Competition for red blood cells can enhance Plasmodium vivax parasitemia in mixed-species malaria infections
McQueen, P.G.; McKenzie, F.Ellis.
American Journal of Tropical Medicine and Hygiene 75(1): 112-125
2006
ISSN/ISBN: 0002-9637 PMID: 16837717 Document Number: 600827
We assess the consequences of competition for red blood cells (RBCs) in co-infections with the two major agents of human malaria, Plasmodium vivax and Plasmodium falciparum, using differential equations to model the population dynamics of RBCs and parasites. P. vivax parasitizes only the youngest RBCs, but this can reduce the broader RBC population susceptible to P. falciparum. We found that competition for RBCs typically causes one species to suppress the other, depending on their relative reproduction rates and timing of inoculation. However, if the species' reproduction rates are nearly equal, transient increases in RBC production stimulated by the presence of P. falciparum may boost P. vivax parasitaemia above its single-species infection level. Conversely, P. falciparum parasitaemia is rarely enhanced above its single-species level. Furthermore, transients in RBC production can induce coupled oscillations in the parasitaemia of both species. These results are remarkably robust to changes in model parameters.