Genetic Fingerprinting of the Screwworm (Diptera:Calliphoridae) Infestation in North Africa by Mitochondrial Dna Markers

S. K. Narang, M. E. Degrugillier


A screwworm sample, Cochliomyia hominivorax (Coquerel), collected from Libya in 1990, during the final phase of the eradication program, was analyzed for mitochondrial DNA (mtDNA) RFLP patterns. The goal was to determine whether these fertile flies represented reintroduction from either a new source or contaminants in the shipments of sterile flies from the Mexican screwworm factory, (used for eradication of flies in Libya) or progeny of the original introduction in 1988. Samples of laboratory-strains originating from South America, Mexican factory, Costa Rica, and a 1989 collection from Libya were also analyzed. These patterns were compared with the previously published patterns of 30 laboratory strains originating from Mexico, Central America and Jamaica and earlier sample of flies from Libya. The restriction patterns (with EcoRV, Fnu4HI, HindIII, HpaI, MspI, ScrfI and SstI) of 1990-Libyan screwworm were similar (mitochondrial similarity, F=0.97) to those of South American flies but different from those of Mexico (F=0.53), Jamaica and Central America (F=0.71). The HpaI and SspI digests of DNA amplified by primer flanking mitochondrial CO-I to CO-II region produced patterns which were similar in Libyan and South American flies but different from those of Mexican and Costa Rican samples. These data confirmed that the flies collected in Libya in 1990 did not originate from Mexico, Central America or Jamaica. Our data suggest some region(s) of South America could be the likely source of screwworm infestation in North Africa. However, it would be necessary to analyze several geographical samples from South America to confirm this tentative conclusion.

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