Epidemiology and infectivity of Plasmodium falciparum and Plasmodium vivax gametocytes in relation to malaria control and elimination.

CLINICAL MICROBIOLOGY REVIEWS, Apr. 2011, p. 377–410 0893-8512/11/$12.00 doi:10.1128/CMR.00051-10 Copyright © 2011, American Society for Microbiology. All Rights Reserved. Vol. 24, No. 2 Epidemiology and Infectivity of Plasmodium falciparum and Plasmodium vivax Gametocytes in Relation to Malaria Control and Elimination Teun Bousema and Chris Drakeley* Department of Immunology & Infection, London School of Hygiene and Tropical Medicine, London W1CE 7HT, United Kingdom INTRODUCTION .......................................................................................................................................................378 GAMETOCYTE BIOLOGY AND MORPHOLOGY ..............................................................................................378 Sequestration of Gametocytes ...............................................................................................................................379 Preparing for Environmental Change..................................................................................................................380 GAMETOCYTOGENESIS.........................................................................................................................................381 What Triggers the Sexual Pathway? ....................................................................................................................381 Host immunity, asexual parasite density, and gametocytogenesis ..............................................................381 Host anemia and gametocytogenesis................................................................................................................382 Other factors associated with gametocytogenesis ..........................................................................................382 Gametocyte Sex Ratios...........................................................................................................................................383 GAMETOCYTE LONGEVITY ..................................................................................................................................383 EPIDEMIOLOGY OF GAMETOCYTES ................................................................................................................384 Age-Dependent Carriage of Gametocytes ............................................................................................................384 Gametocyte Carriage in Relation to Season and Transmission Intensity......................................................384 Other Factors Associated with Gametocyte Carriage........................................................................................385 THE TIP OF THE ICEBERG: SUBMICROSCOPIC GAMETOCYTE DENSITIES .......................................386 Detecting Gametocytes by Microscopy.................................................................................................................386 Molecular Gametocyte Detection Tools ...............................................................................................................386 GAMETOCYTES AND MALARIA TRANSMISSION...........................................................................................387 Gametocyte Density and Mosquito Infection Rates...........................................................................................387 Sampling Issues: When and Where Do Mosquitoes Bite?................................................................................388 ANTIMALARIAL DRUGS AND GAMETOCYTEMIA..........................................................................................389 Effects of Drugs on Gametocytemia .....................................................................................................................389 Gametocytes as an Early Marker for Spread of Drug Resistance...................................................................390 Combination Therapy and Gametocytes..............................................................................................................390 IMMUNE RESPONSES TO GAMETOCYTES AND TRANSMISSION-BLOCKING IMMUNITY..............391 Evidence for Immune Responses Influencing Gametocyte Concentrations....................................................391 Immune Responses Influencing Gametocyte Infectivity....................................................................................392 Prefertilization antigens.....................................................................................................................................392 Postfertilization antigens ...................................................................................................................................392 Evidence for Naturally Acquired Transmission-Blocking Activity...................................................................393 Current Status of Transmission-Blocking Vaccines ..........................................................................................393 P. VIVAX GAMETOCYTES .......................................................................................................................................395 P. vivax Gametocyte Biology and Gametocytogenesis ........................................................................................395 Epidemiology of P. vivax Gametocytes .................................................................................................................395 P. vivax Gametocytes and Mosquito Infection Rates .........................................................................................395 Antimalarial Drugs and P. vivax Gametocytemia ..............................................................................................396 P. vivax Transmission-Blocking Immunity and Transmission-Blocking Vaccines ........................................396 GAMETOCYTES AND MALARIA ELIMINATION STRATEGIES ...................................................................396 Who Should Be Targeted with Drug-Based Interventions? ..............................................................................397 MSAT of Asymptomatic Individuals ....................................................................................................................398 MDA..........................................................................................................................................................................398 Predicted impact of MDA in areas with different levels of endemicity.......................................................398 Choice of drug for MDA ....................................................................................................................................400 Targeted Interventions ...........................................................................................................................................400 CONCLUDING REMARKS ........................................................... (...truncated)