Evaluation of Plasmodial Species in Humans and in Malaria Vectors in the Central Arrondissement of Abomey-Calavi and in the Health Zone of Cotonou I and IV in Benin, West Africa

Abstract

Background: Malaria remains a recurrent public health disease. Several plasmodial species are vigorously implicated in malaria infection. The aim of this study is to assess the risk of exposure to malaria in the populations of southern Benin, more specifically in the central arrondissement of Abomey-calavi and in the Cotonou I and IV health zones, by identifying the plasmodial species responsible for malaria. Method: Mosquito collections were carried out in July 2021 following nocturnal captures of mosquitoes from volunteer subjects and intradomiciliary spraying at dawn on the days following the capture nights. At the same time, thick drop-positive blood samples were collected from tributary healthcare facilities per work zone. The species of mosquitoes collected were identified on the basis of their morphological characteristics, and P. falciparum (Pf) CSP antigens were screened for in Anopheles using the enzyme-linked immunosorbent assay (ELISA) technique. PCRs were performed to detect Plasmodium infection in anopheles, with characterization of the anopheles species involved and identification of the plasmodial species involved. The XN 31 automated system was used to identify plasmodial species in blood samples. Results: A total of 112 female anopheles were collected in Abomey-calavi and 264 in Cotonou. The An. gambiae sl complex was the predominant anopheles species, accounting for 20.1% in Abomey-calavi and 15.5% in Cotonou. An. pharoensis is found with a low percentage in Abomey-calavi (0.2%). Following molecular characterization of the An. gambiae sl complex, An. coluzzii was the predominant species in Cotonou (82.2%), in contrast to Abomey-calavi where An. gambiae was in the majority (82.1%). The sporozoites infection rate and entomological inoculation rate were 4.5% and 0.3 bi/h/night or 125 bi/h/year respectively in Abomey-calavi, and 0.75% and 0.12 bi/h/night or 43.8 bi/h/year in Cotonou. Of these anopheles obtained in Abomey-calavi, 17 were carriers of P. falciparum ( Pf ), 02 of Plasmodium vivax ( Pv ) and 01 of P. malariae ( Pm ). In Cotonou, 07 were carriers of P. falciparum and 03 of Plasmodium vivax . In the same period, 118 blood samples were collected in Abomey-calavi and 183 in Cotonou. After analysis, Pf , Po and P. malariae ( Pm ) were found singly or mixed in the blood samples collected and we have the next plasmodial formula: Pf = 97.54%; Po = 1.64%; Pm = 0.82% was obtained in Abomey-calavi, followed by Pf = 96.08%; Po = 3.48%; Pm = 0.43%. Conclusion: The present study mentions the presence of Pv alongside Pf , Pm and Po in Anopheles . This finding was made in vectors and not in humans, who carried the three usually encountered, Pv , Pm and Po . It is therefore important to extend research work to other regions and health centers in the country, in order to obtain a broader estimate of the plasmodia profile.