Notification requirement for rabies and Australian bat lyssavirus
Rabies (Group A disease) must be notified immediately by telephone or fax, followed by written notification within 5 days.
Australian bat lyssavirus (Group B disease) must be notified in writing within 5 days of diagnosis.
These are Victorian statutory requirements.
Rabies is subject to human quarantine controls under the Quarantine Act 1908 (Cwlth). Rabies is a quarantinable disease because of Australia’s freedom from this disease. It is also reportable to the World Health Organization.
Infectious agents of rabies and Australian bat lyssavirus
Rabies virus and Australian bat lyssavirus (ABL) are closely related members of the genus Lyssavirus.
Identification of rabies and Australian bat lyssavirus
Rabies is an acute viral disease of the central nervous system (CNS). The first symptoms of rabies are flu-like, including fever, headache and fatigue. The disease then progresses to involve the respiratory, gastrointestinal and/or central nervous systems after 1–4 days. In the critical stage, signs of hyperactivity (furious rabies) or paralysis (dumb rabies) dominate. Furious rabies makes up two-thirds of presentations and is characterised by a sense of apprehension; parasthaesia (sensory changes) at the bite site; and aerophobia (fear of drafts of air) or hydrophobia (fear of water), causing spasms of the muscles of swallowing. In contrast, dumb rabies is characterised by normal alertness and consciousness. In both furious and dumb rabies, some paralysis eventually progresses to complete paralysis, followed by coma and death in all cases, usually due to breathing failure. Without intensive care, death occurs during the first 7 days of illness. Overall case fatality is close to 100 per cent once symptoms develop.
Symptoms of encephalitis due to ABL infection include numbness, muscle weakness, collapse and coma. A confirmed case requires definitive laboratory evidence only.
The CSIRO Australian Animal Health Laboratory (AAHL) at Geelong is the reference laboratory for diagnosis of rabies and ABL. The state Chief Quarantine Medical Officer at the department should also be advised at the time of submitting any specimen. Transfer of human and animal specimens to AAHL is coordinated by the Chief Quarantine Medical Officer, in consultation with the Chief Veterinary Officer. Animal euthanasia and postmortem specimen collection are arranged through the Department of Environment, Land, Water and Planning.
Rabies and ABL can be diagnosed by:
- detection of virus antigen by direct fluorescent antibody testing of a clinical specimen such as neural tissue (preferred), skin snips from the nape of the neck, saliva or cerebrospinal fluid (CSF)
- isolation in cell culture or laboratory animal of the virus from saliva, CSF or CNS tissue
- identification of rabies neutralising antibody in the serum or CSF of unvaccinated people.
Confirmation by all the above methods is recommended.
Incubation period of rabies and Australian bat lyssavirus
The incubation period for rabies is usually 3–8 weeks. Rarely, it is as short as 9 days or as long as several years, depending on wound severity, location and distance from the brain.
The incubation period for ABL is not well characterised but is assumed to be similar to that of rabies. The first case, reported in 1996, is believed to have had an incubation period of at least several weeks. In the second patient, the incubation period was more than 2 years.
Public health significance and occurrence of rabies and Australian bat lyssavirus
Rabies is endemic in Asia, India, Africa, North and South America, and parts of Europe. High rates of rabies are reported from the Philippines, Thailand and Indonesia. Bali, which had been rabies-free, has had cases since 2008, and is currently considered an area with risk of exposure.
Australia is currently rabies-free. Rabies is a very rare infection of travellers to endemic areas outside Australia. Only two imported human cases were reported between 1900 and 1995 (in 1987 and 1990).
Three human cases of ABL infection have been reported. These were all from Queensland, and occurred in 1996, 1998 and 2013. All patients had a history of bites and scratches from a bat, and died from their infections.
The primary quarantine concern is the prevention of introduction of rabies virus to local dog and wildlife populations.
ABL is an emerging infectious disease that has much in common with rabies. The risk of human exposure increases with increasing human contact with Australian bat environments. This risk would increase significantly if ABL became established in terrestrial animal populations, particularly dogs.
Reservoir for rabies and Australian bat lyssavirus
Rabies is a disease primarily of mammals. Most wild and domesticated dog species (including foxes, coyotes, wolves and jackals) are susceptible to infection. Infected dogs remain the highest risk source for human transmission. Other species include skunks, racoons and bats.
In developed countries, rabies is mainly found in wild animal hosts. Disease is spread from wild hosts to domestic animals and humans. In contrast, domestic dogs continue to be the main hosts in most African and Asian countries, and are responsible for most of the rabies deaths that occur worldwide. South America has implemented a regional control program that has reduced human deaths by 95 per cent, and risk is now greater from exposure to wildlife (particularly bats) than to dogs.
Australia is one of a growing number of countries in the world where the animal population is free from rabies.
ABL is known to infect all four species of Megachiroptera (fruit bats and flying foxes) in Australia and at least seven species of Microchiroptera (insectivorous bats). Ongoing serological testing and virus studies suggest that this lyssavirus is widely distributed in Australia. It is therefore assumed that all Australian bats have the potential to carry and transmit ABL.
