Recombinant Malaria Antigen Pan [His]

Resistance to the artemisinin derivatives, our most effective antimalarial drugs, has not manifest as a classical resistance phenotype in which parasites can tolerate higher drug concentrations. Instead, resistant parasites have an altered maturation. We hypothesize that the short half-life of artemisinin concentrations is an unanticipated driver of this novel resistance phenotype.

Background: Several types of insecticides, treating technologies and materials are available for long-lasting insecticide-treated nets (LLINs). The variations may result in different efficacies against mosquitoes and correspondingly infection risks for thePlasmodium falciparummalaria parasite. This cross-sectional study investigated whether infection risk varied among children who slept under different LLIN brands in rural villages of western Kenya. Methods: Children sleeping under various types of LLINs were tested forP. falciparuminfection using a diagnostic polymerase chain reaction (PCR) assay. Data were collected for other potential factors associated with infection risk: sleeping location (with bed/without bed), number of persons sharing the same net, dwelling wall material, gap of eaves (open/close), proportional hole index, socio-economic status, and density of indoor resting anophelines. Bed-net efficacy against theAnopheles gambiaesusceptible strain was estimated using the WHO cone test and the tunnel test. The residual insecticide content on nets was measured. Results: Seven LLIN brands were identified, and deltamethrin-based DawaPlus (R) 2.0 was the most popular (48%) followed by permethrin-based Olyset (R) Net (28%). The former LLIN was distributed in the area about six months before the present study was conducted, and the latter net was distributed at least three years before. Of 254 children analysed,P. falciparumPCR-positive prevalence was 58% for DawaPlus (R) 2.0 users and 38% for Olyset (R) users. The multiple regression analysis revealed that the difference was statistically significant (adjusted OR: 0.67, 95% credible interval: 0.45-0.97), whereas the confounders were not statistically important. Among randomly selected net samples, all DawaPlus (R) 2.0 (n = 20) and 95% of Olyset (R) (n = 19) passed either the cone test or the tunnel test. Conclusions: Olyset (R) was more effective in reducing infection risk compared with DawaPlus (R) 2.0. Although the data from the present study were too limited to explain the mechanism clearly, the results suggest that the characteristics of the former brand are more suitable for the conditions, such as vector species composition, of the study area.