Widespread Distribution of a Newly Found Point Mutation in Voltage-Gated Sodium Channel in Pyrethroid-Resistant Aedes aegypti Populations in Vietnam

Abstract

BackgroundResistance of Aedes aegypti to photostable pyrethroid insecticides is a major problem for disease-vector control programs. Pyrethroids target the voltage-gated sodium channel on the insects' neurons. Single amino acid substitutions in this channel associated with pyrethroid resistance are one of the main factors that cause knockdown resistance in insects. Although kdr has been observed in several mosquito species, point mutations in the para gene have not been fully characterized in Ae. aegypti populations in Vietnam. The aim of this study was to determine the types and frequencies of mutations in the para gene in Ae. aegypti collected from used tires in Vietnam.Methods and FindingsSeveral point mutations were examined that cause insensitivity of the voltage-gated sodium channel in the insect nervous system due to the replacement of the amino acids L1014F, the most commonly found point mutation in several mosquitoes; I1011M (or V) and V1016G (or I), which have been reported to be associated to knockdown resistance in Ae. aegypti located in segment 6, domain II; and a recently found amino acid replacement in F1269 in Ae. aegypti, located in segment 6, domain III. Among 756 larvae from 70 locations, no I1011M or I1011V nor L1014F mutations were found, and only two heterozygous V1016G mosquitoes were detected. However, F1269C mutations on domain III were distributed widely and with high frequency in 269 individuals among 757 larvae (53 collection sites among 70 locations surveyed). F1269C frequencies were low in the middle to north part of Vietnam but were high in the areas neighboring big cities and in the south of Vietnam, with the exception of the southern mountainous areas located at an elevation of 500–1000 m.ConclusionsThe overall percentage of homozygous F1269C seems to remain low (7.4%) in the present situation. However, extensive and uncontrolled frequent use of photostable pyrethroids might be a strong selection pressure for this mutation to cause serious problems in the control of dengue fever in Vietnam.

Point mutations in domain II of the voltage-gated sodium channel gene in deltamethrin-resistant Aedes aegypti (Diptera: Culicidae)

“…Although these results might imply that both mutations are likely to be associated with deltamethrin resistance, more detailed analyses at a molecular level are required to resolve this issue. Six mutations (923, 982, 1011, 1016, 1552, and 1763) of domain II-III associated with pyrethroid resistance have been reported (Prapanthadara et al, 2002;Brengues et al, 2003;Saavedra-Rodriguez et al, 2007;Rajatileka et al, 2008;Chang et al, 2009;Kawada et al, 2009;Yanola et al, 2010). In this study, we identified the novel coexistence of the two mutations S989P and V1016G.…”

“…Recently, an F1552C substitution of domain III was discovered in DDT/permethrin-resistant Ae. aegypti (Kawada et al, 2009;Yanola et al, 2009).…”

Rotational Symmetry of Two Pyrethroid Receptor Sites in the Mosquito Sodium Channel

“…3; Table 1; and references therein). Among these eight previously known contributors to PyR1, mutations of five residues have been identified in pyrethroid-resistant populations as kdr mutations, as follows: M 2k11 T, L 2o6 I, V 2i18 G, F 3i13 C, and F 3i17 I (Guerrero et al, 1997;He et al, 1999;Morin et al, 2002;Brengues et al, 2003;Kawada et al, 2009). Our PyR2 model described five pyrethroid-sensing residues (…”

New Mosquito Control Techniques as Countermeasures Against Insecticide Resistance

“…Kawada et al (2009a) reported similar tendency in pyrethroid susceptibility in Ae. aegypti in Vietnam, and found that new kdr mutations on domain III were widely distributing in southern Vietnam (Kawada et al, 2009b). The above authors concluded this discrepancy in pyrethroid susceptibility in different regions to be due to the longer and extended use of pyrethroids in malaria and dengue fever control programs and in agriculture in the Southern and Central Highlands.…”