The Science

The disease was named after Ernest Tyzzer who initially described the syndrome in 1917. He observed a bacterium that did not conform with any known bacterial species, so Tyzzer named this newly identified bacterium Bacillus piliformis. For many years, Tyzzer's disease was believed to be restricted to mice, but it has been reported in a wide range of mammalian animal species, including domestic, wild and laboratory animals. In laboratory animals, the disease has been found in rats, mice, gerbils, hamsters, rabbits, guinea pigs and rhesus monkeys. Outbreaks of the disease have occurred worldwide.

Stresses such as overcrowding, change in environmental conditions, and suppression of the immune system may contribute. A high protein diet has also been shown to predispose animals to Tyzzer's disease.

Transmission of the organism is believed to occur primarily via ingestion of spores from contaminated faeces.


The biology of the causative organism and the pathogenesis of the disease are not fully understood.


Clinical signs of acute disease include rough hair coat, weakness, lethargy, and death. Animals may also experience watery to pasty diarrhoea or perianal faecal staining. Death may occur rapidly with mortality rates varying from low to very high.


Acute disease is most often observed in suckling or weanling animals, but animals of any age may be affected. Definitive diagnosis of Tyzzer's disease is often problematic. Diagnosis has traditionally relied on evidence of C. piliforme infection and is based on the presence of the characteristic large, intracellular bacteria.


Antibiotic treatment of infected animals has shown variable results. Tetracycline and penicillin seem to be the most effective. However, these antibiotics have not been shown to effectively eliminate this bacterium and their use should be restricted.


Do not breed from a rat suspected of having the disease.