Epidemiological situation of malaria in Madagascar: baseline data for monitoring the impact of malaria control programmes using serological markers.

The aim of this study was to provide baseline information of the epidemiological situation of malaria in Madagascar using serological markers. We carried out cross-sectional studies in schoolchildren from eight sites in the four different malarious epidemiological strata of Madagascar. We studied the prevalence of anti-MSP1 antibodies to assess the burden, and anti-CSP antibodies to estimate the transmission intensity, of malaria. The overall prevalence of each antibody tested was 46.1% for anti-PfMSP-1, 15.2% for anti-PvMSP-1, 14.9% for anti-PfCSP, 4.9% for anti-PvCSP and 2.4% for anti-PmCSP. The prevalence of the five antibodies varied significantly between the sites (P<10(-6)). We also found significant effects of ethnic origin on the prevalence of anti-PfMSP1 antibodies. With regular testing in the same target populations, this data will be particularly useful for managing the elimination strategy supported by the Malagasy Government.

Performance and reliability of the SYBR Green I based assay for the routine monitoring of susceptibility of Plasmodium falciparum clinical isolates.

The performance and the reliability of a SYBR Green I fluorescence-based assay to assess drug susceptibility in routine monitoring were evaluated in 138 Plasmodium falciparum clinical samples. Blood samples were studied for susceptibility to four antimalarial drugs by the SYBR Green I based assay, with the traditional [(3)H]-hypoxanthine isotopic assay as a reference. The two methods were observed to have similar geometric means of IC50s and IC90s, and high correlation (r=0.93 for IC50s and r=0.94 for IC90s) for the drugs tested. The strength of agreement estimated by using concordance coefficient correlation was from almost perfect to substantial for IC50s. Our data demonstrate (i) the reliability of a simple, rapid and easy to use fluorescence-based assay for the routine monitoring of susceptibility of P. falciparum clinical isolates, and (ii) the possible switch from the traditional in vitro drug sensitivity assay to the SYBR Green I method, because previous data acquired by the isotopic assay were comparable with those obtained by the SYBR Green I method. We conclude that this assay will provide an easier method for testing drug susceptibility of malaria parasites, especially in malaria-endemic countries, where there is massive implementation of new artemisinin-based combination therapies.

Prevalent pfmdr1 n86y mutant Plasmodium falciparum in Madagascar despite absence of pfcrt mutant strains.

We assessed the status of point mutations associated with chloroquine resistance in pfcrt codon 76 and in pfmdr1 codon 86 among Plasmodium falciparum isolates from symptomatic patients in 3 sites in Madagascar. The in vitro susceptibility of P. falciparum isolates to quinoline-containing drugs was also determined. All isolates (N = 117) successfully typed were pfcrt wild-type, except one from Tsiroanomandidy (1 of 27). However, 67.5% (95% CI: 58.2-75.9%) of these isolates contained mutant pfmdr1 86Y. The pfmdr1 N86Y mutation is associated with higher mefloquine susceptibility, but it did not affect the sensitivity of parasites to chloroquine or quinine. Our findings demonstrate that pfmdr1 mutant P. falciparum are prevalent in Madagascar and confirm the low prevalence of pfcrt mutant P. falciparum after 60 years of chloroquine use. They provide additional field-based evidence for increased mefloquine susceptibility in pfmdr1 mutant P. falciparum and are suggestive of the intrahost selection of pfmdr1 mutant parasites.