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Impact of changing over of insecticide from synthetic pyrethroids to DDT for indoor residual spray in a malaria endemic area of Orissa, India.

Sharma SK, Upadhyay AK, Haque MA, Tyagi PK, Kindo BK - Indian J. Med. Res. (2012)

Bottom Line: ACM was effective in killing An. culicifacies on mud and wooden sprayed surfaces and maintained effective bioefficacy ranging from 92 to 100 per cent up to five months, whereas DDT failed to achieve effective mortality in An.culicifacies.However, there was significant decline in the density of An.culicifacies in ACM and DDT areas in comparison to ITNs/LNs.There was 61 per cent reduction in the slide positivity rate in ACM area in comparison to 48 and 51 per cent in DDT and ITN/LNs areas, respectively.

View Article: PubMed Central - PubMed

Affiliation: National Institute of Malaria Research, Field Station, Rourkela, India.

ABSTRACT

Background & objectives: Development of insecticide resistance in malaria vectors has been a major problem for achieving effective vector control. Due to limited availability of insecticides, the only option is management of resistance by judiciously using the insecticides and rotating them to maintain their effectiveness. This study was carried out in a malaria endemic area of Sundergarh district in Orissa where synthetic pyrethroids (SP) were in use for the last couple of years. The change-over from SP to DDT was done in one arm of study, and the other two arms remained on SP and insecticide-treated nets (ITN). Entomological and parasitological monitoring was done to assess the impact.

Methods: The study design comprised of three arms (i) two rounds of indoor residual spraying (IRS) with DDT 1g/m(2) as a change-over insecticide in areas previously under synthetic pyrethroids; (ii) two rounds of IRS with synthetic pyrethroid (alphacypermethrin, ACM) @ 25 mg/m(2) ; and (iii) an unsprayed area under ITN/long lasting insecticide nets (LNs). Indoor residual spraying was undertaken under strict supervision to maintain quality and coverage. Contact bioassays were conducted to know the persistence of insecticide on sprayed surfaces and adult vector density was monitored in fixed and randomly selected houses. Malaria incidence was measured through fortnightly domiciliary surveillance under primary health care system in all the study villages.

Results: The insecticide susceptibility tests showed that An.culicifacies was resistant to DDT but susceptible to malathion and ACM. However, An. fluviatilis was susceptible to all the three insecticides. ACM was effective in killing An. culicifacies on mud and wooden sprayed surfaces and maintained effective bioefficacy ranging from 92 to 100 per cent up to five months, whereas DDT failed to achieve effective mortality in An.culicifacies. However, there was significant decline in the density of An.culicifacies in ACM and DDT areas in comparison to ITNs/LNs. There was 61 per cent reduction in the slide positivity rate in ACM area in comparison to 48 and 51 per cent in DDT and ITN/LNs areas, respectively. The adjusted incidence rate of malaria cases per 1000 population in three study areas also showed significant declines within each group.

Interpretation & conclusions: The present findings show that the change-over of insecticide from synthetic pyrethroids to DDT brings about the same epidemiological impact as envisaged from continuing SP spray or distributing insecticide treated nets/long-lasting insecticidal nets provided there is a good quality spray and house coverage.

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Comparison of crude malaria incidence (number of cases/1000 population/year) in three study areas during pre-intervention and intervention period. A significant decline was observed in all the three areas (P<0.01).
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Figure 2: Comparison of crude malaria incidence (number of cases/1000 population/year) in three study areas during pre-intervention and intervention period. A significant decline was observed in all the three areas (P<0.01).

Mentions: Impact on malaria incidence: The malaria incidence data for the three study sub-centres were collected from Laing PHC and analyzed to determine the impact of each intervention. The slide positivity rate (SPR) during pre-intervention period in ACM, DDT and ITN/LNs area was 5.3, 4.7 and 4.4, respectively and there was no significant difference between the three areas. ACM and DDT areas prior to change over of insecticide were under synthetic pyrethroid (SP) for the last three years though with different coverage and quality. The change-over of insecticide from SP to DDT was undertaken in Buchukupara sub-centre. After intervention, the SPR was dropped to 2.1, 2.5 and 2.2, respectively and there was 61 per cent reduction in the slide positivity rate in ACM area in comparison to 48 and 51 per cent reduction in DDT and ITN/LNs areas, respectively (Table IV). The adjusted incidence rate of malaria cases per 1000 population per year in three study areas before intervention under ACM, DDT and ITN/LNs was 7.6, 10.1 and 5.8, respectively, and significant declines were observed within each group (Table IV). During intervention, involving change-over of insecticide from SP to DDT in one study area and distribution of long-lasting nets in ITN area during January 2010 and closely supervised IRS, there was decline in crude malaria incidence (P<0.01) in all the three study arms (Fig. 2).


