Plasmodium ovale in Bangladesh: Genetic diversity and the first known evidence of the sympatric distribution of Plasmodium ovale curtisi and Plasmodium ovale wallikeri in southern Asia

In spite of the high prevalence of malaria in Bangladesh and other southern Asian countries, there remains a substantial shortage of knowledge about the less common human malaria parasites. Recent studies indicate that Plasmodium ovate is made up of two species, namely Plasmodium ovate wallikeri and Plasmodium ovate curtisi. Genus- and species-specific nested PCR analyses of the ssrRNA gene was used to detect P. ovate infections among 2,246 diagnostic samples. Plasmodium ovate infections were further differentiated by nested PCR of the potra gene and multilocus sequence analysis of the cox1, porbp2 and the ssrRNA genes. Both P. ovate curtisi and P. ovate wallikeri occur sympatrically in the Chittagong Hill Tracts, Bangladesh and all patients presented with a mild or asymptomatic symptom complex at the time of diagnosis. The pathogens can be differentiated by nested PCRs targeting the ssrRNA and potra genes, and display dimorphism in multilocus sequence analyses. We believe that we report the first evidence of sympatric P. ovate curtisi and P. ovate wallikeri in southern Asia within a relatively confined study area of less than 5,000 km(2). High rates of mixed infections, the emergence of "new" human malaria parasite species and the evidence of zoonotic capability call for optimised diagnostic strategies for a new era of eradication. (C) 2012 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.