Evaluating the risk of the establishment of screwworm fly in Australia

Spatial analysis of targeted surveillance for screw-worm fly (Chrysomya bezziana or Cochliomyia hominivorax) in Australia

OBJECTIVE

To assess Australia's targeted surveillance to detect an incursion of screw-worm fly (Chrysomya bezziana).

METHODS

A multi-criteria analysis shell was used to combine data on potential pathways of entry, availability of host species and environmental factors affecting survival of screw-worm fly in order to map spatial variation in the relative likelihood of a screw-worm fly incursion into Australia. Australia's current screw-worm fly surveillance activities were reviewed to determine whether they are located in the areas of highest likelihood of an incursion.

RESULTS

Under average environmental conditions, an incursion of screw-worm fly in Australia is relatively more likely to occur along the north coast, down the eastern seaboard or in the south-east. Cold winter temperatures would limit the environmental suitability for screw-worm fly survival to the north and north-east coast and adjacent inland areas. Australia's current targeted surveillance conducted by the Northern Australia Quarantine Strategy program of the Australian Department of Agriculture (adult screw-worm fly trapping and myiasis sampling) correlated well with areas considered to have a high relative likelihood of an incursion of screw-worm fly. Adult fly trapping conducted at sea ports was less well correlated.

DISCUSSION

Changes to surveillance at sea ports are proposed to better target areas considered to have a higher relative likelihood of screw-worm fly incursion. These include increasing the trapping intensity along the north and north-east coasts and shifting surveillance activity from the west coast to the south-east.

Combining cattle and wound-derived synthetic attractants, POC and Bezzilure B, for sampling Chrysomya bezziana in Indonesia

The myiasis fly Chrysomya bezziana Villeneuve (Diptera: Calliphoridae) is an obligate parasite of body orifices and unnatural openings or wounds of vertebrates. It is a major pest of livestock and responsible for economic losses throughout the Old World. Two chemical lures were tested in the present study to assess their effectiveness at trapping Ch. bezziana. Bezzilure B contains a synthetic lure of 2-mercaptoethanol originally identified from cattle wound volatiles. POC is a synthetic lure comprising 4-methyl phenol, 3-propyl phenol and racemic 1-octen-3-ol, originally identified from volatiles of ox odour and now used to control tsetse flies (Diptera: Glossina). Bezzilure B and POC lures were tested alone, and in combination, in a laboratory free flight room bioassay and in a field trial. Sticky traps were used to capture males and females of Ch. bezziana and to determine the efficacy of the lures. In the laboratory, Bezzilure B caught significantly more male and female flies than Bezzilure B+POC (p<0.001). Similarly, in the field, treatment significantly affected the total number of Ch. bezziana caught (p<0.001) but, contrastingly, Bezzilure B+POC caught significantly more flies than Bezzilure B (p<0.05). The differing results between the laboratory and field may simply reflect the different assays and could suggest different roles of semiochemicals at different operational distances. Although ineffective on its own, POC has a synergistic effect with Bezzilure B to increase fly catches in the field: by proportion, Bezzilure B+POC was 2.17 times as efficient as Bezzilure B for Ch. bezziana, and 1.16-2.68 times as efficient for other flies depending on the species collected.

Advances in biosecurity to 2010 and beyond: towards integrated detection, analysis and response to exotic pest invasions

In order to limit the number and impact of exotic pest invasions, leading-edge technologies must be embraced and embedded within integrated national and international biosecurity systems. Outlined here are recent advances in the detection of exotic pests, and prospects for the early recognition of disease. Applications of new tools are described, using our understanding of the genomes of pathogens and vectors. In addition, the role of mathematical and simulation models to aid both biosecurity planning, and decision making in the face of an epidemic, are discussed, and recent attempts to unify epidemiology and evolutionary dynamics are outlined. Given the importance of emerging diseases and zoonoses, the need to align human and veterinary surveillance within fully integrated systems is underlined.

Chrysomya bezziana in pet dogs in Hong Kong: a potential threat to Australia

The Old World Screwworm fly (Chrysomya bezziana) has recently been causing aggressive myiasis in pet dogs in Hong Kong, and the Agriculture, Fisheries and Conservation Department of Hong Kong has confirmed the presence of Chrysomya bezziana in the territory. This report describes screwworm infestation in pet dogs presented for treatment at our clinic in the past year. Screwworm fly larvae were found in typically punched out round wounds or embedded in exposed or neglected wounds. Infested wounds had a characteristic strong offensive smell and oozed a sero-sanguineous exudate or frank blood. Removal of the larvae, wound treatment, continuous monitoring for re-infestation, application of insect repellants and protective housing were essential for successful treatment. Because Hong Kong is a source of pet migration or a transit point to Australia, the fly could threaten Australia.

Mating competitiveness of irradiated flies for screwworm fly eradication campaigns

Should the screwworm fly invade Australia, the sterile insect technique (as used successfully overseas) is currently the only feasible method of eradication. Used in conjunction with chemical control methods, it relies on large numbers of factory-reared, sterilized males competing successfully with wild males for the wild females. However, laboratory and field studies have shown that the processes of mass rearing, irradiation and distribution seriously impair the competitiveness of the sterilized flies. This study collates and analyses the relatively sparse information on the relative mating competitiveness of sterilized screwworm flies, from both controlled experiments and large-scale field studies. A population dynamics example then demonstrates that competitiveness will be a key parameter in the effectiveness and economic feasibility of any future eradication campaign.