Duoquan Wang

Vector capacity of Anopheles sinensis in malaria outbreak areas of central China

BackgroundBoth falciparum and vivax malaria were historically prevalent in China with high incidence. With the control efforts, the annual incidence in the whole country has reduced to 0.0001% except in some areas in the southern borders after 2000. Despite this, the re-emergence or outbreak of malaria was unavoidable in central China during 2005–2007. In order to understand the role of the vector in the transmission of malaria during the outbreak period, the vector capacity of An. sinensis in Huanghuai valley of central China was investigated.FindingsThe study was undertaken in two sites, namely Huaiyuan county of Anhui province and Yongcheng county of Henan province. In each county, malaria cases were recorded for recent years, and transmission risk factors for each study village including anti-mosquito facilities and total number of livestock were recorded by visiting each household in the study sites. The specimens of mosquitoes were collected in two villages, and population density and species in each study site were recorded after the identification of different species, and the blood-fed mosquitoes were tested by ring precipitation test. Finally, various indicators were calculated to estimate vector capacity or dynamics, including mosquito biting rate (MBR), human blood index (HBI), and the parous rates (M). Finally, the vector capacity, as an important indicator of malaria transmission to predict the potential recurrence of malaria, was estimated and compared in each study site.About 93.0% of 80 households in Huaiyuan and 89.3% of 192 households in Yongcheng had anti-mosquito facilities. No cattle or pigs were found, only less than 10 sheep were found in each study village. A total of 94 and 107 Anopheles spp. mosquitos were captured in two study sites, respectively, and all of An. sinensis were morphologically identified. It was found that mosquito blood-feeding peak was between 9:00 pm and 12:00 pm. Man biting rate of An. sinensis was 6.0957 and 5.8621 (mosquitoes/people/night) estimated by using half-night human bait trap method and full-capture method, respectively. Human blood indexes (HBI) were 0.6667 (6/9) and 0.6429 (18/28), and man-biting habits were 0.2667 and 0.2572 in two sites, respectively. Therefore, the expectation of infective life and vector capacity of An. sinensis was 0.3649-0.4761 and 0.5502-0.7740, respectively, in Huanhuai valley of central China where the outbreak occurred, which is much higher than that in the previous years without malaria outbreak.ConclusionsThis study suggests that vivax malaria outbreak in Huanhuai valley is highly related to the enhancement in vector capacity of An. sinensis for P. vivax, which is attributed to the local residents’ habits and the remarkable drop in the number of large livestock leading to disappearance of traditional biological barriers.

A potential threat to malaria elimination: extensive deltamethrin and DDT resistance to Anopheles sinensis from the malaria-endemic areas in China

BackgroundInsecticide resistance in malaria vectors is a growing concern in many countries and requires immediate attention because of the limited chemical arsenal available for vector control. There is lack of systematic and standard monitoring data of malaria vector resistance in the endemic areas, which is essential for the ambitious goal of malaria elimination programme of China.MethodsIn 2010, eight provinces from different malaria endemic region were selected for study areas. Bioassays were performed on F1 progeny of Anopheles sinensis reared from wild-caught females using the standard WHO susceptibility test with diagnostic concentrations of 0.25% deltamethrin and 4% DDT.ResultsFor An. sinensis, the results indicated that exposure to 0.25% deltamethrin of F1 families with mortalities ranging from 5.96% to 64.54% and less than 80% mortality to DDT at the diagnostic concentration of 4% across the study areas.ConclusionsAnopheles sinensis was completely resistant to both deltamethrin and DDT, and resistance to pyrethroid has risen strikingly compared to that recorded during 1990s. The results highlight the importance of longitudinal insecticide resistance monitoring and the urgent need for a better understanding of the status of insecticide resistance in this region.

Predicting malaria vector distribution under climate change scenarios in China: Challenges for malaria elimination

Projecting the distribution of malaria vectors under climate change is essential for planning integrated vector control activities for sustaining elimination and preventing reintroduction of malaria. In China, however, little knowledge exists on the possible effects of climate change on malaria vectors. Here we assess the potential impact of climate change on four dominant malaria vectors (An. dirus, An. minimus, An. lesteri and An. sinensis) using species distribution models for two future decades: the 2030 s and the 2050 s. Simulation-based estimates suggest that the environmentally suitable area (ESA) for An. dirus and An. minimus would increase by an average of 49% and 16%, respectively, under all three scenarios for the 2030 s, but decrease by 11% and 16%, respectively in the 2050 s. By contrast, an increase of 36% and 11%, respectively, in ESA of An. lesteri and An. sinensis, was estimated under medium stabilizing (RCP4.5) and very heavy (RCP8.5) emission scenarios. in the 2050 s. In total, we predict a substantial net increase in the population exposed to the four dominant malaria vectors in the decades of the 2030 s and 2050 s, considering land use changes and urbanization simultaneously. Strategies to achieve and sustain malaria elimination in China will need to account for these potential changes in vector distributions and receptivity.

Malaria imported from Ghana by returning gold miners, China, 2013.

