Asymptomatic Plasmodium infection among primary schoolchildren and Anopheles-mediated malaria transmission: A cross-sectional study in Ouidah; south-western Benin

Adandé A Medjigbodo; Laurette Djossou; Constantin J Adoha; Oswald Y Djihinto; Aurore Ogouyemi-Hounto; Martin J Donnelly; David Weetman; Luc S Djogbénou

doi:10.1016/j.parepi.2023.e00285

Asymptomatic Plasmodium infection among primary schoolchildren and Anopheles-mediated malaria transmission: A cross-sectional study in Ouidah; south-western Benin

Parasite Epidemiol Control. 2023 Jan 19:21:e00285. doi: 10.1016/j.parepi.2023.e00285. eCollection 2023 May.

Authors

Adandé A Medjigbodo¹, Laurette Djossou^{1

2}, Constantin J Adoha³, Oswald Y Djihinto¹, Aurore Ogouyemi-Hounto⁴, Martin J Donnelly⁵, David Weetman⁵, Luc S Djogbénou^{1

2

5}

Affiliations

¹ Tropical Infectious Diseases Research Centre (TIDRC), University of Abomey-Calavi, 01BP 526 Cotonou, Benin.
² Regional Institute of Public Health/ University of Abomey-Calavi, BP 384 Ouidah, Benin.
³ Centre de Recherche Entomologique de Cotonou (CREC), Bénin.
⁴ Health Science Faculty, University of Abomey-Calavi, Cotonou, Benin.
⁵ Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK.

Abstract

Understanding the contribution of asymptomatic Plasmodium carriers in malaria transmission might be helpful to design and implement new control measures. The present study explored the prevalence of asymptomatic and symptomatic Plasmodium infections (asexual and sexual stages) and the contribution of asymptomatic P. falciparum carriers to Anopheles-mediated malaria transmission in Ouidah (Benin). Thick and thin blood smears were examined from finger-prick blood specimens using light microscopy, and the density of both asexual and sexual stages of Plasmodium species was calculated. Infectivity of gametocyte-infected blood samples to Anopheles gambiae was assessed through direct membrane feeding assays. The prevalence of asymptomatic Plasmodium infections was 28.73% (289/1006). All the asymptomatic gametocyte-carriers (19/19), with gametocytaemia ranging from 10 - 1200 gametocytes/μL of blood, were infectious to An. gambiae mosquitoes. The mean oocyst prevalences varied significantly (χ ² = 16.42, df = 7, p = 0.02) among laboratory mosquito strains (6.9 - 39.4%) and near-field mosquitoes (4.9 - 27.2%). Likewise, significant variation (χ ² = 56.85, df = 7, p = 6.39 × 10^-10) was observed in oocyst intensity. Our findings indicate that asymptomatic Plasmodium carriers could significantly contribute to malaria transmission. Overall, this study highlights the importance of diagnosing and treating asymptomatic and symptomatic infection carriers during malaria control programmes.

Keywords: An. gambiae; An., Anopheles; Asymptomatic; CX, Carbamates; DDT, Dichlorodiphenyltrichloroethane; DMFAs, Direct membrane feeding assays; G119S, Glycine substitution by Serine at codon 119; Gametocyte; IPT, Intermittent Preventive Therapy; IRS, Indoor residual spraying; ITNs, Insecticide-treated bed nets; L1014F, Leucine substitution by Phenylalanine at codon 1014; MDA, Mass Drug Administration; MSaT, Mass Screening and Treatment; NMCP, National Malaria Control Programme; OP, Organophosphates; PYR, Pyrethroids; Plasmodium falciparum; Transmission; USA, United States of America; WBCs, White blood cells; WHO, Word Health Organization; s.l., sensu lato; s.s., sensu stricto; spp., species.