Paper presented at the Annual District Veterinarian’s Conference, Deniliquin, 2014
Australian bats (including flying foxes and microbats) are the natural reservoirs for a range of viruses that may infect and sometimes kill humans and other animals. The viruses carried by Australian bats include Hendra virus, Menangle virus and Australian Bat Lyssavirus (ABLV). Since November 1996, three people have died as a result of ABLV infection from bats. ABLV infection has been seen in two horses in Australia and there is evidence that transmission to other animal species is likely.
Australian bat lyssavirus (ABLV) is one of seven types of lyssavirus which are found around the world. Six of these are known to exist in bats but only ABLV is known to occur in Australia. The best known lyssavirus is classical rabies virus.
Bats are known host reservoirs for a range of viruses, and with the exception of Lyssavirus, they do not cause overt bat disease. In Australia, public health concerns relate to the bat’s ability to act as a reservoir for ABLV and Hendra virus. Human infection with ABLV has resulted from scratches or bites from bats. The disease has clinical features identical to classical rabies. Two horses were infected with ABLV in May 2013, after contact with an infected microbat. Both horses showed severe nervous signs such as seizures, swallowing problems and movement abnormalities and had to be euthanased.
Overseas, other Lyssaviruses naturally infect and cause rabies like disease in a broad spectrum of domestic mammal species. Bat biotypes of rabies virus infect a range of mammals, including cats, cattle and horses, and natural infection with European bat lyssavirus type 1 has been demonstrated in cats and sheep suffering from neurological disorders. McColl (2007) reported that in a laboratory setting, cats and dogs seroconverted after ABLV exposure with some abnormal clinical signs in both species (1). This suggests that occasional transmission of ABLV to animal species other than horses is likely.
ABLV may cause overt disease in bats and is more likely associated with abnormal bat behaviour. Clinical signs seen in bats include aggression, paralysis, vocalisation changes, respiratory difficulties, weaknesses, tremors and convulsions. However, cases can vary in range and severity of clinical signs.
Serological testing and viral studies have confirmed a wide distribution of infected bats along the entire eastern seaboard, including NSW where the Australian population is most concentrated (2). Approximately 5 % of tested Australian bats have evidence of ABLV infection, but this increases to 20 % for sick or injured bats (3).
It is important that precautions are taken if there is any likelihood your pet or horse has been bitten, scratched or exposed to bat body fluids. It is quite common for dogs and cats to come in direct contact with injured or sick bats as they are often found on the ground or low down on trees. If the bat was infected with ABLV, it is possible that an animal could be exposed to the virus while interacting with the bat.
In Australia, bats are highly mobile and frequently found in large camps close to, or located in urban areas, making bat-human/ bat-animal interactions a relatively common event. This also means that dogs and cats are more likely to play or catch sick bats and are at risk of being scratched or bitten.
There were 39 cases of human/pet contact with bats that resulted in testing for ABLV during 2013 at the Elizabeth Macarthur Agricultural Institute (EMAI). These are the reported cases, and there is likely to be many more unreported contacts between bats and companion animals (data courtesy of Diane Ryan). In another study done by Paterson et al, 12 % of bat exposures involved domestic pets (4).
The virus is short lived outside the host and is rapidly inactivated by heat, direct sunlight and soap. It lasts up to 24 hrs in saliva but less when unprotected and exposed to the elements.
The incubation period for ABLV infection is assumed to be similar to rabies. It can be as short as few days or as long as several years and varies according to dose of virus, site of entry and the immune status of the exposed animal.
Only experienced bat handlers who have been vaccinated for rabies should attempt to capture and care for sick or injured bats.
Avoid or minimise bat handling where possible.
The following precautions should be taken when handling live bats:
Where possible have a vaccinated, experienced bat handler hold the bat when conducting a clinical examination or euthanasia
Only vaccinated people with a monitored titre >0.5 IU/mL should handle bats
Wear appropriate protective clothing, long sleeves, long pants, shoes and double gloves (e.g. nitrile rubber which is puncture resistant) or Kevlar gloves
Prevent mucous membrane exposure (eyes/mouth) by a face mask and safety glasses or a face shield.
Take all reasonable steps to avoid being bitten or scratched.
Saliva or neural tissue from dead bats is potentially infectious and contact with dead bats should be minimal. Avoid handling the body if at all possible. Use gloves if it needs to be handled. If the bat is to be tested, triple bag it in a leakproof labelled plastic bag and store it in the refrigerator until submitted. If testing is not required dispose of the body by burial or incineration.
