Acta Tropica 90 (2004) 61–64 High prevalence of Plamodium malariae infections in a Brazilian Amazon endemic area (Apiacás—Mato Grosso State) as detected by polymerase chain reaction Kézia K.G. Scopel a , Cor J.F. Fontes b , Álvaro C. Nunes c , M. Fátima Horta d , Érika M. Braga a,* a Departamento de Parasitologia, Instituto de Ciˆ encias Biológicas, Universidade Federal de Minas Gerais, Av. Antˆ onio Carlos, 6627, 31270-901 Belo Horizonte, Minas Gerais, Brazil b Departamento de Cl´ ınica Médica, Universidade Federal de Mato Grosso, Rua L, s/n, Alvorada, 78048-170 Cuiabá, Mato Grosso, Brazil c Departamento de Biologia Geral Instituto de Ciˆ encias Biológicas, Universidade Federal de Minas Gerais, Av. Antˆ onio Carlos, 6627, 31270-901 Belo Horizonte, Minas Gerais, Brazil d Departamento de Bioqu´ ımica e Imunologia, Instituto de Ciˆ encias Biológicas, Universidade Federal de Minas Gerais, Av. Antˆ onio Carlos, 6627, 31270-901 Belo Horizonte, Minas Gerais, Brazil Received 24 July 2003; received in revised form 4 November 2003; accepted 4 November 2003 Abstract Plasmodium malariae is commonly confounded with Plasmodium vivax at the microscopic examination of thick blood smear. In the present study, we used a nested PCR assay to amplify a species-specific sequence of the 18S SSU rRNA gene of Plasmodium in blood samples of 497 individuals living in an endemic region of the Brazilian Amazon basin. We have found that, while the microscopic examination of thick blood smears showed a P. malariae prevalence of 1.2% (6 out of 497), the nested PCR revealed 11.9% (59 out of 497) of positive cases for this specie. These results point to the need of the development or use of a more accurate diagnosis method to distinguish between P. malariae and P. vivax, which is particularly important in view of the fact that the choice of drug for the antimalarial therapy depends on the parasite species. © 2003 Elsevier B.V. All rights reserved. Keywords: Plasmodium malariae; PCR; Diagnosis The standard method for malaria diagnosis is the microscopic examination of thick blood smear stained with Giemsa. Although this method is highly sensitive, the hemolysis of erythrocytes during the preparation of slides impairs the correct identification of malaria * Corresponding author. Tel.: +55-31-3499-2876; fax: +55-31-3499-2970. E-mail address: embraga@icb.ufmg.br ( ´ E.M. Braga). parasites. The non-assessed morphology of infected red blood cells and the parasite altered shape interfere with the recognition of the species, often leading to a mistaken identification of Plasmodium malariae as P. vivax. As a result, the thick blood smears-based preva- lence and distribution of P. malariae might be underes- timated. Lately, alternative diagnostic methods based in parasite DNA detection, such as the polymerase chain reaction (PCR), have been used for identification 0001-706X/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.actatropica.2003.11.002