Download Zoonoses in Australian Bats Aug 2016

Zoonoses in Australian
bats
Fact sheet
Introductory statement
A recent literature survey identified 1407 recognised species of human pathogen, 58% of which are zoonotic.
Of these 177 are regarded as emerging or re-emerging, with 73% of these being zoonotic (Woolhouse and
Gowtage-Sequeria 2005). Bats have been identified as reservoir hosts for a number of emerging diseases
including severe acute respiratory syndrome (SARS; a coronavirus), Ebola virus (a filovirus), Nipah virus,
Menangle virus (MenPV) and Hendra virus (HeV) (all paramyxoviruses) and Australian bat lyssavirus (ABLV; a
rhabdovirus).
Ungulates support the majority of zoonoses (over 250) and emerging diseases (over 50). However bats, which
harbor less than 2% of human pathogens (Dobson 2005), have gained attention because of the potentially
high human mortality rates associated with the diseases they carry. Some of these diseases, such as SARS and
Ebola, are currently exotic to Australia. This fact sheet summarises information on ABLV (first recognized in
1996), HeV (first recognized in 1994) and MenPV (first recognized in 1997) and also briefly mentions some
other non-viral zoonoses of Australian bats. ABLV and HeV are discussed in more detail in specific WHA fact
sheets.
Aetiology
Australian bats may be infected with ABLV, HeV or MenPV. ABLV is a rhabdovirus while HeV and MenPV are
both paramyxoviruses. They may also be carriers of Leptospira spp. (Mühldorfer 2013). For more specific
information on Leptospira consult the WHA ‘Leptospirosis’ fact sheet.
Outside Australia, bats have also been found to be carriers of enteropathogenic bacteria, arthropod-borne
bacteria and Pasteurella spp.
Natural hosts
ABLV has been isolated from all four Australian species of flying-fox: the little red flying-fox (Pteropus
scapulatus), black flying-fox (Pteropus alecto), grey-headed flying-fox (Pteropus poliocephalus) and spectacled
flying-fox (Pteropus conspicillatus), and one species of insectivorous bat, the yellow-bellied sheath-tailed bat
(Saccolaimus flaviventris).
HeV, MenPV and Leptospira spp. have also been found in all four species of flying-fox.
World distribution
ABLV has only been confirmed in Australian bats. HeV is present in Papua New Guinea as well as Australia and
seropositive bats have been identified in Ghana and Madagascar (Arguin et al. 2002; Iehlé et al. 2007; Breed
2008; Hayman et al. 2008; Newman et al. 2011).
Occurrences in Australia
ABLV appears to be widespread throughout Australia. To date, disease caused by HeV has only occurred in
Queensland (Qld) and NSW, although neutralising antibodies have been found in all four flying-foxes across
their geographic range. MenPV infection appears to be widespread with neutralising antibodies having been
found in flying-foxes in Western Australia (WA), Qld and NSW. However, to date, disease has only occurred in
NSW (Philbey et al. 2008).
Leptospira antibodies and DNA have been found in all four species of flying-fox tested in NSW, Qld, WA and
the NT (Smythe et al. 2002; Cox et al. 2005).
Epidemiology
ABLV is found in saliva, so transmission is generally by biting. Infection can also occur through exposure of the
virus to mucous membranes or open wounds.
HeV can be found in foetal tissues, uterine fluid and urine while MenPV is present in urine and faeces (Halpin
et al. 2011). There are no cases of human infections with HeV or MenPV acquired directly from bats. HeV has
always infected horses first and the horses have then infected people. In the case of MenPV pigs were
infected from bats and the pigs then infected people. See relevant fact sheets for more information.
Clinical signs
ABLV infections in bats may be subclinical or bats may present with a variety of neurological signs such as
aggression, abnormal vocalisation, paralysis, inability to fly or sitting on the ground and not attempting to
escape handling.
Infection with HeV and MenPV is asymptomatic in bats. Horses infected with HeV can develop dyspnoea, a
frothy nasal discharge, neurological signs, pyrexia, depression and death in approximately 75% of cases.
MenPV is associated with stillbirths and craniofacial and spinal deformities in piglets.
Diagnosis
Diagnosis of ABLV infection is usually by direct fluorescent antibody testing or immunohistochemistry. PCR
and cell culture can also be used.
HeV and MenPV infections can be diagnosed by cell culture, immunohistochemistry, and PCR. Blood samples
can be screened for antibodies using the sero-neutralisation test (SNT). See specific fact sheets for more
details.
