Tyzzer's disease in a quarterhorse foal

Tyzzer's disease is an acute, fulminante bacterial hepatitis. In some cases myocarditis can also be found. The disease is caused by Clostridium piliforme, previously called Bacillus piliformis. The filamentous bacterium is an obligate intracellular pathogen and causes disease in a variety of animal species. In the horse Tyzzer's disease occurs sporadically, however has been reported in outbreaks and is endemic in certain geographic regions. Fools, a few days to 6 weeks old, are afflicted by the disease. Clostridium piliforme is excreted in the feces of clinically healthy horses. Fools are infected via oral ingestion of feces or contaminated soil. In the present case a 3 week old, female Quarterhorse foal become suddenly ill and was submitted to the clinic because of fever and a severe depression. Upon arrival it was comatous, recumbent and showed icterus. Examination of blood revealed severe metabolic acidosis and hypoglycemia. Due to a rapid progression of the disease the foal was euthanised. Postmortem examination revealed a severe, multifocal, necrotizing hepatitis and a mild, multifocal, necrotizing myocarditis. For diagnostic purpose tissue sampling immediately post mortem as well as the use of special histological staining techniques (Warthin-Starry and Giemsa) were decisive. Clostridium piliforme was detected in the cytoplasma of hepatocytes and myocardial cells. This is the third case report of Tyzzer's disease in a foal in Germany. Even though the disease is not common, it is of differential diagnostic importance when dealing with an acute, rapidly progressive, fatal disease in fools, a few days to 6 weeks old. In cases of presumptive Tyzzer's disease it is necessary to inform the veterinary laboratory, because most cases require special techniques for histological diagnosis.