Parasites & Vectors: Anopheles mosquitoes on the Laos – Cambodia – Thailand border carry the ace-1 G119S organophosphate and carbamate resistance mutation at high frequency

A study published in Parasites & Vectors on 10 September 2026 (Naval Medical University, Shanghai, and the Yunnan Institute of Parasitic Diseases, with the participation of Lao PDR’s National Malaria Centre) identified 15 Anopheles species at four border sites between Laos, Cambodia and Thailand; in Anopheles peditaeniatus, the ace-1 G119S mutation was found at high frequency.

InsectsVector-borne disease

Main points

• Mosquitoes were collected overnight with CDC light traps at four cross-border sites in 2017–2019, 650 specimens in total, identified by sequencing the COII and ITS2 markers together with morphology. The dominant species were An. kochi (38.46%) and An. sinensis (21.69%); species composition varied clearly between sites.
• Of 18 An. peditaeniatus (An. hyrcanus group), 5 were homozygous susceptible (GG, 27.8%), 12 were heterozygous carriers of the resistance allele (GS, 66.7%) and 1 was homozygous resistant (SS, 5.6%) at the ace-1 locus, the mutation behind resistance to organophosphates and carbamates.
• No kdr L1014F mutation (pyrethroid resistance) was found in any of the species tested.
• MaxEnt modelling projects that for 2021–2040, under the SSP245, SSP370 and SSP585 climate scenarios, highly suitable habitat for An. peditaeniatus expands markedly in the tri-border region; under SSP126, by contrast, suitable habitat fragments and shrinks to major wetlands.

VPMA’s note

The study area is in the Greater Mekong Subregion, close to Vietnam. The authors recommend that insecticide rotation be based on local resistance data: switching from pyrethroids to organophosphates may work less well if mosquitoes already carry the ace-1 allele. This is reference information; when choosing active ingredients, members should follow the guidance and surveillance data of Vietnam’s preventive health agencies.

Source: Parasites & Vectors – Anopheline diversity, ace-1 resistance and climate-driven habitat projections for Anopheles peditaeniatus in Lao PDR border regions (summarised in English by VPMA). Read the Vietnamese page.

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