Historical applications of induced sterilisation in field populations of mosquitoes

Abstract

Research on sterile mosquito technology from 1955 to the 1980s provided a substantial body of knowledge on propagation and release of sterile mosquitoes. Radiation sterilisation and chemosterilisation have been used effectively to induce dominant lethality and thereby sterilise important mosquito vectors in the laboratory. Experimental releases of chemosterilised males provided complete control of Anopheles albimanus in a small breeding population (14-15 sq km) in El Salvador. Releases of radiation sterilised males failed to control either Aedes aegypti or Anopheles quadrimaculatus in the USA. Releases of radiation-sterilised and chemosterilised male Culex quinquefasciatus in the USA and India were successful in some instances. Development of genetic sexing systems for Anopheles and improved physical separation methods for Culex have made it possible to rear and release males almost exclusively (> 99%) minimizing the release of potential vectors, the females. Factors that affected efficacy in some field programmes included reduction of competitiveness by radiation, immigration of fertilized females from outside the release zones, and inability of laboratory-bred males to perform in the wild. Despite significant progress, institutional commitments to carry the process further were generally lacking in the late 1970s and until recently. Now, with renewed interest and support for further assessment of this technology, this paper summarizes the current knowledge base, prioritizes some areas of investigation, and challenges scientists and administrators to maintain an awareness of progress, remain realistic about the interpretation of new findings, and make decisions about the sterile insect technique on the basis of informed scientific documentation. Areas recommended for priority research status include the establishment of genetic sexing mechanisms that can be transferred to other mosquito species, re-examination of radiation sterilisation, aerial release technology and mass rearing.

Genetic control ofAedesmosquitoes

“…[27][28][29][30] Several field trials using radiation-or chemo-sterilised mosquitoes have been conducted, with some success, but there are also problems including poor performance of irradiated mosquitoes. 31 the radiation doses used induce dominant lethal mutations in the irradiated sperm such that most eggs die after being fertilised by such sperm. About 95-99% sterility is typical for Mediterranean fruit fly SIT programmes; 37,38 higher sterility can be achieved with more radiation, but at the cost of further damaging the insects.…”

“…arabiensis in El Salvador. 31,59 However, modern genetics provides more options and also allows such systems to be transferred more readily from one species to another. Several have been developed.…”

The development of new radiation protocols for insect sterilization using long wavelength x-rays

“…Males subjected to sterilization procedures using this high-energy radiation suffered from a reduced life span and other debilitating effects that made them uncompetitive with the wild population. [35] Sterilization is typically accomplished with gamma ray exposure employing 60 Co or 137 Cs as a source [8]. These radiation sources provide a combination of intense short wavelength gamma rays which do not readily interact with the biological tissue.…”

Large indoor cage study of the suppression of stableAedes aegyptipopulations by the release of thiotepa-sterilised males

“…The performance of sterile mosquitoes following release is essential for the success of SIT (Dame et al 2009). Somatic damage as a consequence of the sterilisation process has been well documented (Proverbs 1969) and is known to affect the longevity (Oliva et al 2013), sexual vigour and competitiveness of sterilised male mosquitoes , with severity depending on the species ).…”

“…Several alkylating agents and aziridinyl compounds have been tested as mosquito sterilants (Dame et al 2009). Thiotepa is an alkylating agent developed in the 1950s that is being used in many chemotherapy regimens for the treatment of human solid tumours (van der Wall et al 1995).…”