RESUMO
To understand the current condition of pyrimethamine-sulfadoxine (PS) resistant falciparum malaria in Lao PDR, the frequency of point mutations in dihydrofolate reductase (DHFR) and dihydropteroate synthase (DHPS) genes of Plasmodium falciparum were examined in 50 blood samples collected from the patients with P. falciparum infection in Southern Lao PDR. Point mutations in 5 codons of the DHFR gene, which is known to be related to pyrimethamine resistance, were detected in 15 out of the 50 samples (30%). Among the 15 samples, 10 samples showed a double mutation of codons 59 and 108 (Cys59Arg with Ser108Asn). In the remaining 5 samples, an additional mutation was observed in codon 51 (Asn51 lle), providing a triple mutation of codons 51, 59 and 108. On the other hand, point mutations in the 4 codons of DHPS gene related to sulfadoxine resistance were observed only in 2 samples (4.0%), namely in codon 437 (Ala437Gly). Only one sample showed mutations in both DHFR and DHPS genes. From the results, it should be considered that the frequency of PS resistant malaria is still low in Lao PDR. Continuous monitoring for the PS resistant malaria, however, is necessary because of the increasing use of PS in this country.
Assuntos
Animais , Antimaláricos/farmacologia , Códon , Di-Hidropteroato Sintase/genética , Resistência a Medicamentos/genética , Epidemiologia Molecular , Humanos , Laos , Malária Falciparum/tratamento farmacológico , Plasmodium falciparum/efeitos dos fármacos , Mutação Puntual/genética , Reação em Cadeia da Polimerase , Pirimetamina/farmacologia , Sulfadoxina/farmacologia , Tetra-Hidrofolato Desidrogenase/genéticaRESUMO
Field application and evaluation of a rapid immunochromatographic test (ICT) for detection of Plasmodium falciparum infection were performed in 13 villages in a southern province of Lao PDR in 1999. More than 2,000 inhabitants, accounting for 61.8% of the total estimated population, were examined. Malaria infection was confirmed in all villages surveyed by ICT and microscopic diagnosis. The positive rates of P. falciparum malaria by microscopy ranged from 9.7% to 59.2% (mean 27.2%), whereas by ICT they were from 11.6% to 64.5% (mean 29.8%). The positive rates by ICT were generally higher in 8 out of 13 villages. However, a significant difference between the positive rates by microscopy and ICT was not observed in all villages. Plasmodium falciparum infection was actually confirmed by microscopy in 84.1% of specimens that tested positive by ICT. The results by ICT were consistent with those of the microscopic diagnosis, the discrepancy of the results was less than 10% (141/2,066). The ICT was falsely-positive in 4.7% and falsely-negative in 2.1% of the test cases. These results showed the efficacy of ICT not only in the diagnosis of the respective cases, but also in the mass-examination in the field.