Mass drug administration with dihydroartemisinin-piperaquine was able to rapidly interrupt malaria transmission in four villages in Myanmar where the prevalence of asymptomatic infection was high, but researchers reported that infections from a common malaria parasite recurred within months, demonstrating the importance of asymptomatic infections to malaria transmission in Southeast Asia.
“The objective of mass antimalarial drug administration (MDA) is to eliminate malaria rapidly by eliminating the asymptomatic malaria parasite reservoirs and interrupting transmission,” the researchers wrote in The Journal of Infectious Diseases.
“In the Greater Mekong Subregion, where artemisinin-resistant [Plasmodium] 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 characterized previously.”
From 2013 to 2015, the researchers provided treatment doses of dihydroartemisinin-piperaquine and a single low dose of primaquine to four villages in the Kayin State of Myanmar. Additionally, they captured mosquitoes before, during after the intervention and tested them for Plasmodium infections, then estimated the relationship between the entomological inoculation rate, malaria prevalence in humans and MDA.
They found that the prevalence of P. falciparum and P. vivax asymptomatic infection was reduced to zero during the MDA and remained below 1% for 3 months afterward. The MDA also led to a 12.5-fold reduction in P. vivax entomological inoculation rate — a measure of transmission intensity. However, the reservoir of asymptomatic P. vivax reconstituted within 3 months, “presumably because of relapses,” the researchers wrote, and there was a coinciding 5.3-fold increase in the vector infection rate.
“An argument against the use of MDA as an elimination accelerator has been that sub-microscopic parasite densities do not transmit malaria. This study describes a unique opportunity to assess the contribution of asymptomatic malaria infection to the vectoral transmission of malaria in a low transmission setting of Southeast Asia,” the researchers wrote.
“In low transmission settings of Southeast Asia, the asymptomatic parasites’ reservoir contributes to the transmission of malaria and its persistence in affected communities,” they wrote. “Three monthly rounds of MDA with dihydroartemisinin-piperaquine and a single low dose of primaquine is an effective intervention which interrupts the transmission cycle of malaria rapidly in these areas where the prevalence of infection is relatively high and where artemisinin-resistance in P. falciparum is established. Without primaquine radical cure, vivax malaria rapidly returns because of relapse.” – by Bruce Thiel
Disclosures: The researchers report no relevant financial disclosures.