Molecular Evidence on Changing Pattern of Mixed Plasmodium falciparum and P. vivax Infections during Year-Round Transmission of Malaria in Chahbahar, Iran

Mixed malaria infections, Plasmodium falciparum and P. vivax, are suspected to occur at a greater frequency than is detected by conventional light microscopy. In order to determine the year round pattern of transmission and the frequency of mixed infections in malaria endemic area, we carried out a prospective comparison of diagnosis by conventional light microscopy and nested PCR in Chahbahar district, south-eastern part of Iran. Out of 280 Giemsa-stained slides, 158 (56.42%) were identified as having only P. vivax and 89 (31.78%) were P. falciparum infection by microscopy. Only eight slides (2.8%) were interpreted as having mixed P. vivax-P. falciparum infections and 25 (8.9%) were negative. Comparing to the microscopy results, the PCR detected 33 more mixed infections. These results showed that the number, of mixed infections was increased during April to September and reduced after September, although malaria cases with only P. falciparum were increased. The possibility that malaria patients in Chahbahar district may have undetected mixed infections during first peak of transmission should be kept in mind because of the specific therapy required both for P. falciparum and for radical cure of P. vivax