Γιώργος Διαλλινάς, Καθηγητής Μοριακής Μικροβιολογίας, Τμήμα Βιολογίας, ΕΚΠΑ
Mosquitoes, especially species of the genera Aedes, Anopheles and Culex, are the most common disease vectorsworldwide, responsible for more than 500 million human cases annually, due to malaria, Dengue virus, West Nile virus, Zika virus, etc., transmission. Mosquito-borne diseases occur mainly in Africa, Central and Latin America and southeastern Asia, but during the last two decades they have (re-)emerged also in Europe.
Prevention of mosquito-borne diseases depends to a great extent on vector control; insecticides (e.g. pyrethroids, organophosphates, growth regulators, etc) are the most powerful tool. However, the limited number of available formulations along with the increasing occurence of insecticide resistance highlight the importance of continuous surveillance and evidence-based control. There is a small number of such recent studies in Greece. Aedes albopictus, commonly known as the Asian tiger mosquito, is a major risk for public health, being globally dispersed. Its presence in Greece is also wide and potentially associated with West Nile virus circulation, over the last years. Therefore, we conducted an extended analysis on the insecticide resistance status of Ae. albopictus populations throughout Greece, using molecular diagnostic techniques. Target-site resistance mutation F1534C in the vssc gene leading to pyrethroid resistance was spread across the country, with the highest frequency in Athens, while mutation vssc I1532T was reported for the first time in Greece, in low frequencies. Metabolic resistance to temephos attributed to carboxylesterases 3 and 6 overexpression was also recorded extensively in many sampling areas. No mutation correlated with resistance to the larvicide diflubenzuron was detected.
Limitations arisen by the extended use of insecticides determine the necessity of integrated vector control methods. In the second part of the present study, RNAi was used as a gene silencing mechanism to block malaria parasite transmission to humans; polyamidoamines (PAAs) were evaluated as polymeric carriers of dsRNA molecules in Anopheles gambiae, against mosquito genes that promote Plasmodium invasion of the midgut. dsRNAs against CACTUS and ESP genes were conjugated to PAAs. Nanoparticle stability was estimated, and then they were administered to adult mosquitoes both by injecting and feeding them. A moderate knock-down efficiency of the nanoparticles against the genes expression in the mosquito midgut was measured. Many experiment modifications are required and our findings are still preliminary, but of fundamental importance for the next steps.
mosquito-vectors of diseases, mosquito surveillance, Asian tiger mosquito, insecticide resistance, public health, malaria, nanoparticles