Impact of changing over of insecticide from synthetic pyrethroids to DDT for indoor residual spray in a malaria endemic area of Orissa, India.

Sharma SK, Upadhyay AK, Haque MA, Tyagi PK, Kindo BK - Indian J. Med. Res. (2012)

Comparison of crude malaria incidence (number of cases/1000 population/year) in three study areas during pre-intervention and intervention period. A significant decline was observed in all the three areas (P<0.01).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3361876&req=5

Figure 2: Comparison of crude malaria incidence (number of cases/1000 population/year) in three study areas during pre-intervention and intervention period. A significant decline was observed in all the three areas (P<0.01).
Mentions: Impact on malaria incidence: The malaria incidence data for the three study sub-centres were collected from Laing PHC and analyzed to determine the impact of each intervention. The slide positivity rate (SPR) during pre-intervention period in ACM, DDT and ITN/LNs area was 5.3, 4.7 and 4.4, respectively and there was no significant difference between the three areas. ACM and DDT areas prior to change over of insecticide were under synthetic pyrethroid (SP) for the last three years though with different coverage and quality. The change-over of insecticide from SP to DDT was undertaken in Buchukupara sub-centre. After intervention, the SPR was dropped to 2.1, 2.5 and 2.2, respectively and there was 61 per cent reduction in the slide positivity rate in ACM area in comparison to 48 and 51 per cent reduction in DDT and ITN/LNs areas, respectively (Table IV). The adjusted incidence rate of malaria cases per 1000 population per year in three study areas before intervention under ACM, DDT and ITN/LNs was 7.6, 10.1 and 5.8, respectively, and significant declines were observed within each group (Table IV). During intervention, involving change-over of insecticide from SP to DDT in one study area and distribution of long-lasting nets in ITN area during January 2010 and closely supervised IRS, there was decline in crude malaria incidence (P<0.01) in all the three study arms (Fig. 2).

Bottom Line: ACM was effective in killing An. culicifacies on mud and wooden sprayed surfaces and maintained effective bioefficacy ranging from 92 to 100 per cent up to five months, whereas DDT failed to achieve effective mortality in An.culicifacies.However, there was significant decline in the density of An.culicifacies in ACM and DDT areas in comparison to ITNs/LNs.There was 61 per cent reduction in the slide positivity rate in ACM area in comparison to 48 and 51 per cent in DDT and ITN/LNs areas, respectively.

View Article: PubMed Central - PubMed

Affiliation: National Institute of Malaria Research, Field Station, Rourkela, India.

ABSTRACT

Background & objectives: Development of insecticide resistance in malaria vectors has been a major problem for achieving effective vector control. Due to limited availability of insecticides, the only option is management of resistance by judiciously using the insecticides and rotating them to maintain their effectiveness. This study was carried out in a malaria endemic area of Sundergarh district in Orissa where synthetic pyrethroids (SP) were in use for the last couple of years. The change-over from SP to DDT was done in one arm of study, and the other two arms remained on SP and insecticide-treated nets (ITN). Entomological and parasitological monitoring was done to assess the impact.

Methods: The study design comprised of three arms (i) two rounds of indoor residual spraying (IRS) with DDT 1g/m(2) as a change-over insecticide in areas previously under synthetic pyrethroids; (ii) two rounds of IRS with synthetic pyrethroid (alphacypermethrin, ACM) @ 25 mg/m(2) ; and (iii) an unsprayed area under ITN/long lasting insecticide nets (LNs). Indoor residual spraying was undertaken under strict supervision to maintain quality and coverage. Contact bioassays were conducted to know the persistence of insecticide on sprayed surfaces and adult vector density was monitored in fixed and randomly selected houses. Malaria incidence was measured through fortnightly domiciliary surveillance under primary health care system in all the study villages.

Results: The insecticide susceptibility tests showed that An.culicifacies was resistant to DDT but susceptible to malathion and ACM. However, An. fluviatilis was susceptible to all the three insecticides. ACM was effective in killing An. culicifacies on mud and wooden sprayed surfaces and maintained effective bioefficacy ranging from 92 to 100 per cent up to five months, whereas DDT failed to achieve effective mortality in An.culicifacies. However, there was significant decline in the density of An.culicifacies in ACM and DDT areas in comparison to ITNs/LNs. There was 61 per cent reduction in the slide positivity rate in ACM area in comparison to 48 and 51 per cent in DDT and ITN/LNs areas, respectively. The adjusted incidence rate of malaria cases per 1000 population in three study areas also showed significant declines within each group.

Interpretation & conclusions: The present findings show that the change-over of insecticide from synthetic pyrethroids to DDT brings about the same epidemiological impact as envisaged from continuing SP spray or distributing insecticide treated nets/long-lasting insecticidal nets provided there is a good quality spray and house coverage.

Show MeSH
Related in: MedlinePlus