New research indicates that the pathogen causing Snake Fungal Disease (SFD) is occurring in more locations and impacting more snakes in California than previously known. The California Department of Fish and Wildlife’s (CDFW) Snake Fungal Disease project is conducting a three-year study of SFD in California. In the first year of statewide surveillance, scientists discovered new cases of the fungal pathogen.

“Early results of our study are in, and they paint a different picture than what we understood before. Prior to this project, we had only two instances of the pathogen in California,” said CDFW Scientific Aid Raquel Elander.

CDFW’s Snake Fungal Disease project is funded by a State Wildlife Grant from the U.S. Fish and Wildlife Service and undertaken in collaboration with the Wildlife Epidemiology Lab at the University of Illinois College of Veterinary Medicine and partners in the wildlife rehabilitation and herpetological communities. The study was initiated after CDFW confirmed the first two detections of SFD in California in 2019. Those detections were found in a California kingsnake (Lampropeltis californiae) and an invasive Florida banded watersnake (Nerodia fasciata pictiventris).

To date, the fungal pathogen that causes SFD, Ophidiomyces ophidiicola, has been detected in seven additional species from two families, Viperidae and Colubridae. The detections were found in common, threatened, endangered and non-native species. Positive cases were detected from skin swab samples collected between July 2021 and October 2022 from 10 counties throughout the Sacramento Valley, San Francisco Bay Area and the San Diego area. Skin swabs collected from the following species tested positive for presence of the pathogen: Northern Pacific rattlesnake (Crotalus oreganus oreganus), Western yellow-bellied racer (Coluber constrictor mormon), Pacific gophersnake (Pituophis catenifer catenifer), Valley gartersnake (Thamnophis sirtalis fitchi), giant gartersnake (T. gigas), San Francisco gartersnake (T. sirtalis tetrataenia) and a non-native milksnake (L. triangulatum). Ophidiomyces ophidiicola was also detected on additional California kingsnakes.

Detections and prevention

Since 2008, SFD has been detected in free-ranging and captive snakes from more than 30 species worldwide. Signs of SFD infections may appear as scabs, crusty or flaking scales, open wounds or severe facial swelling and may result in death. Snakes may carry the fungus without showing signs of infection. In California, not all individuals infected with the fungus had visible signs of SFD, suggesting some snakes may have been asymptomatic carriers or were detected with mild or early-stage infections due to the comprehensive surveillance plan as part of this project.

Ophidiomyces ophidiicola can be transmitted via snake-to-snake contact or from a contaminated environment to a snake. There is no evidence that SFD can be transmitted to humans. However, it is possible for humans to transmit the fungus to snakes while handling them or from moving fungal contaminated soil and organic debris with footwear.

To reduce the risk of transmission:

CDFW encourages the public to report sick or dead snakes through its Mortality Reporting web page.

For further information and resources on Snake Fungal Disease visit CDFW’s Snake Fungal Disease web page.

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