A molecular survey of febrile cases in malaria-endemic areas along China-Myanmar border in Yunnan province, People's Republic of China

Background: Imported malaria is a major threat to neighboring malaria-eliminating countries such as P. R. China and is difficult to monitor. A molecular survey of febrile patients with a history of traveling abroad along the Myanmar-China endemic border areas from January 2008 to August 2012 was carried out. The rates of infection with species of Plasmodium and compliance of microscopy diagnosis with nested PCR (Polymerase Chain Reaction) results were calculated. Results: Plasmodium genus-specific nested PCR confirmed that 384 cases were positive. Further species-specific nested PCR showed that the rate of Plasmodium vivax infection was 55% (213/384); that of Plasmodium falciparum was 21% (81/384) and 17% (67/384) of cases were co-infection cases of P. vivax and P. falciparum; the remaining 6% (23/384) of cases were caused by other species, such as Plasmodium ovale, P. malaria, P. knowlesi or mixed infections of Plasmodium. In total there was 13% (50/384) false microscopy diagnosis including 6% (22/384) error in species diagnosis and 7% (28/384) undiagnosed cases in co-infection or low parasitemia malaria cases. Conclusions: This study indicates that there are considerable numbers of malaria cases in the China-Myanmar endemic border areas that remain undiagnosed or misdiagnosed by microscopy, especially in low-level and/or complex co-infection cases. It is urgent to develop accurate rapid diagnostic tests and apply PCR confirmation for efficient surveillance.