Pythiosis

Pythiosis is a rare and deadly tropical disease caused by the oomycete Pythium insidiosum. Long regarded as being caused by a fungus, the causative agent was not discovered until 1987. It occurs most commonly in horses, dogs and humans, and there have been isolated cases in other large mammals. The disease is contracted after exposure to stagnant freshwater such as swamps, ponds, lakes, and rice paddies. Pythium insidiosum is different from other members of the genus in that human and horse hair, skin, and decaying animal and plant tissue are chemoattractants for its zoospores. Additionally, it is the only member in the genus known to infect mammals, while other members are pathogenic to plants and are responsible for some very well known diseases in plants.