Rabies and Australian bat lyssavirus

Notification requirement for rabies and Australian bat lyssavirus

Rabies, Australian bat lyssavirus (ABLV) and other lyssavirus infections are urgent notifiable conditions.

They must be notified by medical practitioners and pathology services to the Department of Health by telephone on 1300 651 160 (24/7) upon initial diagnosis or clinical suspicion as soon as practicable and within 24 hours.

Pathology services must follow up with written notification within 5 days.

Infectious agents of rabies and Australian bat lyssavirus

Rabies is caused by the rabies virus. Rabies virus, ABLV and other lyssaviruses (for example, European bat lyssavirus) are closely related viruses of the Rhabdoviridae family, genus Lyssavirus.

Identification of rabies and Australian bat lyssavirus

Clinical features

Rabies and ABLV infection are viral diseases that affect the central nervous system. They are almost always fatal.
Initial symptoms include fever, headache, fatigue, malaise, paraesthesia (sensory changes) and difficulty swallowing. The disease progresses to an acute viral encephalomyelitis.

There are two clinical forms of rabies:

• Encephalitis (furious) rabies in approximately two-thirds of cases, characterised by hyperactivity, aerophobia (fear of drafts of air), hydrophobia (fear of water), confusion and convulsions.
• Paralytic (dumb) rabies in approximately one-third of cases, characterised by progressive paralysis involving extremities and respiratory muscles with sparing of consciousness.

Death from respiratory, cardiac or central nervous system failure occurs within 7 to 10 days of illness onset.

Diagnosis

Rabies and ABLV infection is diagnosed through laboratory testing. Testing is only available to confirm infection following onset of clinical disease. Collection of specimens from multiple sites, analysis through different testing modalities and repeat testing may be required for diagnosis. Clinicians should notify the Department and the receiving laboratory before testing for rabies or ABLV.

Testing for rabies and ABLV infection include:

• Polymerase chain reaction (PCR) of saliva, CSF, CNS tissue, skin biopsy containing hair follicles from the nape of neck or salivary gland tissue
• Virus culture of saliva, cerebrospinal fluid (CSF), central nervous system (CNS) tissue or salivary gland tissue
• Serology of serum or CSF, which should be interpreted in the context of any history of previous immunisation against rabies

Post-mortem, diagnostic testing can also include fluorescent antibody testing and immunocytochemistry of clinical specimens, ideally CNS tissue.

Animal testing

The Australian Centre for Disease Preparedness (ACDP) at CSIRO Geelong is the reference laboratory for testing of rabies virus and ABLV in Victoria.

Only trained and vaccinated people wearing appropriate personal protective equipment should handle potentially infected animals.

If a bat is suspected to have potentially exposed a person to ABLV , call the Department of Health Communicable Diseases Section on 1300 651 160 for advice on bat capture, transport for euthanasia and specimen testing.

If the bat has been captured by a member of the public, the bat should be taken to a local veterinary clinic if safe and feasible to do so.

Incubation period of rabies and Australian bat lyssavirus

The incubation period for rabies is usually 2 to 3 months. Rarely, it is as short as 5 days or as long as several years.

The incubation period for ABLV is less certain but is assumed to be similar to rabies, ranging from several weeks to years.

Public health significance and occurrence of rabies and Australian bat lyssavirus

Rabies is endemic in Asia, Africa, North, Central and South America, and parts of Europe. Most cases and deaths are reported in Asia and Africa, with children under 15 years disproportionately impacted. Dogs are responsible for up to 99% of transmission to humans.

Globally, dog vaccination and dog bite prevention efforts are implemented to reduce rabies risk as part of a One Health approach. Australia is currently rabies-free and public health measures are in place to prevent the introduction of rabies virus to the Australian ecology. Extremely few human cases of rabies have been reported in Australia, mainly in travellers who have lived in or visited overseas rabies-enzootic areas.

ABLV is endemic to Australia and is carried by several species of bats. Three human cases of ABLV infection have been reported, in 1996, 1998 and 2013. While human cases are extremely rare, bat exposures in Australia pose a potential risk of infectious exposure.
For further information on rabies-enzootic countries refer to the:

• World Health Organization: The Global Health Observatory - Rabies
• US Centers for Disease Control and Prevention: Rabies status assessment by country

Reservoir for rabies and Australian bat lyssavirus

Dogs are the primary reservoir of rabies. However, all mammals are susceptible to rabies. Other animal reservoirs include other canines (such as foxes, coyotes, jackals and wolves), monkeys, cats, bats, raccoons, mongooses and skunks. Wild and domestic animals can become infected and transmit infection to humans.