There is no evidence that lyssaviruses in bats can establish and spread among terrestrial animals, although isolated cases in humans may occur on rare occasions.
Mode of transmission of rabies and Australian bat lyssavirus
Rabies virus and other lyssaviruses are usually transmitted to humans via bites or scratches, which provide direct access of the virus in saliva to exposed tissue and nerve endings. Transmission can also occur from exposure of mucous membranes, such as eyes, nose or mouth, to bat saliva.
The most frequent way that humans become infected with rabies virus is through the bite of infected dogs; cats; wild carnivorous species such as foxes, raccoons, skunks, jackals and wolves; and insectivorous and vampire bats. Cattle, horses, deer and other herbivores can become infected with rabies virus but rarely transmit the virus to other animals, although they may transmit the disease to humans.
Transmission from person to person is theoretically possible but has only ever been documented through corneal and organ transplantation.
People are not exposed to ABL through tactile contact with bats where parenteral or mucous membrane exposure does not occur. Contact such as patting bats or exposure to urine and faeces does not constitute a likely exposure to ABL, although bat urine and faeces may carry other human pathogens, including Hendra virus.
Period of communicability of rabies and Australian bat lyssavirus
In dogs and cats, rabies is usually communicable 3–7 days before onset of clinical signs and throughout the course of the illness. Viral excretion up to 14 days before the appearance of clinical signs has been observed in some animal species. Similar communicability can be assumed for human cases.
Communicability for ABL is not known but is assumed to be similar to that of rabies.
Susceptibility and resistance to rabies and Australian bat lyssavirus
All mammals are susceptible to varying degrees. In one case series, only 40 per cent of children bitten by known rabid dogs developed the disease.
Control measures for rabies and Australian bat lyssavirus
Pre-exposure vaccination is recommended for people whose occupation or recreational activities place them at increased risk of being bitten or scratched by a bat. It is not routinely recommended for travellers (see rabies/ABL vaccination information sheet in ‘Immunisation’).
Control of case
There is no well-established specific treatment for symptomatic cases. Recent use of the Milwaukee protocol (involving induced coma and antiviral treatment) or versions of this protocol suggest a possible survival rate of 8 per cent. Intensive supportive treatment is required.
The patient should be placed in a private room, with standard isolation precautions implemented for respiratory secretions for the duration of the illness. There should be concurrent disinfection of all saliva-contaminated articles. Although transmission from a patient to attending carers has not been documented, healthcare workers should be advised to wear gowns, gloves and masks while attending patients. Blood and urine are not considered infectious.
Control of contacts
Other individuals exposed to the source animal are identified and offered post-exposure prophylaxis. Contacts who have exposure of open wounds or mucous membranes to a patient’s saliva should be offered full post-exposure prophylaxis.
Proper cleansing of the wound is the single most effective measure for reducing the transmission of rabies virus, and this is likely to be also true for ABL.
When a person has been injured by a potentially infected animal overseas, or any Australian bat, the wound should be washed thoroughly as soon as possible, for approximately 5 minutes, with soap and water. If available, a virucidal antiseptic such as povidone-iodine, iodine tincture, aqueous iodine solution or alcohol (ethanol) should be applied after washing. Exposed mucous membranes such as eyes, nose or mouth should be flushed well with water.
The decision to offer post-exposure prophylaxis (rabies vaccine and rabies immunoglobulin) to a potentially exposed person should be made in consultation with the Communicable Diseases Section of the department.
Control of environment
See ‘Outbreak measures for rabies and Australian bat lyssavirus’.
Outbreak measures for rabies and Australian bat lyssavirus
If the source of ABL infection is likely to be in Australia, a search should be made for the infected animal, in collaboration with animal health authorities. Where possible, without placing other people at risk of exposure, the bat should be kept and the department consulted about arranging testing of the bat for virus carriage. For assistance with handling, local Department of Environment, Land, Water and Planning staff can be contacted.
If a rabies case (human or animal) is believed to have been locally acquired, the AUSVETPLAN rabies control procedures should be implemented. In designated areas, animal owners may be required to have susceptible animals vaccinated with rabies vaccine. Animal movements are restricted, and stray animals are destroyed.
ABL is unique to Australia and is currently found only in Australian bat species. If a human case of ABL is diagnosed in Victoria or ABL is found in another animal species, such as a dog or cat, investigation and control measures similar to those for a rabies case should be instigated.
Pre-exposure prophylaxis – rabies and Australian bat lyssavirus
Pre-exposure vaccination should be recommended to people whose occupation or recreational activities place them at increased risk of being bitten or scratched by a bat – for example:
- bat carers, bat handlers, researchers and students
- veterinarians and veterinary assistants
- veterinary laboratory staff
- fruit pickers
- wildlife officers (including local government officers)
- managers of display or research colonies of bats
- powerline workers who frequently remove bats from powerlines.
Pre-exposure prophylaxis consists of three intramuscular doses of 1.0 mL rabies vaccine given on days 0, 7 and 28. The intramuscular or subcutaneous route can be used for human diploid cell vaccine (HDCV). Doses should be given in the deltoid area, because rabies neutralising antibody titres may be lower after administration in other sites. In children, administration into the anterolateral aspect of the thigh is also acceptable.
