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A low technology emanator treated with the volatile pyrethroid transfluthrin confers long term protection against outdoor biting vectors of lymphatic filariasis, arboviruses and malaria

View Article: PubMed Central - PubMed

ABSTRACT

Background: The vapor phase of the volatile pyrethroid transfluthrin incapacitates mosquitoes and prevents them from feeding. Although existing emanator products for delivering volatile pyrethroids protect against outdoor mosquito bites, they are too short-lived to be practical or affordable for routine use in low-income settings. New transfluthrin emanators, comprised simply of treated hessian fabric strips, have recently proven highly protective against outdoor-biting vectors of lymphatic filariasis, arboviruses and malaria, but their full protective lifespan, minimum dose requirements, and range of protection have not previously been assessed.

Methodology: The effects of transfluthrin-treated hessian strips upon mosquito biting exposure of users and nearby non-users, as well as dependence of protection upon treatment dose, were measured outdoors in rural Tanzania using human landing catches (HLC).

Principal findings: Strips treated with 10ml of transfluthrin prevented at least three quarters (p < 0.001) of outdoor bites by Anopheles arabiensis, Culex spp. and Mansonia spp. mosquitoes, and >90% protection against bites on warmer nights with higher evaporation rates, for at least one year. Strips treated with this high dose also reduced biting exposure of non-users at a distance of up to 5m from the strips for An. arabiensis (p < 0.001) and up to 2m for Mansonia spp. (p = 0.008), but provided no protection to non-users against Culex spp. No evidence of increased risk for non-users, caused by diversion of mosquitoes to unprotected individuals, was found at any distance within an 80m radius. A dose of only 1ml provided equivalent protection to the 10ml dose against An. arabiensis, Culex spp. and Mansonia spp. mosquitoes over 6 months (p < 0.001).

Conclusions/significance: Transfluthrin-treated hessian emanators provide safe, affordable, long-term protection against several different pathogen-transmitting mosquito taxa that attack humans outdoors, where they are usually active and cannot be protected by bed nets or residual sprays with conventional, solid-phase insecticides.

No MeSH data available.


Related in: MedlinePlus

Duration of relative protection conferred by treated hessian strips against biting mosquitoes over time.Weekly aggregate crude estimates of protection against all three of the most common mosquito taxa present over the course of a 2.5 year period following initial transfluthrin treatment of the sacking strips (Fig 1, Experiment 1, Objective 1.1). Estimated mean weekly daily mean temperature is also plotted to illustrate how cold spells were initially observed to be associated with reduced protective efficacy.
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pntd.0005455.g003: Duration of relative protection conferred by treated hessian strips against biting mosquitoes over time.Weekly aggregate crude estimates of protection against all three of the most common mosquito taxa present over the course of a 2.5 year period following initial transfluthrin treatment of the sacking strips (Fig 1, Experiment 1, Objective 1.1). Estimated mean weekly daily mean temperature is also plotted to illustrate how cold spells were initially observed to be associated with reduced protective efficacy.

Mentions: Strips treated with 10ml of transfluthrin prevented at least three quarters of outdoor bites by An. arabiensis, Culex spp. and Mansonia spp. mosquitoes for at least one year (Relative protection (RP) [95% confidence interval (CI)] = 0.85 [0.71, 0.91], 0.92 [0.78, 0.97] and 0.94 [0.80, 0.98], respectively, P<0.001 in all cases), and conferred significant protection for the entire 2.5 year study duration (Fig 3). Treated strips significantly reduced relative biting exposure to mosquitoes (An. arabiensis: p < 0.004; Culex spp.: p < 0.001 and Mansonia spp.: p < 0.001), particularly when preceding mean daily temperatures were greater than 23°C (Fig 4). During the first year, strips prevented more than 90% of bites by all three major mosquito taxa whenever preceding mean daily temperature reached 23°C or more: (RP [95% CI] = 0.91 [0.80; 0.96], p < 0.001) for An. arabiensis, 0.98 [0.93; 0.99], p < 0.001 for Culex spp., and 0.99, [0.99; 0.99], p < 0.001 for Mansonia spp.) When data was pooled for all nights over the first year with preceding daily mean temperatures below 21°C, mean protection was nevertheless reasonably satisfactory, at approximately 80% for An. arabiensis (RP [95% CI] = 0.80 [0.63; 0.90], p < 0.001) and Culex spp. (RP = 0.80 [0.48; 0.93], p < 0.0001), and closer to 90% for Mansonia spp. (RP [95% CI] = 0.89 [0.89; 0.89], p < 0.001).


