Combining the Sterile Insect Technique with the Incompatible Insect Technique: I-Impact of Wolbachia Infection on the Fitness of Triple- and Double-Infected Strains of Aedes albopictus

Abstract

The mosquito species Aedes albopictus is a major vector of the human diseases dengue and chikungunya. Due to the lack of efficient and sustainable methods to control this mosquito species, there is an increasing interest in developing and applying the sterile insect technique (SIT) and the incompatible insect technique (IIT), separately or in combination, as population suppression approaches. Ae. albopictus is naturally double-infected with two Wolbachia strains, wAlbA and wAlbB. A new triple Wolbachia-infected strain (i.e., a strain infected with wAlbA, wAlbB, and wPip), known as HC and expressing strong cytoplasmic incompatibility (CI) in appropriate matings, was recently developed. In the present study, we compared several fitness traits of three Ae. albopictus strains (triple-infected, double-infected and uninfected), all of which were of the same genetic background (“Guangzhou City, China”) and were reared under the same conditions. Investigation of egg-hatching rate, survival of pupae and adults, sex ratio, duration of larval stages (development time from L1 to pupation), time to emergence (development time from L1 to adult emergence), wing length, female fecundity and adult longevity indicated that the presence of Wolbachia had only a minimal effect on host fitness. Based on this evidence, the HC strain is currently under consideration for mass rearing and application in a combined SIT-IIT strategy to control natural populations of Ae. albopictus in mainland China.

Biological Control of Mosquito Vectors: Past, Present, and Future

“…Current targets for IIT include Ae. albopictus through the generation of a triple Wolbachia -infected strain ( w AlbA, w AlbB, and w Pip infected) [99] and Ae. polynesiensis , a vector of lymphatic filariasis in the South Pacific [100].…”

“…In addition, the fitness of three Ae. albopictus strains (triple-infected, double-infected, and uninfected) of the same genetic background revealed that the presence of Wolbachia had only minimal effects on host fitness [99]. Irradiation with a female-sterilizing dose had no negative impact on the longevity of triple infected males, while a reduced lifespan was seen in wild type males ( w AlbA and w AlbB) irradiated with a higher male-sterilizing dose [103].…”

Interaction ofWolbachiaand Bloodmeal Type in Artificially InfectedAedes albopictus(Diptera: Culicidae)

“…In mosquitoes, Wolbachia can induce CI, which causes a decrease or absence of brood hatch when infected males mate with females that are uninfected or infected with a different Wolbachia type (Sinkins 2004). Individuals can be infected with one or more Wolbachia strains (i.e., superinfections), and as an example of unidirectional CI, doubleinfected females can be incompatible with triple-infected males, producing no or reduced progeny, while the reciprocal cross is compatible producing normal progeny (Fu et al 2010, Zhang et al 2015.…”

“…albopictus populations via unidirectional CI, it is hypothesized that a mosquito strain that is triple infected with Wolbachia would be required, such that unidirectional CI occurs in crosses with wild-type Ae. albopictus (Fu et al 2010, Zhang et al 2015.…”

14. Genetic control of vectors

“…This strategy is presently tested in a pilot trial in Thailand against Aedes aegypti (P. Kittayapong, personal communication) and in China against Ae. albopictus (Zhang et al 2015).…”