Radiation dose fractionation and its potential hormetic effects on male Glossina palpalis gambiensis (Diptera: Glossinidae): a comparative study of reproductive and flight quality parameters.

One of the most critical factors for implementing the sterile insect technique for the management of tsetse is the production of large quantities of highly competitive sterile males in the field. Several factors may influence the biological quality of sterile males, but optimizing the irradiation protocols to limit unwanted somatic cell damage could improve male performance. This study evaluated the effect of fractionation of gamma radiation doses on the fertility and flight quality of male Glossina palpalis gambiensis. Induced sterility was assessed by mating irradiated males with virgin fertile females. Flight quality was assessed using a standard protocol. The male flies were irradiated as pupae on day 23-27 post larviposition with 110 Gy, either in a single dose or in fractionations of 10 + 100 Gy and 50 + 60 Gy separated by 1-, 2- and 3-day intervals or 55 + 55 Gy separated by 4-, 8-, and 24-hour intervals. All treatments induced more than 90% sterility in females mated with irradiated males, as compared with untreated males. No significant differences were found in emergence rate or flight propensity between fractionated and single radiation doses, nor between the types of fractionations. Overall, the 50(D0) + 60(D1) Gy dose showed slightly higher induced sterility, flight propensity, and survival of males under feeding regime. Dose fractionation resulted in only small improvements with respect to flight propensity and survival, and this should be traded off with the required increase in labor that dose fractionation entails, especially in larger control programs.

Title: Fractionnement de la dose de rayonnement et ses effets hormétiques potentiels sur les Glossina palpalis gambiensis mâles (Diptera : Glossinidae) : une étude comparative des paramètres de reproduction et de qualité de vol. Abstract: L'un des facteurs les plus critiques pour la mise en œuvre de la technique de l'insecte stérile pour la gestion des glossines est la production de grandes quantités de mâles stériles hautement compétitifs sur le terrain. Plusieurs facteurs peuvent influencer la qualité biologique des mâles stériles, mais l'optimisation des protocoles d'irradiation pour limiter les dommages indésirables aux cellules somatiques pourrait améliorer les performances des mâles. Cette étude a évalué l'effet du fractionnement de la dose d'irradiation gamma sur la fertilité et la qualité de vol des mâles de Glossina palpalis gambiensis. La stérilité induite a été évaluée en accouplant des mâles irradiés avec des femelles vierges et fertiles. La qualité du vol a été évaluée à l'aide d'un protocole standard. Les mouches mâles ont été irradiées sous forme de pupes agées de 23 à 27 jours après la larviposition avec 110 Gy, soit en dose unique, soit en fractions de 10 + 100 Gy et 50 + 60 Gy séparées par 1, 2 et 3 jours ou 55 + 55 Gy séparés par des intervalles de 4, 8 et 24 heures. Tous les traitements ont induit plus de 90 % de stérilité chez les femelles accouplées avec des mâles irradiés par rapport aux mâles non traités. Aucune différence significative n'a été trouvée dans le taux d'émergence ou la propension au vol entre les doses d'irradiation fractionnées et uniques ni entre les types de fractionnements. Dans l'ensemble, la dose de 50 (J0) + 60 (J1) Gy a montré une stérilité induite, une propension à voler et une survie légèrement plus élevées chez les mâles sous régime alimentaire. Le fractionnement de dose n'a entraîné que de légères améliorations en ce qui concerne la propension à voler et la survie, et cela devrait être compensé par l'augmentation nécessaire du travail qu'implique le fractionnement de dose, en particulier dans les programmes de contrôle de grande envergure.

Evaluation of radiation sensitivity and mating performance of Glossina brevipalpis males.

BACKGROUND: Area-wide integrated pest management strategies that include a sterile insect technique component have been successfully used to eradicate tsetse fly populations in the past. To ensure the success of the sterile insect technique, the released males must be adequately sterile and be able to compete with their native counterparts in the wild. METHODOLOGY/PRINCIPAL FINDINGS: In the present study the radiation sensitivity of colonised Glossina brevipalpis Newstead (Diptera; Glossinidae) males, treated either as adults or pupae, was assessed. The mating performance of the irradiated G. brevipalpis males was assessed in walk-in field cages. Glossina brevipalpis adults and pupae were highly sensitive to irradiation, and a dose of 40 Gy and 80 Gy induced 93% and 99% sterility respectively in untreated females that mated with males irradiated as adults. When 37 to 41 day old pupae were exposed to a dose of 40 Gy, more than 97% sterility was induced in untreated females that mated with males derived from irradiated pupae. Males treated as adults with a dose up to 80 Gy were able to compete successfully with untreated fertile males for untreated females in walk-in field cages. CONCLUSIONS/SIGNIFICANCE: The data emanating from this field cage study indicates that, sterile male flies derived from the colony of G. brevipalpis maintained at the Agricultural Research Council-Onderstepoort Veterinary Institute in South Africa are potential good candidates for a campaign that includes a sterile insect technique component. This would need to be confirmed by open field studies.

Improving the Diet for the Rearing of Glossina brevipalpis Newstead and Glossina austeni Newstead: Blood Source and Collection - Processing - Feeding Procedures.

One of the challenges to maintain tsetse fly (Diptera: Glossinidae) colonies is the sustainable supply of high quality blood meals. The effect of using anticoagulants during collection of the blood, the addition of phagostimulants to the blood meals as well as using mixtures of bovine and porcine blood in different proportions for feeding on colony productivity was assessed. Defibrinated bovine blood was found to be suitable to maintain both the Glossina brevipalpis Newstead and Glossina austeni Newstead colonies. Blood collected with the anticoagulants sodium citrate, citric sodium combination, citrate phosphate dextrose adenine and citric acid did not affect colony performance of both species. Defibrinated bovine and porcine blood in a 1:1 ratio or the feeding of either bovine or porcine blood on alternating days improved pupae production of G. austeni and can be used to enhance colony growth. Bovine blood is appropriate to maintain G. brevipalpis colonies, however, feeding either bovine or porcine blood on alternating days did improve productivity. Adding the phagostimulants inosine tri-phosphate, cytosine mono-phosphate and guanosine mono-phosphate to the blood at a concentration of 10-4 M improved pupae production of the G. brevipalpis colony. The addition of adenosine tri-phosphate and inosine tri-phosphate improved the performance of the G. austeni colony. Decisions on the most suitable rearing diet and feeding protocols will not only depend on the biological requirements of the species but also on the continuous supply of a suitable blood source that can be collected and processed in a cost-effective way.