Browsing by Author "Bourtzis, K."

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Aedes aegypti lines for combined sterile insect technique and incompatible insect technique applications: the importance of host genomic background
(Blackwell Publishing Ltd, 2020) Carvalho, D.O.; Torres-Monzon, J.A.; Koskinioti, P.; Wijegunawardana, N.D.A.D.; Liang, X.; Pillwax, G.; Xi, Z.; Bourtzis, K.
ABSTRACT: Aedes aegypti L. (Diptera: Culicidae), being the primary vector of pathogenic arboviruses, is a target for the development of novel genetic approaches to complement current conventional vector control strategies such as the combined sterile insect and incompatible insect technique (SIT/IIT). A transinfected line of Ae. aegypti carrying the wAlbB Wolbachia strain (WB2) was introgressed into two genomic backgrounds, Brazil and Mexico, producing two new Ae. aegypti strains (WB2-BRA and WB2-MEX). These strains were evaluated with respect to several life-history traits such as fecundity, fertility, longevity, pupa size, pupation curve, and male mating competitiveness, as well as their response to irradiation. Our results show that the impact of Wolbachia infection depends on the genomic background and that the Brazilian one had no significant effect, whereas the Mexican one negatively affected fertility, longevity, and pupal size. Interestingly, Wolbachia-infected Ae. aegypti lines required a lower irradiation dose to achieve complete female sterility than the uninfected ones. The present findings are discussed given the potential use of Wolbachia-infected Ae. aegypti lines in combined SIT/IIT population suppression programs.
Development of the Sterile Insect Technique (SIT) package for mosquito population control
(Molecular Medicine Unit, Faculty of Medicine, University of Kelaniya, Sri Lanka, 2015) Bourtzis, K.
Mosquitoes (Diptera: Culicidae) are bloodsucking vector insects of major human pathogens including Plasmodium, dengue and chikungunya which cause infectious diseases resulting to severe morbidity or lethality. According to World Health Organization (WHO), malaria transmitting mosquito species are responsible for more than 600,000 deaths annually, mainly very young children, while more than 2.5 billion people in over 100 countries are at risk due to dengue transmitting mosquitoes. In the absence of efficient, safe and inexpensive drugs and vaccines to combat malaria, dengue and chikungunya, research efforts have focused on the population control of mosquito vector species (mainly Aedes and Anopheles species). In this presentation, I will review recent advances on the development and application of the Sterile Insect Technique (SIT) package for mosquitoes as well as in the field of transgenic and symbiont-based approaches. The pros and cons of each one of these methods, and of their potential combination, will be discussed as well as issues regarding their regulatory approval, stability, sustainability, biosecurity, intellectual property, economic costs and quality control. The results of field trials and future challenges will also be presented.
Potential Use of a Combined Sterile Insect Technique (SIT) and Wolbachia-Based Approach for the Control of the Dengue Vector Aedes albopictus in Sri Lanka
(19th Conference on Postgraduate Research, International Postgraduate Research Conference 2018, Faculty of Graduate Studies,University of Kelaniya, Sri Lanka, 2018) Wijegunawardana, N.D.A.D.; Chandrasena, T.G.A.N.; Abeyewickreme, W.; Dassanayake, R.S.; Xi, Z.; Bourtzis, K.; Gunawardene, Y. I. N.S.
This study addresses the possibility of using a novel and environmental friendly strategy of combined sterile insect technique (SIT) and a Wolbachia-based approach in Aedes albopictus population control efforts in Sri Lanka. The above strategy combines irradiation and the intracellular endosymbiont bacteria Wolbachia, in insects which are vertically transmitted from mother to offspring. Releasing sterile male mosquitoes in the wild will introduce sterility for suppression of Ae. albopictus wild mosquito population. The strategy aims at the releasing of sexually incompatible Wolbachia triple infected and irradiated male mosquitoes on a large scale to the natural environment. By integrating irradiation, any accidentally released female mosquito will be made fully sterile, and hence the risk of population replacement of the target population with triple infected mosquitoes is eliminated. Therefore, the combined SIT/IIT approach offers a safe and bio-secure strategy for the population suppression of Ae. albopictus in Sri Lanka. The overall work involved assessment of the density and species abundance of wild mosquito populations, introgression, and characterization of Wolbachia triple infected Ae. albopictus line in a Sri Lankan genetic background and determination of minimum sterility dose for the males and females of the introgressed line. Results revealed that Ae. albopictus mosquito was the dominant vector species in the study area (Narangodapaluwa PHI area) with an average ovitrap index of 75.25% (range; 56.9% - 94.7%) over the study year. The frequency of Wolbachia infection among the mosquito population was ~17% (13/78). The most prominent Wolbachia super group infecting the wild mosquito species was the B group and Ae. albopictus was naturally infected with both strains A and B. Eighty-five new alleles and 8 complete allelic profiles were submitted to the Wolbachia MLST database. All sequencing data were deposited in the Genebank under the accession numbers MH447376-MH470292 and MH756095-MH777430. Successful transfer of Wolbachia triple infection to Ae. albopictus into Sri Lankan genetic background was achieved through an introgression experiment and characterization of the newly developed Ae. albopictus line expressed partial CI and revealed competitive fitness cost for fecundity, fertility, and longevity compared with wild-type while there was no cost for pupation rate, adult emergence and sex ratio. Therefore, integration of an irradiation (dose; 30Gy) is recommended to achieve complete male and female sterility prior to mosquito release (minimum sterility dose for males - 28 Gy and females - 30 Gy). This minimum sterility dose is lower than the irradiation dose applied for SIT and had not resulted in a significant effect on male competitiveness. Therefore, a combined SIT and Wolbachia based approach in Ae. albopictus dengue vector control is recommended as an additional tool in integrated vector management in Sri Lanka.