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.

X-rays are as effective as gamma-rays for the sterilization of Glossina palpalis gambiensis Vanderplank, 1911 (Diptera: Glossinidae) for use in the sterile insect technique.

An area-wide integrated pest management strategy with a sterile insect technique (SIT) component requires a radiation source for the sterilisation of male insects. Self-contained gamma irradiators, which were exclusively used in past SIT programmes, are now facing increasing constraints and challenges due to stringent regulations. As a potential alternative, new generation high output X-ray irradiators have been proposed. The feasibility of using X-ray irradiators was assessed by comparing the effects of both gamma- and X-ray irradiators on biological parameters of Glossina palpalis gambiensis (Vanderplank, 1911), that are important for SIT applications. The gamma irradiator Foss Model 812 and two X-ray irradiators, the Rad Source 2400 and the blood irradiator Raycell Mk2 were used. Glossina palpalis gambiensis males were exposed to radiation as pupae. A radiation dose of 110 Gy or above induced more than 97% sterility in females that mated with the irradiated males for all the irradiators. Adult emergence rate, flight propensity, survival and mating performance did not differ between gamma- and X-rays irradiators. These results suggest that irradiating pupae with a dose of 110 Gy is optimal for both gamma-and X-ray irradiators used in this study, to achieve a sterility of approximately 99%. Similar research on other tsetse species could gradually phase out the use of gamma-ray irradiators in favour of X-rays irradiators, especially for smaller SIT programmes.

Gamma-radiation of Glossina palpalis gambiensis revisited: effect on fertility and mating competitiveness.

African animal trypanosomoses are vector-borne diseases that cause enormous livestock losses in sub-Saharan Africa, with drastic socio-economic impacts. Vector control in the context of an area-wide integrated pest management program with a sterile insect technique component requires the production of high-quality sterile male tsetse flies. In our study, we evaluated the effect of irradiation on the fecundity of Glossina palpalis gambiensis to identify the optimal dose that will induce maximum sterility while maintaining biological performance as much as possible. In addition, male mating performance was evaluated in semi-field cages. The irradiation doses used were 90, 100, 110, 120, 130, 140, and 150 Gy, and untreated males were used as the control. The results showed that pupal production and emergence rates were higher in batches of females that had mated with fertile males than in those that had mated with irradiated males with any experimental dose. A dose of 120 Gy administered to male flies induced 97-99% sterility after mating with virgin females. For the semi-field cage experiments, males irradiated with 120 Gy showed good sexual competitiveness as compared to fertile males and those irradiated with 140 Gy, considering the level of filling of spermatheca and the number of pairs formed. The optimal radiation dose of 120 Gy found in this study is slightly different from the traditional dose of 110 Gy that has been used in several eradication programmes in the past. The potential reasons for this difference are discussed, and an argument is made for the inclusion of reliable dosimetry systems in these types of studies.

Title: Le rayonnement gamma pour Glossina palpalis gambiensis revisité : effet sur la fertilité et la compétitivité sexuelle. Abstract: Les trypanosomoses animales africaines sont des maladies à transmission vectorielle qui causent d'énormes pertes de bétail en Afrique subsaharienne, avec des impacts socio-économiques importants. La lutte antivectorielle dans le cadre d'un programme de lutte intégrée contre les ravageurs à l'échelle d'une zone avec une composante de technique d'insectes stériles nécessite la production de glossines mâles stériles de haute qualité. Dans notre étude, nous avons évalué l'effet de l'irradiation sur la fécondité de Glossina palpalis gambiensis afin d'identifier la dose optimale qui induira une stérilité maximale tout en maintenant au maximum les performances biologiques. De plus, les performances d'accouplement des mâles ont été évaluées en cages de semi-terrain. Les doses d'irradiation utilisées étaient de 90, 100, 110, 120, 130, 140 et 150 Gy, et des mâles non traités ont été utilisés comme contrôle. Les résultats ont montré que les taux de production et d'émergence de pupes étaient plus élevés dans les lots de femelles qui s'étaient accouplées avec des mâles fertiles que dans les lots de celles accouplées avec des mâles irradiés, avec n'importe quelle dose expérimentale. Une dose de 120 Gy administrée à des mouches mâles a induit une stérilité de 97 à 99 % après accouplement avec des femelles vierges. Pour les expériences en cages de semi-terrain, les mâles irradiés à 120 Gy ont montré une bonne compétitivité sexuelle par rapport aux mâles fertiles et à ceux irradiés à 140 Gy, en considérant le niveau de remplissage de leur spermathèque et le nombre de couples formés. La dose de rayonnement optimale de 120 Gy trouvée dans cette étude est légèrement différente de la dose traditionnelle de 110 Gy qui a été utilisée dans plusieurs programmes d'éradication dans le passé. Les raisons potentielles de cette différence sont discutées et un argument est avancé pour l'inclusion de systèmes de dosimétrie fiables dans ce type d'études.

