Heterogeneous mosquito exposure increases Plasmodium vivax and Plasmodium falciparum co-infections: a modelling study

In malaria-endemic regions, Plasmodium vivax and Plasmodium falciparum coexist and may interact. For instance, fevers induced by P. falciparum might activate dormant P. vivax parasites and concurrent radical cure of both species has been proposed to prevent relapses. Heterogeneous mosquito exposure may contribute to the dependence of both parasites. We conducted a literature review on their respective prevalence and that of co-infections. The data revealed a positive correlation between P. vivax and P. falciparum prevalence, and co-infection prevalences exceeding expectations assuming infections occur independently. We used the review data to fit a compartmental model of co-infections that features heterogenous mosquito exposure. The fit suggests that heterogeneous exposure sufficiently explains the observed departure from independence. Finally, we performed simulations under the model assessing the impact on P. vivax prevalence of the activation-by-fever hypothesis and the radical cure proposition. We demonstrated a moderate impact of allowing P. falciparum fevers to reactivate P. vivax and a substantial impact of treating P. falciparum cases with radical cure. Our model highlights dependence between P. falciparum and P. vivax and emphasizes the influence of heterogeneous mosquito exposure. This simple framework can inform the design of more complex models assessing integrated malaria control strategies in coendemic regions.