Culling vampire bats in South American nations does not curb the spread of rabies, in fact it could actually be counterproductive, a study suggests.

Until now, it had been assumed that controlling bat numbers would, in turn, control the spread of the rabies virus.

Researchers say rabies is found in most bat populations, but vampire bats - which feed on mammals' blood - are responsible for most infections.

The findings have been published in the Proceedings of the Royal Society B.

"We found that rabies is there no matter what," said co-author Daniel Streicker, an ecologist at the University of Georgia, US.

"The size of the bat colony didn't predict the proportion of bats that were exposed to the virus.

"That's important because if there is no relationship between bat population density and rabies, then reducing the bat population won't reduce rabies transmission within bats."