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The 2000 edition of the Control of communicable diseases manual1 allots five lines to the
Australian bat lyssavirus (ABL). This virus is now known to be
widespread in Australian bats and to have caused two human
infections, the second of which is described in this issue of the
Journal by Hanna and colleagues.2 While the five
lines in the Manual provide some perspective on the international
importance of ABL, they reflect neither the suffering of the
victims' families nor the impact of this event on the
Australian public health community.
The first isolation of the new Lyssavirus genotype, from a
flying fox in June 1996,3 was preceded by the first
reported incursion of Japanese encephalitis into Australia and the
discovery of the Hendra virus (originally known as equine
morbillivirus). While the significance of the Lyssavirus
discovery was unclear, this conjunction of events demanded
investigation of the interplay between humans and their
environment. Improved channels of communication between medical
and public health specialists, an alert media, and a more aware and
informed public meant that the outcomes of this investigation would
be closely followed and debated. Furthermore, the finding of
antibodies to Hendra virus in flying foxes a month before the
discovery of ABL4 meant that these animals and
the wildlife carers who worked with them would be a focus of this
investigation. Five months later, the death of a bat-carer in
Rockhampton from ABL infection5 confirmed this focus.
The ecology of ABL was then completely unknown. Evidence from the
United States and Europe suggested that rabies-related viruses are
not readily transmitted naturally from bats to other animals.
However, in the US, where rabies virus variants are endemic in all
states except Hawaii and bats are the reservoirs, sporadic human
deaths from these infections do occur.6
In Australia, programs to survey potential hosts and vectors for
spread of ABL and Hendra virus were developed and implemented. Close
working relationships developed quickly between the government
departments responsible for animal and human health, laboratories
involved in animal and human testing, and other government agencies
responsible for quarantine and surveillance of animal diseases.
These relationships have been maintained on a strong footing to this
day. Unfortunately, many questions about ABL remain unanswered, and
further significant injections of research funding will be required
to address them.
Was ABL a recent import from a neighbouring country, or had it been
present and unrecognised in our wildlife for some time? Clearly,
authorities had little knowledge of disease activity or
distribution of disease agents (both known and unknown) in our
northern neighbours. The incursion of Japanese encephalitis into
northern Australia suggested that this disease might be active to our
north, but at the time we had no proof. For the previously unrecognised
viruses, ABL and Hendra virus, there was at that time no evidence at
all. A program of serosurveillance has now been established in
Australia and New Guinea, along with trapping programs to identify
agents responsible for the spread of Japanese encephalitis virus,
ABL and Hendra virus. The result is an improved understanding of
disease activity in northern Australia and neighbouring areas, but
significant research remains to be done before an accurate picture is
developed to cover all areas of potential concern.
At home, bat carers, and those involved with the care and management of
wildlife more generally, were confronted with the real risk of a
previously unknown disease infecting the animals with which they
routinely worked. Intense media coverage of the issue meant that even
those members of the public not immediately caring for wildlife might
live with the threat of "killer bats" that could swoop at any time. Bats
had been known as the natural hosts for a range of diseases, both in
Australia and in other countries, for some time,7 but they were now
presented as unclean threats to innocent populations of adults and
children alike.
This emotional atmosphere made the task of ensuring dissemination of
accurate information to bat-carers and the broader population quite
difficult. A significant debt is owed to responsible members of
bat-carer organisations who worked hard to ensure that credible
mechanisms were established to transmit information on the need for
pre- and post-exposure prophylaxis to their members and to the
broader public. At the same time, human and animal health authorities
contributed long hours in teleconferences, round-table
consultations, and discussions with the media to ensure that the best
advice was made available, based on well-conceived, defensible
protocols. Media management remains an area of major significance
across a broad range of public health issues.
With no readily available test for exposure before clinical illness
emerged and evidence of a potentially long incubation period, a
conservative approach to prophylaxis was adopted. Thousands of
doses of pre- and post-exposure rabies vaccine and immune globulin
were distributed, straining already fully committed budgets and
sometimes the country's reserves of vaccine and globulin.
Surprisingly, potentially avoidable bat bites and scratches
continued to be reported, and post-exposure prophylaxis was often
required when simple preventive measures would have been more
appropriate. Health promotion and broader behavioural approaches
(such as education programs for children, and fact sheets for the
general public) remain key planks of a good public health response.
Equally, informed health practitioners able to provide accurate,
practical advice to those bitten or scratched are a key.
We now have evidence for widespread exposure of all species of bats
in Australia to ABL, and also for sick and injured animals to pose a
greater public health threat.7 Clinical signs of infection
in flying foxes are well known (H. Fields, Veterinary Scientist,
Queensland Department of Primary industries, personal
communication), although the level of subclinical infection
remains unclear. We have secured our five lines in the Manual. What
work remains?
In the laboratory, we need to investigate the susceptibility of other
animal species to the disease. We also need a definitive test for the
disease and methods to determine the species and geographic source of
viral isolates. In addition, how closely related is ABL to rabies, and
is rabies vaccine effective protection?
In the wild, we need a better understanding of the ecology of ABL, its
natural history, and the environmental niche from which it has
emerged or been disturbed. Finally, we need to promote media coverage
that further informs the public on the delicate balance between our
environment and human health. We need to further explore this balance
and the impact of human interaction with that environment and the
native animals therein. Generally, we need better communication of
balanced, non-sensationalised information on new infections to the
public. One thing is certain -- this won't be the last!
John G Scott
Manager, Public Health Services
Queensland Health, Brisbane, QLD.
John_ScottAThealth.qld.gov.au
- Chin J, editor. Control of communicable diseases manual. 17th ed.
Washington: American Public Health Association, 2000: 411.
-
Hanna JN, Carney IK, Smith GA, et al. Australian bat lyssavirus
infection: a second human case, with a long incubation period. Med
J Aust 2000; 172: 597-599.
-
Gould AR, Hyatt AD, Lunt RA, et al. Characterisation of a novel
lyssavirus isolated from Pteropid bats in Australia.
Virus Res 1998; 54: 165-187.
-
Young PL, Halpin K, Selleck PW, et al. Serological evidence for the
presence in Pteropus bats of a paramyxovirus related to equine
morbillivirus. Emerg Infect Dis 1996; 2: 239-240.
-
Allworth A, Murray K, Morgan J. A human case of encephalitis due to a
lyssavirus recently identified in fruit bats. Comm Dis Intell
1996; 20: 504.
-
Krebs JW, Smith JS, Rupprecht CE, Childs JE. Rabies surveillance in
the United States during 1997. J Am Vet Med Assoc 1998; 213:
1713-1728.
-
Constantine DC. Bats in relation to the health, welfare and economy
of man. In: Wimsatt WA, editor. Biology of bats. Vol 2. New York:
Academic Press, 1970: 319-449.
©MJA 2000
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