwort poisoning) caused the death of a 14-month old heifer, from a farm where one other animal
had died and another had just recently become ill. All showed similar signs, which included
incoordination and tremors but excluded tenesmus.
Clostridium chauvoei was demonstrated in a pulmonary lesion from a sudden death weanling
submitted to Sligo. No lesions were found in the musculature. Athlone reported blackleg as the
cause of death in cattle varying in age from two months to 18 months.
Athlone examined a 15-month old Charolais bullock that had a history of chronic ill-thrift and
lameness. Vegetative endocarditis and septic arthritis of the fetlocks were found. Sligo reported
polyarthritis in a two-year old bullock, affecting all of the major limb joints with extensive erosion
of articular cartilage (figure 1). The lesions were most severe and extensive on the articular surfaces
of the stifle, hock and carpal joints, while some semi-healed lesions were observed in the hip and
metacarpal joints. This animal had a history of lameness that responded to therapy, but relapsed
when the treatment course was completed. Tests to determine the aetiology of the condition are
continuing.
Tick-borne fever (TBF), a rickettsial disease associated with Ehrlichia phagocytophila, was
diagnosed by Cork as the cause of milk-drop and pyrexia in dairy cows in a herd where access to
new grazing was considered to be the source of the infection. In another dairy herd in the Cork area
newly purchased cows contracted both TBF and babesiosis (red water). No clinical signs of these
two diseases had ever been recorded in the indigenous home-reared animals that were presumably
resistant.
An outbreak of suspected bovine botulism is being investigated by Limerick. Seven pedigree
Friesian heifers from a group of 25 were affected. All showed similar signs of ascending paralysis,
beginning with the hind limbs. The seven animals died. Toxicological testing will be carried out in
mice to try to reach a definitive diagnosis. The heifers were grazing in a field a short distance from
a broiler unit. Outbreaks occurred in the same area in 2004.
Sheep and Goats
Athlone reported a cervical spinal abscess in a three-month old lamb that had shown lateral
recumbency, opisthotonos and blepharospasm. Sligo isolated Mannheimia haemolytica from a
cervical spinal abscess in a three-month old lamb with a history of incoordination and muscular
weakness, progressing to recumbency and quadriplegia.
A two-year old ram that had been found in lateral recumbency showed evidence of pre-mortem
bloat when examined by Athlone. Brain histopathology showed lesions consistent with a diagnosis
of listeriosis. Athlone diagnosed sheep pulmonary adenomatosis (Jaagsiekte) in a Texel-cross ewe.
Sligo reported that aspiration pneumonia caused the death of a five-year-old goat. This animal was
found dead, but had access to rhododendron shrubs, and rhododendron poisoning (caused by
andromedatoxin) was supected but could not be confirmed.
Pigs
Cork diagnosed post-weaning multi-systemic wasting syndrome (PMWS) in 14 to 15 week old pigs
from a seventy-sow unit. The pigs were submitted as cases of suspect proliferative ileitis but the
histopathological features were consistent with PMWS.
Specimens submitted to Cork from a pig, the carcass of which was condemned in an abattoir
(figure 2), had histopathological findings of acute nephritis, mild multifocal myositis and lymph
node haemorrhage. A septicaemic condition would appear to have been present although
bacteriology did not identify a pathogen.
Poultry
Broiler-breeder pullets, from a group with ill thrift but low mortality, were received by Cork and
found to have thickened caecal tubes with necrotic cores. Histopathology showed changes
consistent with a chronic bacterial infection. The distribution of the lesions would suggest that
bacterial infection was most likely to be secondary to coccidiosis. The birds were twelve weeks
old and were at the restricted diet stage of the rearing regime and pullets and cocks were segregated
within the same house. Although mortalities had been in the pullets only, both groups showed an
improvement following treatment with taltrazuril for coccidiosis. Cocks aged 15 weeks, from
another broiler breeder flock, had impaction of the proventriculus/gizzard. These birds were also at
the restricted feeding part of rearing and this was considered the factor that encouraged some birds
to ingest the litter, leading to the impaction.
Horses
A four-day old foal that died after a brief episode of respiratory distress (breathlessness, which
seemed to be worse when the animal lay down) was submitted to Sligo. At post-mortem
examination, there was a large thrombus, approx 500ml in volume, in the pericardial sac, with
the result that the heart was grossly compressed. There was a 3cm irregular laceration in the intimal
lining of the aorta at the base of the heart (figure 3), which communicated with a sub-epicardial
haematoma. It was not possible to identify a precise site where leakage occurred from this
haematoma into the pericardium, but it seems highly likely that this was the source for the intrapericardial haemorrhage. Rupture of the aorta has been described in horses, and characteristically
occurs at this site, at the base of the heart, but is extremely unusual in such a young foal.
Limerick diagnosed nutritional/metabolic myopathy in a five-week old foal. The foal was being
treated for a pneumonic-type condition. Gross post-mortem examination showed pale muscles with
ecchymoses throughout the musculature, and a myoglobinuria. Histopathology of muscle tissue
showed segmental necrosis, early dystrophic calcification and haemorrhages. Athlone diagnosed
nephritis in a three-month old Irish Draft colt foal.
Other Species
Sligo reported that acute leptospirosis, probably caused by Leptospira icterohaemorrhagiae
(Weil's disease) caused the death of a Springer Spaniel. Clinically the dog showed jaundice,
diarrhoea, haematuria and pyrexia. At post-mortem examination there was marked jaundice with
hepatomegaly and splenomegaly. Haematuria was not evident, although the kidneys were enlarged
and very congested. Histologically in the liver, there was generalised hepatitis, multifocal necrosis,
individualisation of hepatocytes and retention of bile in the canaliculi. The results of special stains
to confirm the presence of spirochaetes are awaited. This was the third death on the same breeding
premises, all with similar clinical signs. This dog had been apparently been fully vaccinated, but by
the owner rather than by a veterinary surgeon. The referring practitioner did not regard this case as
suggestive of "vaccine failure", as there was some substantial doubt regarding the storage and
administration of the vaccine. Limerick suspected anticoagulant rodenticide toxicity in a threemonth old greyhound pup with multiple haemorrhages that were not associated with trauma.
Two adult pet rabbits from the same household were submitted to Cork as sudden deaths. Both
animals had liver lesions consistent with Rabbit Haemorrhagic Disease. Sligo reported that
hepatic coccidiosis (Eimeria stiediae) was the cause of death of six young domestic rabbits in a
breeding colony. At post-mortem examination, the principal findings were fibrin coated enlarged
livers with multifocal circumscribed coalescing nodules containing inspissated purulent material.
The affected animals were noted as being listless and inappetent for a day or two before dying.
CAPTIONS FOR PHOTOS
Figure 1 “Erosion of the articular cartilage in a two-year old bullock – photo Michéal Casey”
Figure 2 “Discoloured, condemned, pig carcass in an abattoir –photo Edmond O’Sullivan, Cork
County Council”
Figure 3 “ Laceration of the aortal wall in a four-day old foal – photo Michéal Casey”