Co-occurrence of Point Mutations in the Voltage-Gated Sodium Channel of Pyrethroid-Resistant Aedes aegypti Populations in Myanmar

Background:Single amino acid substitutions in the voltage-gated sodium channel associated with pyrethroid resistance constitute one of the main causative factors of knockdown resistance in insects. The kdr gene has been observed in several mosquito species; however, point mutations in the para gene of Aedes aegypti populations in Myanmar have not been fully characterized. The aim of the present study was to determine the types and frequencies of mutations in the para gene of Aedes aegypti collected from used tires in Yangon City, Myanmar.Methodology/Principal Findings:We determined high pyrethroid resistance in Aedes aegypti larvae at all collection sites in Yangon City, by using a simplified knockdown bioassay. We showed that V1016G and S989P mutations were widely distributed, with high frequencies (84.4% and 78.8%, respectively). By contrast, we were unable to detect I1011M (or I1011V) or L1014F mutations. F1534C mutations were also widely distributed, but with a lower frequency than the V1016G mutation (21.2%). High percentage of co-occurrence of the homozygous V1016G/S989P mutations was detected (65.7%). Additionally, co-occurrence of homozygous V1016G/F1534C mutations (2.9%) and homozygous V1016G/F1534C/S989P mutations (0.98%) were detected in the present study.Conclusions/Significance:Pyrethroid insecticides were first used for malaria control in 1992, and have since been constantly used in Myanmar. This intensive use may explain the strong selection pressure toward Aedes aegypti, because this mosquito is generally a domestic and endophagic species with a preference for indoor breeding. Extensive use of DDT for malaria control before the use of this chemical was banned may also explain the development of pyrethroid resistance in Aedes aegypti

ミャンマー連邦共和国ヤンゴン市の公立学校において実施したデングウイルス媒介蚊に対する長期残効性ピリプロキシフェン幼虫剤(SumiLarv®2MR)の効果試験

長崎大学学位論文 [学位記番号]博（医歯薬）甲第1060号 [学位授与年月日]平成30年3月20

Genotyping of the V1016, F1534, and S989 point mutations in <i>Aedes aegypti</i> larvae.

<p>The larvae were collected from used tires in Yangon City. The total number of larval samples used for the analysis was 204.</p

Distribution of the F1534C point mutation in <i>Aedes aegypti</i> larvae.

<p>The larvae were collected from used tires in Yangon City. Each circle indicates the allelic composition of the point mutations/wild types.</p

Distribution of susceptibility indices in <i>Aedes aegypti</i> larvae.

<p>The susceptibility index was determined by using the simplified knockdown bioassay. The color in each circle indicates the susceptibility index. The larger the index, the lower the susceptible to <i>d</i>-allethrin.</p

Enhancing respiratory disease surveillance to detect COVID-19 in shelters for displaced persons, Thailand–Myanmar border, 2020–2021

We developed surveillance guidance for COVID-19 in 9 temporary camps for displaced persons along the Thailand-Myanmar border. Arrangements were made for testing of persons presenting with acute respiratory infection, influenza-like illness, or who met the Thailand national COVID-19 Person Under Investigation case definition. In addition, testing was performed for persons who had traveled outside of the camps in outbreak-affected areas or who departed Thailand as resettling refugees. During the first 18 months of surveillance, May 2020-October 2021, a total of 6,190 specimens were tested, and 15 outbreaks (i.e., >1 confirmed COVID-19 cases) were detected in 7 camps. Of those, 5 outbreaks were limited to a single case. Outbreaks during the Delta variant surge were particularly challenging to control. Adapting and implementing COVID-19 surveillance measures in the camp setting were successful in detecting COVID-19 outbreaks and preventing widespread disease during the initial phase of the pandemic in Thailand

ミャンマー連邦共和国ヤンゴン市の公立学校において実施したデングウイルス媒介蚊に対する長期残効性ピリプロキシフェン幼虫剤(SumiLarvR2MR)の効果試験

Background: Mosquito-borne diseases are prevalent in Myanmar, with the number of dengue cases showing a significant increase in recent years. Dengue vectors have developed resistance to insecticides and currently used larvicides show only short-term effectiveness. As a result, an alternative larvicide is urgently needed. The present study evaluated the larvicidal effectiveness of long-lasting pyriproxyfen resin discs (SumiLarvR2MR) against dengue virus vectors in schools in Hlaing Thar Yar Township, Yangon. Results: The proportion of Aedes mosquito-infested containers was significantly reduced in the schools applied with the larvicide (OR: 0.24, 95% CI: 0.12?0.48) while there was little reduction noted in the control schools (OR: 0.97, 95% CI: 0.55?1.72). The density of infested containers was also significantly reduced in the intervention schools (Beta: -1.50, 95% CI: -1.98? -1.04), but there was no significant reduction in density in the control schools (Beta: -0.19, 95% CI: -0.53?0.14). The proportion of adult emergence was less than 20% in the treated water collected from the intervention schools for six months, while the proportion was over 90% in the untreated water. In addition, eight-month-old SumiLarvR2MR resin discs were still 100% effective when tested in the laboratory. More than 50% of the discs disappeared from treated containers within two months of intervention. Conclusions: SumiLarvR2MR was effective in reducing Aedes-infested containers at least six months after its application in schools. This new pyriproxyfen formulation has great potential for improving the current dengue vector control program in Myanmar.長崎大学学位論文 学位記番号:博(医歯薬)甲第1060号 学位授与年月日:平成30年3月20日Author: Sai Zaw Min Oo, Sein Thaung, Yan Naung Maung Maung, Khin Myo Aye, Zar Zar Aung, Hlaing Myat Thu, Kyaw Zin Thant and Noboru MinakawaCitation: Parasites & Vectors, 11, 16; 2018Nagasaki University (長崎大学)課程博