RESUMO
A study was undertaken in the villages of Korea and Bastar district (Chhattisgarh) during the years 2012-2015 to investigate the bionomics of malaria vectors and the prevalence of their sibling species complexes. Entomological surveys carried out every month included indoor resting collections, pyrethrum spray catches, light trap catches, and insecticide susceptibility status of Anopheles culicifacies using World Health Organization (WHO) methods. Anopheles culicifacies and Anopheles fluviatilis species were assayed by polymerase chain reaction (PCR) for the detection of malaria parasite, and sibling species were identified using PCR and DNA sequencing. A total of 13,186 samples of Anopheles comprising 15 species from Bastar and 16 from Korea were collected. An. Culicifacies was recorded as the most dominant species and also the only active vector at both sites. This species was found to be resistant to dichlorodiphenyltrichloroethane (DDT) and Malathion, showing signs of emerging resistance against pyrethroids. Among the sibling species of An. culicifacies, the group BCE was found in maximum numbers, while sibling species T of the An. fluviatilis was recorded to be dominant among its complex. The study provides a comprehensive view of the vector bionomics in the highly malarious regions of India that may have importance in developing vector control strategies.
RESUMO
BACKGROUND: Indoor residual spray (IRS) and long-lasting insecticidal nets are the two principal intervention methods of vector control. Zero vector durable lining (ZVDL), a relatively new vector control method, was evaluated to assess its efficacy against malaria vectors in hard to reach areas in the Balaghat district, where malaria transmission is perennial. METHODS: ZVDL was installed in six experimental villages during November-December 2012. In control villages, IRS was carried out with Alphacypermethrin. Cone bioassays were performed to assess the efficacy and persistence of insecticide-treated ZVDL following WHO bioassays. RESULTS: The mean per man hour density of Anopheles caught during 2013 was 12.1 in experimental villages and 16.2 in control villages. No sporozoite-positive Anopheles culicifacies were found in experimental villages; however, in control villages, four sporozoite-positive A. culicifacies were found (two Plasmodium vivax and two P. falciparum). The knock-down rate of A. culicifacies was 95-100% with 100% mortality during the 24 h recovery period. Malaria declined sharply in experimental villages showing a slide positivity rate of 22.3% compared with control villages (36.4%) (p<0.05). CONCLUSIONS: A supplementary vector control intervention such as ZVDL has the potential to become a viable alternative to IRS in malaria endemic areas.
