Comparative field cage tests of the population suppressing efficiency of three genetic control systems for Aedes Aegypti.

Cycling populations of Aedes aegypti were set up in cages and managed in such a way that the populations had a maximum of threefold recovery potential in response to control measures. Into three such populations daily releases were made of males which had been chemosterilised, or were double translocation heterozygotes (T1T3) or T1T3 with sex ration distortion (DT1T3). Eradication of the populations was achieved with all cases, but the rate of suppression was markedly slower with T1T3 than the other two systems, with which the rates were similar. T1T3 and DT1T3 releases introduced considerable inherited genetic loads into the target populations. The results were in general agreement with computer predictions.

Chemosterilization of the tropical house mosquito Culex pipiens fatigans Wied.: laboratory and field cage studies.

Tris(1-aziridinyl)phosphine sulfide was found to be an excellent sterilant for male Culex pipiens fatigans. When male pupae were exposed to a 0.6% solution for 3 hours, the ensuing adults were rendered permanently sterile with no apparent reduction in their vigour or longevity based on laboratory and field cage studies. Females, however, exposed to the same dosage for the same length of time were partially fertile.

Genetic manipulation of Aedes aegypti: incorporation and maintenance of a genetic marker and a chromosomal translocation in natural populations.

Studies with Aedes aegypti were undertaken to determine if an alien genotype can be (1) incorporated into a natural population and (2) maintained for several generations on its own without any subsequent introductions. Such information is an essential prerequisite for successful application of any genetic control method. Data from a walk-in, field population cage and from field releases of a genetic marker and a chromosomal translocation have demonstrated both genetic incorporation and persistence for at least three successive generations. This is the first demonstration of its type with any vector species.

Chemosterilization of Culex pipiens fatigans Wiedemann by exposure of aquatic stages. 3. Induction of dominant lethal mutations in the F 1 generation by certain aziridines, phosphoramides, and s-triazines.

In insects it is known that the chemosterilant treatment induces dominant lethal mutations which bring about embryonic death. The possibility of delayed expression of the chemosterilant-induced dominant lethals in F(1) progeny of the tropical house mosquito, Culex pipiens fatigans Wiedemann has been investigated. The chemosterilants employed were 8 aziridinyl compounds, 3 phosphoramides, and 4 s-triazines. In general, all the chemosterilants tested were found to cause different degrees of mortality at different life stages of the F(1) progeny. In this respect the aziridinyl compounds were more effective than the phosphoramides and s-triazines. This effect of the chemosterilants may be useful in the sterile-male technique.

The mating ability of males of Culex pipiens fatigans Wiedemann sterilized with apholate or tepa.

The chemosterilants apholate and tepa are known to induce a high degree of sterility in the males of Culex pipiens fatigans. The studies reported show that 36-hour-old apholate-and tepa-sterilized laboratory-bred males can inseminate the same number of laboratory-bred or wild females as can normal laboratory or wild males in the first 48 hours of their lives. Males sterilized by either compound were found to be more competitive in mating with normal laboratory females than were the normal laboratory males. When normal virgin females were mated first with sterile and then with normal males or vice versa, the sperms of the first mating always decided the fate of eggs. Apholate-sterilized laboratory males were not only compatible with wild females but could even induce the same level of sterility in them and were fully as competetive in mating as normal wild males. The authors stress that it has still to be ascertained whether these encouraging laboratory findings would apply in field conditions.