Competitiveness and survival of two strains of Glossina palpalis gambiensis in an urban area of Senegal

Background In the Niayes area, located in the west of Senegal, only one tsetse species, Glossina palpalis gambiensis Vanderplank (Diptera: Glossinidae) was present. The Government of Senegal initiated and implemented an elimination programme in this area that included a sterile insect technique (SIT) component. The G. p. gambiensis strain (BKF) mass-reared at the Centre International de Recherche-Développement sur l'Elevage en zone Subhumide (CIRDES) in Burkina Faso was used for the SIT component. Methodology/principal findings Studies conducted in 2011 in four localities in the Niayes area (Pout, Sébikotane, Diacksao Peul and the Parc de Hann) showed that the BKF strain demonstrated inferior survival in the ecosystem of the Parc de Hann, a forested area in the city centre of the capital Dakar. Therefore, G. p. gambiensis flies from the Niayes area (SEN strain) were colonized. Here we compared the competitiveness and survival of the two strains (BKF and SEN) in the Parc de Hann. Released sterile males of the SEN colony showed a daily mortality rate of 0.08 (SD 0.08) as compared with 0.14 (SD 0.08) for the BKF flies but the difference was not significant (p-value = 0.14). However, the competitiveness of the SEN males was lower (0.14 (SD 0.10)) as compared with that of the BKF males (0.76 (SD 0.11)) (p-value < 10−3). Conclusions/significance Based on the results of this study, it can be concluded that the BKF strain will remain the main strain to be used in the elimination programme. Despite the slightly longer survival of the SEN males in the Parc de Hann, the superior competitiveness of the BKF males is deemed more important for the SIT component, as their shorter survival rates can be easily compensated for by more frequent fly releases.
Author summary Senegal is one of the many African countries infested by tsetse flies responsible for the transmission of trypanosomes to humans and animals, causing health and economic losses. In the Niayes area, located in the west of Senegal, only one tsetse species, Glossina palpalis gambiensis Vanderplank (Diptera: Glossinidae) is present, which is targeted by an elimination effort including the sterile insect technique (SIT). The quality of the strain used to implement any SIT effort is instrumental for its success. Here we compared the competitiveness and survival of irradiated males of two strains (BKF and SEN) released in the Parc de Hann, to assess their usefulness in eradicating this isolated population, located within the capital city, Dakar. We observed that the mating competitiveness of the SEN males was significantly lower as compared with that of the BKF males. Based on this study, we concluded that the BKF strain will remain the main strain to be used in the elimination programme in the Niayes.