Manual for Diagnosis of Screw-worm Fly - xcs consulting

A Manual for the Diagnosis of Screw-Worm Fly
Measure solids first and add liquids, adding dimethyl disulphide last. It is crucial that the
correct chemicals be used, especially the n-isomers of butyric and valeric acids. Care must
be taken when mixing and dispensing swormlure which is very caustic, and has a long-lasting
and unpleasant odour. Store in a refrigerator not used for foodstuffs.
The traps are suspended by cords from trees or posts at a height of about 1.5m. For
surveillance, maximising the opportunity for catching SWF is important and shady sites at
the edge of wooded areas, near water sources or cattle camps are recommended. Close
proximity to rubbish dumps or animal carcasses will result in large numbers of secondary
blowflies on the traps and these sites should be avoided.
Traps can be serviced at convenient intervals from daily to weekly. Up to 10 days exposure
can be used but trapped flies deteriorate with time. In some locations, foraging stingless
bees may remove the adhesive. When serviced, the aluminium plate is replaced and the
swormlure container replenished. When large numbers of traps are being serviced, trap
plates can be stored in plywood boxes (35 x 60cm in cross section) of sufficient length to
hold the number of (paired) plates required.
Flies on the trap plate are removed with forceps and placed on appropriately labelled (locality,
trap number, date, etc.) cards or plastic petri dishes, using the residual adhesive to attach fly
to card or dish. Cards or dishes can be stored in a freezer to await microscopical examination
and identification.
Larva of the New World screw-worm fly Cochlimyia hominivorax.
Scanning electron microscope photograph by Colin Beaton
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