Bats are the primary reservoir of ABLV. All four species of Megachiroptera (fruit bats and flying foxes) and at least seven species of Microchiroptera (insectivorous bats) are known to carry the virus. ABLV is thought to be widely distributed across Australia.

Mode of transmission of rabies and Australian bat lyssavirus

Rabies virus and ABLV are transmitted from infected animals to humans through bites or scratches or from contact with saliva or neural tissue to broken skin or mucous membranes. Exposure to blood, urine or faeces is not known to transmit infection.

Person-to-person transmission has only been documented in extremely rare cases involving organ transplants.

Period of communicability of rabies and Australian bat lyssavirus

The infectious period for rabies in dogs commences 3 to 10 days before onset of clinical signs and persists throughout the course of the illness.

The infectious period for ABLV and other lyssaviruses is not known.

Susceptibility and resistance to rabies and Australian bat lyssavirus

The risk of infection following exposure is presumably related to the size of the inoculum, severity of bite, nerve density in the area of the bite, proximity of the bite to the central nervous system, vaccination status and immune system function.

People who undertake occupational, volunteering, or recreational activities in endemic countries that put them at increased risk of animal exposures are at increased risk of infection.

Control measures for rabies and Australian bat lyssavirus

Preventive measures

Only appropriately trained and vaccinated people, wearing appropriate personal protective equipment, should handle bats and other wildlife.

People are advised to avoid close contact with wild and domestic animals when travelling to rabies-enzootic areas.

Pre-exposure prophylaxis

Pre-exposure prophylaxis through vaccination is recommended as a preventive measure for:

• people whose occupation, volunteering or recreational activities place them in close contact with bats, such as bat handlers and carers, veterinarians and associated workers, wildlife officers and researchers
• people working with mammals in rabies-enzootic areas
• people travelling to or living in rabies-enzootic areas (based on risk assessment)
• laboratory workers working with live lyssaviruses

Pre-exposure prophylaxis consists of three doses of rabies vaccine given on days 0, 7 and between 21 to 28. Medical practitioners should refer to the Australian Immunisation Handbook for further information. People with ongoing exposures are recommended periodic blood testing every three years to check whether a booster dose is needed.

The Department of Health funds an initial schedule of up to three doses of rabies vaccine for volunteer Australian wildlife handlers. Booster doses are not funded.

Medical practitioners seeking to provide pre-exposure prophylaxis for volunteer Australian wildlife handlers are requested to submit thepre-exposure rabies treatment order form to the Department of Health Immunisation Unit – immunisation@health.vic.gov.au. Ensure the form is filled in correctly with all relevant information. Forms completed and submitted by a volunteer wildlife handler or organization will not be processed and will be returned to the sender for completion by a medical practitioner.

Control of case

There is no known effective treatment available for rabies and ABLV infection. A small number of patients have survived rabies with intensive supportive treatment.

Patients should be cared for under standard, contact and droplet precautions for the duration of illness in a suitable care setting. Health services should refer to internal infection prevention and control team and infectious diseases service.

It is important to identify the source of infection, such as any history of contact with bats (in Australia or overseas) or any other mammal in a rabies-enzootic country, and whether other people or animals may also have been exposed.

Control of contacts

People who have been exposed to a potential source of infection should seek urgent medical attention for wound care and assessment for post-exposure prophylaxis.

Wound care

All wounds should be washed thoroughly with soap and water for at least 15 minutes, as soon as possible after the exposure. A virucidal antiseptic containing iodine (such as povidone-iodine, iodine tincture or aqueous iodine solution) or alcohol (ethanol) should be applied after washing if available. The wound should not be sutured unless unavoidable, and only after human rabies immunoglobulin has been administration, where indicated.

In the event of mucous membrane (eyes, nose, and mouth) exposure, immediately flush with copious water.

Consideration should also be given to the possibility of tetanus and other wound infections, and appropriate measures taken.

Post-exposure prophylaxis

People who have been exposed to a potential source of infection should be assessed for post-exposure prophylaxis (PEP). PEP through a combination of rabies vaccine and human rabies immunoglobulin (HRIG) can help reduce the risk of rabies and ABLV infection following exposure.

