Figure 2

Malaria parasite developmental cycles and possible targets for sustainable malaria control and elimination strategies. Sporozoites are transmitted when female Anopheles mosquitoes take a human blood meal, where after the ~100 parasites transmitted infect human liver cells and mature for up to 14 days. Hundreds of thousands of daughter merozoites are subsequently released into the bloodstream to infect human erythrocytes and initiate the rapid and massive asexual replication cycle. Single parasites mature within 48 hours from rings to schizonts, releasing up to 32 daughter merozoites. Within a short amount of time, billions of parasites can be present in a patient’s bloodstream, resulting in the pathogenesis of the disease. Only a few parasites (<1,000) are required to develop into sexual gametocyte forms and allow transmission of the parasites back to the mosquitoes to undergo sexual replication in the insect vector. Targets within this complete developmental cycle that are viable in sustained control and elimination strategies include population bottlenecks (A and B) resulting in a block in transmission; targeting hypnozoite forms (Plasmodium vivax) or liver-stage maturation (C) and D, targeting the massive asexual replication cycle to treat patients symptomatic of the disease.