Researchers have discovered six people living in remote areas of Peru (Truenococha and Santa Marta) with natural antibodies against rabies despite never having received a vaccination for this deadly virus. They hypothesize that vampire bats actually transmitted small doses of the virus to people over time creating the natural antibodies. All six individuals reported having been exposed to the bats either through a bite or direct contact (scratch, touching).
While the levels of antibodies in the individuals were low, they might be enough to trigger an immune response against the rabies virus if exposed. Since this was such a small sample of people with natural immunity against the virus, more studies are needed to verify if repeated exposure to the bats (and hence small doses of the virus) really would be sufficient to build up natural antibodies to thwart an infection.
Gilbert AT, Petersen BW, Recuenco S, Niezgoda M, Gomez J, Laguna-Torres VA, and Rupprecht C. Evidence of rabies virus exposure among humans in the Peruvian Amazon. The American Journal of Tropical Hygiene and Medicine. 87(2): 206-215, 2012.
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