Parasite multiplication potential and the severity of falciparum malaria

The multiplication rates and invasiveness of Plasmodium falciparum parasite s isolated from adult Thai patients hospitalized with uncomplicated malaria (n = 34) were compared with those from persons with severe malaria (n = 42 ), To simulate severe malaria and control for host effects, the in vitro cu ltures were adjusted to 1% parasitemia and used the same red blood cell don or. P. falciparum isolates from persons with severe malaria had initial cyc le multiplication rates in vitro that were 3-fold higher than those from un complicated malaria (median [95% confidence interval], 8.3 [7.1-10.5] vs. 2 .8 [1.7-3.9]; P = .001), Parasites causing severe malaria exhibited unrestr icted red blood cell invasion, whereas those from uncomplicated malaria wer e restricted to a geometric mean of 40 (31%-53%) of red blood cells. P. fal ciparum parasites causing severe malaria were less selective and multiplied more at high parasitemias than those causing uncomplicated malaria.