Date Published: April 25, 2019
Publisher: Public Library of Science
Author(s): Rokhaya Sane, Cheikh Talla, Babacar Diouf, Fatoumata Diene Sarr, Nafissatou Diagne, Joseph Faye, Abdoulaye Badiane, Pape Mbacké Sembène, Cheikh Sokhna, Aissatou Toure-Balde, Makhtar Niang, Luzia Helena Carvalho.
Submicroscopic Plasmodium infections are common in malaria endemic countries, but very little studies have been done in Senegal. This study investigates the genetic diversity and complexity of submicroscopic P. falciparum infections among febrile patients in low transmission areas in Senegal.
Hundred and fifty blood samples were collected from febrile individuals living in Dielmo and Ndiop (Senegal) between August 2014 and January 2015, tested for microscopic and sub-microscopic P. falciparum infections and characterized for their genetic diversity and complexity of infections using msp-1 and msp-2 genotyping.
Submicroscopic P. falciparum infections were 19.6% and 25% in Dielmo and Ndiop, respectively. K1 and 3D7 were the predominant msp-1 and msp-2 allelic types with respective frequencies of 67.36% and 67.10% in microscopic isolates and 58.24% and 78% in submicroscopic ones. Frequencies of msp-1 allelic types were statistically comparable between the studied groups (p>0.05), and were respectively 93.54% vs 87.5% for K1, 60% vs 54.83% for MAD20 and 41.93% vs 22.5% for RO33 while frequencies of msp-2 allelic types were significantly highest in the microscopy group for FC27 (41.93% vs 10%, Fisher’s Exact Test, p = 0.001) and 3D7 (61.29% vs 32.5%, Fisher’s Exact Test, p = 0.02). Multiplicities of infection were lowest in submicroscopic P. falciparum isolates.
The study revealed a high submicroscopic P. falciparum carriage among patients in the study areas, and that submicroscopic P. falciparum isolates had a lower genetic diversity and complexity of malaria infections.
The scale-up of malaria control interventions has substantially reduced malaria burden and transmission across several malaria endemic countries over the past 15 years with the number of malaria infections and malaria-related mortality that dropping significantly . In Senegal, similar results were obtained with a globally significant reduction of the proportional malaria-related morbidity and mortality from 35.72% and 28.72% in 2001 to 28.72% and 1.73% in 2017, respectively despite significant disparities between regions . In fact, while malaria elimination strategies have been implemented in the North, applied preventive and control measures had limited impact in the South and Southeast regions where malaria transmission is still active .
To date, very few studies have investigated the genetic structure of submicroscopic malaria parasites populations circulating in endemic countries. Our study aimed at filling this major gap and evaluated the genetic diversity, allelic frequency of msp-1 and msp-2, and complexity of submicroscopic P. falciparum infections in isolates from patients in Dielmo and Ndiop, two low-transmission areas in Senegal.
The findings revealed a high proportion of submicroscopic P. falciparum carriage among patients and a low genetic diversity and MOI associated with submicroscopic P. falciparum infections.