ARS | Publication request: Feasibility of using a Caribbean strain of the New World Screwworm for SIT campaigns in Brazil

Submitted to: Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 20, 2012
Publication Date: N/A

Interpretive Summary: Screwworms are insidious pests of all warm blooded animals including humans. Successful eradication, using the sterile insect technique (SIT), from the North American continental area saves cattle producers in excess of $1 billion annually. There is interest in using SIT in areas of South America. The rapid implementation of existing resources requires that we understand if the strain of screwworm currently used by the Eradication and Barrier Maintenance Program Against Screwworms is compatible with wild –type flies from South America. Tests were done to determine mating compatibility and preference, mating competitiveness, and crosses of progeny back to the parent type using the strain mass produced for the Eradication Program, and a strain developed from Brazil. Results indicated that there were no barriers to using the current strain, which was developed from flies collected in Jamaica, for a SIT Program in Brazil. Efforts to control or eradicate the screwworm would greatly benefit human and animal health in areas of South America where the SIT is applied..

Technical Abstract: The New World Screwworm (NWS) is one of the most damaging parasites of livestock in South America with annual losses of millions of dollars. Recently, Mercado Común del Sur countries demonstrated interest for the control of this pest by the Sterile Insect Technique (SIT). A pilot-project was conducted at the Brazil-Uruguay border in 2009. Molecular studies have suggested the existence of NWS regional groups. Here, we present results of several crossing tests to evaluate competitiveness, mating preference and reproductive compatibility between NWS strains from the Caribbean (Jamaica-06) and Brazil. In the crosses conducted to examine the sexual compatibility between Jamaican males and Brazilian females, the mating rates ranged between 82% and 100% and each male inseminated from 3.3 to 3.95 females. All the estimated competitiveness indices were close to one, indicating that the sterile males, regardless of the strain, competed equally for females from Brazil against the fertile males from Jamaica. Experimental crosses testing the preference of Jamaican sterile males and Brazilian fertile males for fertile or sterile females yielded mating preference indices around 0.5, which indicated that males mated randomly. All the biological parameters from the hybridization crosses were high and no evidence of genetic incompatibility or hybrid dysgenesis were found. No mating barrier would compromise the use of Caribbean sterile males for SIT campaigns in Brazil once the quality of the mass produced flies is assured.