During May-August 2013, a malaria outbreak comprising 874 persons in Shanglin County, China, was detected among 4,052 persons returning from overseas. Ghana was the predominant destination country, and 92.3% of malarial infections occurred in gold miners. Preventive measures should be enhanced for persons in high-risk occupations traveling to malaria-endemic countries.

Transmission Risk from Imported Plasmodium vivax Malaria in the China-Myanmar Border Region.

Malaria importation and local vector susceptibility to imported Plasmodium vivax infection are a continuing risk along the China–Myanmar border. Malaria transmission has been prevented in 3 border villages in Tengchong County, Yunnan Province, China, by use of active fever surveillance, integrated vector control measures, and intensified surveillance and response.

Spatio-temporal analysis of malaria vectors in national malaria surveillance sites in China

BackgroundTo reveal the spatio-temporal distribution of malaria vectors in the national malaria surveillance sites from 2005 to 2010 and provide reference for the current National Malaria Elimination Programme (NMEP) in China.MethodsA 6-year longitudinal surveillance on density of malaria vectors was carried out in the 62 national malaria surveillance sites. The spatial and temporal analyses of the four primary vectors distribution were conducted by the methods of kernel k-means and the cluster distribution of the most widely distribution vector of An.sinensis was identified using the empirical mode decomposition (EMD).ResultsTotally 4 species of Anopheles mosquitoes including An.sinensis, An.lesteri, An.dirus and An.minimus were captured with significant difference of distribution as well as density. An. sinensis was the most widely distributed, accounting for 96.25% of all collections, and its distribution was divided into three different clusters with a significant increase of density observed in the second cluster which located mostly in the central parts of China.ConclusionThis study first described the spatio-temporal distribution of malaria vectors based on the nationwide surveillance during 2005–2010, which served as a baseline for the ongoing national malaria elimination program.

Preparation for Malaria Resurgence in China: Approach in Risk Assessment and Rapid Response

With the shrinking of indigenous malaria cases and endemic areas in the Peoples Republic of China (P.R. China), imported malaria predominates over all reported cases accounting for more than 90% of the total. On the way to eliminate malaria, prompt detection and rapid response to the imported cases are crucial for the prevention of secondary transmission in previous endemic areas. Through a comprehensive literature review, this chapter aims to identify risk determinants of potential local transmission caused by the imported malaria cases and discusses gaps to be addressed to reach the elimination goal by 2020. Current main gaps with respect to dealing with potential malaria resurgence in P.R. China include lack of cross-sectoral cooperation, lack of rapid response and risk assessment, poor public awareness, and inadequate research and development in the national malaria elimination programme.

Capture and Ligation Probe-PCR (CLIP-PCR) for Molecular Screening, with Application to Active Malaria Surveillance for Elimination

BACKGROUND Malaria control programs have achieved remarkable success during the past decade. Nonetheless, sensitive and affordable methods for active screening of malaria parasites in low-transmission settings remain urgently needed. METHODS We developed a molecular screening method, capture and ligation probe-PCR (CLIP-PCR), which achieved the sensitivity of reverse-transcription PCR but eliminated the reliance on RNA purification and reverse transcription. In this method, 18S rRNA of genus Plasmodium is released from blood, captured onto 96-well plates, and quantified by the amount of ligated probes that bind continuously to it. We first used laboratory-prepared samples to test the method across a range of parasite densities and pool sizes, then applied the method to an active screening of 3358 dried blood spot samples collected from 3 low-endemic areas in China. RESULTS Plasmodium falciparum diluted in whole blood lysate could be detected at a concentration as low as 0.01 parasites/μL, and a pool size of ≤36 did not significantly affect assay performance. When coupled with a matrix pooling strategy, the assay drastically increased throughput to thousands of samples per run while reducing the assay cost to cents per sample. In the active screening, CLIP-PCR identified 14 infections, including 4 asymptomatic ones, with <500 tests, costing <US

China-Africa Cooperation Initiatives in Malaria Control and Elimination

0.60 for each sample. All positive results were confirmed by standard quantitative PCR. CONCLUSIONS CLIP-PCR, by use of dried blood spots with a pooling strategy, efficiently offers a highly sensitive and high-throughput approach to detect asymptomatic submicroscopic infections with reduced cost and labor, making it an ideal tool for large-scale malaria surveillance in elimination settings.

Spatial-Temporal Variation and Primary Ecological Drivers of Anopheles sinensis Human Biting Rates in Malaria Epidemic- Prone Regions of China

Abstract Malaria has affected human health globally with a significant burden of disease, and also has impeded social and economic development in the areas where it is present. In Africa, many countries have faced serious challenges in controlling malaria, in part due to major limitations in public health systems and primary health care infrastructure. Although China is a developing country, a set of control strategies and measures in different local settings have been implemented successfully by the National Malaria Control Programme over the last 60 years, with a low cost of investment. It is expected that Chinese experience may benefit malaria control in Africa. This review will address the importance and possibility of China–Africa collaboration in control of malaria in targeted African countries, as well as how to proceed toward the goal of elimination where this is technically feasible.