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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

Overall impact of insecticides on mosquito behaviour insides houses. The graph illustrates the mode of action of DDT, Transfluthrin and Metofluthrin coils on mosquito behaviour. The outcomes measured included deterrence, irritancy, feeding inhibition and toxicity. The value of deterrence was derived from the effect of insecticides on An. arabiensis mosquitoes from field experiments and irritancy, feeding inhibition, mortality and fecundity of An. gambiae s.s. mosquitoes from the semi field system experiment.
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Figure 7: Overall impact of insecticides on mosquito behaviour insides houses. The graph illustrates the mode of action of DDT, Transfluthrin and Metofluthrin coils on mosquito behaviour. The outcomes measured included deterrence, irritancy, feeding inhibition and toxicity. The value of deterrence was derived from the effect of insecticides on An. arabiensis mosquitoes from field experiments and irritancy, feeding inhibition, mortality and fecundity of An. gambiae s.s. mosquitoes from the semi field system experiment.

Mentions: A critical look at the modes of action of insecticides by several authors indicate that toxicity may not be the single most important action of insecticides as far as malaria transmission is concerned [7,10,27,28]. Experimental hut studies enable detailed observation of the impact of insecticides on mosquito behaviour [29,30]. This study substantiates the mode of action of reduced blood feeding by mosquitoes [9] and irritancy [7,31] (Figure 7). It is worth noting that despite the irritant effect of chemicals, 49% 46% and 57% of the mosquitoes that left DDT, Transfluthrin and Metofluthrin huts respectively died after 24 hours (Table 7). Moreover this study shows that the magnitude of these effects was similar between coils and DDT (Figure 7).


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)

Overall impact of insecticides on mosquito behaviour insides houses. The graph illustrates the mode of action of DDT, Transfluthrin and Metofluthrin coils on mosquito behaviour. The outcomes measured included deterrence, irritancy, feeding inhibition and toxicity. The value of deterrence was derived from the effect of insecticides on An. arabiensis mosquitoes from field experiments and irritancy, feeding inhibition, mortality and fecundity of An. gambiae s.s. mosquitoes from the semi field system experiment.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 7: Overall impact of insecticides on mosquito behaviour insides houses. The graph illustrates the mode of action of DDT, Transfluthrin and Metofluthrin coils on mosquito behaviour. The outcomes measured included deterrence, irritancy, feeding inhibition and toxicity. The value of deterrence was derived from the effect of insecticides on An. arabiensis mosquitoes from field experiments and irritancy, feeding inhibition, mortality and fecundity of An. gambiae s.s. mosquitoes from the semi field system experiment.
Mentions: A critical look at the modes of action of insecticides by several authors indicate that toxicity may not be the single most important action of insecticides as far as malaria transmission is concerned [7,10,27,28]. Experimental hut studies enable detailed observation of the impact of insecticides on mosquito behaviour [29,30]. This study substantiates the mode of action of reduced blood feeding by mosquitoes [9] and irritancy [7,31] (Figure 7). It is worth noting that despite the irritant effect of chemicals, 49% 46% and 57% of the mosquitoes that left DDT, Transfluthrin and Metofluthrin huts respectively died after 24 hours (Table 7). Moreover this study shows that the magnitude of these effects was similar between coils and DDT (Figure 7).

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