Moving population is a challenge for malaria elimination in India: A cross-sectional study to assess malaria parasite infections in walking pilgrims in western Rajasthan, India.

Objectives: India is vigorously pursuing malaria elimination by 2030 and one of the key challenges is how to prevent the malaria risk associated with long-distance migrations of populations from endemic to non-endemic areas. Millions of pilgrims walking to the holy Ramdevra temple stay in temporary shelters along the route in district of Jaisalmer, Rajasthan state in western India. The main pilgrimage period coincides with the post-monsoon period with elevated vector densities. We investigated this situation to assess the potential risk posed by migrant pilgrims along the four highways in the temple district in disseminating malaria infections associated with their annual movements.

Methods: A cross-sectional study was conducted for screening malaria in walking pilgrims from neighboring states at selected sites and a follow-up study for screening residents in Rajasthan from 2021 to 2023. The study comprises state entry routes, Ramdevra shrine, and pilgrimage route villages situated in western Rajasthan. Epidemiologic and entomologic surveillance was conducted during the "fair" period (August-September) and in pilgrimage route villages in three different seasons of the year to assess malaria in humans and the vector's infectivity.

Results: Of the 5251 individuals tested for malaria, a total of 76 (1.4%) tested positive for malaria, of whom 40.7% were infected with (n = 31), 36.8% with (n = 28), and 22.3% with and (n = 17). Anopheles density was highest during the fair season, peaking in August. exhibited a higher human blood index (0.65) than (0.50). No mosquitoes were found positive for parasites.

Conclusions: Up to 1.5% of pilgrims carried malaria parasites, posing a risk of spreading malaria to surrounding communities that otherwise would have low or no malaria burden. Moving populations pose the risk of local malaria transmission and reintroduction to the areas undergoing elimination. Sentinel point surveillance at the border of states will be helpful for states to share information on malaria and subsequently for the prevention of malaria transmission.