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16 December 2002
Bats and Rabies, No. 2
Comment on letter from Bat Conservation Trust, Courier 30 November
The prevalence of European Bat Lyssavirus (EBL) in the UK
Dr James Irvine
The Courier newspaper published a letter from
Jean Stubbs on 26th November, who was clearly concerned by the fact
that there were bats in her house and that a bat conservation worker
had died from rabies after having been bitten by one or more bats
(1). The Bat Conservation Trust (BCT) responded
with a letter also published in the Courier on 30th Nov 2002 (1).
The somewhat disingenuous nature of the BCT response to the perfectly
understandable concerns of Jean Stubbs requires comment.
1. BCT argue that tests on 3000 bats have shown
that the incidence of rabies is tiny: only two have been found to
be infected over the past 15 years. Clearly they preferred
not to quote the figures from the DEFRA Press release dated 1st
October 2002 (2). In the notes to Editors it states:
Tests have confirmed that the bat in Lancashire was infected
with European Bat Lyssavirus (EBL), a strain of rabies which has
been found sporadically in insectivorous bats in Northern Europe...
" EBLs are closely linked to classical rabies virus ...
In Europe, between 1977 and 2000, a total of 630 EBL cases in
bats have been confirmed, mainly in Denmark, the Netherlands and
Germany. There has been a previous bat-associated rabies case
in the UK, where a Daubentons bat (Myotis daubentonii) was
found in Newhaven, Sussex during 1966.
The primary objective of BCT is to conserve bats
of all types and to encourage biodiversity. Clearly with the legal
powers at their disposal in the UK they might may have achieved
some success in this regard. That is to say that they may well be
encouraging species of bats to the UK from Northern Europe (or even
further afield) to settle in the UK. What would be more relevant
is whether there is currently an increase in the incidence of EBL
virus in bats in the UK or a significant risk of this happening.
The DEFRA Press Release would suggest that there is such a risk.
Strenuous efforts to keep rabies from spreading from the Continent
of Europe (and from elsewhere) to the UK have been made, and there
is some anxiety that the regulations have been recently eased under
political pressure. It would not be difficult to imagine that Northern
European bats could get a lift in some part of the immense traffic
that goes to and from the Continent and other countries where EBL
virus in bats is endemic. Once in the UK they have the privilege
of tight, legally enforced conservation thanks largely to the efforts
of the BCT, SNH and others.
The BCT does not say what kinds of bats made up
the 3000 bat corpses that were sampled. It is possible that only
certain species of bats carry the virus: such as the Daubenton.
In which case the incidence of EBL virus in that species may be
higher than they are leading us to believe.
Quite apart from the possible changes in the distribution
of the various species of bat within the UK during the past 15 years,
there is the important matter that diseases (be they clinical or
subclinical) can change their pattern of behaviour and distribution
over the years. It could well be that the incidence of EBL virus
in bats can change quite dramatically in a relatively short period
of time. One has only to remember the complacency that prevailed
in relation to Foot and Mouth Disease as the UK had not had a case
since 1967, apart from an isolated episode in the sea bound Isle
of Wight in 1981. Arguing that rabies related virus has only been
found in two bats out of 3000 tested in the UK over the past 15
years is not convincing and smells of twisting science to fit some
narrowly focused agenda.
The BCT might also have chosen to quote the press
release from SNH which states:
"Since 1987, when it became apparent that bat-rabies was
reasonably widespread in serotines (a species of bat) on the western
seaboard of continental Europe DEFRA has maintained surveillance
for the disease by testing bat corpses sent in by bat workers.
Over 3000 bats have been tested in the fifteen year period with
only two positive results - Lancashire in 2002 and Newhaven, Sussex
Indeed, BCT might have referred to their own website
which shows the distribution of serotine bats in the south of England.
While SNH is primarily concerned with Scotland, BCT relates to the
whole of the UK. Yet BCT makes no mention of the fact that the same
type of bat in which bat-rabies has been found to be reasonably
widespread just across the Channel (3), is
also resident in the south of England (Figure 1).
Figure 1: Distribution of Serotine bats in Europe and the South
of England. Reproduced from the Bat Conservation Trust Website
Perhaps the BCT might have been honest enough
to point out that over a fifteen year period no case of bat rabies
was noted for 11 years. Then there was a case in 1996, and there
have already been two cases established in 2002 (including the tragic
death that has precipitated this debate). This should have been
enough to at least look to see if there is any evidence elsewhere
that the incidence of rabies-linked virus in bat populations could
change quite suddenly and dramatically. The evidence is in fact
readily available on the Centers for Disease Control website (4).
Figure 2 (reproduced from that website) shows
that in the USA the incidence of rabies-linked virus in wild animals
has indeed markedly increased in recent years, and most of that
increase is due to bats.
Wild animals accounted for 93% of reported cases of rabies
in 2000. Raccoons continued to be the most frequently reported
rabid wildlife species (37.7% of all animal cases during 2000),
followed by skunks (30.1%), bats (16.8%), foxes (6.1%), and other
wild animals, including rodents and lagomorphs (0.7%). Reported
cases in raccoons, decreased 3.2% from the totals reported in
1999. Reported cases in skunks, foxes and bats increased 7.1%,
17.9% and 25.38% respectively from the totals reported in 1999.
Figure 2: Cases of animal rabies in the USA,
1955-2000. Source, Centers for Disease Control.
If the incidence of rabies in bats can increase
in the USA by 25% between 1999 and 2000, it could conceivably do
something similar in Europe and specifically in the UK. Other countries,
such as the USA, are well aware of the need for increased vigilance
1. Letters reproduced from the
Dundee Courier regarding rabies in bats. Land-Care. (Click
here to view).
2. DEFRA News Release. Confirmed case
of bat rabies in Lancashire. 1st October 2002. (Click
here to view).
3. SNH News Release. Suspected
Case of Rabies in Tayside. 20th November 2002. SNH website - News
and Views. (Click
here to view).
4. Rabies Epidemiology. Centers
for Disease Control and Prevention, National Center for Infectious
here to view).
A future article in this series will describe how
differently the Americans approach the possibility of persons being
infected with rabies from bats. This is in comparison to the carelessly
cavalier approach in the UK promoted by the BCT and others, whose
main concern is conservation and biodiversity.