Abstract
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.
Highlights
Malaria is a major infectious disease in the Greater Mekong Subregion (GMS) countries, namely P.R
A variety of Polymerase Chain Reaction (PCR)-based assays have been described for the specific diagnosis of all the five species of Plasmodium, i.e. Plasmodium falciparum, P. vivax, P. ovale, P. malariae, and P. knowlesi [23, 25, 32, 22, 5], one of which is based on the sequence of the small subunit ribosomal RNA gene used to detect human Plasmodium spp. [24]
The nested PCR confirmed all of the MP group malaria cases (100%, 371/ 371) and diagnosed 13 malaria cases in the MN group (6.9%, 13/189) which may have been ignored because of the low parasitemia conditions
Summary
Malaria is a major infectious disease in the Greater Mekong Subregion (GMS) countries, namely P.R. China, Laos, Myanmar, and Vietnam. Yunnan province still has the highest transmission area in P.R. China, in the southern border areas adjacent to Myanmar [7, 8, 30]. In the malaria elimination program, routine surveillance uses the standard method for detection of Plasmodium spp. infection by examining Giemsa-stained blood smears under the microscope. The Polymerase Chain Reaction (PCR) method has been widely used for the detection and identification of malaria parasites. A molecular survey was carried out of samples collected randomly in the malaria-endemic area along the border line of southern China, in Yunnan province from January 2008 to August 2012. The present study aims to evaluate PCR amplification in comparison with light microscopy examination
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