Rabies: Bat research
European Bat Lyssavirus (EBLV) is a strain of rabies virus that is found in European bats. In particular, European Bat Lyssavirus type-2 has been detected in Myotis daubentonii (commonly referred to as Daubenton’s bat). The number of Daubenton’s bats in Great Britain (GB) is estimated at 150,000. Rabies virus, including EBLV, can be transmitted to humans and to other animals. One such example was the tragic death of a Scottish bat conservationist from rabies caused by EBLV-type 2 in 2002. Bats can also succumb to this infection; in GB for example there have been a small number of confirmed cases of rabies in Daubenton’s bats due to EBLV-type 2. In addition a limited survey has shown about 2% of this species in England to be seropositive and this indicates that these bats have been exposed to the virus.
There is little information available on how bats transmit EBLV-type 2 or the relationship between the virus and its bat host. It is possible that bat variants of rabies virus, including EBLV-type 2, are less virulent than classical strains of rabies virus (e.g. dog rabies). This suggests that EBLV-type 2 might have a longer incubation period than other strains of rabies virus before being intermittently excreted in saliva. Of particular concern is the public health aspect where it could be found that a healthy Daubenton’s bat may be infected with EBLV-type 2 and be capable of transmitting the disease without showing signs of rabies.
Research has therefore been carried out to provide firm scientific evidence to support the current policy on bat rabies and in order to give clear unequivocal advice to bat handlers and the general public on any risks to which they may be exposed when coming into direct contact with bats. Such research will also help to provide a better understanding of the results of rabies surveillance work on bats in the UK undertaken previously. The particular importance of carrying out this research in the natural host is supported by international organisations such as the OIE – the World Organisation of Animal Health, and Eurobats.
A research study has therefore been undertaken to further our understanding of these issues using live Daubenton’s bats caught under licence from English Nature (now Natural England). The experiment was undertaken in Germany as the UK did not have the capacity in its specialised facilities to undertake this work. There was strict adherence to welfare standards which are equivalent to those in the UK. These were regularly checked and monitored by staff from the UK. The results of the research will be published in due course and will be used to help inform current policy on public health. From a conservation perspective the study will also help us to understand how this species of bat is affected by infection with EBLV-type 2, and whether it causes illness and or death.
Further information
- Defra's Science and Research pages: Host response to European Bat Lyssavirus Infection: EBLV replication and host response in Neuronal, Salivary and Splenic Tissue (SE0524)
- OIE
Rabies in Europe Conference report
(link to OIE website) - Further information on bat research in Europe can also be found on the Eurobats website.
Bat research Q&A
Can bats carry rabies?
Yes. European Bat Lyssavirus (EBLV) is a strain of rabies virus found in European bats. EBLV–type 2 has been detected in Daubenton’s bats in the UK. Rabies viruses can be transmitted to humans from an animal that is excreting the virus through a bite, scratch or through contact with mucus membranes (e.g. eyes, nose, mouth)
How many cases of rabies in bats have been found in the UK?
Since 1986, there have been seven confirmed cases of EBLV-type 2 in over 130 Daubenton’s bats tested under the UK's passive surveillance scheme. The latest was in Surrey in May 2008. In addition, a limited survey has shown that about 2% of Daubenton’s bats in England are seropositive which suggests they have been exposed to rabies virus and may be capable of transmitting it.
Has anyone died after being bitten or scratched by a bat?
The risk of EBLV infection to humans is thought to be low. However, since 1977 there have been five human deaths in Europe (three confirmed, two possible) from EBLVs, all in cases where the person had not received rabies vaccination either before or after being bitten by bats. These cases include a bat conservationist in Scotland who tragically died from EBLV-type 2 in 2002.
Why is Defra carrying out this research?
There is little information on how bats transmit the virus or the relationship between the virus and its host. It is possible that EBLV-type 2 may have a longer incubation period than other strains of rabies virus before being intermittently excreted in saliva. The public health aspect is important here as it may be that a healthy Daubenton’s bat could be infected with EBLV-type 2 without showing signs of rabies. This study will enable us to gain information on the transmission cycle of EBLV-type 2 and its host relationship.
What are the benefits?
The study will provide firm scientific evidence regarding these issues in order to inform and support current and future policy on rabies. In turn, this will enable clear advice to be given to bat handlers and workers as well as the general public on any risks to which they may be exposed when coming into contact with bats.
How was the experiment conducted?
The experiment challenged several groups of Daubenton's bats with European Bat Lyssavirus-type 2 (EBLV2), each by a different route. Control groups (negative and positive) were required to ensure that the experiment was performed rigorously. It was anticipated that a maximum of 50 bats would be required to conduct this experiment. In the event 34 bats were caught and the experiment was adjusted accordingly. Three bats were removed at the beginning of the experiment resulting in 31 bats available for the experiment. One of these had not gained weight and so was not included in the experiment and remained in captivity in Germany. The other two succumbed shortly after inoculation, for reasons unrelated to the virus challenge. The final groups therefore contained 7 bats in each of the 3 challenge groups and 5 in both control groups. This adjustment to the experiment was necessary to ensure that its worth and statistical validity were maintained.
Why were British bats used?
It was important to carry out the experiment on the natural native host of EBLV2 - in this case British Daubenton's bats. As the licence for their collection was issued by English Nature, now Natural England, they could only be collected in England. EBLV-2 is currently a public health issue in the UK and we are not aware of any other source in Europe that would provide Daubenton's bats. In recent years only Switzerland has reported EBLV-2 in Daubenton's bats and the Swiss are not part of the research collaboration.
Where were the bats collected?
The bats were collected from a number of roosts in accordance with the
conditions imposed by the Natural England licence. These included ensuring
the continued viability of the populations from which the bats were drawn.
A form (Link to Natural England website) submitted to Natural England following the expiry of the licence provides more details.
Why was the work done in Germany and not the UK?
This study was undertaken in Germany because there was not the capacity to carry it out in the UK’s specialised facilities. It is an Anglo-German collaboration.
How was the welfare of the bats protected during the experiment?
The bats were fed and watered regularly and their body weight monitored.
What happened to the bats at the end of the experiment?
They were humanely euthansed and an analysis of tissue samples and organs was carried out.
Are there conservation issues?
The number of Daubenton’s bats being taken for this study was very small compared to the overall population, thought to be around 150,000 in GB.
What are the implications for existing regulations?
Collection of bats for the experiment did not affect their protected status or weaken the enforcement of the Conservation (Natural Habitats) Regulations 1994 that protects bats from harm by the public. However, this does not apply to anything done for specified reasons in accordance with the terms of a licence issued by the appropriate authority. The reasons include scientific and research purposes. In this case, the licence for their collection was issued by Natural England under the Wildlife & Countryside Act 1981 and the Conservation (Natural Habitats) Regulations 1994. Without this licence, the experiment could not have take place.
Will any more bats be caught for this experiment?
No more bats will be caught for this experiment.
When will a report of the research be published?
The results from the experiment need to be analysed and will then be subject to external peer review. The report will be made public in due course following the peer review.
What information has been released under the Freedom of Information Act 2000 on the Daubenton's bats research?
Information available on the access to information pages: Daubenton's bat research documents.
Please also see Natural England disclosure log.
Page published: 12 June, 2008