Suitability of Raycell MK2 Blood X-ray Irradiator for the Use in the Sterile Insect Technique: Dose Response in Fruit Flies, Tsetse Flies and Mosquitoes.

The sterile insect technique (SIT) is based on the inundatory field release of a target pest following their reproductive sterilization via exposure to radiation. Until recently, gamma irradiation from isotopic sources has been the most widely used in SIT programs. As isotopic sources are becoming increasingly expensive, especially for small programs, and regulations surrounding their procurement and shipment increasingly strict, irradiation capacity is one of the limiting factors in smaller or newly developing SIT projects. For this reason, the possibility of using X-ray irradiators has been evaluated in the recent decade. The availability of "off-the-shelf" blood X-ray irradiators that meet the technical requirements for insect irradiation can provide irradiation capacity for those SIT projects in which the acquisition of gamma ray irradiators is not feasible. Following the recent technical characterization of a Raycell MK2 X-ray blood irradiator, it was found in this study, that MK2 instruments were suitable for the sterilization of fruit flies, tsetse flies and mosquitoes, inducing comparable, even slightly higher, sterility levels compared to those achieved by gamma ray irradiation. This, together with its estimated processing efficiency, shows that MK2 irradiators are suitable for small- to mid-sized SIT programs.

Dog ownership, demographics, owners' knowledge of rabies, and factors associated with canine rabies vaccination in urban and rural areas of Dedougou, Burkina Faso.

Rabies is a prioritized zoonotic disease in Burkina Faso and is known as a major zoonotic disease with high public health importance. This investigation was conducted to assess community knowledge, dog ecology and demographics, and factors associated with dog vaccination against rabies in the urban and rural areas of Dedougou. Three hundred and sixteen (316) dog-owning households were surveyed in the rural and urban areas of Dedougou using a semi-structured questionnaire. Among participants, 55.7% lived in rural area, and 59.8% were farmers. Only 34.5% of participants had satisfactory knowledge of rabies. About 22% were aware of the required age of dogs' primo vaccination against rabies while 55.7% knew the frequency of booster vaccination. Participants living in households with less than five persons were significantly more likely to be aware of rabies than those living in households with the higher number of persons (P<0.05). Participants who were aware of rabies were more likely to vaccinate their dogs compared to those who were not aware of rabies (P<0.05). In total, 2930 persons were recorded in visited households with 60.6% from rural area, and an average household size of 9.27 persons. Three hundred and thirty seven dogs were found in surveyed households' and 54.9% were from rural area. In overall, a dog per human ratio of 1:8.7 was determinated. Regarding dog ownership practices, the majority of respondents reported that they provided their dogs with water (84.5%) and food (84.8%). This research reported supplementary data on dog ecology and rabies, which could be useful for rabies control planning in Burkina Faso.

Optimizing the feeding frequency to maximize the production of sterile males in tsetse mass-rearing colonies.

Tsetse flies are cyclical vectors of trypanosomes, the causative agents of sleeping sickness or Human African Trypanosomosis and nagana or African Animal Trypanosomosis in Sub-Saharan Africa. The Insectarium de Bobo-Dioulasso (IBD) was created and equipped in the frame of Pan African Tsetse and Trypanosomosis Eradication Campaign (PATTEC) with the main goal to provide sterile males for the different eradication programs in West Africa which is already the case with the ongoing eradication program in Senegal. The aim of this study was to identify the best feeding regime in mass-rearing colonies of Glossina palpalis gambiensis to optimize the yield of sterile males. We investigated the mortality and fecundity for various feeding regimes and day alternation (3×: Monday-Wednesday-Friday, 4×: Monday-Wednesday-Friday-Saturday, 4×: Monday-Wednesday-Thursday-Friday and 6×: all days except Sunday) on adult tsetse flies in routine rearing over 60 days after emergence. The day alternation in the 4 blood meals per week (feeding regimes 2 and 3) had no effect on tsetse fly mortality and fecundity. The best feeding regime was the regime of 4 blood meals per week which resulted in higher significant fecundity (PPIF = 2.5; P = 0.003) combined with lower mortality of females (P = 0.0003) than the 3 blood meals per week (PPIF = 2.0) and in similar fecundity (PPIF = 2.6; P = 0.70) and mortality (P = 0.51) than the 6 blood meals per week. This feeding regime was extended to the whole colonies, resulting in an improved yield of sterile males for the ongoing eradication program in Senegal and would be more cost-effective for the implementation of the next-coming sterile insect technique (SIT) programs in West Africa.