Viruses

Until 1996 there were no known diseases that spread from flying-foxes to humans or to other animals. Two viruses have now been identified in bats.

HENDRA VIRUS

Some species of flying-fox can be infected with Hendra Virus (originally Equine Morbilli Virus). This disease has only ever been transmitted to people from infected horses. There is no evidence to show that bats can transmit this virus to humans.

AUSTRALIAN BAT LYSSAVIRUS

This virus can only be contracted by a bite or scratch from an infected bat. Scientists do not yet know what percentage of bats carry the virus but it appears to be quite low (less than 1% of the total wild population). Infection of humans is extremely rare (only two cases ever documented in Australia).

ABL is a potentially fatal disease. If a person is bitten or scratched by a bat they should wash the wound carefully with soap and water for at least 5 minutes. Do not scrub the wound. Vaccinations are available for the prevention of this disease. If bitten or scratched contact your local health authority or doctor immediately. They will organise for you to be vaccinated.

People will not be exposed to lyssavirus when bats fly overhead or when they feed or roost in garden trees.

Only vaccinated carers should handle bats. So, if you find a bat on the ground or hanging low in a tree please call a wildlife care group (See the "Bat Rescue" page on this website) who will arrange to have the animal collected.

Further information on Australian Bat Lyssavirus, by Dr Paula Fogarty, is provided below.

Australian Bat Lyssavirus by Dr Paula Fogarty (Medical Director, The Travel Doctor TMVC)

Clinical features

There have only been two human cases of ABL recorded; thus, we have little data on the clinical features specific to the disease in Australia. However, the virus is very similar in its makeup to that of the classic rabies virus, and the cases of ABL followed a course typical of rabies. The usual incubation period of classic rabies is 3 weeks to 3 months. Occasionally, periods of several years delay in onset of symptoms have been documented. The virus causes an encephalitis (infection of the brain) which is almost invariably fatal.

The initial stage of the disease which may last for up to 10 days may include symptoms of fever, cough, headache, tiredness, muscle pain, and vomiting.

The second stage involves signs of encephalitis, with bizarre behaviour, agitation, and disorientation. The person affected may either die of cardiorespiratory arrest or coma.

Transmission
The transmission of lyssavirus in Australia has been solely through the saliva of an infected bat being inoculated into another bat or human through bites or scratches. Lyssavirus has been found to occur in all bat classes in Australia, both microbats and flying foxes. There has been no infection in other native species, or in introduced species such as foxes, cats or dogs. This is in keeping with the behaviour of other types of lyssavirus found internationally.

Prevention

For those at high risk of transmission, e.g. bat handlers, pre exposure vaccination is recommended. The regimen consists of three injections of human diploid cell vaccine at a dose of 1 ml given intramuscularly at days 0, 7, and 21-28. This is still the recommendation of the National Medical and Research Council. The individual is then tested to ensure that the vaccine has generated a sufficient antibody response. A response greater than 0.5 IU/ml indicates immunity, but it is preferable to have a cut off point higher than this (at least 0.75) to ensure that the individual remains immune over the bat handling season.

If exposure occurs after this course, two booster shots may be required, dependent upon the nature of the exposure and the time elapsed since a positive antibody response was elicited.

Last modified by KBCS Inc. on 2007/01/14.