House screening with insecticide-treated netting provides sustained reductions in domestic populations of Aedes aegypti in Merida, Mexico.

There is a need for effective methods to control Aedes aegypti and prevent the transmission of dengue, chikungunya, yellow fever and Zika viruses. Insecticide treated screening (ITS) is a promising approach, particularly as it targets adult mosquitoes to reduce human-mosquito contact. A cluster-randomised controlled trial evaluated the entomological efficacy of ITS based intervention, which consisted of the installation of pyrethroid-impregnated long-lasting insecticide-treated netting material fixed as framed screens on external doors and windows. A total of 10 treatment and 10 control clusters (100 houses/cluster) were distributed throughout the city of Merida, Mexico. Cross-sectional entomological surveys quantified indoor adult mosquito infestation at baseline (pre-intervention) and throughout four post-intervention (PI) surveys spaced at 6-month intervals corresponding to dry/rainy seasons over two years (2012-2014). A total of 844 households from intervention clusters (86% coverage) were protected with ITS at the start of the trial. Significant reductions in the indoor presence and abundance of Ae. aegypti adults (OR = 0.48 and IRR = 0.45, P<0.05 respectively) and the indoor presence and abundance of Ae. aegypti female mosquitoes (OR = 0.47 and IRR = 0.44, P<0.05 respectively) were detected in intervention clusters compared to controls. This high level of protective effect was sustained for up to 24 months PI. Insecticidal activity of the ITS material declined with time, with ~70% mortality being demonstrated in susceptible mosquito cohorts up to 24 months after installation. The strong and sustained entomological impact observed in this study demonstrates the potential of house screening as a feasible, alternative approach to a sustained long-term impact on household infestations of Ae. aegypti. Larger trials quantifying the effectiveness of ITS on epidemiological endpoints are warranted and therefore recommended

Deltamethrin resistance in Aedes aegypti results in treatment failure in Merida, Mexico

The operational impact of deltamethrin resistance on the efficacy of indoor insecticide applications to control Aedes aegypti was evaluated in Merida, Mexico. A randomized controlled trial quantified the efficacy of indoor residual spraying (IRS) against adult Ae. aegypti in houses treated with either deltamethrin (to which local Ae. aegypti expressed a high degree of resistance) or bendiocarb (to which local Ae. aegypti were fully susceptible) as compared to untreated control houses. All adult Ae. aegypti infestation indices during 3 months post-spraying were significantly lower in houses treated with bendiocarb compared to untreated houses (odds ratio < 0.75; incidence rate ratio < 0.65) whereas no statistically significant difference was detected between the untreated and the deltamethrin-treated houses. On average, bendiocarb spraying reduced Ae. aegypti abundance by 60% during a 3-month period. Results demonstrate that vector control efficacy can be significantly compromised when the insecticide resistance status of Ae. aegypti populations is not taken into consideration

Efectividad de repelentes comerciales disponibles contra el mosquito Aedes aegypti (L.) en Yucatán, México

Objetivo. Determinar la eficacia de repelentes comerciales disponibles en Yucatán contra el mosquito Aedes aegypti, vector del dengue, Chikungunya y Zika. Material y métodos. Se determinó el tiempo de protección con base en el protocolo WHO/CTD/WHOPES/IC y la NOM-032- SSA2-2014. Resultados. Sólo el repelente con DEET (N, N-dietil-3-metilbenzamida) al 25% cumplió con la protección recomendada. La eficacia fue directamente proporcional a la concentración del DEET; aquéllos con componentes botánicos fueron poco o nada protectores. Conclusiones. Los resultados muestran que los repelentes con DEET proveen protección contra Ae. Aegypti; los repelentes botánicos, incluyendo las pulseras impregnadas, ofrecen nula protección. ABSTRACT Objective. We assessed the efficacy of commercial repellents available in Yucatan against Aedes aegypti, vector of dengue, Chikungunya and Zika. Materials and methods. Protection time was determined based on WHO/CTD/ WHOPES/IC y la NOM-032-SSA2-2014. Results. Products with DEET (N, N-diethyl-3-methylbenzamide) at 25% met the recommended protection. Efficacy was directly proportional to the concentration of DEET; botanicals repellents resulted no protective. Conclusions. Repellents with DEET provided more protection against Ae. aegypti and botanical repellents, including impregnated wristbands, provided no protection

