Bat attacks on humans increasing due to urbanisation and deforestation

'Diseases in bats have been around for a long time and historically have not been a problem. Now, there is cause for concern,' expert says

Big-Eared Woolly Bats also called Woolly False Vampire Bats roosting in a cave in Campeche, Mexico (Roberto González / Creative Commons)

Bats have been attacking humans in increasing numbers because their natural habitats are being destroyed through deforestation in the Brazilian Amazon, scientists have found.

In the last three months alone, vampire bats have bitten over 40 residents in the country’s north-eastern region, one of whom has died.

The wave of night-time attacks has caused blood-soaked beds and inflicted deep wounds on victims, many of whom are being treated for possible rabies exposure.

“Diseases in bats have been around for a long time and historically have not been a problem. Now, there is cause for concern as cities expand displacing bats creating increased contact with humans,” Dr Julian Drewe from the Royal Veterinary College told The Independent.

“In light of the Brazil attacks, the authorities are trying to control the bats, poisoning them and removing their roosting sites. However, this is likely to displace the bats to another area rather than solve the problem.”

He explained that the location of bites determined how fast rabies occured.

“If you are bitten on your toe, it takes a longer time for you to succumb to the disease than if you are bitten on the head," Dr Drewe said.

"This is because the virus has further to travel to reach the brain.”

He stressed that the Brazilian authorities must take the threat of rabies seriously, and encourage the public to seek medical attention should they be bitten.

Dr Ron Behrens, Associate Professor of Tropical and Travel Medicine at the London School of Hygiene and Tropical Medicine said that “If bitten... there is approximately 24 hours where treatment with rabies immunoglobulin will prevent the virus entering the nervous system.

“In the early stages the symptoms are mild... A unique symptom is that of hydrophobia where the patient has a fear of water - the sound, sight and thought of water causes anxiety and panic, and they are not able to drink or swallow as a result of this. The prognosis is bleak as most patients with rabies encephalitis die.

“[Treating rabies] is very expensive... and most centres outside capital cities and even in capital cities in many countries won't have it available.

“Fortunately if you have had a course of three rabies vaccines before you are exposed, known as a pre-exposure course, this will provide life-long protection should you be bitten.”

Dr Drewe, a Veterinary Epidemiologist whose research interests include diseases which transmit between wildlife, domestic animals and humans, said he had noticed other instances of human activity prompting the transmission of viruses from bats.

“In Malaysia, pens were built for pigs in orchards,” he said.

“At night, fruit bats would come to roost in the trees, eat the fruit and in the process drop saliva, half-eaten fruit and contaminated droppings into the pig pens below. The pigs became infected with what later became known as the Nipah virus which the pigs then transmitted to humans.”

More than one hundred people died during the 1998 Nipah outbreak, resulting in a widespread pig cull.

Bats in the UK do not pose a threat to the human population. The only known case of a man being infected with a disease transmitted from a bat occurred in 2002 when a wildlife worker was bitten and infected with the Lyssavirus, closely related to rabies.

“The main cause for concern for the transmission of rabies into Britain would be illegally bringing a dog or a cat into the UK without a passport, as pet quarantine is no longer standard and they could be incubating rabies,” Dr Drewe said.