Advances in Malaria Testing: Screening and Identification of Carriers from Saliva

Abstract

Plasmodium is a parasite that can infect red blood cells and cause flu-like symptoms with malaria infection. Traditional diagnostic methods do not include counting or testing for gametocytes, which can reservoir in the liver for long periods of time and recirculate. These carriers may have no symptoms, but they can transmit infection to others or to mosquitos. Currently, no diagnostic tests have been approved to detect Plasmodium gametocytes in either symptomatic or asymptomatic whole blood samples. Therefore, we developed real-time PCR assays to detect active and carrier states of malaria. The first is a traditional screening test that can detect any of the five Plasmodium species that cause malaria infection. The second is a companion test to differentiate and quantitate Plasmodium falciparum and P. vivax gametocytes in samples of whole blood from patients who may be asymptomatic and present negative results from screening tests. The screening test showed amplification of P. falciparum, P. vivax, P. ovale, P. malariae, and P. knowlesi in saliva with an overall detection limit of 565 copies/μL. The gametocyte test showed no cross-reactivity between P. falciparum and P. vivax with a limit of detection of RNA at 1000 copies/μL.