Beware of all types of bat exposure, BC MDs warned

CMAJ 2000;162(13):1862

Dr. Danuta Skowronski, physician epidemiologist at the BC Centre for Disease Control, says that such action should be taken when people awaken to find a bat in the room, or when unattended children and mentally handicapped or impaired persons are found in the presence of a bat (see CMAJ 1997;157[1]:55). In such cases, she says, RPEP should be offered even if a bite or scratch is not obvious. "All bat contact should be assessed very cautiously," says Skowronski says. "We're beginning to recognize that cases we couldn't specify previously were actually bat rabies."

A check with some other provinces showed that CDC guidelines are also being followed in Alberta and Ontario, but not in New Brunswick.

Although the last rabies death in Canada occurred in 1985, there have been 36 such deaths in the US since 1980, and 21 were due to bat-variant rabies. More troubling is that "a bite was identified in only 1 or 2 of them."

Experts aren't certain why the contact has been so hard to pin down, but there are several possibilities. Bat teeth are thin and needle-like and it's possible individuals are bitten without realizing it. Bats are also inclined to lick their claws and wings, and may deposit infected saliva there that can be transferred through a scratch or by touching an existing wound rather than by biting. (Aerosol transmission is not a concern, except for individuals who receive extended or severe exposure, perhaps by spending time in a cave filled with bats.)

But while the method of transmission may be up for debate, the response is clear. Once exposure has been verified, patients should be offered the standard prophylaxis even if it is many days after the exposure, because the incubation period for rabies varies.

Although bats are not the only carriers of rabies in Canada — skunks, foxes and, more recently, raccoons in Ontario are all vectors for the disease — their ability to get into homes and cottages makes them a special concern. Although the prevalence of rabies in bats is less than 1% in random surveys, it is somewhere between 5% and 10% in bats submitted for testing, probably because sick bats are more likely to come into human contact.

Still, the message is not always getting through to physicians. Last year, an 11-year-old BC girl was bitten on the lip by a bat when it flew in her bedroom via an open skylight. Two hospitals failed to advise the girl's parents that she should receive immediate RPEP. Fortunately, the parents contacted their local health unit and the girl received prophylaxis. The bat tested positive for rabies.

"We clearly need to get the information out to more health care workers," Skowronski says of the case. "Rabies is not a disease you take chances with." — Daphne Gray-Grant, Vancouver

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