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Pathology
ABLV causes a non-suppurative encephalitis in bats. Eosinophilic intracytoplasmic inclusion bodies may or
may not be present. There are no pathological lesions in bats infected with HeV or MenPV. See specific fact
sheets for more details.
Differential diagnoses
Differential diagnoses for bats infected with ABLV include any diseases that can cause neurological signs. Bats
infected with the rat lungworm, Angiostrongylus cantonensis, have presented with symptoms very similar to
ABLV infection (Reddacliff et al. 1999; Barrett et al. 2002).
There are no differential diagnoses for HeV or MenPV infection as infected bats show no clinical signs.
Laboratory diagnostic specimens
A complete necropsy should be performed. For ABLV detection samples of CNS, particularly brain stem
should be submitted fresh and in formalin. For HeV and MenPV detection the standard range of tissues
should be submitted, but especially kidney and any foetal tissue for HeV.
Laboratory procedures
The standard test to detect ABLV is the direct fluorescent antibody test conducted on fresh CNS tissue. This
test is highly specific, approximately 100% sensitive and can be completed within four hours.
Immunohistochemistry has similar specificity and sensitivity, can be performed on formalin fixed tissue and
provides a result within an hour. Histology may detect evidence of encephalitis and eosinophilic inclusion
bodies but lacks the specificity and sensitivity of the previous tests. Real time PCR can also be used and is very
sensitive, specific and fast to perform. Virus neutralisation tests can be used to detect antibodies in blood and
CSF.
HeV is a biosafety level 4 agent and any procedures using live virus need to be carried out under appropriate
safety conditions. Virus isolation can be used as the virus grows well in Vero cells from brain, lung, kidney and
spleen. Immunohistochemistry can be performed on formalin fixed tissue and has the advantage that
biosafety constraints do not apply. PCR can be performed on fresh or formalin fixed tissue and has a very high
level of sensitivity. Electron microscopy can be used to complement the other methodologies. The SNT is
regarded as the gold standard for detecting HeV antibodies. It requires live virus. An ELISA test is also
available and has a 91% sensitivity and 75% specificity compared with the SNT (Food and Agriculture
Organisation of the United Nations 2011).
For MenPV diagnosis virus isolation can be used. The virus grows in cells from a variety of species including
human and porcine. Electron microscopy can also be used to detect virus particles and the SNT can screen
blood samples (Philbey et al. 1998).
Treatment
There is no treatment for any of these viral infections in bats. Leptospiral infection is treatable using
antibiotics, but this would rarely be used for free-ranging bats.
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Prevention and control
Prevention and control measures are not applicable to bats as all three viruses appear to be endemic in freeranging populations. However, due to the potentially fatal consequences of infection in other hosts measures
are required to prevent spillover to other susceptible species.
To guard against ABLV infection anyone handling bats should receive a full course of rabies vaccinations. Any
bites or scratches from bats should be washed immediately with soap and water and reported to a medical
practitioner who will advise on further rabies prophylaxis. Guidelines for prevention can be found in “Rabies
Virus and Other Lyssavirus (Including Australian Bat Lyssavirus) Exposures and Infections”,
http://www.health.gov.au/internet/main/publishing.nsf/Content/cdna-song-abvl-rabies.htm.
A vaccine to protect against Hendra infection is available for horses.
Domestic animals, in particular horses and pigs should be denied access to flying-fox colonies and any
material such as fruit that could be contaminated with flying-fox urine, faeces or birthing fluids. Appropriate
personal protective equipment is required for anyone investigating suspicious cases in horses or pigs.
Surveillance and management
Management of ABLV and HeV is covered by the AUSVETPLAN series. The Australian bat lyssavirus disease
strategy, version 3.0, 2009, and the Hendra virus response policy brief, version 3.5, 2013 can be found at
www.animalhealthaustralia.com.au.
Statistics
Prevalence of ABLV in opportunistic submissions of sick, injured and/or orphaned flying-foxes is typically 5–
10%, but may be as low as 1% or as high as 17% depending on the species. Adult bats and bats with CNS signs
have a higher prevalence than bats of the same species that are juveniles or have non-CNS clinical signs
(Animal Health Australia 2009). Seroprevalence in sick, injured and rescued microchiroptera (up to 5%) is
lower than for megachiroptera (up to 20%), but also appears to vary with species. One study found that the
yellow-bellied sheath-tailed bat had significantly higher antibody prevalence (up to 62.5%) than other species
(Animal Health Australia 2009). See ABLV fact sheet for more information.
