Background: Tyzzer's disease is a rapidly progressive and highly fatal hepatitis of foals caused by Clostridium piliforme. Survival of a confirmed case has not been reported previously. Hypothesis: Successful therapy of C piliforme infection in foals is possible. Polymerase chain reaction (PCR) can be used to diagnose Tyzzer's disease antemortem or postmortem. Animals: Seven foals were included in the study. Methods: Retrospective study was made to evaluate the clinical and pathologic characteristics of foals with Tyzzer's disease. Medical records of the Veterinary Medical Teaching Hospital at University of California Davis were reviewed. Foals < 3 months old were included in the study if typical clinical signs were present and histologic examination identified multifocal coagulative necrosis and hepatitis with intracytoplasmic filamentous bacilli, consistent with C piliforme. A real-time TaqMan assay was developed to detect C piliforme gene sequences in liver tissue from affected foals. Results: Median survival time from onset of disease in nonsurviving foals was 30 hours (mean 34.5 +/- 20.1; range, 16-62 hours). Common clinical findings included lethargy, recumbency, seizures, and fever. Laboratory findings included metabolic acidosis, hypoglycemia and increased activity of hepatobiliary enzymes. Treatment consisted of IV fluids, antimicrobial and antiinflammatory drugs, and parenteral nutrition. One filly survived, whereas 6 died. Postmortem examination of the 6 foals that died disclosed hepatomegaly with multifocal necrosis. Liver tissue from 4 foals was positive for C piliforme gene sequences using PCR. Conclusions and clinical importance: Although the mortality rate of Tyzzer's disease is high, successful outcome is possible if intensive care is initiated promptly. PCR can be used for early and specific diagnosis.
