Genetic characterisation of Plasmodium falciparum populations in Sao Tome and Principe Islands, West Africa

José L. Vicente, P. Salgueiro, A. P. Arez, P. V. L. Cravo, C. Ferreira, V. E. Rosario, J. Pinto

Research output: Contribution to journalMeeting Abstractpeer-review

Abstract

Objectives: We have characterised the genetic diversity of Plasmodium falciparum populations in São Tomé and Príncipe islands (STP), West Africa, in order to assess patterns of population substructure and to relate these with epidemiological and control aspects of malaria. Methods: Blood samples were collected from 3 localities of São Tomé and 1 from Príncipe in 2000 (rainy season). Plasmodium falciparum isolates identified by nested-PCR were genotyped for the surface antigen genes msp1 and msp2 and for genes associated with chloroquine-CQ (pfcrt) and pyrimethamine/sulfadoxine-SP (pfdhps, pfdhfr) resistance, by PCR-RFLP. Results: 121 P. falciparum isolates were identified in 267 blood samples. Prevalence of infection was 44% in São Tomé and 49% in Príncipe. The 6-15 years-old group presented the highest prevalence. Sixteen and 19 different alleles were obtained for msp-1 and msp-2, respectively. Genetic diversity was significantly higher in the northern sample of São Tomé. MOI values were comparable between islands (1.3-1.6) and highest in 6-15 year-olds. The pfcrt K76T mutation related with CQ resistance was found in 97% of the isolates. All pfdhps and pfdhfr codons examined were polymorphic. The most frequent mutations at pfdhfr were: S108N (89%), N51I (85%) and C59R (60%). The triple mutation (51I/59R/108N) occurred in 45% of the samples. For pfdhps, the A437G mutation was found in 71% of isolates and the K540E in 3%. Four isolates (3%) carried the quintuple mutation (51I/59R/108N/437G/540E). Conclusion: Both prevalence and MOI were higher in 6-15 year-olds, which may reflect lower immune status and higher infection exposure in this group. Genetic diversity at msp1 and msp2 was comparable with continental populations. Genetic differences within São Tomé suggest restrictions to gene flow coupled with different selective pressures between north and south of this island. The high frequency of mutations found in drug resistance genes agrees with high levels of resistance to CQ and SP observed in STP.
Original languageEnglish
Pages (from-to)78
Number of pages1
JournalTropical medicine & international health : TM & IH
Volume12
Issue numberSuppl I
DOIs
Publication statusPublished - May 2007

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