June 2009 RVL Monthly Report
Dublin diagnosed Neospora caninum infection in a large dairy herd where 13 cows had aborted within a two-week period. Non-suppurative encephalitis (figure 1) and myocarditis were detected in the first foetus submitted and Neospora antibodies were detected by parasitology division in serum samples collected from several of the aborted cows. It emerged that during a period of poor grass growth in the spring, mowed grass from a public park was collected and fed to the cows. This grass was considered to be the most probable source of infection as large numbers of dog owners are likely to have used the park to exercise their pets.
Figure 1: A focus of gliosis in the brain of a bovine foetus associated with Neospora caninum infection (photo: William Byrne).
A very large full-term Charolais calf was presented to Athlone. It had died six hours after an assisted delivery in which hip lock was reported. After birth it was bright but was unable to stand and had developed respiratory difficulties prior to death. At post-mortem examination it was found to have a dislocation of the last thoracic from the first lumbar vertebra, with resultant haemorrhage and damage to the spinal cord. This lesion is usually seen in large calves after an assisted birth in which excessive and uneven pressure is applied to the vertebral column by downward traction of the head and thorax while the hind quarters are fixed in the pelvis.
Salmonella dublin was isolated by Limerick from an osteomyelitic lesion of the 7th cervical vertebra in an eleven week-old calf showing signs of tetraparesis prior to euthanasia. Kilkenny diagnosed Salmonella dublin enteritis on four farms during the month. Animals presented with severe diarrhoea, and raised temperatures (up to 106oF). In one outbreak, three autumn calving suckler cows developed clinical signs a week after weaning, emphasising the importance of stress in precipitating clinical signs.
Limerick examined a four month-old calf that had a history of recurrent bouts of pneumonia. Caudal vena caval syndrome was diagnosed. There was occlusion of the pulmonary artery with a large thrombus (figure 2) and vegetative endocarditis involving the semi-lunar valve.
Figure 2: A thrombus in the pulmonary artery of a four-month old calf (photo: Dave Kelly).
Lead poisoning was diagnosed by Athlone in a yearling bullock with clinical signs of blindness, grinding teeth and constipation. Lead poisoning was also diagnosed in a three-month old calf with nervous signs. This was the second to die in a week. Grossly there were few significant lesions. There were petechial haemorrhages noted on the surface of both kidneys. Lead analysis of the kidney confirmed lead poisoning. The source of the lead was a discarded battery. Lead poisoning was also diagnosed in a four-month old calf by Kilkenny and in a fourteen month-old heifer submitted to Limerick. The latter animal showed signs of convulsions, blindness and frothing from the mouth. Three animals were affected. A battery was also found to be the source in this outbreak.
Malignant Catarrhal Fever (MCF) was diagnosed by Athlone in a ten-month old weanling which had clinical signs of nasal discharge, diarrhoea, blindness and hypersensitive skin. Gross post-mortem examination showed oesophagitis which was especially severe at the anterior end, and laryngitis. A segment of the small intestine contained blood stained faecal material and the lymph nodes were prominent. The diagnosis was made on histopathology. In another case, a fourteen-month old heifer with a history of high temperature (106oF), swollen eye, nose and head was examined by Athlone. Post mortem examination revealed bilateral purulent conjunctivitis and ulceration of the nasal planum. There was consolidation and bronchiectasis of the cranial lung lobes. Sections of lung and lymph node exhibited multifocal lymphocyte-rich arteritis and peri-bronchiolar lymphoid cuffing on histopathology. When considered with the clinical and gross pathology findings, a diagnosis of MCF was made. MCF is caused by Ovine Herpesvirus 1, with affected bovines considered to be end hosts and unable to shed virus. Infection is acquired directly from sheep, or by grazing or being housed on ground that sheep have recently grazed or lambed on.
A large outbreak of bovine botulism occurred on a dairy and poultry farm in north Cork. Twenty seven cows from a herd of fifty were affected with clinical signs of flaccid paralysis, and all of these either died or were euthanased. The outbreak appears to have begun when the dairy cows gained access to poultry litter which contained the carcasses of young birds.
Kilkenny diagnosed nephrosis in two eleven-week old lambs. Both were dull and had a ¿goose stepping¿ action, possibly due to muscle weakness. The principal gross finding was marked enlargement and pallor of both kidneys. Histological examination confirmed nephrosis, with hyaline and cellular casts in the kidney tubules and degenerative changes in the convoluted tubules. Both lambs had very high concentrations of serum urea and creatinine.
Two hoggets were presented to Athlone with a history of colic-like symptoms before death. On gross examination the kidneys were noted to be large and pale with a strong smell of ammonia from both carcases. On histological examination large numbers of crystals were present in the renal tubules. On further enquiry it was discovered that the hoggets belonged to a batch that were introduced to a new paddock with no access to water. The restricted water intake had facilitated the precipitation of magnesium crystals in the kidney tubules, leading to kidney failure and death.
Kilkenny diagnosed extensive liver damage as a result of fluke in a yearling hogget that was reported to have lost weight and to be moving slowly. Cumulative copper poisoning was diagnosed by Limerick in an eighteen month-old ewe.
Kilkenny diagnosed Clostridium sordellii enterotoxaemia in a four-year old ram that was found dead. There was extensive haemorrhagic lesions on both the serosal and mucosal surfaces of the large and small intestines.
Dublin diagnosed caseous lymphadenitis (CLA) in a suffolk ewe, which presented with a number of one to three centimetre diameter well demarcated caseous lung lesions each surrounded by a very well defined two to four millimetre thick white capsule. Similar lesions were found in the bronchial and mediastinal lymph nodes. Corynebacterium pseudotuberculosis was isolated from the lesions. The well-defined capsule is a relatively consistent finding that helps to distinguish CLA from tuberculosis lesions in goats.
Kilenny diagnosed exudative epidermitis (greasy pig disease) in two pigs, aged seven days and six weeks, from the same farm. Both had multifocal thickly encrusted skin lesions on the head, dorsum and at pressure points on the distal limbs. Staphylococcus hyicus was isolated from the skin of both animals and fungal spores were seen in a skin scraping from one animal.
Six broiler breeders were submitted to Dublin from a poultry unit that reported an increased mortality rate and a reduced appetite among a proportion of the flock. Of the six birds submitted, one had a prolapsed rectum, a second had a blood stained anus, intestinal contents were blood tinged in all cases and all birds were confirmed to have a burden of coccidial oocysts on parasitology and in some cases this burden was severe. Escherichia coli was isolated from several organs in a minority of cases. A diagnosis of coccidiosis was made in all submitted cases with the possibility of a secondary colisepticaemia in some cases.
Kilkenny examined a hollow spherical bony mass found attached to the placenta of an aborted foal. It was 18 centimetres in diameter and consisted of a thin (3 to 7 mm) outer bony wall surrounding a blood clot and some serous fluid (figure 3). On histological examination it was diagnosed as a remnant of the yolk sac. These are more often of tennis ball size.
Figure 3: A hollow bony mass attached to the placenta of an aborted foal (photo: Donal Toolan).
Delayed swayback was diagnosed by Limerick in three month-old goat kids that had a history of neurological signs. Two adult female goats were presented to Athlone from one farm. One was found dead and was in kid while the other, which had kidded that morning, had severe depression and was euthanased. On gross examination the liver of both was a yellow colour, friable and enlarged. The serum betahydroxybutyrate level was elevated (10mmol/L; range <0.7mmol/L) in a blood sample taken from the goat which was euthanised. Severe hepatic lipidosis was confirmed on histological examination of both livers. A diagnosis of pregnancy toxaemia was made.