Case study: Tyzzer's disease

From the June 2020 Newsletter:

The other case of neonatal disease is from a 10-day-old female Quarterhorse foal that became recumbent and died after being treated for diarrhea. Field autopsy notes described a possible pneumonia, as well as hemorrhage along the ventricles of the heart.

Microscopically, within the liver, were multiple and coalescing, random, nodular regions of cellular debris (necrosis) admixed with acute inflammation (Figure A). Along the periphery of the necrotic nodules were few hepatocytes with intracellular bacilli that were arranged in “haystacks” (Figure B). Special histochemical silver stain (Figure C highlighted bacteria consistent with Clostridium piliforme, the causative agent of Tyzzer’s disease.

Necrosis and acute inflammation in the liver of a neonatal foal (A). Hepatocytes along the periphery occasionally contain intracytoplasmic bacilli that form haystacks consistent with *Clostridium piliforme* (B). Histochemical silver stain highlights the bacilli, confirming the diagnosis of Tyzzer’s disease (C).

Besides hepatitis, C. piliforme infection can be associated with diarrhea and heart lesions – both of which were seen in this foal. Most cases of Tyzzer’s occur in 1- to 2-week-old foals; however, foals up to 6 weeks may succumb to the disease. Clinical signs may include diarrhea, jaundice (yellow tint to the skin, eyes or mucous membranes), fever, anorexia and recumbency. Tyzzer’s is more common in the spring when mares are out on lush pasture.

View the full June 2020 Newsletter or browse older editions.