Contribution of Asymptomatic Plasmodium Infections to the Transmission of Malaria in Kayin State, Myanmar

Author(s): Chaumeau, Victor; Kajeechiwa, Ladda; Fustec, Benedicte; Landier, Jordi; Nyo, Saw Naw; Hsel, Saw Nay; Phatharakokordbun, Phabele; Kittiphanakun, Prapan; Nosten, Suphak; Thwin, May Myo; Tun, Saw Win; Wiladphaingern, Jacher; Cottrell, Gilles; Parker, Daniel M; Minh, Myo Chit; Kwansomboon, Nittpha; Metaane, Selma; Montazeau, Celine; Kunjanwong, Kitti; Sawasdichai, Sunisa; Andolina, Chiara; Ling, Clare; Haohankhunnatham, Warat; Christiensen, Peter; Wanyatip, Sunaree; Konghahong, Kamonchanok; Cerqueira, Dominique; Imwong, Mallika; Dondorp, Arjen M; Chareonviriyaphap, Theeraphap; White, Nicholas J; Nosten, Francois H; Corbel, Vincent | Abstract: The objective of mass antimalarial drug administration (MDA) is to eliminate malaria rapidly by eliminating the asymptomatic malaria parasite reservoirs and interrupting transmission. In the Greater Mekong Subregion, where artemisinin resistant P. falciparum is now widespread, MDA has been proposed as an elimination accelerator, but the contribution of asymptomatic infections to malaria transmission has been questioned. The impact of MDA on entomological indices has not been characterised previously. MDA was conducted in four villages in Kayin State (Myanmar). Malaria mosquito vectors were captured three months before, during and three months after MDA, and their Plasmodium infections were detected by PCR. The relationship between the entomological inoculation rate, the malaria prevalence in humans determined by ultra-sensitive PCR, and MDA was characterised by Generalized Estimating Equation regression. Plasmodium falciparum and P. vivax asymptomatic infections were cleared by MDA. The P. vivax entomological inoculation rate was reduced 12.5 fold (95%25CI= [1.6; 100]) but the reservoir of asymptomatic P. vivax reconstituted within three months presumably because of relapses. This was coincident with a 5.3-fold (95%25CI= [4.8; 6.0]) increase in the vector infection rate. Asymptomatic infections are a major source of malaria transmission in Southeast Asia.