Molecular epidemiological study on the variant type of Plasmodium falciparum and trial for in vitro culture of gametocytes

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During epidemiological study on malaria from 2005 to 2006, Plasmodium falciparum (Pf) with very thin morphology of gametocytes was found in 4 patients in Cambodia and Indonesia. Analysis of 18S ribosomal RNA gene indicated that they are belonging to the variant type of Pf detected from Vietnam, and they had the same sequence variation at the target region for molecular diagnosis. Therefore, in this study, we continued similar epidemiological study on the variant Pf whether the strange shape of gametocytes belongs to the variant Pf or not by analyzing the 18S ribosomal RNA gene. In addition, our study had another aim ; a trial to cultivate in vitro from gametocytes to sporozoites in the variant or ordinary Pf (also gametocytes of Plasmdium vivax ; Pv) at the field.We surveyed malaria in Indonesia, Cambodia, Vietnam and Thailand from April 2007. In 2007, we found 2 patients infected with the variant Pf in Cambodia, but these bloods did not contain gametocytes. In addition, we detected 1 patient infected with Pv gametocytes, but trial of in vitro culture was failed. In 2008, we found 2 patients infected with gametocytes of the ordinary Pf, and tried in vitro culture of gametocytes. Furthermore, we detected 1 patient infected with Pv gametocytes in Cambodia. However, all these trials of in vitro culture were also failed. In 2009, no patient infected with the variant Pf was found in Indonesia and Vietnam. Therefore, it is still not clear whether morphology of gametocytes is different or not between the ordinary Pf and the variant Pf.