Vampire bats: Ugly, scary and tough

It sounds like something out of a badly made 1970s horror film, and it would appear the practice of “vampiricide” is proving just about as effective as one would expect if it actually were a big screen offering.

Vampiricide involves applying a poisonous paste to captured vampire bats, which then spread it to others through mutual grooming back in the roost.

However, researchers working in Latin America now believe that the effort not only does not reduce rabies’ prevalence in vampire bat colonies in the region; it may, in fact, increase it, according to Agence France-Presse.

“We detected something that is a little bit worrying,” University of Georgia researcher Daniel Streicker said Wednesday.

The study was conducted in Peru from July 2007 to October 2010 by a team from the United States and Peru.

“In areas that were sporadically culled during the course of the study, we saw an increase in the proportion of bats exposed to rabies,” he said.

Colonies that were never culled had the lowest prevalence, the researchers reported.

Rabies causes some 50,000 human deaths around the world every year; bats can live with infections for years.

In Latin American farming areas, livestock is the primary food source for vampire bats – the only the only parasitic mammalian species in the world – which are the prime transmitter of rabies in the region.

They sometimes turn to humans for food, especially in areas where their habitat has been destroyed, Agence France-Presse reported.

Bats also carry other transmissible viruses like those that cause Nipah and Ebola, but are a vital help for humans by eating mosquitos and acting as pollinators.

Over the past 40 years, efforts to control the spread of rabies in Peru have focused on culling vampire bats, with the assumption being that if the number of infected bats could be sufficiently reduced, the rabies virus would die out in targeted colonies.

Instead, the scientists found the virus was present in every colony they tested, no matter its size.

“That’s important because if there’s no relationship between bat population density and rabies, then reducing the bat population won’t reduce rabies transmission within bats,” Streicker said.

The researchers theorized that bats repeatedly exposed to rabies may develop immunity to the disease.

Vampiricide would be effective at killing these immune, adult bats but perhaps not juveniles, which are unlikely to groom older bats, according to the wire service.

“When you kill off the adult bats that may be immune, you’re making space for susceptible juvenile bats,” said Streicker.

It could also be that bats immigrate from neighboring colonies to fill roost space left vacant by culling, or that the number of births increase as humans reduce competition for resources and space.

The scientists are hopeful that the findings, published in the journal Proceedings of the Royal Society B: Biological Sciences, will help officials in Peru develop more effective methods of combatting rabies infection.

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