Current Findings in the Regional Veterinary Laboratories
December 2004
· Pathogens associated with abortions in cattle.
· Chronic pneumonia in a bullock associated with Mannheimia [Pasteurella] haemolytica
· Black disease in a pedigree heifer
· Parasitic gastro-enteritis in a hogget
· Ionophore toxicity in a flock of turkeys
· Clostridial enterotoxaemia in a Greyhound bitch
· Rupture of an hepatic abscess in an Alpaca
Cattle
The regional laboratory service accepted 2068 bovine foetuses for examination during 2004. Standard examination of bovine foetal submissions consists of a post-mortem examination and bacteriology. Should the herd history suggest a serious problem, additional tests may be undertaken (Neospora, BVD etc.). It is considered impractical to subject every foetus to every test, especially as so many abortions are single cases in herds, the majority of which are not due to infectious agents.
Salmonella dublin was the most common bacterial pathogen identified. It was isolated from 166 (8.0%) of the bovine foetuses. Other pathogens isolated were Arcanobacter pyogenes (4.8%), Bacillus licheniformis (2.9%), Listeria monocytogenes (2.2%), Escherichia coli (1.6%), Aspergillus spp. (1.0%), Streptococcus spp. (0.7%), Neospora caninum (0.6%), Staphylococcus spp. (0.5%), BVD virus (0.3%), Brucella abortus (0.2%) and others (0.9%). Results of the dam blood sample analyses, that often accompany an aborted foetus to the laboratory, are not included in these figures.
Aspergillus fumigatus was isolated from a foetus submitted to Kilkenny. The accompanying placenta showed gross lesions of severe inter-cotyledonary placentitis (Figure 1).
A calf that died following a brief period of abdominal pain and distension was submitted to Sligo, where it was found to have had an intestinal obstruction (intussusception) and a moderate coccidial infection. Increased gut motility due to enteritis is thought to be the cause of many intussusceptions. A 10 day-old calf with a similar history was submitted to Cork, where an abomasal torsion was diagnosed (Figure 2). Laboratory tests also revealed a moderate cryptosporidial infection.
A 10 month-old weanling with a history of sudden death was submitted to Kilkenny where blackleg was diagnosed. Lesions seen included a fibrinous pericarditis and a classical lesion in the hindquarter musculature. A fluorescent antibody test (FAT) was positive for Clostridium chauvoei.
Pneumonia was diagnosed in all laboratories during the month. Pasteurella multocida was the most common pathogen isolated. Kilkenny used an FAT to diagnose RSV pneumonia in weanlings from two separate herds. In both cases Pasteurella multocida was also isolated. A four month-old calf with a history of chronic pneumonia was presented to Kilkenny RVL. Enlarged heart, ascites, hydrothorax, nutmeg liver, oedema of the mesentery and abomasal mucosa, and congestion of the abomasal and ileal mucosal surfaces was seen. A diagnosis of right-sided heart failure was made, the cause of which was not ascertained. Athlone carried out a post-mortem examination on a one and a half year old bullock that had showed severe respiratory signs for day prior to death. Diffuse consolidation of the lungs with pleural adhesions indicating chronic active pneumonia was seen on gross examination. Mannheimia [Pasteurella] haemolytica was isolated on culturing. This organism was also isolated from the lungs of two yearling heifers that had also shown respiratory signs. Some of the affected animals in that outbreak were reported also to have had a scour. A bullock from another herd, the fifth similar death on the farm, was submitted to Athlone. Gross post-mortem examination showed severe antero-ventral pneumonia, with bullous emphysema in the diaphragmatic lobes. There was a considerable amount of subcutaneous oedema. Arcanobacter pyogenes was isolated from the lung.
Sligo reported that the death of a pedigree Limousin heifer was due to infectious necrotic hepatitis (black disease). Post-mortem examination showed the classical gross changes associated with this disease, i.e. acute not-purulent peritonitis, and focal hepatic necrosis. Large numbers of gram-positive rods with sub-terminal spores were seen in a gram-stained smear from the liver lesion. Anaerobic culture of a swab taken from the lesion lead to a good growth of clostridia. Black disease was formerly the commonest cause of deaths in cattle submitted to Sligo, but there have been only three cases in the autumn-winter of 2004.
