Figure 4.

A simulation of the effects of drug treatment in 2 patients with long-standing mixed-species infections, who arrive at a clinic after a month of intermittent fevers. Both patients are treated immediately, as follows: A, high Plasmodium vivax parasitemia relative to P. falciparum (35,000 versus 10,000 parasites/μl) leads to misdiagnosis as a single-species P. vivax infection. The patient is treated with mefloquine and primaquine on day 30 of the infection. P. vivax is eliminated, but mefloquine-resistant P. falciparum recrudesces once mefloquine concentration decreases below the minimum parasiticidal concentration for this resistant strain. B, high P. falciparum parasitemia relative to P. vivax (6,575 versus 720 parasites/μl) leads to misdiagnosis as a single-species P. falciparum infection. The patient is treated with quinine on day 30 of the infection. Both P. falciparum and P. vivax blood forms are eliminated but there is a relapse from P. vivax hypnozoites, following the elimination of quinine from the blood. In A, x = y = 0, c_s = 0.001, c_n = 0.01, s_s = 0.001, s_n = 0.001. In B, x = y = 0, c_s = 0.001, c_n = 0.001, s_s = 0.001, s_n = 0.01. In both A and B, drugs are given on day 30, parasite reduction ratio = 100.