First detection of a putative knockdown resistance gene in major mosquito vector, Aedes albopictusArchived

Kasai S1, Ng LC2, Lam-Phua SG2, Tang CS3, Itokawa K1, Komagata O1, Kobayashi M1, Tomita T1.1 Department of Medical Entomology, National Institute of Infectious Diseases, Tokyo 162-8640, Japan2 Environmental Health Institute3 Environmental Health Department, National Environmental Agency, SingaporeJapanese journal of infectious diseases 2011 May;64(3):217-21.

The Asian tiger mosquito, Aedes albopictus (Skuse), is the major vector of Chikungunya fever and the secondary vector of dengue fever.  Ae. albopictus from Singapore was collected and  genotyping assay was performed to detect mutations of the voltage-gated sodium channel, which is the target site of pyrethroid insecticides. An amino acid substitution, F1534C was detected, which is suspected to confer knockdown resistance (kdr) to pyrethroid insecticides. Of the collected mosquitoes, 53.8% were homozygous for this mutation, and the allele frequency of this mutation was estimated to be 73.1%. No kdr mutation was detected in the 5 other loci of domains II and IV. This is the first evidence for the presence of the kdr gene in Ae. albopictus, and our findings highlight the need for studying the global distribution of this allele in this important vector insect.

VBORNET comment, 30/9/2011: Vector control programmes are faced with increasing challenges due to growing number of vector species and populations that have developed resistance to biocides. In general, four different categories of resistance to insecticides are recognized: metabolic resistance, target site resistance, reduced penetration and behavioural resistance. Kdr mutations, indicators of target site resistance, have been detected in many pest insects and in the current study from Singapore shows that Ae. albopictus is not an exception. The Insecticide Resistance Action Committee (IRAC), formed in 1984, defines resistance as the selection of a heritable characteristic in an insect population that results in the repeated failure of an insecticide product to provide the intended level of control when used as recommended. According to this definition, differences in susceptibility apparent in laboratory bioassays may not necessarily constitute resistance if the difference does not result in a change in the field performance of the insecticide. Despite the fact that the paper does not report any bioassay results the finding of kdr mutations in Ae. albopictus is worrisome for the future of control attempts of this species in Europe. In September 2011, IRAS released a new Operational Insecticide Resistance Management Vector manual containing practical knowledge and tools required to implement insecticide resistance management in vector control programmes.