Tyzzer's Disease
Description
Tyzzer's disease is an acute, highly fatal bacterial infection that is seen in a wide range of animals. It most commonly affects foals and laboratory animals and occasionally dogs, cats and calves. Foals are usually affected individually in sporadic cases whereas outbreaks of disease occur in rodents and rabbits. The bacteria that causes the disease is Clostridium piliforme, a gram negative spore-forming intracellular bacterium found in soil and faeces.
The aetiology of the disease is poorly understood. Infection most likely results from oral exposure; possible mechanisms include ingestion of spore-forming faeces or contact with carrier animals. Following ingestion, the spores colonise the intestine and liver via the portal circulation. The disease most commonly affects young stressed animals.
Clinical signs
The disease in rabbits and rodents is usually characterised by an unkempt coat, depression and fatal diarrhoea. Affected foals are usually normal at birth and the develop rapidly progressive signs relating to an acute septicaemia hepatitis. Foals aged between one and six weeks of age are affected. Clinical signs include depression, loss of suckle reflex, severe icterus, neurological signs, pyrexia and diarrhoea. Animals may be found dead without known pre-existing clinical signs. The course of the disease from the onset of clinical signs to death is usually around 48 hours.
Diagnosis
Tyzzer's disease should be considered in foals in the above age group with clinical signs indicating hepatic disease and laboratory evidence of hepatic involvement. Clinicopathologic abnormalities often include metabolic acidosis, hypoglycaemia, haemoconcentration (elevated PCV) and increased hepatic enzymes (SDH, GGT and ALP) and serum bilirubin concentration. Coagulation profiles may be abnormal with a prolonged PT, PTT and increased fibrin degredation products. Ultrasound of affected animals may show a grossly enlarged liver with rounded edges. Definitive diagnosis relies on observation of intracellular bacteria at the periphery of liver lesions or bacterial culture. Giemsa stain is used to visualise the bacteria.
Laboratory diagnostic tests are of little value in small mammals as death is usually rapid. Recently, a PCR test has been described for use in these animals but this is not currently commercially available.
Pathology
Grossly, hepatomegaly is present with multifocal white-grey areas of necrosis. The hepatic lymph nodes are often hyperplastic. On cut section the liver displays loss of normal architecture.
Treatment
High dose sodium penicillin and trimethoprim sulpadiazine have been used successfully to treat foals with Tyzzer's disease. Other supportive treatment may include aggressive fluid therapy with dextrose, parenteral nutrition and control of seizure activity using alpha-2 receptor agonists.
Prognosis
The prognosis for foals with Tyzzer's disease is poor with a mortality rate approaching 100%.
Prevention
No vaccines are available for prevention of Tyzzer's disease. Good hygiene is therefore essential for decreasing the risk of clinical disease. Stress factors such as transport and overcrowding have been linked to Tyzzer's disease, therefore these should be minimised. Adequate colostrum intake is particularly important.
References
- Borchers, A., Magdesian, G.K., Halland, S., Pusterla, N. and Wilson, W.D. (2006) Successful Treatment and Polymerase Chain Reaction (PCR) Confirmation of Tyzzer’s Disease in a Foal and Clinical and Pathologic Characteristics of 6 Additional Foals (1986–2005) Journal of Veterinary Internal Mediicne 20:1212–1218
- Knottenbelt, D.C. A Handbook of Equine Medicine for Final Year Students University of Liverpool
- Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition) Merial
- Lavoie, J. P., Hinchcliff, K. W. (2009) Blackwell's Five-Minute Veterinary Consult: Equine Wiley-Blackwell
- Sellon, D. C. and Long, M. T. (2007) Equine Infectious Diseases Elsevier Health Sciences