Featured Research

from universities, journals, and other organizations

First indication of people naturally protected against rabies found in remote Amazonian communities regularly exposed to vampire bats

Date:
August 1, 2012
Source:
Burness Communications
Summary:
Challenging conventional wisdom that rabies infections are 100 percent fatal unless immediately treated, scientists studying remote populations in the Peruvian Amazon at risk of rabies from vampire bats found 11 percent of those tested showed protection against the disease, with only one person reporting a prior rabies vaccination. Ten percent appear to have survived exposure to the virus without any medical intervention.

Challenging conventional wisdom that rabies infections are 100 percent fatal unless immediately treated, scientists studying remote populations in the Peruvian Amazon at risk of rabies from vampire bats found 11 percent of those tested showed protection against the disease, with only one person reporting a prior rabies vaccination. Ten percent appear to have survived exposure to the virus without any medical intervention. The findings from investigators at the U.S. Centers for Disease Control and Prevention (CDC) were published August 2in the August 2012 issue of the American Journal of Tropical Medicine and Hygiene.

"The overwhelming majority of rabies exposures that proceed to infections are fatal. However, our results open the door to the idea that there may be some type of natural resistance or enhanced immune response in certain communities regularly exposed to the disease," said Amy Gilbert with the CDC's National Center for Emerging and Zoonotic Infectious Diseases, who is the paper's lead author. "This means there may be ways to develop effective treatments that can save lives in areas where rabies remains a persistent cause of death."

Rabies experts estimate the disease kills 55,000 people each year in Africa and Asia alone, and appears to be on the rise in China, the former Soviet Republics, southern Africa, and Central and South America. According to the CDC, in the United States, human deaths from rabies have declined over the past century from 100 annually to an average of two per year thanks to an aggressive campaign to vaccinate domestic animals against the disease.

In general, people who believe they may have been exposed to rabies are advised to immediately seek treatment which involves post-exposure prophylaxis (PEP) -- a series of injections -- to prevent the exposure from causing an active infection. These preventive treatments, when administered promptly, are 100 percent successful at preventing disease. Scientists have documented only a small number of individual cases, including one last year in California, in which an exposure to rabies proceeded to infection and the victim survived. Most of those survivors still required intensive medical attention, including one case in Wisconsin in which doctors induced a coma, though this approach has not been successful in most subsequent cases.

This CDC study was conducted in collaboration with the Peruvian Ministry of Health as part of a larger project to understand better bat-human interactions and its relation to rabies and emerging diseases that may be transmitted by bats. For their research, scientists traveled to two communities (Truenococha and Santa Marta) in a remote section of the Peruvian Amazon where outbreaks of fatal infections with rabies caused by bites from vampire bats -- the most common "natural reservoir" for the disease in Latin America -- have occurred regularly over the last two decades. They interviewed 92 people, 50 of whom reported previous bat bites. Blood samples were taken from 63 individuals and seven (11 percent) were found to have "rabies virus neutralizing antibodies."

One out of the seven individuals reported receiving a rabies vaccination -- which generates antibodies to the rabies virus -- but there was no evidence that the other six had received anti-rabies vaccine prior to the blood sampling or had sought out any medical attention for a bat bite, evidence that they had harbored the virus itself.

The researchers acknowledged that they could not conclusively determine whether the antibodies were caused by an exposure to the virus that was somehow insufficient to produce disease. But they believe their evidence "suggests that (rabies virus) exposure is not invariably fatal to humans."

Gilbert said non-fatal exposures may happen more often than some think because "unless people have clinical symptoms of the disease they may not go to the hospital or clinic, particularly where access is limited."

"We all still agree that nearly everyone who is found to be experiencing clinical symptoms of rabies dies," Gilbert said. "But we may be missing cases from isolated high-risk areas where people are exposed to rabies virus and, for whatever reason, they don't develop disease."

In the Amazon region where the study was conducted -- the Province Datem del Maranon in the Loreto Department of northern Peru -- vampire bats, which live off of mammalian blood, regularly come out at night and prefer to feed on livestock. But in the absence of those food sources, they are known to seek out a meal from humans. They can use their extremely sharp teeth and the anticoagulant that naturally occurs in their saliva (appropriately referred to as "draculin") to feed on a sleeping person without awakening them. The rabies virus circulates extensively among vampire bat colonies in the region, and when an infected bat feeds, it passes along the virus to its host.

