American scientists studying remote communities in the Peruvian Amazon ravaged by vampire bats have found the first evidence of humans immune to rabies.
The team from the US government’s Centers for Disease Control and Prevention (CDC) found that six of 63 people tested had rabies anti-bodies in their blood, without ever having been vaccinated for the disease. The 63 were part of a larger sample group of 92, 50 of whom reported having been bitten by bats.
It remains unclear whether the six were born with the anti-bodies or developed them after being infected with rabies and surviving despite the lack of medical facilities in villages rarely visited by doctors.
Either way, the discovery, revealed in this month’s American Journal of Tropical Medicine and Hygiene, turns on its head the traditional notion that without immediate treatment, exposure to rabies means a certain hideous death.
Amy Gilbert, the lead researcher, said that death was still the nearly inevitable fate for anyone developing rabies symptoms, even with the best medical care. However, the new research indicates that some people exposed to the disease may never develop those symptoms.
“These are very small villages and, when they witness ten people dying from what is a horrible disease, it is incredibly traumatic," said Ms Gilbert. "We want to help raise awareness of the problem and try to develop a more proactive response."
The CDC discovery is now expected to pave the way for pioneering research to develop both new kinds of vaccinations and treatment for rabies. That could even involve genome sequencing.
“These genetically unique populations may provide information on which pathways in human biochemistry and physiology promote resistance to human rabies,” noted Rodney Willoughby, a disease expert from the Children’s Hospital of Wisconsin, in an editorial accompanying the study.
Although eliminated from the UK, rabies still kills many in the developing world, mainly in Africa and Asia, where around 55,000 people die annually from the disease. But cases are also rising in China, the former Soviet republics and Latin America.
The Peruvian Amazon is one hotspot, with the disease widespread among the numerous vampire bat colonies there. The bats prefer to feed off wild mammals and livestock but also regularly target humans, biting their victims while they sleep and injecting an anticoagulant called “draculin”, before sucking out mouthfuls of blood.
With many locals rarely seeing a doctor – and now the possibility that some exposed to rabies fail to develop the disease – the CDC team believes that the number of rabies cases in the Peruvian Amazon may be seriously under-reported.
Even so, the problem is now so widespread that authorities here are considering a pre-emptive vaccination campaign in some parts of the jungle.