インドの多様な生態・疫学的状況におけるマラリア媒介蚊の生物学的特性の理解に関する多施設共同研究

India aims to eliminate malaria by 2030; however, a thorough understanding of the current biology and behavior of vector species will facilitate the efforts. Vector species often alter their biting and resting behaviors in response to long-term chemical control measures, posing significant challenges to ongoing vector control interventions. Therefore, it is essential to investigate and update our knowledge of the bionomics of malaria vectors in the current context.

This study was carried out across 14 districts in eight Indian states between 2021 and 2023, employing various entomological techniques. Anopheles mosquito species were tested for human blood meal preference and Plasmodium infection using polymerase chain reaction (PCR). Insecticide susceptibility status was assessed according to World Health Organization (WHO) protocols, and key metrics, such as degree of exophily, trap density, human biting rate (HBR), and man-hour density (MHD), were determined to understand mosquito abundance and behavior.

Anopheles culicifacies, a major malaria vector species, was found in all study states. The highest indoor MHD of this species was 11.95, recorded in the Kanker district of Chhattisgarh, whereas 27.16 was the highest outdoor MHD as observed in the Bareilly district of Uttar Pradesh. In Assam and Tripura, Anopheles minimus exhibited differential resting behavior, whereas An. baimaii was found to be exophilic in Kokrajhar, Udalguri, and South Tripura. An. stephensi showed endophilic behavior with an indoor MHD of 4.36 in Barmer. An. minimus exhibited high anthropophagic behavior, with a human blood index of 0.94 in South Tripura. A high sporozoite infection rate was observed in An. baimaii (5.88) compared with the other vector species. An. culicifacies was found to be resistant to alpha-cypermethrin (0.05%) in the Jagdalpur and Kanker districts, with possible resistance in Barmer study sites, and resistant to deltamethrin (0.05%) in Kanker, Surendranagar, and Dahod. An. stephensi showed resistance to multiple insecticides in the North Goa.

An. culicifacies was prevalent in all eight study states, with a higher abundance in Kanker and Bareilly. Changes in the resting behavior of An. minimus in Tripura, and insecticide resistance that has developed in An. culicifacies and An. stephensi against pyrethroids poses a significant concern. The findings of this study will aid in implementing effective vector control strategies in India's pre-elimination efforts against malaria.