亞馬遜河居民有些人對狂犬病有抵抗力

Bites From Rabid Vampire Bats May Not Be A Death Sentence

by Michaeleen Doucleff

http://www.npr.org/blogs/health/2012/08/01/157714056/bites-from-rabid-vampire-bats-may-not-be-a-death-sentence?ft=1&f=1001

05:52 pm
  August 1, 2012

Michael & Patricia
Fogden/Corbis

Vampire bats are common in Central and
South America, where they feed on livestock and sometimes people.

Rabies is arguably one of the deadliest
infectious diseases in the world. When left untreated, it's almost always
fatal, and it's not
a pleasant way to go.

But now a study from the Centers for
Disease Control and Prevention challenges rabies' reputation as a killer — at
least for some who get rabies from vampire bats.

The report identifies a group of people in
the Peruvian Amazon who show signs of surviving rabies bites, even though they've never
been vaccinated or treated for the disease.

The findings, published
Wednesday in the American Journal of Tropical Medicine and Hygiene,
suggest that some people may develop a natural protection from rabies after
repeated exposure to blood-sucking bats.

Vampire bats survive on the blood of
mammals. They usually dine on cattle and other livestock, but they will attack
humans when they run out of other options.

Sergio
Recuenco

In
the village of Truenococha, Peru, some people may be naturally protected
against rabies infections

In remote regions of the Amazon jungle,
small communities of people live near bat roosts, and rabies infections are
relatively common among them. At least five outbreaks killed 19 people in the
Peruvian Amazon in 2009.

So a team from the CDC, lead by disease
ecologist Amy Gilbert,
went to two villages near these outbreaks looking for signs of rabies exposure
in healthy people. They took blood samples from 63 villagers and measured their
levels of rabies antibodies — signs that someone has fought off an infection or
received a vaccine.

Surprisingly, 10 percent of the people had
rabies antibodies in their blood, despite never receiving a rabies vaccine or
showing symptoms of the disease.

"These people were exposed to the
virus, but they never become ill," Gilbert tells Shots. "We think
that their immune responses were able to clear the virus before it developed
into [a full] infection."

The researchers aren't sure why some people
were getting sick and even dying from the virus while others weren't. But
Gilbert says adults were more likely than children to have rabies antibodies in
their blood, suggesting that repeated, low-level exposure to the virus produces
the protective antibodies over time.

Nevertheless, Gilbert and her co-author
Brett Petersen aren't sure if the people with the antibodies have become
totally resistant to rabies.

"We don't know what level of
antibodies is required for protection," Petersen tells Shots.
"Anybody with any possible exposure to rabies needs to be treated, even if
they've been vaccinated."

Rabies antibodies have been detected a few
times before in hunters — most notably in an Alaskan
trapper who skinned more than 3,000 foxes during a 47-year period.
But these studies were small, and in most cases, the level of antibodies were
very low.

By comparison, the study in Peru is
"well done and the data are convincing," says Hildegund Ertl,
a vaccine researcher at the Wister Institute who was not involved in the study.

But she also emphasizes that these findings
don't mean that we can rest easy about rabies.

Rabies in dogs, which is more virulent,
still causes 99 percent of rabies deaths worldwide. Plus, the researchers
suspect the Peruvians may have special genes that increase their natural
resistance to the virus.

So regardless of where you are or what bites you, anyone who may have come
in contact with rabies is still advised to seek medical treatment immediately