Insect Pest Control Laboratory, Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture, Vienna International Centre, P.O. Box 100, 1400, Vienna, Austria.
Institute of Chemical, Environmental, and Biological Engineering, Research Area Biochemical Technology, Vienna University of Technology, Gumpendorfer Straße 1a, 1060, Vienna, Austria.
BMC Microbiol. 2018 Nov 23;18(Suppl 1):160. doi: 10.1186/s12866-018-1283-8.
Tsetse flies (Diptera: Glossinidae) are the cyclical vectors of the causative agents of African Trypanosomosis, which has been identified as a neglected tropical disease in both humans and animals in many regions of sub-Saharan Africa. The sterile insect technique (SIT) has shown to be a powerful method to manage tsetse fly populations when used in the frame of an area-wide integrated pest management (AW-IPM) program. To date, the release of sterile males to manage tsetse fly populations has only been implemented in areas to reduce transmission of animal African Trypanosomosis (AAT). The implementation of the SIT in areas with Human African Trypanosomosis (HAT) would require additional measures to eliminate the potential risk associated with the release of sterile males that require blood meals to survive and hence, might contribute to disease transmission. Paratransgenesis offers the potential to develop tsetse flies that are refractory to trypanosome infection by modifying their associated bacteria (Sodalis glossinidius) here after referred to as Sodalis. Here we assessed the feasibility of combining the paratransgenesis approach with SIT by analyzing the impact of ionizing radiation on the copy number of Sodalis and the vectorial capacity of sterilized tsetse males.
Adult Glossina morsitans morsitans that emerged from puparia irradiated on day 22 post larviposition did not show a significant decline in Sodalis copy number as compared with non-irradiated flies. Conversely, the Sodalis copy number was significantly reduced in adults that emerged from puparia irradiated on day 29 post larviposition and in adults irradiated on day 7 post emergence. Moreover, irradiating 22-day old puparia reduced the copy number of Wolbachia and Wigglesworthia in emerged adults as compared with non-irradiated controls, but the radiation treatment had no significant impact on the vectorial competence of the flies.
Although the radiation treatment significantly reduced the copy number of some tsetse fly symbionts, the copy number of Sodalis recovered with time in flies irradiated as 22-day old puparia. This recovery offers the opportunity to combine a paratransgenesis approach - using modified Sodalis to produce males refractory to trypanosome infection - with the release of sterile males to minimize the risk of disease transmission, especially in HAT endemic areas. Moreover, irradiation did not increase the vector competence of the flies for trypanosomes.
采采蝇（双翅目：舌蝇科）是导致非洲锥虫病的循环媒介，这种疾病已被确定为撒哈拉以南非洲许多地区人类和动物中的一种被忽视的热带病。当在区域综合虫害管理（AW-IPM）计划框架内使用时，不育昆虫技术（SIT）已被证明是一种控制采采蝇种群的强大方法。迄今为止，仅在减少动物非洲锥虫病（AAT）传播的地区释放不育雄蝇来管理采采蝇种群。在人类非洲锥虫病（HAT）地区实施 SIT 需要采取额外措施来消除与释放需要吸血才能生存的不育雄蝇相关的潜在风险，因此可能会导致疾病传播。共生体遗传工程有可能通过修饰与其相关的细菌（Sodalis glossinidius）来开发对锥虫感染具有抗性的采采蝇，以下简称 Sodalis。在这里，我们通过分析电离辐射对 Sodalis 拷贝数和绝育采采蝇雄蝇媒介能力的影响，评估了共生体遗传工程与 SIT 相结合的可行性。
与未辐照的苍蝇相比，从 22 日龄幼虫期后辐射的蛹中孵化出的 Glossina morsitans morsitans 成虫的 Sodalis 拷贝数没有明显下降。相反，从 29 日龄幼虫期后辐射的蛹中孵化出的成虫和从 7 日龄成虫后辐射的成虫的 Sodalis 拷贝数显著减少。此外，与未辐照对照相比，辐照 22 日龄蛹会降低成虫中 Wolbachia 和 Wigglesworthia 的拷贝数，但辐射处理对苍蝇的媒介能力没有显著影响。
尽管辐射处理显著降低了一些采采蝇共生体的拷贝数，但 Sodalis 的拷贝数随着时间的推移在 22 日龄蛹期辐照的苍蝇中恢复。这种恢复为结合共生体遗传工程方法提供了机会-使用改良的 Sodalis 来产生对锥虫感染具有抗性的雄性-并释放不育雄蝇，以最大程度地降低疾病传播的风险，特别是在 HAT 流行地区。此外，辐射不会增加苍蝇对锥虫的媒介能力。