The PEP recommendations vary depending on the:

• type of animal
• type of exposure: severity and location of wound(s)
• geographic location of exposure
• time interval since exposure
• previous rabies vaccination and/or antibody status of the exposed person
• immune function of the exposed person
• reliability of the information about the exposure event
• availability of the animal for exposure and testing

Medical practitioners should refer to the Australian Immunisation Handbook which provides recommendations on PEP, including two management algorithms based on the exposure:

• For exposures to a terrestrial animal in a rabies-enzootic country - see Figure. Rabies post-exposure prophylaxis: terrestrial animal exposures
• For exposures to a bat (in Australia or overseas) - see Figure. Rabies post-exposure prophylaxis: bat exposures

The Local Public Health Unit or Department of Health can provide advice on PEP.

Post-exposure prophylaxis supply

Medical practitioners should contact their Local Public Health Unit for advice on options regarding PEP supply. Options may include:

• requesting supply from the Department of Health’s Immunisation Unit
• referring the patient to other health services with PEP in stock, such as GPs, travel medicine clinics or hospital. Call ahead to ensure the required PEP is available.

Medical practitioners seeking supply of PEP from the Department of Health are requested to submit the post-exposure rabies treatment order form to the Immunisation unit – immunisation@health.vic.gov.au. Ensure the form is filled and submitted correctly with all relevant information.

Rabies vaccine use

For adults and children one year of age or older, the rabies vaccine should be administered into the deltoid area, as administration in other sites may result in reduced neutralising antibody titres. In infants under 12 months of age, administration into the anterolateral aspect of the thigh is recommended.

Human rabies immunoglobulin use

HRIG is given to provide localised anti-rabies antibody protection while the patient mounts an immune response to the rabies vaccine. HRIG can be given up to and including day 7 following the first dose of vaccine but should not be given from day 8 onwards as it may suppress the immune response to the vaccine.

The recommended dose of HRIG is 20 IU per kg of patient weight. The HRIG product routinely used in Australia is typically supplied in 2mL vials containing 150 IU/mL. The following formula can be used to calculate the volume of HRIG required:

• Total HRIG required (mL) = patient weight in kilogram x 20 ÷ 150

As a guide, medical practitioners are advised to request one vial of HRIG for every 15kg of patient weight to cover adequate dosage.

HRIG should be infiltrated in and around all wounds. It is imperative that as much HRIG as possible is given in and around the wound. The remainder of any HRIG dose that cannot be safely infiltrated in and around the wound, or the whole HRIG dose in situations such as mucous membrane exposures (where there is no wound), should be given intramuscularly at a site distant to that where rabies vaccine is given. If there are multiple wounds, HRIG may be diluted in saline to make up an adequate volume to infiltrate all wounds.

During periods of HRIG shortage prioritisation measures may be implemented. Similarly special arrangements may be made for the use of other immunoglobulin products. In such circumstances, the Communicable Diseases Network Australia and Department of Health will provide advice on variations to recommendations.

Control of environment

Any suspected infected mammals, including bats, should be isolated from other animals and humans, and veterinary management sought including testing where possible, without placing others at risk of exposure. If an animal is suspecting of having rabies or ABLV, report it immediately to the Emergency Animal Disease Watch Hotline on 1800 675 888 (24/7). Agriculture Victoria is the control agency for any animal diseases outbreaks within Victoria.

Environmental contamination by infected animals is considered negligible based on knowledge of persistence of the rabies virus, which is fragile and does not survive for long outside the host. It is readily inactivated by heat and direct sunlight. Bat or other mammal blood, urine, and faeces are not considered to be infectious.

Additional information and resources

Information

• Australian Immunisation Handbook
• Communicable Diseases Network of Australia National Guidelines for Public Health Units: Rabies and other lyssavirus
• World Health Organization: Rabies factsheet
• World Health Organization: The Global Health Observatory - Rabies
• US Centers for Disease Control and Prevention: Rabies status assessment by country
• Animal Health Australia: Australian Veterinary Emergency Plan (AUSVETPLAN)

Resources

• Post-exposure rabies treatment order form
• Pre-exposure rabies vaccine order form
• Patient held record form – rabies or Australian bat lyssavirus
• Local Public Health Units
• Notifiable infectious diseases, conditions and micro-organisms