A low technology emanator treated with the volatile pyrethroid transfluthrin confers long term protection against outdoor biting vectors of lymphatic filariasis, arboviruses and malaria
Duration of relative protection conferred by treated hessian strips against biting mosquitoes over time.Weekly aggregate crude estimates of protection against all three of the most common mosquito taxa present over the course of a 2.5 year period following initial transfluthrin treatment of the sacking strips (Fig 1, Experiment 1, Objective 1.1). Estimated mean weekly daily mean temperature is also plotted to illustrate how cold spells were initially observed to be associated with reduced protective efficacy.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5384659&req=5

pntd.0005455.g003: Duration of relative protection conferred by treated hessian strips against biting mosquitoes over time.Weekly aggregate crude estimates of protection against all three of the most common mosquito taxa present over the course of a 2.5 year period following initial transfluthrin treatment of the sacking strips (Fig 1, Experiment 1, Objective 1.1). Estimated mean weekly daily mean temperature is also plotted to illustrate how cold spells were initially observed to be associated with reduced protective efficacy.
Mentions: Strips treated with 10ml of transfluthrin prevented at least three quarters of outdoor bites by An. arabiensis, Culex spp. and Mansonia spp. mosquitoes for at least one year (Relative protection (RP) [95% confidence interval (CI)] = 0.85 [0.71, 0.91], 0.92 [0.78, 0.97] and 0.94 [0.80, 0.98], respectively, P<0.001 in all cases), and conferred significant protection for the entire 2.5 year study duration (Fig 3). Treated strips significantly reduced relative biting exposure to mosquitoes (An. arabiensis: p < 0.004; Culex spp.: p < 0.001 and Mansonia spp.: p < 0.001), particularly when preceding mean daily temperatures were greater than 23°C (Fig 4). During the first year, strips prevented more than 90% of bites by all three major mosquito taxa whenever preceding mean daily temperature reached 23°C or more: (RP [95% CI] = 0.91 [0.80; 0.96], p < 0.001) for An. arabiensis, 0.98 [0.93; 0.99], p < 0.001 for Culex spp., and 0.99, [0.99; 0.99], p < 0.001 for Mansonia spp.) When data was pooled for all nights over the first year with preceding daily mean temperatures below 21°C, mean protection was nevertheless reasonably satisfactory, at approximately 80% for An. arabiensis (RP [95% CI] = 0.80 [0.63; 0.90], p < 0.001) and Culex spp. (RP = 0.80 [0.48; 0.93], p < 0.0001), and closer to 90% for Mansonia spp. (RP [95% CI] = 0.89 [0.89; 0.89], p < 0.001).

View Article: PubMed Central - PubMed

ABSTRACT

Background: The vapor phase of the volatile pyrethroid transfluthrin incapacitates mosquitoes and prevents them from feeding. Although existing emanator products for delivering volatile pyrethroids protect against outdoor mosquito bites, they are too short-lived to be practical or affordable for routine use in low-income settings. New transfluthrin emanators, comprised simply of treated hessian fabric strips, have recently proven highly protective against outdoor-biting vectors of lymphatic filariasis, arboviruses and malaria, but their full protective lifespan, minimum dose requirements, and range of protection have not previously been assessed.

Methodology: The effects of transfluthrin-treated hessian strips upon mosquito biting exposure of users and nearby non-users, as well as dependence of protection upon treatment dose, were measured outdoors in rural Tanzania using human landing catches (HLC).

Principal findings: Strips treated with 10ml of transfluthrin prevented at least three quarters (p &lt; 0.001) of outdoor bites by Anopheles arabiensis, Culex spp. and Mansonia spp. mosquitoes, and &gt;90% protection against bites on warmer nights with higher evaporation rates, for at least one year. Strips treated with this high dose also reduced biting exposure of non-users at a distance of up to 5m from the strips for An. arabiensis (p &lt; 0.001) and up to 2m for Mansonia spp. (p = 0.008), but provided no protection to non-users against Culex spp. No evidence of increased risk for non-users, caused by diversion of mosquitoes to unprotected individuals, was found at any distance within an 80m radius. A dose of only 1ml provided equivalent protection to the 10ml dose against An. arabiensis, Culex spp. and Mansonia spp. mosquitoes over 6 months (p &lt; 0.001).

Conclusions/significance: Transfluthrin-treated hessian emanators provide safe, affordable, long-term protection against several different pathogen-transmitting mosquito taxa that attack humans outdoors, where they are usually active and cannot be protected by bed nets or residual sprays with conventional, solid-phase insecticides.

No MeSH data available.


Related in: MedlinePlus