Intra-host dynamics of mixed species malaria parasite infections in mice and mosquitoes
- Jianxia Tang†1,
- Megumi Inoue†1,
- Toshihiko Sunahara2,
- Moe Kanda1,
- Osamu Kaneko1 and
- Richard Culleton1
© Culleton et al; licensee BioMed Central Ltd. 2010
Published: 20 October 2010
The distributions of human malaria parasite species overlap in most regions of the world where malaria is present, and co-infections involving two or more malaria parasites are common. Currently, very little is known about the consequences of any interactions that may occur between species during co-infection for disease severity and parasite transmission success. However, current anti-malarial interventions such as vector control and drug interventions and the future application of vaccines will and do have disproportionate effects on some species compared to others; with the ultimate consequence of reducing the number of species in circulation in any one area. We believe that such a situation warrants a clearer understanding of how the interactions between species affect malaria disease and transmission dynamics.
As controlled competition experiments using human malaria parasites are currently practically impossible, we assessed the consequences of mixed-species infections on parasite fitness, disease severity and transmission success using the rodent malaria parasite species Plasmodium chabaudi (strains AS and CB), P. yoelii yoelii (CU) and P. vinckei lentum (DS). We compared the fitness of individual species within co-infections and in single species infections in mice. We also assessed the disease severity of single versus mixed infections in mice by measuring mortality rates, anaemia and weight loss. Finally, we compared the transmission success of parasites in single or mixed species infections by quantifying oocyst development in Anopheles stephensi mosquitoes.
The increased virulence of co-infections containing P. yoelii (reticulocyte restricted) and P. chabaudi or P. vinckei (predominantly normocyte restricted) may be consequences of parasite cell tropism and/or immune modulation of the host. We explain the reduction in transmission success of species in co-infections in terms of inter-species gamete incompatibility.
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