Untreated Rabies May Not Be Lethal for All, Study Says

WEDNESDAY, Aug. 1 (HealthDay News) — Bucking the notion that
untreated rabies always proves lethal to humans, scientists studying the
virus in isolated pockets of the world have found evidence that either
natural resistance or an immune response may stave off certain death for
some.

Traveling to the Peruvian Amazon, where outbreaks of rabies infections
are spurred by highly common vampire bats, researchers from the U.S.
Centers for Disease Control and Prevention learned that 10 percent of
natives appeared to have survived exposure to the virus without any
medical intervention. Another 11 percent were found to have antibodies in
their blood that would neutralize rabies.

“This is a potential game-changer if the study is repeated
successfully,” said Dr. Rodney Willoughby Jr., a pediatric infectious
disease specialist at Children’s Hospital of Wisconsin and the author of
an editorial accompanying the research. “It suggests either that rabies is
not universally severe or fatal [HIV used to be thought of this way] or
that there are ways of conferring relative resistance to rabies in humans.
If the latter could be identified — these days, probably through genetic
sequencing — then that might afford insights into prevention or
treatment.”

The study is published Aug. 1 in the American Journal of Tropical
Medicine and Hygiene
.

An average of two to four people die in the United States each year of
rabies after bites from animals such as bats, dogs or raccoons. Though
nearly wiped out in the United States due to domestic animal vaccinations,
the infection kills about 55,000 annually in Africa and Asia alone. For
those who believe they’re infected, a series of shots are 100 percent
effective at preventing death.

In Peru, vampire bats regularly seek out meals of mammalian blood from
livestock and humans, using extremely sharp teeth and a blood thinner in
their saliva aptly known as draculin to feed on sleeping people without
awakening them.

CDC researchers interviewed 92 people, 50 of whom reported previous bat
bites. Blood samples were taken from 63 participants, with seven found to
have rabies virus-neutralizing antibodies. Only one of the seven reported
receiving a rabies vaccination, which would generate such antibodies, but
no evidence existed that the rest had sought either a vaccination or
treatment for a bat bite.

Study author Amy Gilbert, a postdoctoral fellow with the CDC’s National
Center for Emerging and Zoonotic Infectious Diseases, said the research
suggests the rabies virus is not invariably fatal to people.

“Generally, most folks presume we don’t develop antibodies to respond
to rabies exposures,” she said, “but this was a scenario where clearly
there were exposures to the virus that did not lead to disease. I think
the same recommendations and advice still hold — that anyone with a bite
exposure to a bat or other carnivore needs to seek out post-exposure
[injections].”

In his editorial, Willoughby noted two recent cases in the United
States (in Texas and California) where children recovered from rabies
without intensive treatment after suspected bat bites.

“Knowing that there is a continuum of disease, even for infectious
diseases like rabies, should push us harder to try for cures when
confronted by so-called untreatable infectious diseases,” he wrote.
“Modern therapeutics can move us . . . toward greater survival, even when
specific cures or antidotes remain undiscovered.”

More information

The U.S. National Library of Medicine offers more on rabies.

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