Temporal distribution of CQ and SP drug pressure and drug resistance in Dielmo in 1990–9.

<div><p>The drug pressure is expressed as No of treatments/person/year (first graph) and as overall No of treatment courses administered per year (second graph). Panels A and B refer to CQ and SP, respectively. The prevalence of the <i>Pfcrt</i> mutant alleles was calculated from molecular beacon studies (N = 324) (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000139#pone-0000139-g002" target="_blank">Figure 2</a>), while the prevalence of the <i>Pfdhfr-ts</i> triple mutant was calculated from the full gene sequences available (N = 202) (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000139#pone-0000139-g003" target="_blank">Figure 3</a>). <i>In vitro</i> susceptibility assays were carried out in 1990–4 during the rainy season (N = 26) and from 1995 onwards for the last 2–3 months of the year, namely from 7/11/1995–26/12/1995 (N = 46) ; 6/01/1996–3/12/1996 (N = 59); 27/10/97–15/121997 (N = 26) ; 10/01/1998–15/11/1998 (N = 54) and 29/09/1999–08/11/1999 (N = 25). The proportion of interpretable CQ and pyrimethamine susceptibility tests was 68–81% and 72–81%, respectively, depending on the year. The prevalence of resistance is expressed as the percent of interpretable assays presenting a CI₅₀ for CQ >100 nM or a CI₅₀ for pyrimethamine>2000 nM. The occurrence of a second clinical malaria episode within 7, 14, 21 and 28 days of treatment was calculated as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000139#s2" target="_blank">Materials and Methods</a>. The bars correspond to the 95% confidence interval. The years before implementation of CQ and SP (1990–4) are grouped together.</p> <p> A. CQ pressure, <i>Pfcrt</i> 76T resistance mutation, CQ <i>in vitro</i> resistance and prevalence of clinical attacks following a CQ treatment</p> <p> B. SP pressure, <i>Pfdhfr-ts</i> triple mutant, pyrimethamine <i>in vitro</i> resistance and prevalence of clinical attacks following a SP treatment</p> <p>Colour codes: 1990–4: grey; 1995: purple; 1996: yellow; 1997: light green; 1998: light blue; 1999: orange.</p>