TY - JOUR T1 - The epidemiology of subclinical malaria infections in South-East Asia: findings from cross-sectional surveys in Thailand-Myanmar border areas, Cambodia, and Vietnam. JF - Malar J Y1 - 2015 A1 - Imwong, Mallika A1 - Nguyen, Thuy Nhien A1 - Tripura, Rupam A1 - Peto, Tom J A1 - Lee, Sue J A1 - Lwin, Khin Maung A1 - Suangkanarat, Preyanan A1 - Jeeyapant, Atthanee A1 - Vihokhern, Benchawan A1 - Wongsaen, Klanarong A1 - Van Hue, Dao A1 - Dong, Le Thanh A1 - Nguyen, Tam-Uyen A1 - Lubell, Yoel A1 - von Seidlein, Lorenz A1 - Dhorda, Mehul A1 - Promnarate, Cholrawee A1 - Snounou, Georges A1 - Malleret, Benoit A1 - Rénia, Laurent A1 - Keereecharoen, Lilly A1 - Singhasivanon, Pratap A1 - Sirithiranont, Pasathorn A1 - Chalk, Jem A1 - Nguon, Chea A1 - Tran Tinh Hien A1 - Day, Nicholas A1 - White, Nicholas J A1 - Dondorp, Arjen A1 - Nosten, Francois KW - ADOLESCENT KW - Adult KW - Asia, Southeastern KW - Asymptomatic Infections KW - Child KW - Child, Preschool KW - cross-sectional studies KW - Female KW - Humans KW - Infant KW - Malaria KW - Male KW - Plasmodium falciparum KW - Plasmodium vivax KW - Young adult AB -

BACKGROUND: The importance of the submicroscopic reservoir of Plasmodium infections for malaria elimination depends on its size, which is generally considered small in low transmission settings. The precise estimation of this reservoir requires more sensitive parasite detection methods. The prevalence of asymptomatic, sub-microscopic malaria was assessed by a sensitive, high blood volume quantitative real-time polymerase chain reaction method in three countries of the Greater Mekong Sub-region.

METHODS: Cross-sectional surveys were conducted in three villages in western Cambodia, four villages along the Thailand-Myanmar border and four villages in southwest Vietnam. Malaria parasitaemia was assessed by Plasmodium falciparum/pan malaria rapid diagnostic tests (RDTs), microscopy and a high volume ultra-sensitive real-time polymerase chain reaction (HVUSqPCR: limit of detection 22 parasites/mL). All villagers older than 6 months were invited to participate.

RESULTS: A census before the surveys identified 7355 residents in the study villages. Parasite prevalence was 224/5008 (4 %) by RDT, 229/5111 (5 %) by microscopy, and 988/4975 (20 %) when assessed by HVUSqPCR. Of these 164 (3 %) were infected with P. falciparum, 357 (7 %) with Plasmodium vivax, 56 (1 %) with a mixed infection, and 411 (8 %) had parasite densities that were too low for species identification. A history of fever, male sex, and age of 15 years or older were independently associated with parasitaemia in a multivariate regression model stratified by site.

CONCLUSION: Light microscopy and RDTs identified only a quarter of all parasitaemic participants. The asymptomatic Plasmodium reservoir is considerable, even in low transmission settings. Novel strategies are needed to eliminate this previously under recognized reservoir of malaria transmission.

VL - 14 U1 - http://www.ncbi.nlm.nih.gov/pubmed/26424000?dopt=Abstract M3 - 10.1186/s12936-015-0906-x ER -