Manual for Diagnosis of Screw-worm Fly - xcs consulting

5. Flies causing myiasis
The following lists those flies most likely to be encountered in cases of myiasis plus closely
related or similar looking species, with special reference to SWF myiasis. Distribution maps
for most species are given in Fig. 14.
Chrysomya bezziana – Old World screw-worm fly
Obligatory myiasis fly (primary screw-worm). Serious parasite of man and warm-blooded
animals throughout the tropical and sub-tropical Old World.
Cochliomyia hominivorax – New World screw-worm fly
Eradicated from southern states of U.S.A. and Mexico but still present in Panama and
northern areas of South America and most of the Caribbean. Accidentally introduced to Libya
in North Africa in 1988. The subject of continuing eradication programs in Central America
using sterile flies bred at the Mexican-American Commission for the Eradication of Screwworms
facility at Tuxtla Gutiérrez, Mexico. The facility was established in 1976 with a capacity
of up to 500 million flies per week.
Chrysomya megacephala – Oriental Latrine fly
Very common species. Adults superficially similar to C. bezziana but generally a larger-sized
species. The larvae breed in carrion or dead, decomposing tissues, very rarely found in
C. bezziana-infested myiasis although adults frequently feed at such wounds. Common
around human habitation. From its origins in New Guinea and the nearby Pacific islands,
C. megacephala is now widespread throughout India and SE Asia with many recent
introductions as far afield as South America, Africa and Japan.
Chrysomya saffranea – Steelblue blowfly
A New Guinea/Australia blowfly species occasionally found breeding in the necrotic tissue
associated with C. bezziana myiasis but normally breeding on carrion. Adults superficially
similar to C. bezziana and very similar to C. megacephala. C. saffranea has been recovered
from cattle myiases in tropical Australia.
Cochliomyia macellaria – Secondary screw-worm fly
C. macellaria is the New World equivalent of C. saffranea in its bionomics. It is a carrion
breeder but occasionally found associated with Co. hominivorax myiases as a secondary
invader. The adults are superficially similar to Co. hominivorax with which it was
taxonomically confused until 1933.
Chrysomya rufifacies – Hairy Maggot blowfly
One of a guild of Australian blowflies which occur on sheep. The adults are a metallic green.
The larva, like C. albiceps, has fleshy protuberances (papillae) giving it a hairy appearance.
A secondary blowfly on sheep where its larvae may be predatory on primary blowfly larvae
although large infestations of C. rufifacies can cause the death of a sheep in a short time.
Occasionally, its larvae are associated with C. bezziana myiases. Accidentally introduced to
southern U.S.A., Central and South America.
Chrysomya varipes – Small Hairy Maggot blowfly
A small species occasionally identified from sheep myiases in Australia.
Agriculture, Fisheries and Forestry - Australia
Chrysomya albiceps – Banded blowfly
Very similar to C. rufifacies adults and with a hairy maggot type but found in Africa, Europe,
Arabia and India. Recently introduced to Central and South America and the Caribbean. It
is one of the important blowflies of sheep in South Africa but its larval biology seems to be
similar to the secondary C. rufifacies and it is classed as mainly a scavenger species.
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