Bats and disease
Bats and viruses - coming soon
Bats play a vital role in ecosystems around the world. They are a diverse group of animals accounting for over 20% of the world's mammals.
In the UK, bats are Indicator Species, because changes to our bat populations can indicate changes in aspects of biodiversity. For example bats might suffer when there are problems with insect populations (because our bats feed on insects) or when habitats are destroyed or poorly managed (for example, some bats only live in large woodlands).
In addition to their important roles in many environments around the world, bats have also been recognised as hosts of some viruses that can impact human health. These are called ‘zoonoses’ or 'zoonotic diseases'(human diseases originating in animals).
The transmission of a virus from wild animals to humans is normally the result of human alterations to the environment. For example with bats, destroying their habitat (by deforestation and intensive building for example) and the intensification of livestock farming, can mean that bats are forced to live closer to humans, livestock and pets than they would naturally. This closer contact can result in cases of spillover of a virus into human populations either directly or via an intermediate host (e.g livestock).
The only known zoonotic disease associated with bats in the UK is European Bat Lyssavirus, a rabies virus. It has only been found in a very small number of bats. There is no risk if you do not handle bats. For more information visit the bats and rabies pages.
Globally, bats are considered ‘reservoirs’ (long-term hosts) of a number of viruses, many of which are not harmful and cannot be passed to humans.
In many cases the viruses bats carry do not appear to have any impact on the health of the bats. This may be because bats have evolved over many millions of years and many viruses have evolved with them, meaning that they do not cause disease in the bats themselves.
The relationship between bats and infectious diseases is complex, and this has been recognised by the EcoHealth Alliance: "We face an important challenge in our efforts to protect these important animals from hunting, habitat loss, and disease, while striving to understand the complex situations that cause bat viruses to spill over into human and animal populations and also protect human and domestic animal health."
Some bat life-history traits may explain why bats are reservoirs of a number of viruses. This includes the relatively long life spans of bats, the distances that bats cover by flight when feeding, commuting or migrating and their often social roosting behaviour (sometimes in close proximity to people). There is obviously some variation between species in these traits but one thing all bats have in common is their ability to fly and it is this trait in particular that may be the reason that bats are able to carry, but not be affected by, many viruses.
Flight is very energetically expensive and it is believed that this has resulted in bats developing excellent immune systems which allow them to fight off disease.
Understanding how bats do this may lead to benefits for human health. In fact there are many aspects of bats' ability to fight disease that researchers believe could ultimately lead to advances in human health care.
It is important to consider bats and diseases from a UK perspective. As already explained above, the only known zoonotic disease associated with bats in Britain is rabies, specifically, European Bat Lyssavirus type 2 (EBLV2). This disease has only been associated with one human case in the UK and has been found in just 14 bats (all of one species, Daubenton’s bats) despite over 13,000 bats having been tested, the risk to the public is therefore very small. EBLV2 is transmitted via a bite or scratch therefore there is no risk to the public if they do not handle bats.
There are no other known zoonotic diseases associated with bat populations in the UK.
This page discusses bats and disease in a human health context. There are however some diseases that are affecting the bats themselves with dramatic effects. For more information see our white-nose syndrome pages.