Abstract
Simple SummaryAfrican animal trypanosomosis, also known as nagana, is a neglected disease in South Africa, transmitted by tsetse flies. It has been proposed to manage this disease through the eradication of Glossina austeni, one of the vectors of this disease in South Africa. The strategy would be an integration of various control tactics and the release of sterilised colonised males (sterile insect technique) to eliminate relic pockets. The irradiated colonised males must be able to compete with wild males. In preparation of the technique, the mating performance of colony-reared male flies was assessed. Factors that can influence male mating performance, such as radiation dose, and the development stage that is exposed to radiation were evaluated in the laboratory and under semi-field conditions. Radiation doses of 80 Gy and 100 Gy induced 97–99% sterility in colony females that mated with colony males treated as adults or pupae. Walk-in field cage assessments indicated that a dose of up to 100 Gy did not adversely affect the mating performance of males irradiated as adults or late stage pupae. This study indicated that the colonized G. austeni males irradiated as adults or late stage pupae will be suited for the sterile insect technique. An area-wide integrated pest management (AW-IPM) strategy with a sterile insect technique (SIT) component has been proposed for the management of African animal trypanosomosis (AAT) in South Africa. In preparation for the SIT, the mating performance of colony reared Glossina austeni males under influencing factors such as radiation dose and the development stage that is exposed to radiation, was assessed under laboratory and semi-field conditions. The radiation sensitivity of G. austeni colonized 37 years ago when treated as adults and late-stage pupae was determined. Radiation doses of 80 Gy and 100 Gy induced 97–99% sterility in colony females that mated with colony males treated as adults or pupae. Males irradiated either as adults or pupae with a radiation dose of 100 Gy showed similar insemination ability and survival as untreated males. Walk-in field cage assessments indicated that a dose of up to 100 Gy did not adversely affect the mating performance of males irradiated as adults or late stage pupae. Males irradiated as adults formed mating pairs faster than fertile males and males irradiated as pupae. The mating performance studies indicated that the colonized G. austeni males irradiated as adults or late stage pupae will still be suited for SIT.
Highlights
The sterilizing effect of radiation on insects was already known in the 1930s [1,2], only 20 years later in the 1950s the potential of this technique for the management of insect pests was realized [3,4]
This study further showed that males irradiated as adults with 80 Gy successfully competed with colonized fertile males for colony females under semi-field conditions [25], indicating that the G. brevipalpis colony at the Agricultural Research Council-Onderstepoort Veterinary Institute (ARC-OVI) can provide sterile males suitable for a release program [25]
The results of the present study indicate that G. austeni can be treated as late pupae with a dose of 100 Gy for use in an area-wide integrated pest management (AW-IPM) program with an sterile insect technique (SIT) component
Summary
The sterilizing effect of radiation on insects was already known in the 1930s [1,2], only 20 years later in the 1950s the potential of this technique for the management of insect pests was realized [3,4]. The sterile insect technique (SIT) necessitates the radiation sterilization of male insects obtained from mass-rearing of the target species [5] followed by the release of these males in sufficient numbers to outcompete their wild counterparts [6,7]. The first campaign that incorporated the use of radiation-sterilized adults with aerial spraying of insecticides to suppress the wild fly population was implemented in Tanzania in the 1970s [12]. This was followed by an effort in the 1980s in Burkina Faso, where suppression methods such as insecticide impregnated targets were integrated with the release of sterile males
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