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Screw Worm Fly Surveillance & Preparedness Program

Screw-worm fly is an insect pest of warm blooded animals including people, livestock and wildlife. There are two commonly known screw-worm flies:

  • Old world screw-worm fly (OWS) – Chrysomya bezziana
  • New world screw-worm fly (NWS) – Cochliomyia hominivorax.

Suspicion of screw-worm fly infestation in animals is notifiable under state and territory animal health legislation.

The program

Animal Health Australia (AHA) manages the Screw-worm Fly Surveillance and Preparedness Program (SWFSPP) in consultation with a committee of industry and government stakeholders. The program aims to detect an incursion early enough to ensure a high likelihood of success of an eradication program.

A program review was completed in 2015. The review reassessed the priority of OWS for targeted surveillance as moderate and reaffirmed that the highest risk pathways are still considered to be through Torres Strait or with returning livestock vessels. A revised program was initiated.

The SWFSPP comprises four areas of work:

  1. surveillance (Figure 1):
    1. by fly trapping in Western Australia (four locations), the Northern Territory (two locations) and Queensland (two locations)
    2. by targeted livestock wound surveys for myiasis in Western Australia (two locations), the Northern Territory (three locations) and Queensland (four locations)
  2. entomology training and development of reference resources
  3. awareness promotion to increase general surveillance for myiasis
  4. monitoring of the risk profile for screw-worm fly in Australia.

Figure 1: Locations of targeted myiasis monitoring and fly trapping in the revised Screw-worm Fly Surveillance and Preparedness Program

The threat

The screw-worm fly (Figure 2) lays eggs on wounds or moist body openings, which hatch to release aggressive flesh eating maggots (Figure 3).

Establishment of screw-worm fly in Australia would have major negative impacts including on northern livestock production, livestock export trade and public health.

Figure 2: The adult Old World screw-worm fly (Chrysomya bezziana)

Figure 3: Maggots form a dense feeding infestation in wound

Global distribution

Screw-worm fly is widespread through tropical regions (Figure 4). OWS is considered a greater threat to Australian livestock industries than NWS as it is endemic in a number of Australia’s closes northern neighbours.

Figure 4: Global distribution of screw-worm fly

Potential affected area in Australia

Screw-worm fly is most likely to enter through the Torres Strait or with returning livestock export vessels. Travellers returning from countries where the pest is endemic may also be infested.

Screw-worm fly would most likely establish in northern Australia, particularly in the Torres Strait islands and/or in the regions around livestock export ports in WA, NT and Qld (Figure 5).

Figure 5: Relative likelihood of introduction and establishment of screw-worm fly under climatic extremes (Fruean S & East I, 2014, Australian Veterinary Journal)

How do I spot Screw-worm Fly?

Screw-worm flies look like blowflies found throughout Australia and fly traps are used in northern Australia to look for them.

Tissue damage caused by feeding screw-worm fly maggots, and the appearance of the maggots themselves, are more easily recognised than adult flies. Maggot identification requires specialist expertise.

If screw-worm fly occurrence in Australia is suspected please contact your local vet, a government animal health officer or stock inspector or call the Emergency Animal Disease Watch Hotline 1800 675 888.

Got Maggots?

Keeping Australia screw-worm fly free relies upon early detection, containment and eradication before it can spread to other areas. Regular sampling and laboratory examination of maggots from infested wounds anywhere in Australia is key to early detection. If you see an animal with maggots in a wound please support surveillance by sending some maggots to your government laboratory.

Send Your Maggots!

Please mark Attn: Screw-worm fly surveillance
State/territory Address
Northern Territory: (08) 8999 2249


Berrimah Veterinary Laboratories,

Department of Primary Industry and Resources,

Reply Paid 83108,


Queensland: (07) 3708 8762


Biosecurity Sciences Laboratory,

Health and Food Science Precinct,

Reply Paid 87088,


Western Australia: (08) 9368 3351


DPIRD Diagnostic Laboratory Services (DDLS),

Department of Primary Industries and Regional Development WA,

Reply Paid 85028,


Other Jurisdictions The government veterinary laboratory in your state or territory



Page reviewed: 17/01/2020