European Bat Lyssaviruses (EBLVs) - Exposure and Pathogenesis in British Bats

Daubenton's bat serotine

Background

Rabies viruses are present worldwide, apart from a small number of islands, and have considerable distribution geographically over much of Africa and mainland Europe. Classical rabies (RV, genotype 1) is one of seven lyssaviruses, all rabies-related viruses are thought to be pathogenic for mammals, leading to rabies-like encephalitis (Bourhy et al. 1993). Within Europe and the UK, it is European Bat Lyssavirus (EBLVs), which cause concern. Bats are emerging as significant reservoirs, with over 750 cases recorded in European bats since 1977 (Harris et al ., submitted), 95% of these cases are EBLV-1 infection in the Serotine bat Eptesicus serotinus , ten cases have been recorded in Daubenton's bats Myotis daubentonii , and six cases in the Pond bat Myotis dasycneme . Terrestrial mammals such as sheep, stone marten and man have also been recorded as having been infected with EBLVs.

Since 1996, there have been four reported cases of EBLV-2 infection in Daubenton's bats Myotis daubentonii , and one human death in the UK. In 1996, a Daubenton's bat in Sussex was found to be infected with EBLV-2. In 2002, a Daubenton's bat in Lancashire was found to have active EBLV-2 infection. In 2004, another Daubenton's bat from Lancashire (found dead in 2003, then stored in a freezer for a year) was diagnosed as EBLV-2 positive. In 2004, a Daubenton's bat from Surrey was identified as EBLV-2 positive. These cases indicates that there may be low-level rabies (EBLV2) within areas of British bat populations (Fooks et al ., 2004).

In November of 2002, a Scottish bat-worker was diagnosed as having an EBLV-2 infection, and died thirteen days after admission to hospital. In September of 2002, the bat-worker was bitten by what was thought to have been a Daubenton's bat, although the bat was not retained for identification.

Current passive surveillance for EBLVs within the UK relies on analysis of dead bats by the Veterinary Laboratory Agency (VLA) in Surrey. The VLA has tested over 4000 bats between 1996-2004, with only 113 Daubenton's bats tested (Harris et al ., submitted). However, to ascertain the true prevalence of EBLV within the UK bat population, samples acquired from live bats, in known geographical locations is essential.

Methods

Active Surveillance for EBLV infection in UK bats began in 2003, through collaboration between the University of Bristol and the VLA. Sampling sites are spread throughout Southern England, Northern England and Scotland. M. daubentonii and E. serotinus are the main target species for sampling, with blood and saliva samples being taken.

Results

Antibody prevalence was determined using specific (EBLV-1 or –2) fluorescent antibody virus neutralisation tests, and tissue culture and PCR were used for virus isolation from swabs. At EBLV-2 a priori sites ( n =2), 6-12% of bats were seropositive. When all samples were included, this decreases to 3-8% (Fooks et al., 2004). Pilot EBLV-1 seroprevalence studies suggest a low level of previous exposure in Serotine bats tested, with only a single sample of 51 samples tested giving a positive result. All oral swabs tests were negative suggesting that virus was not being shed in the saliva.

Future work

Continuing surveillance for EBLV-1 and EBLV–2 will be undertaken throughout the UK, on both M. daubentonii and E. serotinus .

Funding

The University of Bristol wishes to acknowledge the financial support of Defra, BBSRC, and JNCC.

Presentations

Since beginning my PhD I have spoken at 2 meetings of the Association of Veterinary Teachers and Research Workers (AVTRW) in 2004 and 2005. I have also given a talk for the Sussex Bat Group to raise awareness of the EBLV research. I am due to give further talks this year at the European Bat Conference (Ireland, 2005) and the National Bat Conference (York, 2005).

Publications

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