Maximizing Impact: Can Interventions to Prevent Clinical Malaria Reduce Parasite Transmission?

Abstract

Malaria interventions may reduce the burden of clinical malaria disease, the transmission of malaria parasites, or both. As malaria interventions are developed and evaluated, including those interventions primarily targeted at reducing disease, they may also impact parasite transmission. Achieving global malaria eradication will require optimizing the transmission-reducing potential of all available interventions. Herein, we discuss the relationship between malaria parasite transmission and disease, including mechanisms by which disease-targeting interventions might also impact parasite transmission. We then focus on three malaria interventions with strong evidence for reducing the burden of clinical malaria disease and examine their potential for also reducing malaria parasite transmission.

Keywords: Plasmodium falciparum; RTS,S/AS01 vaccine; school-based preventive treatment; seasonal malaria chemoprevention.

Figure 1.. Potential intervention effect on Plasmodium falciparum transmission in relation to age.

(A) In moderate- to high-transmission settings, the prevalence of P. falciparum infections changes with age [62]. The proportion of those infections that lead to clinical malaria disease (dark gray), as opposed to remaining sub-clinical or asymptomatic (light gray), decreases with age [63,64]. Both types of infection contribute to transmission (diagonal lines), which also varies with age due to changes in the relative infectiousness and duration of the infections and the frequency of bites by malaria vectors [5,8]. The proportions shown here are hypothetical, and the exact proportions will vary across geographic locations according to epidemiological, environmental and ecological factors [,–64]. (B) In this setting, an intervention that prevents P. falciparum infection in children from five to ten years of age (blue) will prevent more human-to-mosquito transmission of P. falciparum than an intervention that prevents infection in children under five years of age (orange).