A systematic review ofSchistosoma intercalatum: an obscure causative agent of human schistosomiasis

Abstract

AbstractBackgroundHuman schistosomiasis caused bySchistosoma intercalatumis poorly understood compared to other species of public health importance, such asS. haematobium, S. mansoni, andS. japonicum. The restricted distribution ofS. intercalatumin Africa, its perceived low virulence, and poor understanding of its pathological consequences are possible reasons for this neglect. However, schistosomiasis as a public health problem cannot be eradicated without adequate knowledge of existing species of schistosomes and the biological interactions between them, their hosts, and the environment. Current information onS. intercalatumis often confused with the previousS. intercalatum(Lower Guinea strain) which has now been described asS. guineensisn. sp. TheS. intercalatum(Zaire strain) with known foci only in Democratic Republic of the Congo (DRC) is now recognized as the ‘true’S. intercalatumspecies. Investigators not conversant with the present status of both species still get confused in understanding the literature hence this review. It is essential to discuss available knowledge onS. intercalatumand highlight gaps that are critical for deepening our understanding of the parasite in the DRC.MethodsThus, we systematically review existing available literature onS. intercalatumobtained from PubMed Central, Web of Science, Embase, and Scopus databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Relevant publications were screened and publications reportingS. intercalatumfrom other than the DRC were excluded. Eligible studies on the epidemiology and biology ofS. intercalatumwere reviewed.ResultsBased on 38 publications that met our inclusion criteria, we confirm thatS. intercalatumis the most neglected amongSchistosomaspecies responsible for human schistosomiasis. We discuss our synthesis of the available information in the context of the distribution, biology, pathology, and genetics ofS. intercalatum. Also highlighted are outstanding questions onS. intercalatumpopulation genomics, hybridization with otherSchistosomaspecies, snail vector host, zoonotic epidemiology, and pathology.ConclusionThe review calls for a rekindling of research interest in the parasite and the need to answer fundamental questions that can deepen our understanding of the parasite epidemiology, disease ecology, and environmental interactions to help in control strategies and elimination.