Surveys of wild flying-foxes have found up to 40% with antibodies to HeV. Fourteen outbreaks of HeV disease
occurred in horses between 1994 and 2010, 13 in Queensland and one in northern NSW. A further 18 events
occurred between June and October 2011, 11 in Queensland and seven in northern NSW. See Hendravirus
fact sheet for more information.
In a study of MenPV following the outbreak in 1997, antibodies were found in grey-headed flying-foxes, black
flying-foxes and spectacled flying-foxes, but not in little red flying-foxes (Philbey et al. 1998). In another
survey, flying-foxes from NSW, Qld and WA were tested with positive titres in all four Australian flying-fox
species; no virus could be isolated from any tissues or faeces (Philbey et al. 2008). See Menangle virus fact
sheet for more information.
A survey of flying-foxes from Qld, NSW, WA and the NT, found that sera from 87% were positive for one
Leptospira serovar antibody, using a microscopic agglutination test, 12% were positive for two serovars and
1% were positive for three serovars. The most common serovar was Australis, with 75% of the bats testing
positive (Smythe et al. 2002). A study examined kidney samples from all four flying-fox species in Qld, NSW
and the NT: 11% were positive for Leptospira spp. by PCR. Urine from 46 flying-foxes on Indooroopilly Island
in Qld was tested, with 39% positive (Cox et al. 2005).
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Research
Research is required to determine the reasons for the emergence of these zoonotic diseases and their
spillover into both animal and human hosts.
Ongoing HeV research includes investigation of the ecological drivers of infection in bats, determination of
the mechanism of virus transmission between bats and other species and further understanding of the
duration of efficacy of the HeV vaccine in horses.
Human health implications
All three viruses, and Leptospirosis can cause disease in humans. ABLV has caused encephalitis and death in
three people (Allworth et al. 1996; Hanna et al. 2000). See ABLV fact sheet.
HeV infections in humans results in fever, headaches, myalgia, sore throat, enlarged lymph nodes, lethargy,
vertigo and death. Incubation period is five to 14 days. There have been six confirmed human cases resulting
in three deaths.
MenPV infection appears to cause a flu-like illness with affected people experiencing malaise, fever, chills,
headaches, myalgia and a red rash on the torso. Duration of symptoms is approximately 10 days (Chant et al.
1998).
Conclusions
It is likely that these and other diseases are emerging, at least partly, because of habitat destruction which is
driving bats into closer proximity to humans with roosting sites being redistributed into more urban areas.
This results in more frequent and prolonged contact between bats, humans and domestic animals. Bats are
vital to ecosystem survival being important plant pollinators and consumers of vast quantities of potentially
damaging insects. While it is important to alert people to the potential dangers associated with close contact
to wild bats, the public also needs to be informed of the important role bats play in maintaining biodiversity
and ecosystem integrity in order to minimise any future negative impacts on bat populations.
References and other information
Allworth, A, Murray, K, Morgan, J (1996) A human case of encephalitis due to a lyssavirus recently identified in
fruit bats. Communicable Diseases Intelligence 20, 504-504.
Animal Health Australia (2009) AUSVETPLAN Disease strategy: Australian bat lyssavirus (Version 3.0).
Canberra, ACT.
Arguin, PM, Murray-Lillibridge, K, Miranda, M, Smith, JS, Calaor, AB, Rupprecht, CE (2002) Serologic evidence
of lyssavirus infections among bats, the Philippines. Emerging Infectious Diseases 8, 258-262.
Barrett, J, Carlisle, M, Prociv, P (2002) Neuro‐angiostrongylosis in wild Black and Grey‐headed flying foxes
(Pteropus spp). Australian Veterinary Journal 80, 554-558.
Breed, A (2008) Paramyxoviruses in bats. In 'Zoo and wild animal medicine: current therapy.' (Eds ME Fowler,
RE Miller.) Vol. 6 (Elsevier Health Sciences:
Chant, K, Chan, R, Smith, M, Dwyer, DE, Kirkland, P (1998) Probable human infection with a newly described
virus in the family Paramyxoviridae. The NSW Expert Group. Emerging Infectious Diseases 4, 273.
