Asymptomatic/submicroscopic Plasmodium vivax infection: A systematic review and META-analysis on the hidden challenge for preventing re-establishment of malaria transmission

Abstract

Background: Plasmodium vivax is not only the second most prevalent cause of malaria worldwide, but also the second leading cause of imported malaria in China. This poses a significant threat to preventing the re-establishment of malaria transmission, as the competent vector (Anopheles sinensis) suitable for vivax malaria transmission is widely distributed in China. Particularly, the asymptomatic P. vivax infection as another important source of infection deserves further study, but it is rarely reported.

Methods: PubMed, CNKI and Wanfang databases were systematically searched for asymptomatic P. vivax infection relevant studies published between February 2014 and February 2024. I-squared statistics (I ²) was used to assess heterogeneity among included studies. The pooled prevalence and pooled odds ratio and their corresponding 95 % Confidence Interval were estimated using the random effects model in Review Manager 5.4 software.

Results: Seventy-one eligible studies were included in this analysis. Both study countries (P < 0.001, I ² = 95 %) and diagnostic methods (P = 0.001, I ² = 95 %) were the source of heterogeneity. The rates of asymptomatic malaria infection detected by the gold standard method of microscopy in the countries from Africa, Asia, Oceania and Americas were 9.2 %, 4.8 %, 15.6 % and 14.5 %, respectively. And the corresponding rates of asymptomatic P. vivax infection were 4.0 %, 2.1 %, 10.6 % and 13.0 %. In terms of diagnostic methods, the rate of asymptomatic P. vivax infection (5.6 %) detected by polymerase chain reaction in the population was the highest (P < 0.001).

Conclusion: According to the asymptomatic P. vivax infection worldwide, the countries with the higher rate of asymptomatic infection are the main source of vivax malaria cases imported into China, which indicates a potentially higher potential risk of importation of asymptomatic P. vivax infection. Therefore, it is necessary to develop more sensitive, easier to operate, and more cost-effective techniques to detect and screen asymptomatic malaria infections in a timely manner, so as to prevent re-establishment of malaria transmission.

Keywords: Asymptomatic infections; Malaria; Plasmodium vivax; Re-establishment.

Fig. 1

Flow diagram of search strategy and selection criteria. The figure showed the number of manually screened and excluded literature identified in PubMed, CNKI and Wanfang database.

Fig. 2

Subgroup analysis of the prevalence of asymptomatic P. vivax infections and asymptomatic P. falciparum infections in different continents.

Fig. 3

Map of the distribution of countries included in this study. The information in parentheses after the country name indicates the number of included literature. The literature data of China-Vietnam border (1), Thai-Myanmar border (1) and Myanmar-China border (3) were not shown in the figure. * Map lines delineate study areas and do not necessarily depict accepted national boundaries.

Fig. 4

Subgroup analysis of asymptomatic P. vivax infections and asymptomatic P. falciparum infections under different diagnostic methods.