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An experimental hut study to quantify the effect of DDT and airborne pyrethroids on entomological parameters of malaria transmission.

Ogoma SB, Lorenz LM, Ngonyani H, Sangusangu R, Kitumbukile M, Kilalangongono M, Simfukwe ET, Mseka A, Mbeyela E, Roman D, Moore J, Kreppel K, Maia MF, Moore SJ - Malar. J. (2014)

Bottom Line: Outcomes were deterrence--reduction in house entry of mosquitoes; irritancy or excito-repellency--induced premature exit of mosquitoes; blood feeding inhibition and effect on mosquito fecundity.These effects are in addition to significant toxicity and reduced mosquito fecundity that affect mosquito densities and, therefore, provide community protection against diseases for both users and non-users.Airborne insecticides and freshly applied DDT had similar effects on deterrence, irritancy and feeding inhibition.

View Article: PubMed Central - HTML - PubMed

Affiliation: Ifakara Health Institute, Environmental Health and Ecological Sciences, P,O, Box 74, Bagamoyo, Tanzania. sogoma@ihi.or.tz.

ABSTRACT

Background: Current malaria vector control programmes rely on insecticides with rapid contact toxicity. However, spatial repellents can also be applied to reduce man-vector contact, which might ultimately impact malaria transmission. The aim of this study was to quantify effects of airborne pyrethroids from coils and DDT used an indoor residual spray (IRS) on entomological parameters that influence malaria transmission.

Methods: The effect of Transfluthrin and Metofluthrin coils compared to DDT on house entry, exit and indoor feeding behaviour of Anopheles gambiae sensu lato were measured in experimental huts in the field and in the semi-field. Outcomes were deterrence--reduction in house entry of mosquitoes; irritancy or excito-repellency--induced premature exit of mosquitoes; blood feeding inhibition and effect on mosquito fecundity.

Results: Transfluthrin coils, Metofluthrin coils and DDT reduced human vector contact through deterrence by 38%, 30% and 8%, respectively and induced half of the mosquitoes to leave huts before feeding (56%, 55% and 48%, respectively). Almost all mosquitoes inside huts with Metofluthrin and Transfluthrin coils and more than three quarters of mosquitoes in the DDT hut did not feed, almost none laid eggs and 67%, 72% and 70% of all mosquitoes collected from Transfluthrin, Metofluthrin and DDT huts, respectively had died after 24 hours.

Conclusion: This study highlights that airborne pyrethroids and DDT affect a range of anopheline mosquito behaviours that are important parameters in malaria transmission, namely deterrence, irritancy/excito-repellency and blood-feeding inhibition. These effects are in addition to significant toxicity and reduced mosquito fecundity that affect mosquito densities and, therefore, provide community protection against diseases for both users and non-users. Airborne insecticides and freshly applied DDT had similar effects on deterrence, irritancy and feeding inhibition. Therefore, it is suggested that airborne pyrethroids, if delivered in suitable formats, may complement existing mainstream vector control tools.

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Related in: MedlinePlus

Spraying palm woven mats with DDT. Palm woven mats previously cut out to fit on the walls of experimental huts were sprayed with 2 g/m2 DDT. Spraying was conducted in a temporary structure that was later burnt. Spraying the mats instead of the walls ensured that mats could be moved easily from one hut to another without contaminating the walls. This allowed rotation of treatments between huts.
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Figure 1: Spraying palm woven mats with DDT. Palm woven mats previously cut out to fit on the walls of experimental huts were sprayed with 2 g/m2 DDT. Spraying was conducted in a temporary structure that was later burnt. Spraying the mats instead of the walls ensured that mats could be moved easily from one hut to another without contaminating the walls. This allowed rotation of treatments between huts.

Mentions: Palm woven mats were measured and cut out to fit the entire surface of the inside wall of an experimental hut. The reverse side of the mats was covered with plastic sheets (Figure 1) to prevent contamination of experimental hut surfaces with DDT during rotation of mats between huts. Two sets of mats were prepared, the control was sprayed with water and the other set was sprayed with DDT at a dose of 2 g/m2 as recommended by WHOPES [16] using a separate Hudson sprayer for each treatment. The quantity of DDT required to cover walls of one hut was determined by measuring the surface area of walls. The amount of DDT required in g/m2 was calculated and weighed. The volume of water required for mixing DDT was determined by pouring a known amount of water in a Hudson sprayer. The sprayers were calibrated to 55 psi and control mats were sprayed with water. The volume of water used in the control was measured and an equal volume of water was used for mixing DDT in a plastic bucket. Spraying was conducted in a disposable tent located 50 metres from experimental huts (Figure 1). The mats were air dried for 15 minutes then fixed to respective walls using removable staples so that they could be detached easily during rotation (Figure 1).


