Pythium insidiosum is mainly found in standing water and occasionally soil.

It causes pythiosis,[1][2] mainly in horses, dogs, and humans.

[3] It is a non-transmissible disease and occurs mainly in tropical climate, endemic to Thailand, affecting mainly humans and horses and in Brazil, affecting mainly horses.

The cell walls of Pythium insidiosum are composed of β-glucans and cellulose (compared to the chitin walls of fungi), and their cytoplasmic membranes lack sterols, molecules that are targets of antifungals.

For this reason, infection caused by Pythium insidiosum is often difficult to treat.