Efficacy of a spatial repellent for control of malaria in Indonesia: a cluster-randomized controlled trial

Abstract

<jats:p>A cluster randomized, double-blinded, placebo-controlled trial was conducted to estimate protective efficacy of a spatial repellent against malaria infection at Sumba, Indonesia. Following radical cure in 1,341 children aged ≥6 months - ≤5 years in 24 clusters, households were given transfluthrin or placebo passive emanators (devices designed to release vaporized chemical). Monthly blood screening and biweekly human-landing mosquito catches were performed during 10-months baseline (June 2015 to March 2016) and a 24-month intervention period (April 2016 to April 2018). Screening detected 164 first-time infections and an accumulative total of 459 infections in 667 subjects in placebo-control households; and 134 first-time and 253 accumulative total infections among 665 subjects in active intervention households. The 24-cluster protective effect of 27.7% and 31.3%, for time to first-event and overall (total new) infections, respectively, was not statistically significant. Purportedly, this was due in part to zero to low incidence in some clusters, undermining the ability to detect a protective effect. Subgroup analysis of 19 clusters where at least one infection occurred during baseline showed 33.3% (p-value = 0.083) and 40.9% (p-value = 0.0236, statistically significant at the 1-sided 5% significance level) protective effect to first-infection and overall infections, respectively. Among 12 moderate- to high-risk clusters, a statistically significant decrease on infection by intervention was detected (60% protective efficacy). Primary entomological analysis of impact was inconclusive. While this study suggests spatial repellents prevent malaria, additional evidence is required to demonstrate the product class provides an operationally feasible and effective means of reducing malaria transmission.</jats:p>

Behavioral responses to transfluthrin by Aedes aegypti, Anopheles minimus, Anopheles harrisoni, and Anopheles dirus (Diptera: Culicidae)

“…By disrupting or interfering the normal behavioral patterns of vector host-seeking and biting, the vapor-phase properties of chemicals can potentially create a spatial ‘vector-free space’ and thus reduce the risk of so-called ‘residual’ transmission as well as indoor [ 20 , 23 ]. Transfluthrin (TFT) is a relatively recent volatile AI pyrethroid that has been incorporated in a variety of commercial products (i.e., mosquito coils, aerosol sprays) and has been explored for promoting spatial repellent as a new invention class against mosquitoes [ 21 , 22 , 24 ]. Estrada et al [ 25 ] demonstrated that TFT produced the strongest spatial repellency response in Ae .…”

Transfluthrin Eave-Positioned Targeted Insecticide (EPTI) Reduces Human Landing Rate of Pyrethroid Resistant and Susceptible Malaria Vectors in a Semi-Field Simulated Peridomestic Space

“…Although this study suggests that EPTI reduces human landing rate for both mosquitoes, additional evidence is needed to determine whether resistance in mosquitoes is detrimental to the e cacy of trans uthrin. This is particularly important in areas where trans uthrin will be considered for the control of mosquito vectors [20].…”

“…Previous studies have demonstrated that VPs such as trans uthrin and meto uthrin are effective at reducing the human landing rate (HLR) of a range of mosquitoes [16]. Passive emanators treated with trans uthrin or meto uthrin consistently demonstrated personal protective e cacy exceeding 50% in studies conducted in Cambodia [17], Tanzania [18], Belize [19] and Indonesia [20]. Trans uthrin applied to hessian strips as eave-positioned targeted insecticide (EPTI) has provided over 68% reduction in human vector contact in semi-eld studies [10,21] and over 80% in eld studies in Tanzania [10,11].…”

Anopheline and human drivers of malaria risk in northern coastal, Ecuador: a pilot study

“…These data emphasize the need for new tools, such as spatial [ 51 ] or topical repellents, as well as new research that evaluates novel paradigms directed at residual transmission occurring outside the functional scope of present interventions, accelerating progress towards elimination.…”