PCR orLowLevel Detection of Malaria Parasites in Blood

Detection of malaria parasites to as low a level as one organism is essential for epidemiological surveillance and effectiveness of thera peutic treatments. Classical detection of the parasites has always relied on microscopic examination, a method that is relatively simple and inexpensive but subjective and often lacking sensitivity. Alternative detection by serological methods and by nucleic acid hybridization have been introduced in recent years and are constantly improving. The detection of parasites by DNA hybridization depends largely on the ability of a DNA probe to identify a parasite DNA sequence that is absent in the host and other closely related parasites. Several spe cific DNA probes have been developed for detection of P. falciparum malaria (1 –8 ), which could reliably identify the parasites varying in number from 50‐5000. However, a specific P. falciparum DNA sequence can be amplified by the polymerase chain reaction (PCR) to millions of copies (9 ), and thus the PCR allows detection of as low a level as a single parasite.