This study examined trends in notifications of potential exposure to Australian bat lyssavirus reported to the Brisbane Southside Public Health Unit, Australia between 1 November 1996 and 31 January 2003. Notification rates declined among all population groups and potential exposures were notified more promptly. Concern exists regarding possible under-reporting of potential exposure to Australian bat lyssavirus especially among volunteer bat carers. (author abstract

McCall, B. J.

Young, M. K.

University of Queensland eSpace

258 CDI Vol 28 No 2 2004
Short report
Trends in potential exposure to Australian bat 
lyssavirus in South East Queensland, 1996 to 
2003
Megan K Young,1 Bradley J McCall2
Abstract
This study examined trends in notifi cations of potential exposure to Australian bat lyssavirus reported 
to the Brisbane Southside Public Health Unit, Australia between 1 November 1996 and 31 January 
2003. Notifi cation rates declined among all population groups and potential exposures were notifi ed 
more promptly. Concern exists regarding possible under-reporting of potential exposure to Australian 
bat lyssavirus especially among volunteer bat carers. Commun Dis Intell 2004;28:258–260.
Keywords: lyssavirus; epidemiology; Australia
1. Public Health Registrar, Brisbane Southside Public Health Unit, Brisbane, Queensland
2. Public Health Physician, Brisbane Southside Public Health Unit, Brisbane, Queensland
Corresponding author: Dr Megan K Young, Public Health Registrar, Brisbane Southside Public Health Unit, PO Box 333, 
Archerfi eld, QLD 4108. Telephone: +61 7 3000 9148. Facsimile: +61 7 3000 9130. Email: megan_young@qld.health.gov.au
Introduction
Australian bat lyssavirus (ABL) is a member of the 
Rhabdoviridae family, possessing marked similar-
ity to classic rabies virus on both serotyping and 
molecular sequencing.1 To date, two cases of fatal 
ABL infection have been reported in Australia, one 
in 1996 and the second in 1998.2 The epidemiology 
of potential exposure to ABL has been previously 
described.3 The key feature, in a predominantly 
urban population in South East Queensland, was 
that potential exposures were likely to be the result 
of human-initiated contact by people with some 
professional or volunteer interest in caring for bats 
and/or fl ying foxes (53% of potential exposures). A 
lower proportion of potential exposures (35%) were 
reported by members of the general community.
Potential exposures to ABL continue to occur despite 
consistent information and reminders to the commu-
nity about the dangers of handling fl ying foxes and 
insectivorous bats.4 This paper examines population 
trends in potential exposure to ABL reported to the 
Brisbane Southside Public Health Unit (BSPHU) 
between 1 November 1996 and 31 January 2003.
Methods
Since 1 November 1996, all persons reporting a 
potential exposure to ABL have been asked to 
complete a standard questionnaire. The details of 
the questionnaire, methods of study and results until 
31 January 1999, have been described.3 However, 
the geographic boundaries of the area served by 
the BSPHU have changed since 1999. They now 
include South Brisbane (part of the Brisbane City 
Council Area), Logan, Redlands, Ipswich, Laidley, 
Boonah and Esk Local Government Areas (Figure) 
with an estimated resident population of 920,680 as 
at 30 June 2000.5
The time frame of this study was divided into period 1 
(the initial study period from 1 November 1996 to 
31 January 1999, which included the two human 
cases of ABL infection) and period 2 (1 February 
1999 to 31 January 2003). To allow comparison of 
data across these time periods, the original study data 
was restricted to include only that related to people 
who resided within the current Brisbane Southside 
Public Health Unit boundaries. SPSS version 11.5 
was used for analysis.6
Results
Two hundred and forty-six notifi cations were repor ted 
between 1 November 1996 and 31 January 2003. 
One hundred and thirty-six notifi cations of potential 
ABL exposure from the re-defi ned study area were 
reported to the BSPHU in period 1 (duration = 
27 months), an average annual notifi cation rate of 
6.56 per 100,000. One hundred and ten notifi cations 
were reported in period 2 (duration = 48 months), an 
average annual notifi cation rate of 2.98 per 100,000. 
The proportion of notifi cations from females fell from 
60 per cent in period 1 to 46 per cent in period 2. 
CDI Vol 28 No 2 2004 259
 Short report
There was no signifi cant difference between the age 
distributions (χ2 = 8.13, 6 df, p = 0.23), with the peak 
age group between 20 and 49 years in both time 
periods.
The median time interval between potential exposure 
and notifi cation to the BSPHU fell from 14.5 days 
(range 0 to 3,636; 25th, 75th centiles: 2, 79.8) in 
period 1 to one day (range 0 to 1,860; 25th, 75th 
centiles: 0,3) in period 2.
The Table describes the circumstance of potential 
exposure to ABL, the treatment received and the his-
tory of previous vaccination in the two time periods. 
There was a decline in the average annual number 
of reported potential exposures for all population 
groups (professionals, volunteer bat carers and their 
family members, community members). However, 
the proportion of potential exposures reported by 
community members increased (from 40% to 71%). 
The proportion of potential exposures reported by 
professional handlers and volunteer bat carers fell 
substantially, with the greatest fall among volunteer 
bat carers (from 36% to 11%). Professional handlers 
and volunteer bat carers reporting potential expo-
sures in period 2 were more likely to have been 
previously vaccinated. Only 16 per cent of profes-
sional and volunteer handlers reported no previous 
