Transmissibility and virulence of Plasmodium chabaudi chabaudi AS in the mammalian host. a, Frequency of patent blood-stage parasitaemia in C57BL/6 mice injected id or iv with P. c. chabaudi AS sporozoites, or exposed to cups of P. c. chabaudi AS infected mosquitoes (n = 5-34 per group; pooled data from two independent experiments are shown). Parasitaemic mice were defined by thin blood smear, prepared daily between days 3 and 16 post-infection, with a limit of detection of 0.01% pE. b, Parasitaemia of Parkes, C57BL/6, BALB/c and C3H/He mice infected with P. c. chabaudi AS via mosquito bite (n = five per group; data are presented as mean with SEM). Peak parasitaemia is significantly increased in BALB/c mice, as compared to Parkes mice, and in C3H/He mice, as compared to BALB/c mice (**p = 0.0079 (Mann–Whitney test)). Note that on day 14 post-infection one C3H/He mouse succumbed to infection.