Malaria and helminth co-infections in children living in endemic countries: A systematic review with meta-analysis

Abstract

Background: Current knowledge on the burden of, and interactions between malaria and helminth co-infections, as well as the impact of the dual infections on anaemia, remains inconclusive. We have conducted a systematic review with meta-analysis to update current knowledge as a first step towards developing and deploying coordinated approaches to the control and, ultimately, elimination of malaria-helminth co-infections among children living in endemic countries.

Methodology/principal findings: We searched Medline, Embase, Global Health and Web of Science from each database inception until 16 March 2020, for peer-reviewed articles reporting malaria-helminth co-infections in children living in endemic countries. No language restriction was applied. Following removal of duplicates, two reviewers independently screened the studies for eligibility. We used the summary odds ratio (OR) and 95% confidence intervals (CI) as a measure of association (random-effects model). We also performed Chi-square heterogeneity test based on Cochrane's Q and evaluated the severity of heterogeneity using I2 statistics. The included studies were examined for publication bias using a funnel plot and statistical significance was assessed using Egger's test (bias if p<0.1). Fifty-five of the 3,507 citations screened were eligible, 28 of which had sufficient data for meta-analysis. The 28 studies enrolled 22, 114 children in 13 countries across sub-Saharan Africa, Southeast Asia and South America. Overall, the pooled estimates showed a prevalence of Plasmodium-helminth co-infections of 17.7% (95% CI 12.7-23.2%). Summary estimates from 14 studies showed a lower odds of P. falciparum infection in children co-infected with Schistosoma spp (OR: 0.65; 95%CI: 0.37-1.16). Similar lower odds of P. falciparum infection were observed from the summary estimates of 24 studies in children co-infected with soil transmitted helminths (STH) (OR: 0.42; 95%CI: 0.28-0.64). When adjusted for age, gender, socio-economic status, nutritional status and geographic location of the children, the risk of P. falciparum infection in children co-infected with STH was higher compared with children who did not have STH infection (OR = 1.3; 95% CI 1.03-1.65). A subset of 16 studies showed that the odds of anaemia were higher in children co-infected with Plasmodium and STH than in children with Plasmodium infection alone (OR = 1.20; 95% CI: 0.59-2.45), and were almost equal in children co-infected with Plasmodium-Schistosoma spp or Plasmodium infection alone (OR = 0.97, 95% CI: 0.30-3.14).

Conclusions/significance: The current review suggests that prevalence of malaria-helminth co-infection is high in children living in endemic countries. The nature of the interactions between malaria and helminth infection and the impact of the co-infection on anaemia remain inconclusive and may be modulated by the immune responses of the affected children.

Fig 1. PRISMA flow diagram showing the process undertaken for inclusion and exclusion of studies in the systemic review.

Fig 2. Forest plot showing overall pooled prevalence of Plasmodium-helminth co-infections among children living in LMIC in studies which evaluated the prevalence of both groups of infection.

Fig 3. Funnel plot showing distributions of included studies.

Fig 4. Forest plot showing the risk of asymptomatic/uncomplicated or severe P. falciparum infection in children co-infected with STH compared with children who did not have STH infection.

Fig 5. Forest plot showing the risk of asymptomatic/uncomplicated or severe P. falciparum infection in children co-infected with Schistosoma spp compared with children who did not have Schistosoma infection.

Fig 6. Forest plot showing odds of anaemia in children co-infected with Plasmodium species and pooled STH species compared with those who were infected with P. falciparum alone.

Fig 7. Forest plot showing odds of anaemia in children co-infected with Plasmodium species and pooled Schistosoma spp compared with those who were infected with P. falciparum alone.