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==Description==

==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. Tyzzer's disease in foals usually occurs in individual 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.

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. Tyzzer's disease in foals usually occurs in individual cases, whereas outbreaks of disease occur in rodents and rabbits. The disease most commonly affects young, stressed animals.  

 

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==

==Clinical signs==

The disease in rabbits and rodents is usually characterised by an unkempt coat, depression and fatal diarrhoea. Foals are usually normal at birth and then develop rapidly progressive signs relating to an acute hepatitis. The disease mostly affects foals aged between one and six weeks of age. Clinical signs include acute lethargy, 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.  

The disease in rabbits and rodents is usually characterised by an unkempt coat, depression and fatal diarrhoea. Foals are usually aged between one and six weeks of age and are often clinically normal at birth. Affected foals then develop rapidly progressive signs relating to an acute hepatitis. Clinical signs include acute lethargy, 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==

==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.  

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), 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 either on observation of intracellular bacteria at the periphery of liver lesions or on 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.  

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==

==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.  

Grossly, hepatomegaly is present with multifocal white-grey areas of necrosis and hyperplasia of the hepatic lymph nodes. On cut section the liver displays loss of normal architecture with haemorrhagic centres in each hepatic lobule. Whitish streaks may be present on the myocardium.

 

==Treatment==

==Treatment==

''C piliforme'' has been reported to be susceptible to penicillin, tetracycline, erythromycin, and streptomycin in studies using infected embryonated eggs. High dose sodium penicillin and trimethoprim sulpadiazine have been used successfully to treat foals with Tyzzer's disease. Parenteral nutrition is particularly important in affected animals due to a reduction in hepatic metabolism caused by necrosis. Other supportive treatment may include aggressive fluid therapy with dextrose, control of seizure activity using alpha-2 receptor agonists.  

''C piliforme'' has been reported to be susceptible to penicillin, tetracycline, erythromycin, and streptomycin in studies using infected embryonated eggs. High dose sodium penicillin and trimethoprim sulpadiazine have been used successfully to treat foals with Tyzzer's disease. Parenteral nutrition is particularly important in affected animals due to a reduction in hepatic metabolism. Other supportive treatment may include aggressive fluid therapy with dextrose and control of seizure activity using a sedative such as xylazine.