Modeling the Effects of Relapse in the Transmission Dynamics of Malaria Parasites
Águas R., Ferreira MU., Gomes MGM.
<jats:p>Often regarded as “benign,”<jats:italic>Plasmodium vivax</jats:italic>infections lay in the shadows of the much more virulent<jats:italic>P. falciparum</jats:italic>infections. However, about 1.98 billion people are at risk of both parasites worldwide, stressing the need to understand the epidemiology of<jats:italic>Plasmodium vivax</jats:italic>, particularly under the scope of decreasing<jats:italic>P. falciparum</jats:italic>prevalence and ecological interactions between both species. Two epidemiological observations put the dynamics of both species into perspective: (1) ACT campaigns have had a greater impact on<jats:italic>P. falciparum</jats:italic>prevalence. (2) Complete clinical immunity is attained at younger ages for<jats:italic>P. vivax</jats:italic>, under similar infection rates. We systematically compared two mathematical models of transmission for both Plasmodium species. Simulations suggest that an ACT therapy combined with a hypnozoite killing drug would eliminate both species. However,<jats:italic>P. vivax</jats:italic>elimination is predicted to be unstable. Differences in age profiles of clinical malaria can be explained solely by<jats:italic>P. vivax</jats:italic>'s ability to relapse, which accelerates the acquisition of clinical immunity and serves as an immunity boosting mechanism.<jats:italic>P. vivax</jats:italic>transmission can subsist in areas of low mosquito abundance and is robust to drug administration initiatives due to relapse, making it an inconvenient and cumbersome, yet less lethal alternative to<jats:italic>P. falciparum</jats:italic>.</jats:p>