Cutaneous pythiosis

Etiology

• Cutaneous pythiosis is caused by the oomcyte Pythium insidiosum, of the kingdom Stramenopila. An opportunistic pathogen present in warm stagnant waters of tropical and subtropical regions of the world.

Predisposing factors

General

• Most cases occur during the wet season in tropical and subtropical regions of the world.

Specific

• Exposure of animal wounds to stagnant water sources containing the infective zoospores of Pythium insidiosum.
• Cases often occur after a period of heavy flooding or an El Nino event,

Pathophysiology

• Infective Zoospores exhibit a marked chemotaxis towards animal hair, wounds and damaged mucosa. Lesion location therefore correlates directly with those body parts which contact the water containing zoospores. In bovines, this is most often the limbic regions.
• Upon reaching their destination they encyst and release a glycoprotein that aids their adherence. The hosts body temperature stimulates the creation of a hypha which extend from the zoospores into the hosts infected tissue and from here can infiltrate the vasculature and spread to other sites within the body.

Timecourse

• An incubation period of approximately fifteen days has been suggested, with spontaneous recovery occurring over a period of weeks to two months in most cases.

Epidemiology

• Pythiosis is generally considered to be a sporadic disease of cattle in the tropical and subtropical regions of the world, but epizootic events have been reported.