Drug resistance maps to guide intermittent preventive treatment of malaria in African infants

Abstract

Intermittent preventive treatment of infants (IPTi) with sulphadoxine pyrimethamine (SP) is recommended as an additional malaria control intervention in high transmission areas of sub-Saharan Africa, provided its protective efficacy is not compromised by SP resistance. A significant obstacle in implementing SP-IPTi, is in establishing the degree of resistance in an area. Since SP monotherapy is discontinued, no contemporary measures of in vivo efficacy can be made, so the World Health Organisation has recommended a cut-off based upon molecular markers, stating that SP-IPTi should not be implemented when the prevalence of the dhps 540E mutation among infections exceeds 50%. We created a geo-referenced database of SP resistance markers in Africa from published literature. By selecting surveys of malaria infected blood samples conducted since 2004 we have mapped the contemporary prevalence of dhps 540E. Additional maps are freely available in interactive form at http://www.drugresistancemaps.org/ipti/. Eight countries in East Africa are classified as unsuitable for SP-IPTi when data are considered at a national level. Fourteen countries in Central and West Africa were classified as suitable while seven countries had no available contemporary data to guide policy. There are clear deficiencies in molecular surveillance data coverage. We discuss requirements for ongoing surveillance of SP resistance markers in support of the use of SP-IPTi.

Fig. 1

Surveys of 540E prevalence (with 95% confidence intervals) conducted during 1988–2008 and displayed according to their geographic region.

Fig 2

Map of dhfr 164L survey sites. Countries where surveys were conducted are shaded and the survey sites are indicated by open circles. For positive surveys the prevalence of 164L is indicated.

Fig 3

Map of dhps 581G survey sites. Countries where surveys were conducted are shaded and the survey sites are indicated by open circles. For positive surveys the prevalence of 581G is indicated.

Fig 4

Map showing recent measures of the prevalence of 540E. All surveys conducted since 2004 are indicted by pie charts. The red pie charts indicate survey sites where prevalence exceeded 50% and these countries are shaded brown. The black pie charts indicate surveys with less than 50%. Blue circles indicate zero prevalence 540E. The countries shaded pink indicate that 540E has been detected at <50% at some stage whereas the blue ones are where it has never been detected. White indicates countries where no data was available.