Human Antibody Response to Anopheles Saliva for Comparing the Efficacy of Three Malaria Vector Control Methods in Balombo, Angola

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.

Concentración de los anticuerpos en contra de proteínas de las glándulas salivares de Aedes aegypti e historia de la exposición al virus del dengue en residentes de una zona endémica colombiana

“…The use of anti-vector saliva antibodies has been used as a marker for exposure after vector control methods have been performed (11,39). As seasonal variation in human-vector contact is a dynamic process that informs DENV transmission potential, developing methods to detect changes in and risk factors for increased contact are critically important.…”

“…Previous studies have shown that the type and concentration of antibodies against vector salivary gland extract (SGE) can serve as markers for disease transmission and risk (7)(8)(9)(10) and to evaluate the efficacy of vector control efforts (11,12). Additionally, estimating the prevalence of antibodies against all DENV serotypes that have circulated in a specific area gives insight of the population exposure to the virus (13).…”

Insecticide-treated durable wall lining (ITWL): future prospects for control of malaria and other vector-borne diseases

“…ND No significant reductions in human biting rate, sporozoite rate or EIR for all interventionsNo significant reductions in malaria incidence, prevalence or parasite density for ITPS + LLIN, UC of LLIN or LLIN + IRS compared to targeted LLIN[21]Significantly greater proportions of parous mosquitoes and indoor resting vectors in ITPS + LLIN villagesIRSBendiocarb (400 mg/m 2 )All house walls kdr allele frequency increased in all intervention groupsPermaNet ® 2.0 LLINDeltamethrin (55 mg/m 2 )Universal coverageBalombo, Angola, community-levelPolyethylene sheeting (ITPS) (ZeroFly®)Deltamethrin (360 mg/m 2 )Full coverageDeltamethrin LLIN (PermaNet ® 2.0; 55 mg/m 2 ) An. funestus ND and other minor anopheline spp.Significant reductions in indoor vector population density (82% for ITPS + LLINs; 78% for IRS; 73% for WL) and intensity of mosquito bites in most intervention villages, measured using anti- Anopheles saliva IgG antibodies levelsSignificant reductions in malaria incidence (58% for ITPS + LLINs; 54% for IRS; 51% for WL)[45]IRS (lambdacyhalothrin; 25 mg/m 2 )Polyethylene WL (ZeroVector ® )Deltamethrin (175 mg/m 2 ) EIR entomological inoculation rate, Hb haemoglobin, IRS indoor residual spraying, ITPS Insecticide-treated plastic sheeting, LLIN long-lasting insecticidal net, ND not described, r resistant to one or more insecticides under investigation, s susceptible to one or more insecticides under investigation, UC universal coverage, WL wall lining a Indicates traditional, permanent rural households or villages, unless otherwise specified b Full coverage defined as four inner house walls, all interior surfaces in temporary structures or all interior surfaces in a λ-shaped tent, as applicable c Outcomes reported relative to untreated control, unless otherwise specified …”

Human IgG Antibody Response to Aedes Nterm-34kDa Salivary Peptide, an Epidemiological Tool to Assess Vector Control in Chikungunya and Dengue Transmission Area

“…Recent studies have demonstrated the usefulness of anti-saliva Ab response for measuring exposure of humans to arthropods bites, such as, ticks [8] sand fly [9,10], Glossina [11] and mosquitoes [12–19]. Additionally, human Ab IgG response to whole saliva was identified as pertinent tool for evaluating efficacy of vector control against Anopheles [20,21], Phlebotomus [22] and Aedes albopictus [23]. However, the use of whole saliva is not an ideal indicator, because of: i) potential cross-reactivity with other vectors; ii) weak stability / fast degradation of proteins in wholes saliva and iii) poorly reproducible batches produced for large-scale studies.…”