Characterization of the screwworm flies Cochliomyia hominivorax and Cochliomyia macellaria by PCR-RFLP of mitochondrial DNA

The primary screwworm fly Cochliomyia hominivorax (Coquerel) (Diptera: Call iphoridae) is one of the most important insect pests of livestock in neotro pical regions, whereas Cochliomyia macellaria (Fabricius) (Diptera: Calliph oridae), the secondary screwworm, is of medical and sanitary importance bec ause of its role in the dissemination of pathogens. These two species share morphological similarities and both may occur in the same myiasis, but in different developmental stages. In this work, the usefulness of PCR-RFLP (p olymerase chain reaction-restriction fragment length polymorphism) of mitoc hondrial DNA (mtDNA) for the unambiguous identification of C. hominivorax a nd C. macellaria was investigated. Two specific regions of mtDNA were ampli fied: 870bp from Cytochrome oxidase subunit I and 2100bp from the A+T rich/ 12S region from C. hominivorax and C. macellaria specimens from different a reas of Brazil. Reliable species-specific PCR-RFLP results were obtained fo r the CO I region and the A+T rich/12S region using the restriction enzymes Dra I and Ssp I. These results confirm the conservation of CO I diagnostic restriction sites previously reported and demonstrate the usefulness of th e control region sequences as an efficient marker for PCR-RFLP identificati on of Brazilian screwworm flies. The occurrences of intraspecific polymorph ic patterns are discussed based on frequencies and potential conflicts for species identification. PCR-RFLP provides a potentially useful method for i dentifying samples from the areas where these species are monitored.