"This type of thorough and persistent scientific rabies investigation lends continued support to the belief that even the most dangerous of infectious diseases may be amenable to treatment," said James W. Kazura, MD noted infectious disease expert and president of the American Society of Tropical Medicine and Hygiene (ASTMH). "Continued investment of resources is essential for us to protect the health and well-being of innocent people whose lives and livelihoods are needlessly threatened by infectious diseases like rabies."

Gilbert and her colleagues hope their findings will prompt further studies in remote, at-risk communities to see if the results are replicated. In an editorial accompanying the study, Rodney E. Willoughby, a pediatric disease specialist at Children's Hospital of Wisconsin, said if it turns out there are distinct populations of people with "complete or relative resistance to rabies," there could be the potential to use whole genome sequencing to help develop new, life-saving treatments for rabies infections.

"Careful, respectful genetic study of these genetically unique populations may provide information on which pathways in human biochemistry and physiology promote resistance to human rabies," he wrote. "Equally important, 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…."

Gilbert noted that the study was done as part of a larger public health effort to address a series of rabies outbreaks in the Amazon, where some health officials are now considering conducting pre-emptive vaccination campaigns in areas where risk of rabies is high and availability of medical care low. She said that while her study highlights people who appear to have survived an exposure to the virus, the fact remains that rabies outbreaks in small communities in the region have left tragic results.

"These are very small villages and, when they witness ten people dying from what is a horrible disease, it is incredibly traumatic," Gilbert said. "We want to help raise awareness of the problem and try to develop a more proactive response."


Story Source:

The above story is based on materials provided by Burness Communications. Note: Materials may be edited for content and length.


Cite This Page:

Burness Communications. "First indication of people naturally protected against rabies found in remote Amazonian communities regularly exposed to vampire bats." ScienceDaily. ScienceDaily, 1 August 2012. <www.sciencedaily.com/releases/2012/08/120801185110.htm>.
Burness Communications. (2012, August 1). First indication of people naturally protected against rabies found in remote Amazonian communities regularly exposed to vampire bats. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/2012/08/120801185110.htm
Burness Communications. "First indication of people naturally protected against rabies found in remote Amazonian communities regularly exposed to vampire bats." ScienceDaily. www.sciencedaily.com/releases/2012/08/120801185110.htm (accessed July 31, 2014).

Share This




More Health & Medicine News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Health Insurers' Profits Slide

Health Insurers' Profits Slide

Reuters - Business Video Online (July 30, 2014) Obamacare-related costs were said to be behind the profit plunge at Wellpoint and Humana, but Wellpoint sees the new exchanges boosting its earnings for the full year. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com
Concern Grows Over Worsening Ebola Crisis

Concern Grows Over Worsening Ebola Crisis

AFP (July 30, 2014) Pan-African airline ASKY has suspended all flights to and from the capitals of Liberia and Sierra Leone amid the worsening Ebola health crisis, which has so far caused 672 deaths in Guinea, Liberia and Sierra Leone. Duration: 00:43 Video provided by AFP
Powered by NewsLook.com
At Least 20 Chikungunya Cases in New Jersey

At Least 20 Chikungunya Cases in New Jersey

AP (July 30, 2014) At least 20 New Jersey residents have tested positive for chikungunya, a mosquito-borne virus that has spread through the Caribbean. (July 30) Video provided by AP
Powered by NewsLook.com
Xtreme Eating: Your Daily Caloric Intake All On One Plate

Xtreme Eating: Your Daily Caloric Intake All On One Plate

Newsy (July 30, 2014) The Center for Science in the Public Interest released its 2014 list of single meals with whopping calorie counts. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

    Environment News

    Technology News



    Save/Print:
    Share:

    Free Subscriptions


    Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

    Get Social & Mobile


    Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

    Have Feedback?


    Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
    Mobile: iPhone Android Web
    Follow: Facebook Twitter Google+
    Subscribe: RSS Feeds Email Newsletters
    Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins