Prevalence of Francisella noatunensis subsp. orientalis in cultured tilapia on the island of Oahu, Hawaii.

Francisellosis is an emergent disease in cultured and wild aquatic animals. The causative agent, Francisella noatunensis subsp. orientalis (Fno), is a gram-negative bacterium recognized as one of the most virulent pathogens of warmwater fish.