Abstract
.Malaria infections may be symptomatic, leading to treatment, or “asymptomatic,” typically detected through active surveillance, and not leading to treatment. Malaria elimination may require purging both types of infection. Using detection methods with different sensitivities, we conducted a cross-sectional study in two rural communities located along the border between China’s Yunnan Province and Myanmar’s Shan and Kachin States, to estimate the prevalence of asymptomatic and symptomatic malaria. In Mong Pawk, all infections detected were asymptomatic, and the prevalence of Plasmodium falciparum was 0.3%, 4.3%, 4.0%, and 7.8% by light microscopy, rapid diagnostic test (RDT), conventional polymerase chain reaction (cPCR), and multiplexed real-time PCR (RT-PCR), respectively, and Plasmodium vivax prevalence was 0% by all detection methods. In Laiza, of 385 asymptomatic participants, 2.3%, 4.4%, and 12.2% were positive for P. vivax by microscopy, cPCR, and RT-PCR, respectively, and 2.3% were P. falciparum-positive only by RT-PCR. Of 34 symptomatic participants in Laiza, 32.4% were P. vivax-positive by all detection methods. Factors associated with infection included gender (males higher than females, P = 0.014), and young age group (5–17 age group compared with others, P = 0.0024). Although the sensitivity of microscopy was adequate to detect symptomatic infections, it missed the vast majority (86.5%) of asymptomatic infections. Although molecular detection methods had no advantage over standard microscopy or RDT diagnosis for clinically apparent infections, malaria elimination along the Myanmar–China border will likely require highly sensitive surveillance tools to identify asymptomatic infections and guide targeted screen-and-treat interventions.
Highlights
In hopes of preventing the spread of artemisinin-resistant Plasmodium falciparum malaria, in 2015 the World Health Organization (WHO) recommended launching a regional campaign to eliminate P. falciparum malaria from the Greater Mekong Subregion, which includes Myanmar, Thailand, Cambodia, Vietnam, Laos, and China’s Yunnan Province.[1]
Molecular detection methods had no advantage over standard microscopy or rapid diagnostic test (RDT) diagnosis for clinically apparent infections, malaria elimination along the Myanmar–China border will likely require highly sensitive surveillance tools to identify asymptomatic infections and guide targeted screen-and-treat interventions
The epidemiology of subclinical malaria has recently been described for sites in Thailand, Cambodia, and Vietnam, where these infections are being targeted by mass drug administration.[9,13]
Summary
In hopes of preventing the spread of artemisinin-resistant Plasmodium falciparum malaria, in 2015 the World Health Organization (WHO) recommended launching a regional campaign to eliminate P. falciparum malaria from the Greater Mekong Subregion, which includes Myanmar, Thailand, Cambodia, Vietnam, Laos, and China’s Yunnan Province.[1] China developed malaria elimination strategies to interrupt local malaria transmission in the entire nation except for the Yunnan–Myanmar border by 2015, and to be completely malaria-free by 2020.2 The malaria burden in Yunnan decreased dramatically from 2006 to 2013, but local transmission has persisted, in Menglian and Yingjiang counties that are located adjacent to China’s border with Myanmar’s Shan and Kachin States, respectively. We identified malaria infection from a very small volume of blood (40 mL) collected on filter papers using multiplexed real-time PCR (RT-PCR), which has an LoD
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