Infectious Disease Compendium

Pythium insidiosum


An oomycete of the kingdom Chromistaforms. Huh? Has 2 forms: perpendicular branching hyphae and biflagellate zoospore. That doesn't sound good to me. The zoospore swims to attach and invade host tissue. Probably related to diatoms and algae than to true fungi. (PubMed). There are dozens of Pythium that infect plants. The feet of the fungus gnat are vector for their transmission. I just know I will be reincarnated as a fungus gnat.

It is not a curse Harry Potter would say. I think,

Diagnose on biopsy.

Epidemiologic Risks

Found in Thailand/SE Asia in swamps, rice and other agricultural fields. It occurs in patients with hematologic illnesses, especially thalasemias of all kinds after inoculation. Also found in the US South; ubiquitous in Florida.

Often acquired after swimming in stagnant water. What else you going to swim in? Stagnant jello?


Vascular pythiosis mostly presented with arterial insufficiency syndrome of the lower extremities, cutaneous disease, ocular disease (normal hosts) and disseminated disease.

Arteritis, keratitis, and periorbital cellulitis.

"Of 34 human cases reported, 17 (50%) were of the vascular type, 14 (41%) were of the ocular type, and 3 (9%) were of the subcutaneous type. The majority of human cases (76%) have been reported in Thailand "(PubMed).

It tends to spread rapidly and is often fatal.


None of note except debridement. Perhaps caspofungin and its ilk as well as terbenifine (PubMed). Not azoles.

Maybe sensitive to some antibacterials such as "azithromycin, clarithromycin, linezolid, mupirocin, doxycycline, minocycline, and tigecycline" (PubMed) and there is some synergism with antifungals (PubMed).


Causes "swamp cancer" in horses, cattle, dogs, and cats.

Last Update: 04/04/18.