Owners who have animals which are known or suspected of being potentially exposed to ABLV infection should:
Apply first aid to any bite wounds or breaks in the skin that are possibly contaminated with bat saliva or neural tissue. Rinse the affected area liberally with soap and water for five minutes and then apply an iodine- based antiseptic with virucidal activity.
Seek veterinary assistance for your pet by contacting your local veterinary practitioner
Report the incident to the Emergency Animal Disease Hotline on 1800 675 888
Submit the WHOLE bat (or all the available body parts if mutilated) to EMAI for ABLV testing.
Samples for ABLV exclusion may be packed as IATA 650 (Biological Substance Category B) UN 3373 as for routine diagnostic specimen submissions, i.e. small foam Esky inside a cardboard box. Include an ice-brick to keep samples cool but not frozen. Triple bag the samples and disinfect the sample bags. All submissions for the exclusion of ABLV must have a clear warning note, e.g. ‘ABLV exclusion’ inside the Esky and on top of the samples. This should not be recorded on the outside packaging or on the consignment note. Submitters should contact the duty veterinarian at the HYPERLINK "http://www.dpi.nsw.gov.au/agriculture/vetmanual/contact" State Veterinary Diagnostic Laboratory (SVDL) to advise that a suspect ABLV infected bat is being submitted.
If there is a medium, high or extreme risk of human exposure to ABLV, organise same day transport to get the samples to the laboratory as soon as possible. Ring the duty pathologist or the EAD Hotline on 1800 675 88 for assistance with urgent submission. It is essential that virology staff and NSW Health are also notified.
Further information on packaging of specimens is available in the HYPERLINK "http://www.dpi.nsw.gov.au/agriculture/vetmanual/submission/packaging-of-specimens" Vet Lab Manual – sample packaging
Information on sampling for the diagnosis of ABLV infection can be found in the HYPERLINK "http://www.dpi.nsw.gov.au/agriculture/vetmanual/specimens-by-disease-syndrome/diseases_of_livestock/lyssavirus" Vet lab manual - lyssavirus
Figure 1: Guide to ABLV exposure risks
|Human exposure *
(confirmed or suspected)
|Animal exposure *
(confirmed or suspected)
|No Human or animal exposure|
|Bat with confirmed ABLV infection||Extreme||Med||Med||Low||Low|
|Bat with unknown ABLV infection status||High||Med||Med||Low||Low|
|Bat tested negative for ABLV infection||Low||Low||Low||Low||Low|
Bite or scratch by a bat or has mucous membrane or broken skin contact with bat saliva or neural tissue from a bat
bat tests positive
The owner must be advised that the contact animal has a low risk of developing ABLV infection but if it did it could potentially then also transmit the infection to humans or other animals.
Advice to the animal owner should include the following options:
Vaccination – Rabies vaccination of the at-risk animal as soon as possible after the contact with the bat should mitigate the risks of clinical ABLV infection. An application needs to be made to the NSW Chief Veterinary Officer (CVO) by the veterinarian administering the vaccine to access and use rabies vaccine.
Health monitoring – Keep the animal under observation for two years for any changes in behaviour or signs of ill-health (due to the possible long incubation period). If these are seen they should be immediately reported to DPI. The owner needs to also understand that taking no action may result in a potential risk of ABLV infection and that, if clinical signs suggesting ABLV disease are reported, it is likely to be recommended that the animal be euthanased and samples taken for examination.
Euthanasia - To avoid any further risk of humans contracting ABLV infection from a suspect animal, the owner has the option of authorising euthanasia of the animal (especially in those cases where it can be established that physical contact between the animal and the bat definitely occurred)
Testing for ABLV antibodies in animals thought to be exposed is of limited value as antibodies to natural infection appear some time after the virus has spread to the nervous system.
bat not available for testing
The owner must be advised that the in contact animal has a very low risk of developing ABLV infection but if it did it could potentially then also transmit the infection to humans or other animals.
The options for managing this scenario are the same as specified in (i) above.
bat tests negative
No Further action required
Note: all costs associated with post exposure vaccination of domestic mammals, elective euthanasia or ongoing veterinary monitoring of a domestic mammal that has been exposed to a bat will be at the expense of the owner/manager.
Thanks to Diane Ryan for the spreadsheet of human/pet contacts with bats that resulted in ABLV testing during 2013.