House screening with insecticide-treated netting provides sustained reductions in domestic populations of <i>Aedes aegypti</i> in Merida, Mexico

<div><p>Background</p><p>There is a need for effective methods to control <i>Aedes aegypti</i> and prevent the transmission of dengue, chikungunya, yellow fever and Zika viruses. Insecticide treated screening (ITS) is a promising approach, particularly as it targets adult mosquitoes to reduce human-mosquito contact.</p><p>Methodology/Principal findings</p><p>A cluster-randomised controlled trial evaluated the entomological efficacy of ITS based intervention, which consisted of the installation of pyrethroid-impregnated long-lasting insecticide-treated netting material fixed as framed screens on external doors and windows. A total of 10 treatment and 10 control clusters (100 houses/cluster) were distributed throughout the city of Merida, Mexico. Cross-sectional entomological surveys quantified indoor adult mosquito infestation at baseline (pre-intervention) and throughout four post-intervention (PI) surveys spaced at 6-month intervals corresponding to dry/rainy seasons over two years (2012–2014). A total of 844 households from intervention clusters (86% coverage) were protected with ITS at the start of the trial. Significant reductions in the indoor presence and abundance of <i>Ae</i>. <i>aegypti</i> adults (OR = 0.48 and IRR = 0.45, P<0.05 respectively) and the indoor presence and abundance of <i>Ae</i>. <i>aegypti</i> female mosquitoes (OR = 0.47 and IRR = 0.44, P<0.05 respectively) were detected in intervention clusters compared to controls. This high level of protective effect was sustained for up to 24 months PI. Insecticidal activity of the ITS material declined with time, with <i>~</i>70% mortality being demonstrated in susceptible mosquito cohorts up to 24 months after installation.</p><p>Conclusions/Significance</p><p>The strong and sustained entomological impact observed in this study demonstrates the potential of house screening as a feasible, alternative approach to a sustained long-term impact on household infestations of <i>Ae</i>. <i>aegypti</i>. Larger trials quantifying the effectiveness of ITS on epidemiological endpoints are warranted and therefore recommended.</p></div

Impact of ITS on indoor <i>Aedes aegypti</i> adults.

<p>Comparison between treated (solid line) and untreated (broken line) clusters on the percentage of infested houses with <i>Ae</i>. <i>aegypti</i> (left) and their average abundance (right) in Merida, Yucatan, Mexico. The vertical dotted line represents the start of the intervention. The symbol ϴ denotes dates when the index was significantly different between ITS and control arms (with α = 0.05). Error bars show the standard error of the mean.</p

Location of treatment and control clusters within the city of Merida.

<p>The clusters with and without ITS are shown in blue and red, respectively. Source: INEGI, 2010 (<a href="http://www.beta.inegi.org.mx/app/biblioteca/ficha.html?upc=702825292805" target="_blank">http://www.beta.inegi.org.mx/app/biblioteca/ficha.html?upc=702825292805</a>).</p

House screening with insecticide-treated netting.

<p>Photographs show housing improvement with insecticide-treated screens mounted on aluminium frames and fixed to external doors and windows of treated houses in Merida, Mexico.</p

Survival in cone bioassays.

<p>Mean of percentage (±SEM) of susceptible <i>Ae</i>. <i>aegypti</i> survival after exposure to ITS with different deployed times and levels of soiling.</p

Cone bioassays performed at 6, 12, 18 and 24 months post ITS installation.

<p>Results of WHO cone bioassays after 3 min. exposure: knockdown at 60 minutes (KD60) and 24 h mortality and their standard errors of mean (SE) are shown for New Orleans susceptible <i>Ae</i>. <i>aegypti</i> strain.</p

Results of logistic regression models (for presence-absence data) and negative binomial models (for count data) for adult indicators.

<p>Odds ratios (OR) and incidence rate ratios (IRR) with 95% confidence intervals are showed by entomological indicator for each cross-sectional entomological survey.</p