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Bats and rabies in the UK – How different surveillance schemes contribute to rabies risk management

01 March 2017, at 12:00am

Out of the hundreds of thousands of human cases of rabies contracted worldwide, all but ten recent cases have been fatal. This outcome is a key determiner of UK policy for rabies risk management.

Rabies is an acute, progressive viral encephalitis (i.e. it affects the nervous system and brain). It is caused by members of the Lyssavirus genus, of which 15 genotypes have been identified to date, with all but one having a range of host species that include bats (Barrett, 2011). The disease is usually spread via a bite or scratch from an infected animal (though the animal may not be displaying any signs of rabies). A range of animals carry Lyssaviruses but worldwide the most frequent source of infection (responsible for more than 99 percent of human cases) are feral dogs infected with classical rabies virus (RABV) (WHO, 2015).

While some bat species in the Americas carry RABV, it is not found in European bats. Rather the two main genotypes present are: European bat lyssavirus type 1 (EBLV1) and type 2 (EBLV2). However, researchers are still finding new genotypes; in 2010 the Bokeloh bat lyssavirus (BBLV) was isolated from a Natterer’s bat (Myotis nattereri) in Germany (Freuling et al 2011) and was subsequently isolated from the same species in France (Picard-Meyer et al 2013). In 2012 viral genetic material was isolated from a single Schreibers’ bent-wing bat (Miniopterus schreibersii) in Spain, which has been tentatively classified as the Lleida bat lyssavirus (LLEBV) (Aréchiga Ceballos et al, 2013). The lyssavirus found in the UK is EBLV2, and it has only been confirmed in the Daubenton’s bat (Myotis daubentonii) population. While it hasn’t been recorded in any other species in the UK, there has been a small number of mainland European cases found in pond bat (Myotis dasycneme) and a single noctule (Nyctalus noctula) as well as in Daubenton’s bat.

In the UK there has only been one case of human rabies acquired from a native bat, when sadly an unvaccinated bat worker contracted the disease in 2002 (Racey et al, 2012). There have been a further three confirmed cases of human rabies (including another bat worker) acquired from bats in the rest of Europe in the past 30 years. With a population of approximately 590 million people in Europe, bat-related rabies presents a very small risk (Racey et al, 2012). However, out of the hundreds of thousands of human cases of rabies contracted worldwide all but ten recent cases have been fatal (Barrett, 2011) and it is this outcome that is a key determiner of UK policy for rabies risk management.

Packs for submitting dead bats to the APHA for rabies testing are available from the National Bat Helpline
Packs for submitting dead bats to the APHA for rabies testing are available from the National Bat Helpline

A passive surveillance scheme for rabies in Great Britain has been running for the past 20 years. The surveillance is reliant on the submission of dead bats by bat workers, vets and members of the public to the Animal & Plant Health Agency (APHA) with more than 13,000 bats tested to date. This surveillance programme is important for informing our understanding of the disease and as an invaluable educational tool. It is important to acknowledge, however, that both the species data and geographic coverage are skewed. For example, a high percentage of bats submitted have been pipistrelles (Pipistrellus spp.), the species group that the public and bat workers are most likely to come into contact with, and which are not known to be lyssavirus carriers. This skewed distribution led to a change in 2012 so that pipistrelles are no longer required to be submitted for testing (unless involved in a contact incident with a human or other animal (e.g. a dog or cat) or where the species ID is unknown or uncertain – one of the positive Daubenton’s bat cases was initially misidentified as a pipistrelle). The geographical coverage of submitted bats perhaps reflects more where bat workers are to be found than bats.

A total of 13 Daubenton’s bats have been found carrying live EBLV2 through this passive surveillance programme. We would encourage vets who encounter dead bats to submit all non-pipistrelle species for testing (if species ID is in doubt then it is better to submit the bat for testing anyway).

The passive surveillance programme has been supplemented by three active surveillance projects, with blood (to test for the presence of antibodies) and saliva (to test for the presence of live virus) samples being taken primarily from serotine bats (Eptesicus serotinus) and Daubenton’s bats at sites in Scotland and England (the bats were released after the samples were taken). One Daubenton’s bat was found with live EBLV2 virus as a result of this active surveillance work (Horton et al, 2009), making a total of 14 individual bats testing positive across all surveillance schemes in the UK to date. Antibodies for EBLV1 were also found in one serotine and two Natterer’s bats but no live EBLV1 (Racey et al, 2012). The active surveillance projects have confirmed that EBLV2 is present at a low level in the UK Daubenton’s bat population.

The risk from bat-related rabies in the UK can be significantly reduced by following good practice. Anyone handling bats should wear gloves and those people who handle bats regularly as part of their work or volunteering activities are also advised to have appropriate vaccinations (Racey et al, 2013). Pre-exposure vaccinations are required for bat workers employed or volunteering for the UK Statutory Nature Conservation Organisations (SNCOs), as well as all volunteers signed up to BCT’s National Bat Care Network. BCT produces Good Practice Guidelines on Bats and Rabies aimed at bat workers and bat carers, information on gloves suitable for bat handling and details about vaccinations. These are all available on the BCT website. In addition, the National Bat Helpline provides advice to members of the public about rabies, specifically to those who have been bitten or scratched by bats. Rabies is an important issue that all those working with bats both in a voluntary or professional capacity should be aware of. The BCT advocates a proportionate yet transparent approach to rabies communication while ensuring that positive support for bats and bat conservation is maintained.

Managing the issues associated with bats and diseases requires a combined effort with bat workers, volunteers, BCT, APHA and SNCOs working together to manage disease risk. The authors would like to take this opportunity to thank everyone who has contributed to the rabies surveillance schemes and implementing good practice in the UK.

Further information

The packs for sending off dead bats to the APHA can be obtained, without charge, from the National Bat Helpline (0345 1300 228/enquiries@bats.org.uk) and more details about the scheme can be found on the Bat Conservation Trust (BCT) website (www.bats.org.uk).