Davis residents are reminded to avoid contact with dead or sick bats after two dead bats found at the Covell Boulevard pedestrian overpass west of F Street tested positive for rabies.
A total of 12 dead bats were found near the overpass last Saturday, according to Yolo County spokeswoman Beth Gabor, and two were tested for rabies. The county learned Friday that both had tested positive.
Residents are urged not to touch a dead or sick bat on the ground but instead to notify Yolo County Animal Services at 530-666-8900.
Bats are very common in Davis, with the underside of the Covell overpass one of many areas around town serving as home to bat colonies. Bats also tend to roost in the walls and attics of houses, apartment buildings and mobile homes, says local expert Mary Jean “Corky” Quirk, founder of the NorCal Bats rescue and education organization.
The largest colonies of the migratory Mexican free-tailed bats, she said, actually make their home in the Yolo Bypass east of Davis during the summer months, when as many as 250,000 bats gather there, many to give birth to their young under the Yolo Causeway.
Summer is also when Quirk sees the percentage of bats with rabies go up, to as many as one in every seven bats in Yolo County.
“This time of year I see more rabid bats than any other time,” she said.
Nationally, the Centers for Disease Control and Prevention report about 6 percent of bats submitted for testing — including those that appear to be sick or weak — test positive for rabies.
The average for California, Quirk said, is probably more like 10 percent, and higher still for Davis.
Quirk said bats living in the wild tend to have a lower rate of rabies because they aren’t as likely to bite each other and transmit the disease. She suspects urban living — like that in Davis — is much more stressful for bats, which in turn leads to more fighting and biting in the roost. As with humans, the disease can take weeks or even months to manifest symptoms in bats, but it is always fatal.
And while people should be very cautious, particularly when they come across a bat that appears sick, Quirk noted that people “shouldn’t be worried about bats that are doing what they’re supposed to be doing.”
“But we need to be smart,” she added. “Any wild animal lying on the ground is a problem.”
Rabies transmission can occur from minor, even unrecognized bites from bats, the CDC says, and post-exposure vaccination is recommended for anyone with a bite, scratch or mucous membrane exposure, unless the bat has tested negative for rabies.
Introduction of the rabies vaccine has cut down on human cases of rabies significantly, with the CDC reporting a total of 19 human cases between 1997 and 2006. Seventeen of those cases were associated with bats and in eight of them, individuals picked up a bat found inside a building or outside on the ground.
Quirk said the current rabies vaccine series given following exposure is nothing like its early days, which involved a series of painful shots in the abdomen. Now, she said, “it’s no worse than getting a tetanus shot.”
Absent vaccination, symptoms of the rabies virus can occur weeks — even months — after exposure and initially include fever, headache and weakness. As the disease progresses, more specific symptoms appear and may include insomnia, anxiety, confusion, agitation, an increase in saliva, difficulty swallowing and a fear of water. Death usually occurs within days of the onset of these symptoms, the CDC reports.
Pets who may have been bitten should be seen by a veterinarian and pet owners are urged to keep rabies vaccinations current for dogs, cats and other animals.
And while caution is urged to prevent rabies infection, many wildlife experts — including Quirk — are quick to point out that bats play key roles in ecosystems around the globe. In Yolo County, with its significant agricultural production, bats protect crops by eating harmful insects.
Quirk told The Enterprise earlier this year that a colony of 1,000 bats will eat the equivalent of two brown grocery bags full of bugs each night.
Learn more at www.norcalbats.org.
— Reach Anne Ternus-Bellamy at email@example.com or 530-747-8051. Follow her on Twitter at @ATernusBellamy