Tyzzer’s disease in a foal.

The study is about Tyzzer’s disease, a fatal condition, impacting a particular age group of foals, caused by the bacteria Bacillus piliformis. It explains the diagnosis of the disease in a 7-day old foal which was initially treated for scouring symptoms but later found comatosed and convulsing. Despite all the treatments, the foal could not survive the disease.

Disease Overview

• Tyzzer’s disease, first identified in 1917, is an infectious, fatal condition that affects various species, and has been reported in many parts of the world.
• It mainly impacts foals in a specific age group (9 – 42 days).
• The clinical course of the disease is fast (usually 12 to 24 hours), leading to the eventual death of the foal despite treatment.

Disease Epidemiology

• The spread and pattern of Tyzzer’s disease is not well understood.
• Mares are suspected to transmit the bacteria via feces.
• Cortisol present in the mare’s milk could predispose foals to the disease.

Case Study

• A 7-day-old foal showed symptoms of scouring but seemed healthy in other respects.
• The foal was treated with antibiotics, fluids, and other therapies but was found comatosed, jaundiced, and convulsing on the third day.
• The foal was euthanized due to its deteriorating condition.

Post-Mortem Examination

• A post-mortem examination revealed a swollen yellow liver and marked icterus as the only visible abnormalities.
• Two bacteria, Escherichia coli and Streptococcus faecalis, were cultured from the intestinal content, but no organisms were found in the heart blood or liver.
• Histopathological examination of various tissues revealed necrotic foci in the liver and signs of congestion in the intestines, lungs and mesenteric lymph nodes.

Diagnostic Methods and Findings

• The disease was diagnosed using light microscopy on formalin-fixed liver tissues post-fixed in osmium tetroxide.
• Sections were stained and examined under an electron microscope, revealing long slender organisms characteristic of Bacillus piliformis.
• This confirmed the presence of Tyzzer’s disease, as the definitive diagnosis can be based on the histological visualization of the bacteria within host cells.