Objective:
Provide research support to the APHIS screwworm eradication program through studies addressing two general objectives: 1) reduce costs and enhance the quality of sterile insects by developing improvements in rearing technology and strain development procedures for the mass production of screwworms, and 2) develop advanced models and knowledge of screwworm ecology and genetics to improve detection methods and strategies for field release of sterile flies to control outbreaks and maintain the permanent barrier zone in Panama. Projects in the first objective include: 1) develop methods and tools aimed towards producing a male-only, genetically sterile strain of screwworm for mass rearing and release, 2) develop improved diets, rearing methods and production processes for mass production and sterilization of screwworm, and 3) determine the potential for screwworms to serve as vectors for Foot and Mouth Disease (FMD) and Classical Swine Fever (a.k.a. hog cholera) virus. The second objective includes projects to: 1) develop molecular genetic techniques for identification of screwworm samples and evaluate their potential for determination of geographic origin, 2) determine sterile fly dispersal, longevity and habitat use from ground release chambers using GIS modeling and remote sensing analysis, and 3) develop a mathematical model of screwworm fly dispersal based on diffusion theory for analysis of the rate of spread of outbreaks and operational parameters relative to aerial dispersion of sterile flies.

Approach:
Toward developing a male-only strain of screwworm genetic linkage analysis, partial genome sequencing (involving relative expressed sequence tags), homology-based amplification of known insect genes, transgenic and other techniques will be used to identify and characterize genes important in sex determination, sex differentiation, and embryonic development in screwworms. Developing improved diets, rearing methods and production processes will involve testing new dietary ingredients and other components used in diet preparation following standard protocols. A collaboration will be established with personnel at the Foreign Animal Disease Laboratory of Plum Island, New York, to conduct controlled exposures of screwworms to disease-causing viruses and bioassays to determine if screwworms serve as vectors of these disease agents. Random Amplified Polymorphic DNA (RAPD) and Amplified Fragment Length Polymorphism (AFLP) have previously shown, using standard protocols developed by personnel in the Unit, potential for both species identification and determination of geographic origin; thus they will be used to further explore and catalog genetic variability of screwworm samples collected from different geographic regions in the Caribbean and South America. Remote sensing and GIS modeling technology will be used to further correlate screwworm habitat utilization and other geographic parameters with data from ecological studies, data on host density and incidence of screwworm cases to determine if using ground release chambers can enhance eradication efforts. Predictive modeling following reaction diffusion theory will be used to characterize population dynamics in various ecosystems and compared with data from previous field studies on sterile-fly dispersion with a goal of further optimizing release strategies in the screwworm barrier zone and in response to outbreaks. New strains will be developed from wild flies collected from indigenous areas as needed and requested by our customers.