Bats and health worldwide

Bats and Zoonoses

Like all life on earth, bats around the world carry a variety of microbes, including viruses, bacteria, parasites, and fungi. These microbes can be transmitted to humans and other animals. Not all microbes cause disease. In fact, most microbes are harmless and some can even be beneficial. Pathogens are a subset of microbes that cause disease.

Pathogens can cause disease by entering the body and using the body's resources to replicate. Zoonoses are human diseases of animal origin and these are therefore the pathogens of the most interest to public health.

Transmission of zoonotic diseases from bats is primarily by direct contact, ingestion, indirect contact with invertebrate vectors and contaminated inanimate objects, or inhalation of aerosolized materials. We can protect ourselves from most diseases by following basic hygiene procedures.

Viral zoonoses

Bats host a number of viruses but most are not harmful to people or other species and cannot be passed to humans. The most up to date research has demonstrated that bat species do not carry any more disease-causing viruses than other mammal groups.

Over the past 50 years, several viruses, including Ebola virus, Marburg virus, Nipah virus, Hendra virus, severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory coronavirus (MERS-CoV) and SARS-CoV-2, have been linked back to various bat species. Despite decades of research into bats and the pathogens they carry, the fields of bat virus ecology and molecular biology are still young, with many questions largely unexplored.

These viruses often don’t seem to harm the bats that carry them, which points to a long history of co-evolution. ‘Spillovers’ from bats to people either occur directly, through contact with infected bats or indirectly through intermediate hosts such as domestic animals or wildlife that have been contaminated by blood, saliva, urine or faeces of bats.

Outbreaks of such zoonotic diseases have increased in recent decades often as a result of bushmeat consumption as well as human encroachment into natural habitats involving deforestation and agricultural intensification. Our ability to identify the causes of such disease has also increased. Below we present summaries of our current knowledge about bat borne pathogens that cause human disease.

Lyssaviruses cause rabies, a fatal disease of the nervous system. Numerous diverse lyssavirus variants are found in various animal species throughout the world, all of which can cause fatal human rabies. In the UK we have a single zoonotic disease associated with our native bat species The European Bat Lyssavirus - EBLV-1 and EBLV-2 - and found only in our Daubenton’s and Serotine bat populations at low levels. we do not have Classical rabies (RABV) circulating in wildlife or domesticated animals.

Classical rabies (RABV) is well controlled in Europe, Australia and North America, where there have been less than 100 cases ever reported - thanks to good healthcare and education. However, the figure you will often see reported in the media is a worldwide figure of around 59,000 people dying from rabies each year, which also includes cases in Africa and Asia, and Latin America, where circulation of rabies occurs in wildlife and domesticated animals, is poorly controlled, and access to healthcare limited.

Currently 15 species of Lyssavirus are recognised (including EBLV), all but two of which have been isolated from bats. An excellent vaccine is available although its efficacy against some of the newly discovered rabies viruses has yet to be established.

Ebola, a filovirus, causes severe viral haemorrhagic fever. There have been waves of local outbreaks with high human death rates, in isolated forest villages across central and west Africa. It has reached towns and cities due to transport links. Infections result from contact with carcasses of wildlife carrying the virus. This includes chimpanzees, apes and forest duikers. Although antibodies to Ebola have been linked to bat species, investigations have failed to reveal active Ebola infection in a bat. People preparing and eating bushmeat are most at risk. Ebola has a high infection rate from person to person, there is no direct cure, but there is now a vaccine. There is no risk of catching Ebola from any of the UK’s native bat species.

Marburg is the only filovirus that has been isolated from a bat (Rousettus aegyptiacus), which is considered to be the natural reservoir. Marburg is a rare hemorrhagic fever virus, similar to Ebola, and is caught through contact with the body fluids of infected animals, and through broken skin and unprotected sex. It is present across Africa and historically also occurred in labs in Europe and the Soviet Union. The disease in humans is rare, but it has high fatality rates. There have been around 500 recorded deaths. Spillovers to humans occur occasionally, mainly among mine workers in Uganda and tourists who visit caves. The largest outbreak occurred in Angola over decade ago, with 252 cases, 90% of which were fatal. There is currently no vaccine. There is no risk of catching Marburg from any of the UK’s native bat species

Severe Acute Respiratory Syndrome (SARS) is a lung disease caused by the coronavirus SARS-CoV. It was first discovered in people in 2002 in China and spread into a global pandemic. There were over 8,000 confirmed cases, and nearly 800 people died. The virus was traced back to masked palm civets and raccoon dogs in a market in Guangdong Province as intermediate hosts, and horseshoe bats as hosts.

Middle East Respiratory Syndrome (MERS) caused by a coronavirus, MERS-CoV was first reported on the Arabian peninsula in 2012, is spread mainly by human to human contact and has infected around 1200 people worldwide, about 450 of whom have died. Because a small fragment of viral DNA from an Egyptian tomb bat (Taphozous perforatus) was found to be identical with that from the first MERS patient, it was suspected that bats were the natural reservoirs, but that has not been substantiated, and no other bat has been found to carry MERS. Instead most human infections have been traced to close contact with dromedary camels.

