Deadly deer disease found in Northern California, including Sonoma County

An outbreak of a disease sickening and killing deer in at least five counties across the state has prompted the California Department of Fish and Wildlife to ask residents to refrain from feeding wild animals and to report potential cases to the department.

Adenovirus hemorrhagic disease, which causes widespread death in deer and has no cure or vaccine, has been found in Napa, Santa Clara, Sonoma, Tehama and Yolo counties. The disease is not known to affect people, pets or domestic livestock.

The disease can leave deer dead, often by water, without any obvious symptoms. Sick deer may drool or foam at the mouth. They also might experience diarrhea, vomiting or seizures. Deer fawns experience the highest death rates following infection, though the disease can significantly impact deer populations overall.

CDFW began receiving increased reports of deer death, both free-ranging and at farm rehabilitation facilities, in May. Alongside wildlife rehabilitation facilities and the California Animal Health and Food Safety Laboratory, CDFW confirmed cervid adenovirus 1 (CdAdv-1) as the cause of the outbreaks.

To reduce the disease's spread, CDFW is encouraging residents to refrain from feeding deer, which can lead to them congregating in large numbers and spread the disease.

"Providing attractants for deer -- food, salt licks or even water -- is against the law for good reason," Dr. Brandon Munk, senior wildlife veterinarian with CDFW's Wildlife Investigations Laboratory, said in a news release. "Because these artificial attractants can congregate animals and promote the spread of disease, it's particularly imperative to leave wildlife alone during an outbreak. There is no cure or vaccine for this disease, so our best management strategies right now are to track it carefully, and to take preventative measures to limit the spread."

A 1993-1994 outbreak of hemorrhagic disease left thousands of deer dead across at least 18 California counties. Since then, CdAdv-1 has been traced back as the cause of multiple outbreaks in California and other western states.

Anyone who observes a symptomatic deer or that encounters a deer dead from unknown causes can submit the information to CDFW's online mortality reporting system.