Abstract
Human antibody (Ab) response to Anopheles whole saliva, used as biomarker of Anopheles exposure, was investigated over a period of two years (2008–2009), in children between 2 to 9 years old, before and after the introduction of three different malaria vector control methods; deltamethrin treated long lasting impregnated nets (LLIN) and insecticide treated plastic sheeting (ITPS) - Zero Fly®) (ITPS-ZF), deltamethrin impregnated Durable (Wall) Lining (ITPS-DL – Zerovector®) alone, and indoor residual spraying (IRS) with lambdacyhalothrin alone. These different vector control methods resulted in considerable decreases in all three entomological (82.4%), parasitological (54.8%) and immunological criteria analyzed. The highest reductions in the number of Anopheles collected and number of positive blood smears, respectively 82.1% and 58.3%, were found in Capango and Canjala where LLIN and ITPS-ZF were implemented. The immunological data based on the level of anti-saliva IgG Ab in children of all villages dropped significantly from 2008 to 2009, except in Chissequele. These results indicated that these three vector control methods significantly reduced malaria infections amongst the children studied and IRS significantly reduced the human-Anopheles contact. The number of Anopheles, positive blood smears, and the levels of anti-saliva IgG Ab were most reduced when LLIN and ITPS-ZF were used in combination, compared to the use of one vector control method alone, either ITPS-DL or IRS. Therefore, as a combination of two vector control methods is significantly more effective than one control method only, this control strategy should be further developed at a more global scale.
Highlights
Vector control for malaria control programs depends largely upon the use of Insecticide Residual Spraying (IRS) of indoor house walls and, or, the more recently developed Long Lasting Insecticide Treated Nets (LLIN)
Vector control methods The Balombo program started in 2006 with the objective to develop a malaria control program using and comparing three methods of vector control, including IRS, LLIN (PermaNet with deltamethrin at 55 mg a.i./m2) used in combination with Insecticide Treated Plastic Sheeting (ITPS)-ZF (Zero FlyH treated with deltamethrin at 360 mg a.i./m2), and ITPS-DL (ZeroVectorH treated with deltamethrin at 170 mg a.i./m2)
When comparing the data per vector control method, the decrease in vector densities in 2009 varied from 73.2% reduction in villages with ITPS-DL alone (Chissequele Barragem), to 82.1% in villages using a combination of LLIN and ITPS-ZF (Capango – Canjala), with the intermediate value of 77.7% in villages with IRS (Libata – Candiero)
Summary
Vector control for malaria control programs depends largely upon the use of Insecticide Residual Spraying (IRS) of indoor house walls and, or, the more recently developed Long Lasting Insecticide Treated Nets (LLIN). ITPS has great prospect being long lasting (several years instead of months for IRS) [3], more acceptable as they could be implemented by people themselves instead of an external team, and people could have some choices in terms of color, material, and ITPS could overcome some of the cultural, social or psychological reject of LLIN. Durable Lining (Zero VectorH), a newly developed insecticide treated polyethylene shading material, is similar in technology to ITPS, but designed for use on interior walls of traditionally built rural homes, as a replacement for IRS
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