BackgroundTsetse flies transmit trypanosomes that cause human and African animal trypanosomosis, a debilitating disease of humans (sleeping sickness) and livestock (nagana). An area-wide integrated pest management campaign against Glossina palpalis gambiensis has been implemented in Senegal since 2010 that includes a sterile insect technique (SIT) component. The SIT can only be successful when the sterile males that are destined for release have a flight ability, survival and competitiveness that are as close as possible to that of their wild male counterparts.Methodology/Principal FindingsTests were developed to assess the quality of G. p. gambiensis males that emerged from pupae that were produced and irradiated in Burkina Faso and Slovakia (irradiation done in Seibersdorf, Austria) and transported weekly under chilled conditions to Dakar, Senegal. For each consignment a sample of 50 pupae was used for a quality control test (QC group). To assess flight ability, the pupae were put in a cylinder filtering emerged flies that were able to escape the cylinder. The survival of these flyers was thereafter monitored under stress conditions (without feeding). Remaining pupae were emerged and released in the target area of the eradication programme (RF group). The following parameter values were obtained for the QC flies: average emergence rate more than 69%, median survival of 6 days, and average flight ability of more than 35%. The quality protocol was a good proxy of fly quality, explaining a large part of the variances of the examined parameters.Conclusions/SignificanceThe quality protocol described here will allow the accurate monitoring of the quality of shipped sterile male tsetse used in operational eradication programmes in the framework of the Pan-African Tsetse and Trypanosomosis Eradication Campaign.

To monitor the quality of male tsetse for use in the sterile insect technique (SIT), a field cage test was developed and evaluated. Mating competitiveness was tested with male Glossina pallidipes Austen that emerged from pupae stored for different periods at 15°C. Control males emerged from pupae stored at 23–24°C and emerged at 26.5°C. Each sample of test males was divided into two groups with one group being irradiated at 120 Gy; the other group was not irradiated. More than 70% of the maximum possible number of mating pairs occurred in all tests. Males emerged from pupae kept at low temperature and then irradiated formed a greater proportion of mating pairs than the controls. Males emerged from pupae kept at 15°C generally started mating more quickly than the standard colony males although there was no significant difference. Insemination rates were above 99%. Pooled data indicated that mean spermathecal values for females mated with irradiated males were significantly lower than for control males. The duration of copulation varied significantly between treatment groups and was significantly longer for irradiated male flies; there was no correlation between duration of copulation and mean spermathecal value.

The mating performance of Glossina palpalis gambiensis Vanderplank (Diptera: Glossinidae) massreared in Burkina Faso (BKF strain) was compared with that of target populations originating from the Bamako peri-urban area of the Niger River Basin, Mali (MLI strain) and the Niayes area, Senegal (SEN strain). The tests were carried out using a field cage either set up outdoors in Burkina Faso or inside the laboratory in Austria. The target population strains (MLI and SEN) were a few generations from the wild whereas the laboratory-reared flies (BKF) were adapted to laboratory rearing over many generations. The laboratory-reared BKF strain significantly out-competed the MLI strain in the mating tests, but showed close to equal competitiveness with the SEN strain. At least one-third of possible matings occurred during each observation period. The females from the two target populations readily mated with males from the BKF strain. The selected mating parameters and behaviour in the cage showed that there was mating compatibility between the strains and this absence of obvious mating barriers indicates the potential of using BKF strain males in programmes that have a sterile insect technique (SIT) component targeting the two G. p. gambiensis populations of Mali and Senegal.

Bioassays in Zimbabwe with wild-caught Glossina pallidipes Austen and G. morsitans morsitans Westwood showed that formulations of deltamethrin (Decatix, SpotOn and an experimental variant of SpotOn), alphacypermethrin (Renegade) and cyfluthrin (Cylence) applied to oxen at the manufacturers' recommended doses gave knockdowns above 50% for 5-24 days in hot months and 24-55 days at cooler seasons. Within these periods, the average knockdowns were 77-86% with deltamethrin, 74% with alphacypermethrin and 59% with cyfluthrin. None of the insecticides affected the numbers of tsetse attracted to oxen from a distance, the proportion of tsetse that engorged, and the alighting responses on cloth screens. In the hot season most tsetse engorged on the belly. At other times the front legs were preferred, especially in the wet season and for a few months after. Chemical assays indicated that insecticide persisted at greatest concentration on the backs of oxen and least on the legs. Modelling the experimental data suggested that 4-21 annual applications of insecticide in areas >1000 km 2 would give good control at least 10 km from the invasion source if the treated cattle contributed at least 50% of tsetse diet. No treatment regime under any diet conditions would give good control near an invasion front. Insecticide at concentrations up to 0.15 ppm occurred in dung from treated oxen for up 12 days post-treatment. Dead beetles occurred in and near fresh dung.Bioassays and behavioural studies were performed at Rekomitjie Research Station in the Zambezi Valley of Zimbabwe where Glossina pallidipes Austen and G. morsitans morsitans Westwood occur. Test cattle were brown or black oxen with a high proportion of indigenous blood, and weighed an average of 420 kg (range 345-561). Toxicity and persistenceEach of the test oxen was treated separately with one of the following proprietary insecticides, at doses recommended by the manufacturers.

BackgroundProcurement of sterile tsetse flies (Glossina palpalis gambiensis) from Burkina Faso for an eradication programme in Senegal that incorporates the sterile insect technique (SIT) required the development of transport and handling protocols that would allow retaining the female flies in the rearing facility and transport of the male flies as irradiated pupae. The proposed handling scheme included the chilling of the male pupae after the female emergence and transport to Senegal under low temperatures. The effect of exposing male pupae of G. p. gambiensis to low temperature immediately prior to emergence was investigated.MethodsThe parameters of interest were emergence rate, insemination potential, survival of adult male, male ability to participate in mating activities and productivity of females mated with these males. Production was assessed in laboratory rearing cages and mating behaviour in field cages. Male flies that emerged after the female emergence flush from pupae stored at 10°C or 12.5°C for 5 or 7 days were used in the investigations with flies that emerged under standard colony conditions as control. Males that were 3, 6 or 9 days old competed for mating opportunities with 3 day old females.ResultsThe emergence of males after storage of pupae at low temperature (10°C and 12.5°C) for 3, 5, or 7 days was similar to those kept under standard colony conditions while emergence of flies stored at 15°C started before the storage period was over. Survival of males that emerged from pupae stored at low temperature for varying periods was more than 60% at 30 days post emergence (control more than 75%). The fecundity of females inseminated by males that emerged from pupae stored at low temperature for varying periods ranged from 0.33±0.16 to 0.73±0.04 pupae per female per 10 days (control 0.60±0.16). The older males, irrespective of treatment, out-competed the younger males and 3 day- old males transferred lower amounts of seminal contents to the females.ConclusionsStorage of male pupae at low temperature for periods up to 7 days at the end of the male pupal period could not be directly associated with impairment of mating activity.