An experimental hut study to quantify the effect of DDT and airborne pyrethroids on entomological parameters of malaria transmission.

Ogoma SB, Lorenz LM, Ngonyani H, Sangusangu R, Kitumbukile M, Kilalangongono M, Simfukwe ET, Mseka A, Mbeyela E, Roman D, Moore J, Kreppel K, Maia MF, Moore SJ - Malar. J. (2014)

Spraying palm woven mats with DDT. Palm woven mats previously cut out to fit on the walls of experimental huts were sprayed with 2 g/m2 DDT. Spraying was conducted in a temporary structure that was later burnt. Spraying the mats instead of the walls ensured that mats could be moved easily from one hut to another without contaminating the walls. This allowed rotation of treatments between huts.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4230423&req=5

Figure 1: Spraying palm woven mats with DDT. Palm woven mats previously cut out to fit on the walls of experimental huts were sprayed with 2 g/m2 DDT. Spraying was conducted in a temporary structure that was later burnt. Spraying the mats instead of the walls ensured that mats could be moved easily from one hut to another without contaminating the walls. This allowed rotation of treatments between huts.
Mentions: Palm woven mats were measured and cut out to fit the entire surface of the inside wall of an experimental hut. The reverse side of the mats was covered with plastic sheets (Figure 1) to prevent contamination of experimental hut surfaces with DDT during rotation of mats between huts. Two sets of mats were prepared, the control was sprayed with water and the other set was sprayed with DDT at a dose of 2 g/m2 as recommended by WHOPES [16] using a separate Hudson sprayer for each treatment. The quantity of DDT required to cover walls of one hut was determined by measuring the surface area of walls. The amount of DDT required in g/m2 was calculated and weighed. The volume of water required for mixing DDT was determined by pouring a known amount of water in a Hudson sprayer. The sprayers were calibrated to 55 psi and control mats were sprayed with water. The volume of water used in the control was measured and an equal volume of water was used for mixing DDT in a plastic bucket. Spraying was conducted in a disposable tent located 50 metres from experimental huts (Figure 1). The mats were air dried for 15 minutes then fixed to respective walls using removable staples so that they could be detached easily during rotation (Figure 1).

Bottom Line: Outcomes were deterrence--reduction in house entry of mosquitoes; irritancy or excito-repellency--induced premature exit of mosquitoes; blood feeding inhibition and effect on mosquito fecundity.These effects are in addition to significant toxicity and reduced mosquito fecundity that affect mosquito densities and, therefore, provide community protection against diseases for both users and non-users.Airborne insecticides and freshly applied DDT had similar effects on deterrence, irritancy and feeding inhibition.

View Article: PubMed Central - HTML - PubMed

Affiliation: Ifakara Health Institute, Environmental Health and Ecological Sciences, P,O, Box 74, Bagamoyo, Tanzania. sogoma@ihi.or.tz.

ABSTRACT

Background: Current malaria vector control programmes rely on insecticides with rapid contact toxicity. However, spatial repellents can also be applied to reduce man-vector contact, which might ultimately impact malaria transmission. The aim of this study was to quantify effects of airborne pyrethroids from coils and DDT used an indoor residual spray (IRS) on entomological parameters that influence malaria transmission.

Methods: The effect of Transfluthrin and Metofluthrin coils compared to DDT on house entry, exit and indoor feeding behaviour of Anopheles gambiae sensu lato were measured in experimental huts in the field and in the semi-field. Outcomes were deterrence--reduction in house entry of mosquitoes; irritancy or excito-repellency--induced premature exit of mosquitoes; blood feeding inhibition and effect on mosquito fecundity.

Results: Transfluthrin coils, Metofluthrin coils and DDT reduced human vector contact through deterrence by 38%, 30% and 8%, respectively and induced half of the mosquitoes to leave huts before feeding (56%, 55% and 48%, respectively). Almost all mosquitoes inside huts with Metofluthrin and Transfluthrin coils and more than three quarters of mosquitoes in the DDT hut did not feed, almost none laid eggs and 67%, 72% and 70% of all mosquitoes collected from Transfluthrin, Metofluthrin and DDT huts, respectively had died after 24 hours.

Conclusion: This study highlights that airborne pyrethroids and DDT affect a range of anopheline mosquito behaviours that are important parameters in malaria transmission, namely deterrence, irritancy/excito-repellency and blood-feeding inhibition. These effects are in addition to significant toxicity and reduced mosquito fecundity that affect mosquito densities and, therefore, provide community protection against diseases for both users and non-users. Airborne insecticides and freshly applied DDT had similar effects on deterrence, irritancy and feeding inhibition. Therefore, it is suggested that airborne pyrethroids, if delivered in suitable formats, may complement existing mainstream vector control tools.

Show MeSH
Related in: MedlinePlus