The intradermal route is not recommended for administration of the vaccine. If this is being considered, detailed restrictions must be applied. See the 10th edition of the Australian immunisation handbook.
Post-exposure treatment for people bitten or scratched
– rabies and Australian bat lyssavirus
The decision to offer post-exposure prophylaxis to a potentially exposed person should be made in consultation with the department. If post-exposure prophylaxis is indicated, the department will arrange for rapid delivery of vaccine and immunoglobulin, as required.
Post-exposure treatment should be considered in the following scenarios:
- a person bitten or scratched by bats in Australia
- a person bitten or scratched by any animal in a country with endemic rabies.
Rabies virus and other lyssavirusesare usually transmitted to humans via bites or scratches, which provide direct access of the virus in saliva to exposed tissue and nerve endings, or where exposure of mucous membranes (such as in the eyes, nose or mouth) to bat saliva has occurred. This means that people would not be exposed to lyssavirus through only tactile contact with bats or other animals, where parenteral or mucous membrane exposure does not occur. Contact such as patting bats (Australia) or other animals, or exposure to their urine and faeces does not constitute a possible exposure to Australian bat lyssavirus, although bat urine and faeces may carry other human pathogens, including Hendra virus. Pre-exposure vaccination should, however, be offered if the person has ongoing contact with bats.
If the exposure is connected to an Australian bat, where possible – without placing other people at risk of exposure – the bat should be kept so that the department can arrange for testing of the bat. For assistance with handling, local Department of Environment, Land, Water and Planning staff can be contacted.
Proper cleansing of the wound is the single most effective measure for reducing the transmission of classic rabies virus.
Where a person has been injured by a potentially infected animal, the wound should be washed thoroughly for approximately 5 minutes, as soon as possible, with soap and water. If available, a virucidal antiseptic such as povidone-iodine, iodine tincture, aqueous iodine solution or alcohol (ethanol) should be applied after washing. Exposed mucous membranes such as eyes, nose or mouth should be flushed well with water.
Rabies and Australian bat lyssavirus – post-exposure treatment: not previously vaccinated
Post-exposure prophylaxis for people not previously immunised against rabies consists of four doses of 1.0 mL of rabies vaccine given as an intramuscular injection on days 0, 3, 7 and 14. The intramuscular or subcutaneous route can be used for HDCV. Doses should be given in the deltoid area, because rabies neutralising antibody titres may be lower after administration in other sites. In children, administration into the anterolateral aspect of the thigh is also acceptable. The vaccine should not be administered by the intradermal route. Note that, for exposures in Australia from bats considered to pose a risk of Australian bat lyssavirus, a fifth dose needs to be given on day 28–30, but this is no longer used for overseas rabies exposures, as once was the case. A fifth dose on day 28–30 is also required for immunocompromised people.
Rabies immunoglobulin (RIG) should be given as a single dose at the same time as the first dose of the post-exposure vaccination course. The dose for RIG is 20 international units per kilogram of body mass. RIG should be infiltrated in and around all wounds using as much of the calculated dose as possible, and the remainder administered intramuscularly. It should not be given at the same site as the vaccine. If it is administered in the buttock, care should be taken to ensure that the dose is given intramuscularly and not into adipose tissue.
Although the RIG and first dose of rabies vaccine should preferably be given on the same day, if necessary the RIG can be given up to 7 days after the first dose of vaccine. It should not be given more than 7 days after rabies vaccine has commenced.
RIG should be infiltrated into finger wounds using a 25 or 26 gauge needle. To avoid a compartment compression syndrome, the RIG should be infiltrated very slowly, and should not cause the adjacent finger tissue to become pale or white. If necessary, a ring-block using local anaesthesia may be required. If the wounds are severe and the calculated volume of RIG is inadequate for complete infiltration, the RIG may be diluted in saline to make up an adequate volume for the infiltration of all wounds. Because most bat bites are small and fine, this should usually not be necessary.
(Note that HDCV product information recommends a routine fifth dose at 30 days and a routine sixth dose at 90 days. The sixth dose is not considered necessary, and a fifth dose is only recommended for Australian bat lyssavirus exposures and immunosuppressed people. For more information, see the current edition of the Australian immunisation handbook, National Health and Medical Research Council.)
Post-exposure treatment: previously vaccinated
– rabies and Australian bat lyssavirus
Post-exposure prophylaxis for people who have previously completed the recommended course of either pre-exposure vaccination or post-exposure prophylaxis, or who have documented rabies neutralising antibodies, comprises a total of two doses of rabies vaccine (1.0 mL each) given by intramuscular injection on days 0 and 3. The intramuscular or subcutaneous route can be used for HDCV. In cases where prior vaccination status is uncertain, or the person has been vaccinated by inappropriate intradermal injection (or by gluteal route), a full course of post-exposure prophylaxis (RIG plus five doses of vaccine) should be offered. It is therefore advisable to ensure that people are given adequate written documentation regarding any RIG and vaccines administered.
For more information, contact:
- your local doctor
- the department.