Table 1.
Infection parameters for single and mixed strain infections.
Figure 1.
Parasitaemia (Panels A-C), percentage survival (D-F), red blood cell density (G-I) and weight change (J-L) of mice infected with avirulent (CU and 17XNL), intermediately virulent (17X1.1pp) and virulent (17XL) strains of Plasmodium yoelii yoelii in single or in mixed infections.
Data points indicate the mean value for 4 mice per experimental group. † indicates the time points at which individual mice died. Data are representative of two independent experiments.
Figure 2.
Transmission success of strains of Plasmodium yoelii yoelii in single and mixed strain infections.
Panels A, B and C show the numbers of oocysts per mosquito fed on mice infected with CU (avirulent), 17XNL (avirulent), 17X1.1pp (intermediately virulent) and 17XL (virulent) either in single or in mixed infections on days 3 and 4 post-inoculation. Error bars indicate the standard error of the mean. Twenty mosquitoes were allowed to feed on each mouse, and those that were gravid after 7 days were considered blood-fed and included in the analysis. Panels D, E and F; the mean percentage of mosquitoes infected with at least one oocyst following feeding on each of the strains in single or mixed infections. Error bars indicate the standard error of the mean for mosquitoes fed on groups of 4 mice. Data are representative of two independent experiments. * = P < 0.05, ** = P < 0.005, *** = P < 0.001
Figure 3.
The relative proportions of strains of Plasmodium yoelii yoelii in mixed strain infections throughout the course of infections in mice (Panels A-C), and the parasite densities of the strains in single and mixed infections (Panels D-G).
Panels A, B and C show the relative proportions of the avirulent CU strain in combination with the avirulent 17XNL strain, the intermediately virulent 17X1.1pp and the virulent strain 17XL respectively. Individual data points are mean proportions of 4 mice per group. The parasite density (number of asexual stage parasites per mL of blood) of the avirulent strain CU in a single infection is compared to the parasite density of this strain when in competition with the other strains in Panel D; that of avirulent 17XNL in a single infection or in competition with CU in Panel E; the intermediately virulent 17X1.1pp in a single infection or in competition with CU in Panel F; the virulent 17XL in a single infection or in competition with CU in Panel G. Strains in brackets indicate the competing strain. Error bars indicate the standard error of the mean of 4 mice per group. Data are representative of two independent experiments.
Figure 4.
Adjusted mean number of oocysts per infected mosquito of strains of Plasmodium yoelii yoelii derived from mosquitoes fed on mice harbouring single strain or mixed strain infections on days 3 and 4 post-inoculation.
Oocyst numbers are given for strain CU when in competition with all other strains (Panel A), for 17XNL in competition with CU (B), for 17X1.1pp in competition with CU (C) and for 17XL in competition with CU (D). Error bars indicate the standard error of the mean for 4 mice per group, and data are representative of two independent experiments. * = P < 0.05, ** = P < 0.005, *** = P < 0.001
Figure 5.
Relative fitness of avirulent (CU and 17XNL), intermediately virulent (17X1.1pp) and virulent (17XL) strains of Plasmodium yoelii yoelii in single (Panel A) or in mixed (B) infections.
Fitness coefficients were derived from the numbers of oocysts produced by each clone in mixed and single infections. For single strain infections (A), the fitness of 17XNL, 17XL and 17X1.1pp are given relative to that of the fittest strain, CU. In mixed infections, the fitness of each clone in the presence of a competitor or competitors is given relative to its fitness in a single strain infection (B).