Prevalence of Submicroscopic Malaria Parasitaemia among Asymptomatic Populations in Navrongo.

Abstract

The recently observed decrease in cases of malaria achieved through the effective management and control of the disease has been a motivation to strive towards attaining the millennium goal of elimination and eradication of the disease. Asymptomatic infections also referred to as the parasite 'reservoir hosts' which could be microscopic or submicroscopic infections has been implicated in malaria transmission and therefore has become a targeted parasite population for malaria elimination efforts. In this regard, the relative contribution of the microscopic and submicroscopic infections to transmission, which is unknown, needs to be described. This study therefore determined the prevalence of submicroscopic Plasmodium falciparum parasite infections and gametocyte carriage in asymptomatic individuals in northern Ghana. A cross sectional study was conducted using the general population comprising of all age groups, during the dry season in Navrongo Township. Capillary blood samples collected from 209 study participants was used for microscopic identification of parasites and DNA extraction. Submicroscopic infections, for both asexual stage and gametocyte stage were detected by nested reverse transcriptase polymerase chain reaction (RT-PCR). The prevalence of asymptomatic P. falciparum carriage detected was 13.9% (29/209) by RT-PCR and 4.8% (10/209) using microscopy. All the parasites were identified as P. falciparum ring stage with mean parasitaemia of 732 parasites/ l ranging from 40 – 3,520 parasites/ l of blood. Overall submicroscopic prevalence was 9.1% (19/209). P. falciparum gametocytaemia was 3.8%. About 9.1% (19/209) of the asymptomatic infections were eclipsed by microcopy due to its low sensitivity (34.5%). However microscopy was found to be highly specific (100%). Gametocytemia was low, nonetheless, the ability of gametocytes to sustain transmission in an area of seasonal transmission; even at very low densities must be critically examined. Our study has shown that 9.1% (19/209) of the study population carry submicroscopic P. falciparum parasites and also 3.8% carry gametocytes, which persist during the dry season. This study also revealed the importance of conducting active case surveillance to accurately determine submicroscopic malaria prevalence, and highlights the need for updating the malaria guidelines in tracking and treating of sub-microscopic malaria infections.