Drug resistance negatively impacts malaria treatments, making treatment policy revision unavoidable. So far, studies relating sociopolitical and technical issues on policy change with malaria parasite genetic change are lacking. We have quantified the effect of malaria treatment policy on drug pressure and the influence of the media, policy makers, and health worker relationship on parasite population genetic change in Kilombro/Ulanga district. Cross-sectional surveys of asymptomatic infections conducted before, during and after the switch from chloroquine to sulphadoxine/pyrimethamine were used for genetic analysis of SP resistance genes in 4,513 asymptomatic infections identified, and their frequency change was compared with retrospective study of the documented process of policy change. Highly significant changes of dhfr and dhps resistance alleles occurred within one year of switch to SP first line, followed by a decline of their rate of selection caused by reduction of SP usage, as a result of negative media reports on SP usage and lack of adequate preparations. 1. Introduction Malaria remains the world's most important tropical parasitic disease and one of the major public health challenges in the poorest countries of the world, particularly in sub-Saharan Africa, as the prospect of an effective vaccine remains uncertain. Although some African countries have increased their spending in health along with the support from the Global Fund to Fight AIDS, TB, and Malaria (GFATM) and other partners, development assistance has been routed largely through public channels, whereas affected individuals seek treatment mostly through the private sector [1]. Consequently, the rising cost of medical services and the increasing trends of drug resistance raise critical public health concerns, as this constrains the provision of adequate health care in countries where the disease is endemic [1]. Evidence on Plasmodium falciparum resistance to chloroquine (CQ) between 1980s and early 2000 prompted most countries where malaria is endemic to revise their treatment guidelines, most of them replacing it with sulfadoxine-pyrime (SP) [2, 3]. In Tanzania, CQ was officially replaced with SP in 2001, apparently as an interim policy [4]. However, SP resistance became widespread shortly after its adoption as first-line treatment, because its resistance had already been established in Tanzania and the neighbouring countries [5–8], and also, because it had been used as the second-line treatment for malaria in Tanzania until 2001, when it became the first-line treatment drug.
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