Disease and Mortality Monitoring

Bighorn Sheep Capture

The WHL has a critical role in expanding the knowledge of wildlife infectious and non-infectious diseases, the effect of disease on wildlife populations, and health monitoring for the reintroduction of elk, bighorn sheep, and antelope to their native ranges in California.

WHL staff actively collaborate with other researchers. The results of disease investigations are published in scientific journals. This information is used by CDFW, agency partners, universities, and other interested parties across the United States and Canada.

WHL also represents CDFW on matters regarding wildlife health on state, federal, and professional veterinary committees including but not limited to: United States Animal Health Association, California Veterinary Medical Association, Western Wildlife Health Cooperative, and the Regional Emergency Animal Disease Eradication Organization.

Chronic Wasting Disease

Three bull elks in CaliforniaChronic Wasting Disease (CWD) is a fatal neurologic disease of cervids, that include deer, elk, and moose. This disease was first identified in wild deer and has been detected in 26 US states, Canada, Asia, and Europe.

CWD may negatively impact prey populations where it occurs and is a major wildlife conservation and management concern.

CWD has not yet been detected in California. It has the potential to spread to wild deer and elk populations in the state. CWD surveillance is a CDFW priority. Learn more about CWD and how to help!

Rabbit Hemorrhagic Disease

JackrabbitOn May 11, 2020, rabbit hemorrhagic disease virus serotype-2 (RHDV2) was confirmed in a wild black-tailed jackrabbit collected from an area where over 10 dead jackrabbits were found near Palm Springs, Riverside county. Since this initial report, RHDV2 in wild rabbits has been confirmed in the following California counties:

  • Alameda (June 2021)
  • Kern
  • Los Angeles
  • Orange
  • Riverside
  • San Bernardino
  • San Diego

USDA Interactive Map of RHDV2 affected counties

This highly infectious virus affects domestic and wild lagomorphs (members of the rabbit family). RHDV2 can spread quickly and can cause high mortality in affected rabbit populations.

To date, RHDV2 has only been detected in domestic rabbits, wild cottontails, and jackrabbits, but all lagomorph species (including pikas) may be susceptible.

  • RHDV2 poses no risk to humans or other animals.
  • RHDV2 is spread through contact between infected rabbits, their meat or fur, respiratory fluids, urine, feces, contaminated soil or materials in contact with those items.
  • RHDV2 can be easily spread to new areas by moving rabbits or contaminated items, and on shoes or clothing.
  • RHDV2 may also be spread by insects and scavengers after contact with sick or dead rabbits.

Monitoring and Reporting

CDFW is tracking the geographic spread and impact of RHDV2 on wild rabbits, jackrabbits, and hares. Rabbits with RHDV2 may die quickly after infection. Blood may be present at the nose or mouth of the animal.

Help us monitor this new wildlife disease in California!

Please report sick or dead wild rabbits (2 or more) found in an area over a short period of time (3-4 days apart).

Dead wild black-tailed jack rabbitCarcass Disposal and Handling

ALWAYS use disposable glove and/or shovel if you must touch the carcass. Use 10% bleach solution (1 part bleach, 9 parts water) to spray gloves, shovel, and bottom of shoes prior to leaving area where rabbit was found to reduce risk of virus spread.

  • Burial: Carcass should be buried (3 feet minimum) when possible.
  • Incinerate: Carcass may be incinerated. Contact your local animal services agency. They may be able to dispose or incinerate carcasses. Services vary by location and there may be a charge.
  • Landfill Disposal: Carcass may be double-bagged and disposed at a landfill. Spray outer bag with 10% bleach solution. Contact the landfill to ensure they will accept submissions. Local regulations and landfill services vary by location.


Snake Fungal Disease

California is home to nearly 50 native snakes, including 13 species or subspecies listed as Species of Greatest Conservation Need. Many populations are often small, isolated, and vulnerable to infectious diseases. Snake Fungal Disease (SFD) is a newly emerging disease in snakes. It is caused by a fungus, Ophidiomyces ophiodiicola.

  • In 2019, California confirmed its first known case of SFD in a California kingsnake (Lampropeltis californiae) from Amador County.
  • In October 2019, a second case was detected in a non-native Florida water snake (Nerodia fasciata pictiventris) collected in Sacramento County.
  • Since 2008, SFD has been detected in more than 30 snake species in North America and Europe. The fungus is present in at least 38 states. How SFD may impact snakes in California is unknown.

Report sick or dead snakes. Please include photos with your report, if possible to take photos from a safe distance. California’s native snakes thank you!

Symptoms and Signs

signs of snake fungal diseaseSick snakes are often in poor condition and may rest in open areas where exposed to poor weather or predators. The fungal infection may cause the infected skin to shed repeatedly. Visible signs may include:

  • Scabs, skin ulcers, or nodules
  • Crusted or discolored scales
  • Swollen or disfigured face
  • Cloudy eyes (NOTE: eyes can also appear cloudy just prior to natural skin shedding)


Snake-to-snake and contaminated environment-to-snake contact are the primary disease transmission routes. The fungus lives in soil. SFD can be transmitted to snakes through direct contact with other infected snakes, or from mother to offspring at birth in some species.

  • DO NOT attempt to disturb or handle any snake—dead or live.
  • DO NOT move soil from one location to another. The fungus may spread when people track contaminated soil on shoes and clothing.
  • DO NOT release pet snakes into the wild. They can spread disease to native species. Don't let it loose, California!
CDFW works with wildlife rehabilitators, agency partners, and researchers to increase SFD surveillance in California. Biosecurity protocols are used to reduce risk of transmission when handling snakes. There is no evidence SFD is transmittable from snakes to humans. Help us monitor this new wildlife disease in California!


White Nose Syndrome

Little brown bats in caveWhite-nose syndrome (WNS) is a disease caused by a fungus. WNS can kill up to 100% of bats in a colony during hibernation and has major conservation implications. Since 2006, the disease is estimated to have killed million of bats in the United States.

Until recently, the disease had spread slowly from its point of origin in upstate New York. In March 2016, WNS was confirmed in bats in the state of Washington. As part of a national surveillance program, samples were taken from bats at sites in northern California in 2018 and 2019.

In July 2019, the U.S. Fish and Wildlife Service and CDFW announced surveillance results suggesting the fungus that causes WNS is now present in California. Learn more!

Other Diseases

The mission of the WHL is to investigate, monitor, and manage wildlife population health issues in California. WIHL staff responsibilities include the study and surveillance of zoonotic diseases.

Zoonotic disease are caused by harmful germs that can spread from animals to humans - such as viruses, bacteria, parasites, or fungi. Zoonotic diseases are common in the United States and around the world. Learn more about wildlife diseases in California!