Australian bat lyssavirus

Description

Australian bat lyssavirus (ABLV) is an endemic viral infection in Australian bats. ABLV is closely related to classical rabies virus and causes similar progressive neurological disease in naturally-infected bats, humans and horses. A range of bat species (both flying foxes and insectivorous bats) can be infected with ABLV and many remain asymptomatic. A proportion of infected bats show clinical signs consistent with rabies. Based on testing to date, there is a higher likelihood of finding ABLV in sick or injured bats, compared to the normal wild population. Bats showing neurological signs have the highest rates of infection.

Current situation

Since the virus was first identified in 1996, there have been 4 confirmed human ABLV deaths in Australia, and 2 confirmed cases of ABLV infection in horses; both of which occurred in Queensland in 2013.

Disease in animals apart from horses has not been reported to date; however, other closely related lyssaviruses in overseas countries have occasionally caused disease with rabies-like symptoms in a wide variety of domesticated and wild animals.

Human infection with ABLV

ABLV is closely related to the rabies virus and is typically transmitted through the bite or scratch of an infected animal. There is no effective treatment for ABLV once symptoms begin, making prevention critically important.

Clinical signs

Clinical signs in infected bats are variable, ranging from clinically normal to severe neurological disease. Clinical signs may include:

• Bats in unusual locations during the daytime ( i.e. not in normal roosts)
• Bats on the ground or low in a tree with inability to take off or fly normally or appear to be injured
• Behavioural signs (e.g. aggression, docility, shivering and salivation).
• Respiratory difficulties, change of voice
• Paresis or paralysis

Clinical signs in non-bat species are likely to be similar to those of rabies. Horses that became infected developed subtle dullness, ataxia, head pressing, dysphagia, hypermetria, fever, sternal recumbency and seizures.

Control

The general public should be discouraged from rescuing or handling bats. Paralysed, aggressive or unusually docile bats are at high risk of being infected.

People bitten or scratched by bats must be advised to contact their medical practitioner and/or NSW Public Health Unit immediately.  Live bats should be handled only by trained, vaccinated personnel, taking precautions to avoid bites and scratches.

Individuals such as wildlife carers, veterinary staff and veterinary pathologists, who regularly handle potentially infected bats, should be vaccinated against rabies.

Diagnosis and tests available

Diagnosis

Because of the zoonotic risk, live bats must be euthanized before submitting for laboratory testing.  Necropsy and submission of tissue samples is not recommended because of operator exposure risk and ideally whole intact bats or if dismembered, portions containing salivary and nervous tissue (head, spinal column) will give the most reliable results.

There is no test that can reliably diagnose ABLV infection in a live animal. Swab samples collected by vigorous swabbing of the pharynx may allow a diagnosis of ABLV infection to be made by PCR, but a negative result does not exclude it. DO NOT use commercially prepared swabs with plastic sleeves that contain transport medium. Tubes containing PBGS can be supplied by the laboratory. If PGBS is not available, swabs should be placed in 2 ml sterile saline.

Tests available

Click on + in the tables below for sampling requirements and additional test information

Additional Information