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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

Survival curves illustrating the rate at which mosquitoes left huts with DDT, transfluthrin and metofluthrin coils. The curves represent the rate at which mosquitoes exit huts that have different insecticides compared to the control. Time (hours) to which mosquitoes left huts: 1–2100, 2–2200, 3–2300, 4–0000, 5–0100, 6–0200, 7–0300, 8–0400, 9–0500, 10–0600, 11–0700. Analysis was based on a Kaplan-Meier stepped survivorship function. Each curve represents one treatment.
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Figure 6: Survival curves illustrating the rate at which mosquitoes left huts with DDT, transfluthrin and metofluthrin coils. The curves represent the rate at which mosquitoes exit huts that have different insecticides compared to the control. Time (hours) to which mosquitoes left huts: 1–2100, 2–2200, 3–2300, 4–0000, 5–0100, 6–0200, 7–0300, 8–0400, 9–0500, 10–0600, 11–0700. Analysis was based on a Kaplan-Meier stepped survivorship function. Each curve represents one treatment.

Mentions: The proportion of mosquitoes that left huts that had DDT, Transfluthrin and Metofluthrin coils was significantly higher than the control (Table 5). Approximately 48% (95% CI: [0.44 -0.53]; z = 9.950, p < 0.001) of the mosquitoes left DDT huts (Table 5). In huts with Transfluthrin and Metofluthrin coils approximately 56% (95% CI: [0.51 - 0.60]; z = 12.779, p < 0.001) and 55% (95% CI: [0.51 -0.60]; z = 12.890, p < 0.001) left huts, respectively. The rate at which mosquitoes left huts throughout the night is illustrated using Kaplan Meier survival curves (Figure 6). The highest exodus of mosquitoes from huts was observed in the first half of the night (2100 – 0000 hours) regardless of treatment or control, but overall, more mosquitoes exited when huts contained DDT, Transfluthrin or Metofluthrin coils compared to the control.


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)

Survival curves illustrating the rate at which mosquitoes left huts with DDT, transfluthrin and metofluthrin coils. The curves represent the rate at which mosquitoes exit huts that have different insecticides compared to the control. Time (hours) to which mosquitoes left huts: 1–2100, 2–2200, 3–2300, 4–0000, 5–0100, 6–0200, 7–0300, 8–0400, 9–0500, 10–0600, 11–0700. Analysis was based on a Kaplan-Meier stepped survivorship function. Each curve represents one treatment.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 6: Survival curves illustrating the rate at which mosquitoes left huts with DDT, transfluthrin and metofluthrin coils. The curves represent the rate at which mosquitoes exit huts that have different insecticides compared to the control. Time (hours) to which mosquitoes left huts: 1–2100, 2–2200, 3–2300, 4–0000, 5–0100, 6–0200, 7–0300, 8–0400, 9–0500, 10–0600, 11–0700. Analysis was based on a Kaplan-Meier stepped survivorship function. Each curve represents one treatment.
Mentions: The proportion of mosquitoes that left huts that had DDT, Transfluthrin and Metofluthrin coils was significantly higher than the control (Table 5). Approximately 48% (95% CI: [0.44 -0.53]; z = 9.950, p < 0.001) of the mosquitoes left DDT huts (Table 5). In huts with Transfluthrin and Metofluthrin coils approximately 56% (95% CI: [0.51 - 0.60]; z = 12.779, p < 0.001) and 55% (95% CI: [0.51 -0.60]; z = 12.890, p < 0.001) left huts, respectively. The rate at which mosquitoes left huts throughout the night is illustrated using Kaplan Meier survival curves (Figure 6). The highest exodus of mosquitoes from huts was observed in the first half of the night (2100 – 0000 hours) regardless of treatment or control, but overall, more mosquitoes exited when huts contained DDT, Transfluthrin or Metofluthrin coils compared to the control.

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