WHA Fact sheet: Zoonoses in Australian bats | August 2016 | 5
Cox, T, Smythe, L, Leung, L-P (2005) Flying foxes as carriers of pathogenic Leptospira species. Journal of
Wildlife Diseases 41, 753-757.
Dobson, AP (2005) What links bats to emerging infectious diseases? Science 310, 628-629.
Halpin, K, Hyatt, AD, Fogarty, R, Middleton, D, Bingham, J, Epstein, JH, Rahman, SA, Hughes, T, Smith, C, Field,
HE (2011) Pteropid bats are confirmed as the reservoir hosts of henipaviruses: a comprehensive experimental
study of virus transmission. Am J Trop Med Hyg 85, 946-951.
Hanna, JN, Carney, IK, Smith, GA, Tannenberg, A, Deverill, JE, Botha, JA, Serafin, IL, Harrower, BJ, Fitzpatrick,
PF, Searle, JW (2000) Australian bat lyssavirus infection: a second human case, with a long incubation period.
Medical Journal of Australia 172, 597-599.
Hayman, D, Suu-Ire, R, Breed, AC, McEachern, JA, Wang, L, Wood, J, Cunningham, AA, Montgomery, J (2008)
Evidence of henipavirus infection in West African fruit bats. PloS ONE 3, e2739.
Iehlé, C, Razafitrimo, G, Razainirina, J, Andriaholinirina, N, Goodman, SM, Faure, C, Georges-Courbot, M-C,
Rousset, D, Reynes, J-M (2007) Henipavirus and tioman virus antibodies in pteropodid bats, Madagascar.
Emerging Infectious Diseases 13, 159-161.
Mühldorfer, K (2013) Bats and bacterial pathogens: a review. Zoonoses and Public Health 60, 93-103.
Newman, S, Field, H, Epastein, J, De Jong, C (2011) 'Investigating the Role of Bats in Emerging Zoonoses:
Balancing Ecology, Conservation and Public Health Interest.' Rome).
Philbey, A, Kirkland, P, Ross, A, Field, H, Srivastava, M, Davis, R, Love, R (2008) Infection with Menangle virus
in flying foxes (Pteropus spp.) in Australia. Australian Veterinary Journal 86, 449-454.
Philbey, AW, Kirkland, PD, Ross, AD, Davis, RJ, Gleeson, AB, Love, RJ, Daniels, PW, Gould, AR, Hyatt, AD (1998)
An apparently new virus (family Paramyxoviridae) infectious for pigs, humans, and fruit bats. Emerging
Infectious Diseases 4, 269.
Reddacliff, L, Bellamy, T, Hartley, W (1999) Angiostrongylus cantonensis infection in grey‐headed fruit bats
(Pteropus poliocephalus). Australian Veterinary Journal 77, 466-468.
Smythe, LD, Field, HE, Barnett, LJ, Smith, C, Dohnt, MF, Symonds, ML, Moore, MR, Rolfe, P (2002) Leptospiral
antibodies in flying foxes in Australia. Journal of Wildlife Diseases 38, 182-186.
Woolhouse, MEJ, Gowtage-Sequeria, S (2005) Host range and emerging and reemerging pathogens. Emerging
Infectious Diseases 11, 1842-1847.
Acknowledgements
We are extremely grateful to the many people who had input into this fact sheet. Without their ongoing
support production of these fact sheets would not be possible.
Updated: 18 August 2016.
To provide feedback on this fact sheet
We are interested in hearing from anyone with information on these conditions in Australia, including
laboratory reports, historical datasets or survey results that could be added to the National Wildlife Health
Information System. If you can help, please contact us at [email protected].
WHA Fact sheet: Zoonoses in Australian bats | August 2016 | 6
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Disclaimer
This fact sheet is managed by Wildlife Health Australia for information purposes only. Information contained
in it is drawn from a variety of sources external to Wildlife Health Australia. Although reasonable care was
taken in its preparation, Wildlife Health Australia does not guarantee or warrant the accuracy, reliability,
completeness, or currency of the information or its usefulness in achieving any purpose. It should not be
relied on in place of professional veterinary or medical consultation. To the fullest extent permitted by law,
Wildlife Health Australia will not be liable for any loss, damage, cost or expense incurred in or arising by
reason of any person relying on information in this fact sheet. Persons should accordingly make and rely on
their own assessments and enquiries to verify the accuracy of the information provided.
WHA Fact sheet: Zoonoses in Australian bats | August 2016 | 7