Risks from bat bites and scratches in Australia need to be highlighted, say researchers

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A black flying fox at rest, in Brisbane, Queensland. Photo: By James Niland via Flickr via Wikimedia Commons
A black flying fox at rest, in Brisbane, Queensland. Photo: James Niland via Flickr via Wikimedia Commons CC BY 2.0

Public health agencies in Australia are being urged to tackle the strong desire of some members of the public to help injured or distressed bats, whose scratch or bite could lead to a fatal infection.

Researchers with Queensland Health in Brisbane have delved into potential exposures to Australian Bat Lyssavirus (ABLV) between 2009 and 2014.

ABLV poses a threat to both humans and horses, but does not garner the same media attention as the bat-borne Hendra virus. So far, only three known human ABLV cases − all fatal − have been reported in Queensland.

ABLV belongs to the genus Lyssavirus, which includes the classic rabies virus. ABLV is widely distributed in Australian bats, and any bite or scratch from one is considered a potential exposure to the virus. Potential exposure has been a notifiable condition in Queensland since 2005.

Damin Si and his colleagues analysed notification data over the six-year period. They reported in the open-access peer-reviewed journal PLOS Neglected Tropical Diseases that there were 1515 potential exposures to ABLV notified across the state during the period, with an average annual notification rate of 5.6 per 100,000 population per year.

The majority (96%) were potentially exposed via bats, with a small number of cases potentially exposed via two ABLV infected horses and an ABLV infected human.

The most common routes of potential exposure were through bat scratches (47%) or bites (37%), with less common routes being mucous membrane/broken skin exposure to bat saliva/brain tissue (2.2%).

Intentional handling of bats by the general public was the major cause of potential exposures, being responsible for 56% of notifications, they reported.

“Examples of these potential exposures included people attempting to rescue bats caught in barbed wire fences/fruit tree netting, or attempting to remove bats from a home.

“Following potential exposures, 1399 cases (92%) were recorded as having appropriate post-exposure prophylaxis (PEP) as defined in national guidelines, with the remainder having documentation of refusal or incomplete PEP.”

Up to a quarter of notifications occurred after two days from the potential exposure, with some delays being more than three weeks.

Of 393 bats available for testing during the reporting period, 20 (5.1%) had ABLV detected, including four species of megabats (all flying foxes) and one species of microbats (yellow-bellied sheathtail bat).

The overall findings, they said, highlighted the need to address the strong motivation of some members of the public to help injured bats or bats in distress. The findings also pointed to a lack of awareness around the risks of contact with or handling of bats.

This underscored the importance of avoidance of bat handling by contacting vaccinated, experienced, and well-equipped professional animal rescue groups to deal with bats.

There was, they suggested, a need to improve the timeliness of notification to ensure immediate post-exposure management.

Once a potential exposure to ABLV occurs, immediate cleansing of the wound (with soap and water for at least 5 minutes and application of povidone-iodine or alcohol) is required; and appropriate and timely rabies vaccine and human rabies immunoglobulin should be administered.

“Public health strategies should address the strong motivation of some members of the public to help injured bats or bats in distress, by emphasising that their action may harm the bat and put themselves at risk of the fatal ABLV infection,” the study team said.

Public health agencies should push the message that people may harm the bat and put themselves at risk of contracting the fatal ABLV infection if they attempt to rescue/handle the animal, because an untrained person was highly likely to be injured when handling a bat, and the bat involved in human injury will be euthanised for ABLV testing.

Instead, people should take alternative action, such as contacting appropriate animal rescue groups such as the RSPCA, to handle bats, as these professionals were vaccinated, experienced and well equipped to deal with bats.

The researchers’ own data showed that 5.1% of bats tested were ABLV infected (6.0% for megabats and 1.6% for microbats). Recent data from Wildlife Health Australia showed the prevalence of ABLV in bats submitted for testing was 6.7%.

For individual species, the little red flying fox had a relatively high prevalence of ABLV infection – 14.9% in their data, with other studies showing a prevalence of 17.5% and 16.9% .

The ABLV infection rate in sick, injured, or orphaned bats with central nervous symptoms could be as high as 21%, according to research – and sick or injured bats are more likely to be involved in human-bat interactions.

“These findings further reinforce the message of avoiding any bat handling by the general public.”

The researchers noted that eight people were exposed to two ABLV-infected horses which were first confirmed in 2013.

“Spillover of ABLV from natural reservoir bats to horses raises the question of whether ABLV can transmit to other animals, such as dogs.

“Contact between domestic dogs and ABLV infected bats has been reported previously, and our data indicate occasional pet animal-bat interactions (dogs/cats attacking bats on 62 occasions).

“Future research is needed to better understand the potential transmission of ABLV from bats to domestic animals and implications for public health.”

The research team comprised Damin Si, John Marquess, Ellen Donnan, Bruce Harrower, Bradley McCall, Sonya Bennett, and Stephen Lambert.

Si D, Marquess J, Donnan E, Harrower B, McCall B, Bennett S, et al. (2016) Potential Exposures to Australian Bat Lyssavirus Notified in Queensland, Australia, 2009−2014. PLoS Negl Trop Dis 10(12): e0005227. doi:10.1371/journal.pntd.0005227

The study, published under a Creative Commons License, can be read here

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