Multi-focal liver abscessation with pulmonary thrombo-embolism was diagnosed by Dublin in an eighteen month-old Belgian Blue bullock that had died suddenly. Although caudal vena caval thrombosis has been associated with high concentrate diets, there was no such history in this case.
Sheep
Kilkenny investigated a suspected outbreak of enzootic abortion during the month. Examination of a placenta accompanying one foetus submitted from the outbreak showed no gross lesions but was positive on an MZN stain.
Colisepticaemia was diagnosed by Kilkenny in a three day-old lamb with agammaglobulinaemia and signs of starvation.
Parasitic gastro-enteritis was diagnosed in a 10 month-old hogget examined by Athlone. It was the third hogget to die in the flock under similar circumstances.
Weight loss, lethargy and anaemia were described as the signs in a ewe, the third to die, which was submitted to Athlone for post-mortem examination. Evidence of parasitic gastro-enteritis was found as well as a high faecal strongyle egg count. Histopathological examination showed periacinar necrosis in the liver, a lesion consistent with a diagnosis of anaemia.
Pigs
An eight-week old pig submitted to Kilkenny was found to have gastric ulceration and bleeding. Salmonella typhimurium DT104b was isolated on routine culture. The involvement of post-weaning multisystemic wasting syndrome (PMWS) was also suspected and this was confirmed with a positive immunohistochemistry result.
Horses
Bacillus licheniformis was isolated from an aborted equine foetus submitted to Sligo.
Poultry
Birds and bloods were submitted to Cork from a layer farm with a history of poor egg quality. The farm was well managed and birds were caged. There had only been a small number of deaths (1.81%) at the beginning of the problem period. Birds had pale combs and there was a wide variation in bird weight. No significant lesions were seen on post-mortem examination. Serological tests revealed varying titres for Egg Drop Syndrome (EDS) HA, from negative to 1/128. Birds had not been vaccinated for this specific condition.
Ionophore toxicity was suspected by Limerick in a flock of turkeys that showed drowsiness and depression, with evidence of dyspnoea and wings being held away from the body. These signs were followed by paralysis, prostration and death. Gross post-mortem examination showed pink body fat and marked reduction in the size of the spleen. Histopathology showed myonecrosis of the adductor muscles. The degree of microscopic change did not reflect the severity of the clinical signs. There was high morbidity and about a third of the flock died. Ionophores are anti-coccidial products used frequently in broiler ration. Turkeys appear to be quite sensitive to toxicity, particularly at around nine weeks of age.
Granulomatous encephalitis was observed by Dublin in a turkey. Fungal hyphae were evident on histopathological examination of the brain, leading to a diagnosis of mycotic encephalitis.
Other Species
Sligo reported that an alpaca carcass submitted with a history of chronic weight loss had a diffuse fibrinopurulent peritonitis associated with rupture of an hepatic abscess. There were multifocal hepatic abscesses and Arcanobacter pyogenes was isolated from the lesions. Fasciola hepatica eggs were also present in the faeces.
A six year-old greyhound bitch was submitted to Kilkenny with a history of coughing up blood. The mucosal surfaces of the stomach, small intestine and large intestine were haemorrhagic. The serosal surfaces appeared normal. All GIT contents were of a milky consistency and red in colour. An FAT was positive for Clostridium sordellii. A diagnosis of clostridial enterotoxaemia was made. A 10 year-old border collie that died after a short illness was found by Limerick to have extensive haemorrhage into the pleural, peritoneal and pericardial cavities and into the sub-capsular space of the right kidney. Further investigation revealed that the owner had recently laid anti-coagulant rodenticide around the farm and had not taken adequate precautions to prevent access by domestic animals.
Sligo reported that rabbit haemorrhagic disease was diagnosed in a pet rabbit following histological examination of the liver. The likely source of the disease was contact with wild rabbits.
CAPTIONS FOR PHOTOS
Figure 1 “Fungal placentitis. Aspergillus fumigatus isolated – photo Donal Toolan”
Figure 2 <insert 0412cork> “Abomasal torsion in a 10 day-old calf – photo Pat Sheehan”