Impact of outdoor residual spraying on the biting rate of malaria vectors: A pilot study in four villages in Kayin state, Myanmar

Chaumeau, Victor; Kajeechiwa, Ladda; Kulabkeeree, Thithiworada; Vishwakarma, Ramesh; Wasisakun, Praphan; Hsel, Saw Nay; Oo, Kyi; Dah, Tee; Sawasdichai, Sunisa; Trakoolchengkaew, Muesuwa; Phanaphadungtham, Monthicha; Inta, Aritsara; Akararungrot, Yanada; Lee, Naw Yu; Kankew, Prasan; Wiladphaingern, Jacher; Mukaka, Mavuto; Delmas, Gilles; Nosten, François

doi:10.1371/journal.pone.0240598

Cited by 1 publication

(8 citation statements)

References 49 publications

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“…The twelve villages were selected by mean of mutual agreement between community members and the study team had no role in the final selection process. ORS was carried out in six villages between October 2 nd and October 17 th for two days per village as previously described [21]. No intervention was carried out in the villages of the control group.…”

Section: Methodsmentioning

confidence: 99%

“…No intervention was carried out in the villages of the control group. Entomological surveys were conducted as previously described [21] and yielded 25 personnights of collection indoors, 25 person-nights outdoors and 5 cow-nights per survey. Anopheles specimens were sorted macroscopically and then identified using a dichotomic identification key [22].…”

Section: Methodsmentioning

confidence: 99%

“…Anopheles specimens were sorted macroscopically and then identified using a dichotomic identification key [22]. Malaria mosquitoes captured in the cow-baited trap and still alive at the end of the survey were used to perform standard insecticide susceptibility tests with papers impregnated with 18 mg/m 2 of lambda-cyhalothrin as previously described [21]. Mosquito susceptibility to additional insecticides, including deltamethrin (18 mg of active ingredient [a.i.]…”

Section: Methodsmentioning

confidence: 99%

“…dirus, the residual effects of a capsule suspension of lambda-cyhalothrin sprayed on outdoor vegetation at a target concentration of 500 g of active ingredient per hectare lasted for several weeks to months during the rainy and dry seasons respectively [20]. Furthermore, the effects of ORS on wild populations of malaria mosquitoes are not well documented (reviewed in [21]). In a pilot study in four villages, ORS with a capsule suspension of lambda-cyhalothrin sprayed rapidly reduced the biting rate of malaria vectors but intervention impact on additional outcome measures (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…In a pilot study in four villages, ORS with a capsule suspension of lambda-cyhalothrin sprayed rapidly reduced the biting rate of malaria vectors but intervention impact on additional outcome measures (e.g. vector longevity and resistance, malaria incidence) was not assessed [21]. The objective of the herein study was to further assess at scale the efficacy of ORS for malaria vector-control in Kayin state, thereby contributing to knowledge of the impact of vector-control on the entomological indices, vector resistance and vivax malaria in this region.…”

Section: Introductionmentioning

confidence: 99%

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Outdoor residual spraying for malaria vector-control in Kayin (Karen) state, Myanmar: A cluster randomized controlled trial

et al. 2022

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Outdoor and early biting by mosquitoes challenge the efficacy of bed nets and indoor residual spraying against malaria in the Greater Mekong Subregion. The objective of this study was to assess the efficacy of outdoor residual spraying (ORS) for malaria vector-control in this region. A cluster randomized controlled trial was conducted between July 2018 and April 2019 in twelve villages in Karen (Kayin) state, Myanmar. Villages were randomly assigned to receive either a single round of ORS with a capsule suspension of lambda-cyhalothrin for two days in October or no intervention (six villages per group). The primary endpoint was the biting rate of malaria mosquitoes assessed with human-landing catch and cow-baited trap collection methods, and was analyzed with a Bayesian multi-level model. In the intervention villages, the proportion of households located within the sprayed area ranged between 42 and 100% and the application rate ranged between 63 and 559 g of active ingredient per hectare. At baseline, the median of Anopheles biting rate estimates in the twelve villages was 2 bites per person per night (inter-quartile range [IQR] 0–5, range 0–48) indoors, 6 bites per person per night (IQR 2–16, range 0–342) outdoors and 206 bites per cow per night (IQR 83–380, range 19–1149) in the cow-baited trap. In intention-to-treat analysis, it was estimated that ORS reduced biting rate by 72% (95% confidence interval [CI] 63–79) from Month 0 to Month 3 and by 79% (95% CI 62–88) from Month 4 to Month 6, considering control villages as the reference. In conclusion, ORS rapidly reduces the biting rates of malaria mosquitoes in a Southeast Asian setting where the vectors bite mostly outdoors and at a time when people are not protected by mosquito bed nets.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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