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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

Examples of the rapidly diversifying array of physical formats for hessian strip transfluthrin emanators derived from the prototype evaluated here.A: The previously described lead prototype emanator [17,18] which was evaluated in detail in this manuscript. B: A second, more convenient “flag” prototype [31], with the fabric strip enclosed in a welded iron frame, leaning up against a user’s chair on her porch. C: The same second flag prototype hanging in a public bar [31]. D: The same second prototype placed up against an end user’s front door, to prevent house entry by Culex spp. mosquitoes which rest upon the door and then enter when it is opened in the morning. E: The third and latest, foldable, self-standing prototype, in which the hessian strip is protected from moisture on the ground, and users are protected from physical contact with the active ingredient, by sandwiching it within a wire mesh cover with wide margins.
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pntd.0005455.g007: Examples of the rapidly diversifying array of physical formats for hessian strip transfluthrin emanators derived from the prototype evaluated here.A: The previously described lead prototype emanator [17,18] which was evaluated in detail in this manuscript. B: A second, more convenient “flag” prototype [31], with the fabric strip enclosed in a welded iron frame, leaning up against a user’s chair on her porch. C: The same second flag prototype hanging in a public bar [31]. D: The same second prototype placed up against an end user’s front door, to prevent house entry by Culex spp. mosquitoes which rest upon the door and then enter when it is opened in the morning. E: The third and latest, foldable, self-standing prototype, in which the hessian strip is protected from moisture on the ground, and users are protected from physical contact with the active ingredient, by sandwiching it within a wire mesh cover with wide margins.

Mentions: This study demonstrated that hessian strips treated with 10ml of transfluthrin reduced exposure to vectors of lymphatic filariasis, several arboviruses and malaria by more than three quarters for one year after treatment, and continued to provide some degree of protection for over two years. These results highlight the potential of such low-technology crude fabric emanators for integrated, simultaneous protection against multiple mosquito species that exhibit outdoor biting behavior, overlap geographically, and co-transmit multiple disease pathogens. Control tools that target more than one vector maximize disease-control benefits and are therefore more cost effective than those targeted against single specific species [1]. While more practical formats for routine use of these fabrics in everyday life in a range of settings (Fig 7) will need to be fully developed and evaluated, and existing systems for bed net delivery and retreatment will need to be adapted to the specific requirements of this technology, it is nevertheless encouraging that this prototype has such high efficacy for so long and can be safely formulated anywhere with minimal safety precautions in the same way as an LLIN retreatment kit.


A low technology emanator treated with the volatile pyrethroid transfluthrin confers long term protection against outdoor biting vectors of lymphatic filariasis, arboviruses and malaria
Examples of the rapidly diversifying array of physical formats for hessian strip transfluthrin emanators derived from the prototype evaluated here.A: The previously described lead prototype emanator [17,18] which was evaluated in detail in this manuscript. B: A second, more convenient “flag” prototype [31], with the fabric strip enclosed in a welded iron frame, leaning up against a user’s chair on her porch. C: The same second flag prototype hanging in a public bar [31]. D: The same second prototype placed up against an end user’s front door, to prevent house entry by Culex spp. mosquitoes which rest upon the door and then enter when it is opened in the morning. E: The third and latest, foldable, self-standing prototype, in which the hessian strip is protected from moisture on the ground, and users are protected from physical contact with the active ingredient, by sandwiching it within a wire mesh cover with wide margins.
© Copyright Policy
Related In: Results  -  Collection

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

pntd.0005455.g007: Examples of the rapidly diversifying array of physical formats for hessian strip transfluthrin emanators derived from the prototype evaluated here.A: The previously described lead prototype emanator [17,18] which was evaluated in detail in this manuscript. B: A second, more convenient “flag” prototype [31], with the fabric strip enclosed in a welded iron frame, leaning up against a user’s chair on her porch. C: The same second flag prototype hanging in a public bar [31]. D: The same second prototype placed up against an end user’s front door, to prevent house entry by Culex spp. mosquitoes which rest upon the door and then enter when it is opened in the morning. E: The third and latest, foldable, self-standing prototype, in which the hessian strip is protected from moisture on the ground, and users are protected from physical contact with the active ingredient, by sandwiching it within a wire mesh cover with wide margins.
Mentions: This study demonstrated that hessian strips treated with 10ml of transfluthrin reduced exposure to vectors of lymphatic filariasis, several arboviruses and malaria by more than three quarters for one year after treatment, and continued to provide some degree of protection for over two years. These results highlight the potential of such low-technology crude fabric emanators for integrated, simultaneous protection against multiple mosquito species that exhibit outdoor biting behavior, overlap geographically, and co-transmit multiple disease pathogens. Control tools that target more than one vector maximize disease-control benefits and are therefore more cost effective than those targeted against single specific species [1]. While more practical formats for routine use of these fabrics in everyday life in a range of settings (Fig 7) will need to be fully developed and evaluated, and existing systems for bed net delivery and retreatment will need to be adapted to the specific requirements of this technology, it is nevertheless encouraging that this prototype has such high efficacy for so long and can be safely formulated anywhere with minimal safety precautions in the same way as an LLIN retreatment kit.

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