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

As at August 2016, three people have died from ABLV infection, and there were two cases of ABLV infection in horses in Queensland in May 2013.  Disease in animals apart from horses has not been reported to date however other closely related lyssaviruses in overseas countries do cause disease with rabies- like symptoms in a wide variety of domesticated and wild animals.

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.  Live bats should be handled only by trained, vaccinated personnel, taking precautions to avoid bites and scratches. Bats should be euthanased and sent intact to the laboratory for necropsy and Lyssavirus testing.

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

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

Test

Sample(s) required

Days of the week test is conducted

Turnaround time1

Australian bat lyssavirus PCR3

Whole deceased animal
(chilled not frozen)

According to demand2

Same day to 3 days depending on urgency

Australian bat lyssavirus antigen FAT

Whole deceased animal
(chilled not frozen)

According to demand2

Outsourced test

Histopathology and immunohistochemistry

Fixed tissue

Monday – Friday

Up to 5 days

1 Turnaround times are provided as a guide only. For specific information about your submission please contact Customer Service.
2 Prior approval of delivery and testing on Saturday is required. Please contact Customer Service on 1800 675 623 to seek approval.
3 This test is not NATA accredited.

Specimen requirements

Whole deceased animal

  • Submit whole deceased bat, small domestic or wild animal. If ABLV is suspected in large animals contact the laboratory for further information on sample submission.
    • Do not euthanase by shooting the animal in the head
    • Ensure carcase is securely packed (i.e. triple-bagged in a rigid container)
    • Submit chilled (not frozen)
  • If only parts of the body are available, they may still be suitable for testing (head or neural tissue is best).
  • Necropsy of suspect bats should only be undertaken under laboratory conditions by vaccinated pathologists where  brain and salivary gland can be collected for testing.
  • If you have adequate vaccine immunity and take recommended safety precautions including use of appropriate PPE, remove salivary glands and submit chilled as well as entire head or brain, divide longitudinally  and submit half fresh and half fixed in neutral buffered formalin at a 10:1 ratio of formalin: tissue.

Further information

Note

  • Fees for tests undertaken to confirm or exclude a diagnosis of lyssavirus infection are paid by NSW Department of Primary Industries.
  • Human exposure during the shipment of suspect material must be avoided.  Samples must be triple-bagged in leak-proof bags, with refrigerant, in an insulated container which is rigid and leak-proof.
  • Non approved after-hours submissions will incur a handling fee. Customers are encouraged to contact the laboratory Customer Services to seek advice on submission and approval requirements.
  • Operators should not handle animals suspected to be infected with ABLV unless they have adequate vaccinal immunity and take recommended safety precautions including using appropriate PPE (see Australian bat lyssavirus guidelines for veterinarians (PDF, 367.83 KB) ).
  • Saliva and other body tissues may have detectable virus at the time clinical signs are displayed however, there is no reliable, ante-mortem, diagnostic test for ABLV.
  • In horses, Hendra virus should be excluded (see Hendra virus) before invasive necropsy procedures, such as head and brain removal, are performed. Oral swabs in PBGS and parotid salivary gland may be sampled for Lyssavirus PCR at the time that samples are taken for Hendra virus testing however, it should be noted that, without the brain, it is impossible to detect all cases of Lyssavirus infection.