By Tom Gibb
BBC News, Sao Paulo
Health authorities in northern Brazil are trying to cope with a wave of attacks on humans by vampire bats infected with the deadly rabies virus.
Vampire bats feast on the blood of mammals
Rabies caused by bat bites has killed 23 people in the last two months.
It is not the first wave of attacks by vampire bats in the Amazon, but Brazilian authorities say this latest outbreak is unusually serious.
Some experts are blaming deforestation in the Amazon region for this latest wave of attacks.
Sixteen people died of rabies after being bitten by bats in an area of marshlands in the northern state of Maranhao. Seven more died in another part of the state.
Health authorities say they have treated more than 1,300 people for rabies after being attacked by vampire bats, almost always at night in their houses.
In the affected areas, people have been trying to fill gaps in the walls of their huts with banana leaves to stop the bats getting in.
Some experts have blamed the attacks on destruction of the rainforest, denying the bats of their natural habitat.
But others have suggested the vampire bat population may have grown rapidly, with the spread of cattle farming in the region providing an ample food supply.
Mass attacks on humans have occurred in other cattle regions in Latin America when the cattle are suddenly removed.
The bats drink the blood of other mammals while they are asleep. They are the main carriers of rabies in Brazil.