Hendra (a Henipavirus) was first detected in Australia during an outbreak of infectious respiratory disease in horses and humans in 1994. There have been several subsequent spillovers resulting in seven human cases and four deaths. Pteropodid bats have been confirmed as reservoirs of the disease. Horses became infected when they grazed on pastures infected with bat urine and passed on the disease to those caring for them. However with appropriate horse husbandry, the disease has been contained.

Another Henipavirus, Nipah, was first isolated in 1998 in pigs and pig workers suffering from encephalitis in Malaysia, where 265 cases resulted in 105 deaths. Cessation of pig movements and culling over a million pigs brought the disease under control. The experience with Hendra soon led to fruit bats being identified as the source of infection, with pigs eating fallen fruit contaminated by bats. Since 2001 however human cases have occurred almost annually in Bangladesh and occasionally nearby in India, with higher fatality rates than in Malaysia and with a different route of infection. This occurs mainly by drinking palm sap infected with the virus by the Indian flying fox (Pteropus giganteus). Preventing access by bats to the pots which collect the sap has reduced the infection rate.

Bat pox The poxvirus IsrRAPXV causes painful lesions on hands, may cause flu-like symptoms and leave scars. The infection is carried by Egyptian fruit bats, present in Africa, the Middle East, Pakistan and northern India. There have been five cases of the virus infecting people since 2020. They worked or volunteered in a bat sanctuary in Isreal, and reportedly were not wearing gloves or PPE, whilst feeding, handling, grooming and caring for injured Egyptian fruit bat pups rescued from war and conflict areas. These suckling bats tend to bite and scratch caregivers’ fingers during social play, increasing the risk of a zoonotic infection. Despite the bat host species being abundant in urban areas, there are no other known cases, which indicates this disease has very limited capacity to infect people. Risk of infection is removed if people always follow PPE health advice when handling bats.

Bacterial, parasitic and fungal zoonoses

Salmonellosis and yersiniosis are bacterial diseases acquired by contact and ingestion of fecal material from infected animals. A variety of enteric pathogens such as Salmonella, Shigella, Yersinia and Campylobacter species have occasionally been found in bats.

Few parasites of bats are known to be pathogenic to humans and are usually transmitted mechanically via an intermediate vector.Many species of trypanosomes can infect bats, but one of main concern is Trypanosoma cruzi, the agent of Chagas disease. In addition, several vector-borne bacteria (Bartonella, Borrelia and Rickettsia) have occasionally been found in bats and in soft ticks (family Argasidae) and other ectoparasites commonly found on bats or in bat habitats - posing a potential risk of intra- and interspecies transmission cycles between bats, humans and domestic animals.

Histoplasmosis, cryptococcosis and blastomycosis are fungal infections that occasionally infect bats and can be present in bat guano in certain countries.

How do I stay healthy and prevent diseases spreading?

The best way to stay healthy and protect people, pets and wildlife from illness is to stay informed. Bats and other wild animals sometimes suffer persecution due to misguided fears and poor information around public health. Many such species are threatened or even endangered, and their conservation is vital not just for their intrinsic and heritage value, but also for the health and protection of ecosystems, which in turn safeguard human health and wellbeing.

There are lots of ways we can reduce or prevent the risk and spread of infections to us, our communities and other animals, including following safe guidelines for self care, animal care, how to work and live safely alongside wildlife, and protective measures we should take, such as field hygiene, vaccination, biosecurity and risk management, learning and sharing knowledge.

If you do handle a bat (i.e. if it is grounded/injured) always wear bite-proof gloves and a mask, always seek advice from your country’s bat or wildlife advice service, and seek immediate disease prevention advice from a health professional when needed.

Virus-related bat mortality events do occur but these seem to be infrequent, and zoonotic viruses seem to have little effect on bat populations. Mass die-offs of Schreibers' bent-winged bat (Miniopterus schreibersii)reported in caves across southern France extending into Spain and Portugal in 2002 reduced the population by 60-65% although the cause was never established at the time and other bat species in the caves were unaffected. More recently a new virus, named Lloviu and closely related to Ebola and Marburg, has been identified in a cave in Spain in populations of M.schreibersii that succumbed to the 2002 die-off.

Bats have some distinctive life-history traits which may be relevant to understanding why they are reservoirs of these viruses, including the fact that they form the largest known mammalian aggregations. The fact that in general they don’t succumb to viral disease suggests adaptations of the immune system. One of the most interesting recent suggestions is that daily flight, which elevates metabolism and body temperature analogous to a fever, provides a selective force for coexistence with viral parasites.

[Text by Prof Paul Racey, Dr Allyson Walsh, Lisa Worledge and Alex Morss.]
Last updated : January 2025