Seasonal bionomics of Anopheles mosquitoes in the cold-western Himalayan region of Kangra, Himachal Pradesh, India

Malaria remains a major global public health concern. Climatic warming in Himachal Pradesh, a hilly and forested state in India, may increase the suitability for mosquito-borne diseases. Kangra district, historically reporting low anopheline densities, is projected to develop conditions favorable for malaria transmission in the coming decade. This study evaluated anopheline vector prevalence, seasonality, and climatic influences to assess the district’s vulnerability in the context of India’s malaria elimination target for 2030. From October 2017 to September 2019, vector–climate associations were investigated through longitudinal surveys in six villages and cross-sectional surveys in 22 villages of Kangra district. Temperature and relative humidity were recorded indoors, outdoors, and in water bodies using Onset HOBO data loggers. Immature stages were surveyed in potential breeding habitats, and adult mosquitoes were morphologically identified up to species level. Blood meal sources of fully fed and half-gravid female Anopheles mosquitoes (n = 670) were determined using human and bovine antisera by the simple precipitin test. Exploratory statistical analyses were conducted to assess associations between climatic variables (monthly mean temperature, relative humidity, and rainfall) and mosquito abundance. Anopheles culicifacies s.l. was the primary vector, with man-hour density (MHD) peaking at 15 in September and declining to zero by May. The An. fluviatilis complex was present throughout the year, with peak MHD values of 31 in May and 30 in September. Post-monsoon survival was highest (30% for An. culicifacies and 34% for An. fluviatilis, with longevity up to 42 days), decreasing sharply during winter (6–8%) and the monsoon (4–6%). Anthropophagic indices were low for An. culicifacies (0.08) and An. fluviatilis (0.09). Blood meal sources were identified in 95% (638/670) of females. Six prevalent and fifteen uncommon anopheline species were recorded. Larval and pupal abundance differed significantly among streams, ditches, and rivulets (P < 0.05). Anopheles fluviatilis s.l. persists year-round under favorable microclimatic conditions, whereas An. culicifacies s.l. exhibits strong seasonality and rainfall dependence, remaining absent during the dry summer months. Both vectors are predominantly zoophagic, rest mainly in cattle sheds, and peak during May and September, posing a sustained malaria transmission risk despite low anthropophagy and sporadic secondary vector presence.