Wild bats emerging from roosts are testing positive for rabies

Public health officials reported last week that seven wild bats tested positive for rabies in Los Angeles County so far this summer, and more are expected as bat season gets underway.

Bats are the primary carrier of rabies, a neurological disease that is fatal to humans and pets without immediate post-exposure treatment. And Los Angeles County has led all counties in the state with the highest number of rabid bats for several decades, state records show.

Summer and early fall months are the primary time for rabid bats to begin showing up in homes or public spaces, according to the Los Angeles County Department of Public Health. A bat with rabies will fly in the daytime, or hang lifeless on the side of a wall or lie on a sidewalk. Anyone who sees a bat in distress should not touch it or try to revive it, officials said.

“Rabies is 100% fatal. It is really serious. It has one of the highest fatality rates of any disease out there,” emphasized Dr. Karen Ehnert, director of veterinary public health for the county.

Of the seven rabid bats found this year, four were in the Santa Clarita area, and one each in Glendale, Altadena and Los Feliz, county health officials reported last week.

Most were in backyards or on the outside wall of a house. The rabid bat in the Los Feliz area was alive in the common area of an apartment complex.

A bite from a rabid bat, even a slight puncture from the bat’s sharp, needle-like teeth, can transmit the Rhabdovirus, which causes severe zoonotic encephalitis. It can take a week or even years to produce symptoms, such as headache, fever, chills, cough or sore throat, nausea, vomiting and malaise. If not treated before symptoms manifest, it is usually too late, Ehnert said.

No human rabies cases have been reported in L.A. County for a least a decade. The last case was a Central American immigrant who was bitten by a dog in his home country, she said. Only about 1% of the wild bats in nature have rabies. But 15% of bats found near people and pets in L.A. County test positive for rabies, county health reported.

Rabid bats are found every year in Los Angeles County and the numbers have skyrocketed for the past two years.

In 2021, the county health department found 68 rabid bats, the highest number discovered in the county since testing of bats for rabies began in 1961. L.A. County had the highest number of any county in the state, and Orange County was second with 17 rabid bats.

The number of rabid bats in L.A. County dropped slightly, to 50 in 2022. But that number is still way above 15 years ago when there were about eight or 12 infected bats, Ehnert said.

This year, the number of rabid bats is much lower than in the last two years at this time, she said. “We may be on the downhill slope of this surge in rabies cases. I’m hopeful this will start going down. We will see.”

Last year, bats carrying the rabies virus were found in unusual places, such as a swimming pool, inside a car and in several businesses, while most were found outside homes, the county reported.

If a bat is found inside a home overnight, the occupants should not release it. Instead, they should call their local animal control office so the bat can be tested, Ehnert said. Likewise, if a bat was found in a mountain cabin or at a summer camp, authorities should be called so the bat can be tested for the rabies virus, otherwise all those exposed need to be tested and receive injections that can cost from $25,000 to $40,000, she explained.

Bats with the rabies virus are more prevalent in certain areas.

Of the 50 infected bats identified in 2022, 30 were in Santa Clarita, Stevenson Ranch and Canyon Country.

The county often finds that 50% of bats they test in Santa Clarita in late summer and early fall are positive for rabies. The county asks homeowners associations and local veterinarians to spread the word.

“We have a lot of bats here where I live,” said Dianne Hellrigel, Santa Clarita resident and naturalist who started the Community Santa Clarita Hiking Club. “We probably have more bats than most areas because we are right near the Angeles National Forest.”

“I see them flying in the air catching bugs,” she said. “Generally they live in caves or where the rocks have spread apart.”

Hellrigel said if you leave them alone, they will leave you alone. In fact, bats in the foothills and near the forest are beneficial because they eat insects. But if they have the virus, contact with pets and humans can be deadly.

There are more than 20 species of bats in Southern California. Some like to roost in pine trees and palm trees. Others like to hang out on the roofs of newer homes. They especially like Spanish-style tile roofs, which could explain why bats are more prevalent in newer housing developments in Santa Clarita and Stevenson Ranch, Ehnert said.

She used to think they lived in the forest but with the recent spate of hotter wildfires due to climate change, many forest plants are burned, leaving fewer insects for the bats to eat. Since they like to munch on moths, they are following them to street lamps in newer housing tracts, she said.

“It could be all these fires are forcing the bats to become more suburban bats,” she said.

In June 2022, a bat flew into the dining area at the Malibu Café at Calamigos Ranch and one person and possibly more handled the bat. It also came in proximity to a group of children. County health officials put out a bulletin urging anyone at that restaurant that came in contact with the bat to get evaluated for post-rabies treatment.

Since no one is counting bats, their numbers are a mystery. But Ehnert knows they come out of their roosts in July, August and September. “We know at this time of year there are more bats and more bats with rabies. And the percentage of positive tests goes up, especially in Santa Clarita,” she said.

For a look at where rabid bats were found and tips on how to protect yourself, family and pets, go to publichealth.lacounty.gov. 

After a bat encounter, call 213-288-7060 or email vet@ph.lacounty.gov.