Detecting Malaria Parasites outside the Blood

In 1880, Charles Laveran first visualized the protozoan parasite that causes malaria in a smear of blood under a microscope, and from the early decades of the 20th century to date, microscopy has been the mainstay of malaria detection. In laboratories throughout the world, routine diagnosis is carried out by microscopic examination of Giemsa-stained blood films for the intraerythrocytic asexual stages of the Plasmodium parasite that are indicative of active malaria infection. Clinical trials of antimalarial interventions also rely on good-quality slide reading for endpoint determination. In recent years, molecular methods for detecting the DNA of Plasmodium species that infect humans have been incorporated into some trial protocols to increase the sensitivity of detection (polymerase chain reaction [PCR] is typically 1–2 orders of magnitude more sensitive than microscopy), to distinguish genetically distinct parasite lineages, and to answer additional questions, such as the prevalence of mutations associated with drug resistance [1, 2]