Global trend of Plasmodium malariae and Plasmodium ovale spp. malaria infections in the last two decades (2000-2020): a systematic review and meta-analysis

Abstract

Background: Recent studies indicate that the prevalence of non-falciparum malaria, including Plasmodium malariae and Plasmodium ovale spp., is increasing, with some complications in infected individuals. The aim of this review is to provide a better understanding of the malaria prevalence and disease burden due to P. malariae and P. ovale spp.

Methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and the Joanna Briggs Institute prevalence study assessment tool were used to select and evaluate the studies, respectively. Six databases: PubMed, WHOLIS, Wiley Library, ScienceDirect, Web of Science and Google Scholar were used to screen articles published during the period January 2000-December 2020. The pooled prevalence estimates for P. malariae and P. ovale spp. were analysed using a random-effects model and the possible sources of heterogeneity were evaluated through subgroup analysis and meta-regression.

Results: Out of the 3297 studies screened, only 113 studies were included; among which 51.33% were from the African Region. The P. malariae and P. ovale spp. pooled prevalence were 2.01% (95% CI 1.31-2.85%) and 0.77% (95% CI 0.50-1.10%) respectively, with the highest prevalence in the African Region. P. malariae was equally distributed among adults (2.13%), children (2.90%) and pregnant women (2.77%) (p = 0.862), whereas P. ovale spp. was more prevalent in pregnant women (2.90%) than in children ≤ 15 years (0.97%) and in patients > 15 years old (0.39%) (p = 0.021). In this review, data analysis revealed that P. malariae and P. ovale spp. have decreased in the last 20 years, but not significantly, and these species were more commonly present with other Plasmodium species as co-infections. No difference in prevalence between symptomatic and asymptomatic patients was observed for either P. malariae or P. ovale spp.

Conclusion: Our analysis suggests that knowledge of the worldwide burden of P. malariae and P. ovale spp. is very important for malaria elimination programmes and a particular focus towards improved tools for monitoring transmission for these non-falciparum species should be stressed upon to deal with increased infections in the future.

Keywords: Malaria infections; Meta-analysis; Plasmodium malariae; Plasmodium ovale spp.; Prevalence.

Fig. 1

PRISMA flow chart of study selection for review

Fig. 2

a Distribution of included studies depending on the year. b Map of WHO regions where included studies were conducted. The regionalization used on this map is that of the WHO Global Health Observatory map. WHO Member States are grouped into six regions. The European region is not represented here, as it was not included in our study. (AFR: African Region, WPR: Western Pacific Region AMR: Region of the Americas, SEAR: South-East Asia Region, EMR: Eastern Mediterranean Region). n: number of included studies in each region. Pm: Plasmodium malariae, Po: Plasmodium ovale spp.

Fig. 3

Forest plots of prevalence between asymptomatic and symptomatic participants: a P. malariae; b P. ovale spp. The prevalence of each study is represented by a spot and the horizontal bar centred by the prevalence gives the dispersion of the data

Fig. 3

Forest plots of prevalence between asymptomatic and symptomatic participants: a P. malariae; b P. ovale spp. The prevalence of each study is represented by a spot and the horizontal bar centred by the prevalence gives the dispersion of the data

Fig. 4

Forest plots of Plasmodium prevalence in studies conducted in specific groups (pregnant women, children under 15 and participants over 15 years old). a P. malariae prevalence, b P. ovale spp. prevalence. The prevalence of each study is represented by a spot and the horizontal bar centred by the prevalence gives the dispersion of the data

Fig. 5

Meta-regression of prevalence over the period of data collection: a meta-regression of P. malariae prevalence, b meta-regression of P. ovale spp. prevalence