Age-specific malaria vulnerability and transmission reservoir among children

Abstract

Purpose: The pediatric population, especially under-five children, is highly susceptible to malaria and accounts for 76 % of global malaria deaths according to the World Malaria Report 2022. The purpose of this manuscript is to discuss the various factors involved in the susceptibility of the pediatric population to Malaria and the importance of this age group for malaria elimination.

Methodology: Data on pediatric malaria epidemiology that includes prevalence, risk factors, immune factors, socioeconomic factors, control methods, etc. were extracted from published literature using PubMed and Google Scholar. This data was further correlated with malaria incidence data from the World Health Organization (WHO) and the National Center for Vector Borne Diseases Control (NCVBDC).

Results: The younger age group is vulnerable to severe malaria due to an immature immune system. The risk of infection and clinical disease increases after the waning of maternal immunity. In the initial years of life, the developing brain is more susceptible to malaria infection and its after-effects. The pediatric population may act as a malaria transmission reservoir due to parasite density and asymptomatic infections. WHO recommended RTS,S/AS01 has limitations and may not be applicable in all settings to propel malaria elimination.

Conclusion: The diagnosis of malaria is based on clinical suspicion and confirmed with microscopy and/or rapid diagnostic testing. The school-age pediatric population serves as a transmission reservoir in the form of asymptomatic malaria since they have acquired some immunity due to exposure in early childhood. Targeting the hidden reservoir in the pediatric population and protecting this vulnerable group will be essential for malaria elimination from the countries targeting elimination.

Keywords: Asymptomatic malaria; Malaria elimination; Malaria pathogenesis; Malaria transmission reservoir; Pediatric malaria.

Fig. 1

Immune factors in Pediatric Malaria: Due to lack of acquired functional immunity, Lower INF-α, impaired monocytes, Low NK cells and complement concentration, malaria susceptibility is increased in children below 5 years of age. Because of low complement concentration, the antibody-based killing of gametocytes gets hampered in children, including in older children. They can act as parasite reservoirs due to gametocyte survival for extended periods.

Fig. 2

The biomarkers for different clinical presentations of pediatric malaria: Potential biomarkers have been identified for different clinical presentations. Fractalkine, Monokine induced by gamma (MIG)/ (CXCL9), and Neopterin were found to be good indicators of asymptomatic infections. A combination of three biomarkers, soluble urokinase-type Plasminogen Activator (suPAR), Pentraxin 3 (PTX3), and soluble triggering receptor expressed on myeloid cells 1 (sTREM-1), is a good indicator of uncomplicated plasmodium infection. Along with other biomarkers Neopterin, suPAR, and Fractalkine are found to be good predictors of severe malaria. + represents increase and – represents decrease.

Fig. 3

Age-group specific interventions for sustained Malaria control and elimination: Protecting the under-five vulnerable group and targeting the parasite reservoir in older children with particular interventions will help achieve the target of malaria control and elimination.