vaccination in period 2 compared to 86 per cent in 
period 1.
Figure. The geographical area covered by the 
Brisbane Southside Public Health Unit
Table. Circumstance, treatment and history of previous vaccination of potential exposures 
to Australian bat lyssavirus for each time period, Brisbane Southside Public Health Unit area, 
1 November 1996 to 31 January 2003*
Period 1
(1/11/96 – 31/1/99)
n=136
Period 2
(1/2/99 – 31/1/03)
n=110
Circumstance n % n %
Community member bat initiated contact 3 2.2 17 15.5
Community member intentionally handled bat 51 37.5 61 55.5
Professional handlers 17 12.5 10 9.0
Volunteer bat carers 49 36.0 12 10.9
Family member of volunteer bat carers 13 9.6 3 2.7
Treatment
Nil (bat tested negative) 5 3.7 40 36.4
Course ceased (bat tested negative) 18 13.2 2 1.8
2 doses of vaccine 12 8.8 12 10.9
5 doses of vaccine 69 50.7 8 7.3
Rabies immunoglobulin and 5 doses of vaccine 31 22.8 47 42.7
Recommended treatment but declined 0 0.0 1 0.9
Previous vaccination
Nil 121 89.0 85 77.3
Pre-exposure prophylaxis 3 2.2 10 9.1
Pre-exposure prophylaxis and booster/s 0 0.0 4 3.6
Previous post-exposure prophylaxis 10 7.4 6 5.5
* Percentages may not total 100 because of missing values.
260 CDI Vol 28 No 2 2004
Short report
Discussion
The notifi cation rate of potential exposure to ABL 
fell markedly during the study. This rate may more 
accurately estimate baseline potential exposure 
rates since earlier rates were infl ated by the large 
number of retrospective reports received after the 
initial recognition of this disease in humans in 1996. 
However, it is possible that a proportion of recent 
potential exposures are not being notifi ed. This may 
arise from waning concern about the risks of bat 
bites or scratches among the community or medical 
profession, especially as no cases of human ABL 
infection have been reported since 1998.
Professional handlers and volunteer bat carers may 
be unwilling to notify potential exposures within their 
groups, a reluctance that has been communicated 
to both authors. This unwillingness may be an unde-
sired consequence of the public health requirement 
to euthanase and test all bats involved in human 
potential exposures. Unwillingness to notify potential 
exposure may also refl ect preformed opinions about 
the risk posed by scratches, the protection afforded 
by pre-exposure vaccination, or the level of risk asso-
ciated with the clinical appearance of the bat. These 
suggestions are further supported by the fi nding that 
volunteer bat carers have the largest decrease in 
proportion of notifi cations from time period 1 to period 
2 [36% (n=49) to 11% (n=12)], with a corresponding 
increase in community notifi cations [40% (n=54) to 
71% (n=78)], despite no recognisable change to vol-
unteer bat carer numbers in the Brisbane Southside 
area over recent years (personal communication, 
Allan McKinnon, Manager, Moggill Koala Hospital, 
Queensland Parks and Wildlife Services).
The reduction observed in notifi cations among 
females may also be explained by the fall in the pro-
portion of volunteer bat carer notifi cations. The high 
proportion of females in period 1 was infl uenced by 
the high proportion of female volunteer bat carers in 
the study population.
The time between potential exposure and notifi ca-
tion decreased substantially over the study, with 
fewer long-term retrospective reports of potential 
exposure in period 2. A corresponding decrease 
was observed in the proportion of people requir-
ing treatment after their potential exposure. Post 
exposure treatment may be delayed for 48 hours 
pending the results of tests on the bat involved.7 In 
period 2, potential exposures were notifi ed more 
promptly. This allowed a greater proportion of the 
bats involved to be tested and the negative results 
to be obtained within the required 48 hours. This 
represented an important cost saving through the 
reduced use of rabies immune globulin (RIG), rabies 
vaccine and fewer doctors’ visits.
Future public health messages should continue to 
emphasise the need for the community to maintain 
a safe distance from all bats or fl ying foxes, even 
if they are orphaned or distressed. Messages 
should reinforce that it is usually impossible for an 
untrained person to handle a bat without sustaining 
a bite or scratch, even if protective measures are 
used. Members of the public can be of most help to 
orphaned or injured bats by contacting a trained, vac-
cinated bat handler. Volunteer bat carers must also 
be aware of the potential risks associated with bites or 
scratches from apparently healthy looking bats, and 
seek medical advice regardless of their pre-exposure 
prophylaxis or the nature of the wound.
Acknowledgements
Staff of Public Health Virology, Queensland Health 
Scientifi c Services, Archerfi eld, Queensland, Australia
Staff of Brisbane Southside Public Health Unit, 
Archerfi eld, Queensland
Allan McKinnon and staff at Wildlife Rangers 
Conservation Services, Queensland Parks and 
Wildlife Services, Moggill, Queensland
References
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3. McCall BJ, Epstein JH, Neill AS, Heel K, Field H, 
Barrett J, et al. Potential exposure to Australian bat 
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4. Scott JG. Australian bat lyssavirus: the public health 
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5. Australian Bureau of Statistics. 2000 estimated resi-
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Trends in potential exposure to Australian bat lyssavirus in South East Queensland, 1996 to 2003

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Trends in potential exposure to Australian bat lyssavirus in South East Queensland, 1996 to 2003

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