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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

Local huts. Local houses in the study area are constructed with corrugated iron sheets or thatched roofing and the walls are constructed with bricks or mud. Most houses are rectangular in shape and have open eaves.
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Figure 3: Local huts. Local houses in the study area are constructed with corrugated iron sheets or thatched roofing and the walls are constructed with bricks or mud. Most houses are rectangular in shape and have open eaves.

Mentions: Studies were conducted in Ifakara experimental huts [19] (Figure 2). Initially, information about the size, design of the houses and the materials required for constructing the roofs and walls was collected through a house hold survey conducted in Kilombero valley. The local houses (Figure 3) in this region are constructed with corrugated iron sheets or thatched roofing and walls are constructed with bricks or mud. This information was used in the construction of experimental huts to ensure a good representation of local houses in Kilombero valley. The experimental huts measure 6.5 m long, 3.5 m wide and 2.5 m high at the roof apex. They are made of galvanized pipe framework, the roof is made of corrugated iron sheets and the inner walls are made of removable mud panels while outer walls are covered with canvas. The outer roof is grass thatched. This provides cool temperatures inside huts just like in local houses. Each experimental hut has one door and four windows. The huts have open spaces (eaves) between the roof and the wall similar to local huts. This results in volume, surface area, temperature and air-flow profiles similar to local homes, which is extremely important when measuring spatially active vector control tools. Half of the eaves and all of the windows are fitted with exit traps suspended outside the huts to trap those mosquitoes that attempt to leave. The traps are made of metal frames and UV resistant black plastic coated fibreglass netting (Phifer, USA). The traps are fitted with cotton sleeves through which mosquitoes can be collected. On the eaves there are spaces left between traps. These spaces are fitted with netting baffles through which mosquitoes enter huts but cannot leave. Mosquitoes can only leave through exit traps. Previous studies indicated that entry behaviour of mosquitoes in experimental huts was similar to local houses [17].


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)

Local huts. Local houses in the study area are constructed with corrugated iron sheets or thatched roofing and the walls are constructed with bricks or mud. Most houses are rectangular in shape and have open eaves.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 3: Local huts. Local houses in the study area are constructed with corrugated iron sheets or thatched roofing and the walls are constructed with bricks or mud. Most houses are rectangular in shape and have open eaves.
Mentions: Studies were conducted in Ifakara experimental huts [19] (Figure 2). Initially, information about the size, design of the houses and the materials required for constructing the roofs and walls was collected through a house hold survey conducted in Kilombero valley. The local houses (Figure 3) in this region are constructed with corrugated iron sheets or thatched roofing and walls are constructed with bricks or mud. This information was used in the construction of experimental huts to ensure a good representation of local houses in Kilombero valley. The experimental huts measure 6.5 m long, 3.5 m wide and 2.5 m high at the roof apex. They are made of galvanized pipe framework, the roof is made of corrugated iron sheets and the inner walls are made of removable mud panels while outer walls are covered with canvas. The outer roof is grass thatched. This provides cool temperatures inside huts just like in local houses. Each experimental hut has one door and four windows. The huts have open spaces (eaves) between the roof and the wall similar to local huts. This results in volume, surface area, temperature and air-flow profiles similar to local homes, which is extremely important when measuring spatially active vector control tools. Half of the eaves and all of the windows are fitted with exit traps suspended outside the huts to trap those mosquitoes that attempt to leave. The traps are made of metal frames and UV resistant black plastic coated fibreglass netting (Phifer, USA). The traps are fitted with cotton sleeves through which mosquitoes can be collected. On the eaves there are spaces left between traps. These spaces are fitted with netting baffles through which mosquitoes enter huts but cannot leave. Mosquitoes can only leave through exit traps. Previous studies indicated that entry behaviour of mosquitoes in experimental huts was similar to local houses [17].

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