Asymptomatic Plasmodium falciparum malaria and gametocyte carriage are common in Coastal Kenya

Abstract

Adequate malaria diagnosis and treatment remain a major problem in rural sub Saharan Africa. Molecular parasite detection has shown that submicroscopic Plasmodium falciparum asexual and gametocytes are common in patients, and can infect mosquitoes in low endemic areas. The significance of the infectious reservoir of malaria in the general population remains unknown. In this study we investigated submicroscopic asexual parasitaemia and gametocytaemia in inhabitants of areas of hypo-endemic and seasonal malaria in which no molecular analysis on malaria survey has been done before. Cross-sectional stuies during the staging of two clinical trials clinical trial in Mokowe and Lamu, Coastal Kenya were conducted in the dry and wet seasons of 2010. Finger prick blood samples used to determine the prevalence of Plasmodium falciparum parasites by microscopy, Fluorescence In-situ hybridization (FISH), rapid diagnostic test and real time nucleic acid sequence-based amplification (QT-NASBA). A total of 450 individuals participated in the surveys of whom, 2.7% had microscopically confirmed asexual parasites while 2.4% had gametocytes. In contrast, FISH revealed that 8.9% (29/327) and QT-NASBA 24.6% (59/240) of the individuals harbored asexual parasites and 29.2% (70/240) gametocytes. There were a few cases of mixed infection with Plasmodium malariae, 1.8% (8/ 450) by microscopy and 4% (13/327) by FISH. No age dependency or seasonality was observed in the submicroscopic parasite carriage. In conclusion, molecular detection techniques disclose that carriage of submicroscopic asexual parasite and gametocyte is relatively common in these low transmission areas and that submicroscopic gametocytaemia is likely to be responsible for maintaining malaria transmission in the study area.

Keywords: submicroscopic, gametocytaemia, FISH, rapid diagnostic test, QT-NASBA

Afr J Health Sci. 2013; 26:314-323