Xinyu Feng

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.

The Plasmodium vivax in China: decreased in local cases but increased imported cases from Southeast Asia and Africa

Currently the local P. vivax was sharply decreased while the imported vivax malaria increased in China. Despite Southeast Asia was still the main import source of vivax malaria, the trend of Africa become serious, especially for west and central Africa. Herein we have clarified the trend of P. vivax in China from 2004–2012, and made some analysis for the differences of imported vivax back from different regions. There are significantly different of P. vivax between Southeast Asia and Africa, also the difference was observed for different regions in Africa. Additionally, we have explored the possibility for the difference of the P. vivax between migrant workers back from west and central Africa and the prevalence of local population. This reminds us that surveillance and training should be strengthened by medical staffs on the imported P. vivax cases reported especially from west and central Africa, in order to reduce the risk of malaria reintroduction and, specific tools should be developed, as well as the epidemiological study to avoid the misdiagnosis such as P. ovale and P. vivax.

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.

Imported Malaria in China, 2012

To the Editor: Imported malaria has become a major public health challenge in China. Despite an 89.8% decrease in total cases from 2008 (26,873) through 2012 (2,729), the proportion of imported malaria cases has increased from 14.7% to 89.0% (1). We analyzed the malaria situation in China in 2012 by using data obtained from the national information reporting system of infectious diseases.

Evaluation of Antimalarial Resistance Marker Polymorphism in Returned Migrant Workers in China

ABSTRACT Imported malaria has been a great challenge for public health in China due to decreased locally transmitted cases and frequent exchange worldwide. Plasmodium falciparum has been mainly responsible for the increasing impact. Currently, artesunate plus amodiaquine, one of the artemisinin combination therapies recommended by the World Health Organization, has been mainly used against uncomplicated P. falciparum malaria in China. However, drug resistance marker polymorphism in returning migrant workers has not been demonstrated. Here, we have evaluated the prevalence of pfmdr1 and pfcrt polymorphisms, as well as the K13 propeller gene, a molecular marker of artemisinin resistance, in migrant workers returned from Ghana to Shanglin County, Guangxi Province, China, in 2013. A total of 118 blood samples were randomly selected and used for the assay. Mutations of the pfmdr1 gene that covered codons 86, 184, 1034, and 1246 were found in 11 isolates. Mutations at codon N86Y (9.7%) were more frequent than at others, and Y86Y184S1034D1246 was the most prevalent (63.6%) of the four haplotypes. Mutations of the pfcrt gene that covered codons 74, 75, and 76 were observed in 17 isolates, and M74N75T76 was common (70.6%) in three haplotypes. Eight different genotypes of the K13 propeller were first observed in 10 samples in China, 2 synonymous mutations (V487V and A627A) and 6 nonsynonymous mutations. C580Y was the most prevalent (2.7%) in all the samples. The data presented might be helpful for enrichment of molecular surveillance of antimalarial resistance and will be useful for developing and updating antimalarial guidance in China.

Lessons from malaria control to elimination: case study in Hainan and Yunnan provinces.

Reduction patterns of Plasmodium falciparum and P. vivax malaria transmission and the role of an integrated strategy of case management and vector control are compared between different ecological zones. The epidemiology of malaria in Hainan and Yunnan provinces was disparate, even though distinct malaria control strategies have been adapted to different situations based on risk group, vector behaviours, local health infrastructure, and environmental conditions. The island Hainan appears to be victorious in eliminating malaria. However, there is still a long way to go to prevent the reintroduction of malaria in Hainan province and eliminating malaria in the border areas of Yunnan province. This review of the experiences and challenges from malaria control to elimination in Hainan and Yunnan provinces of southern China will provide a basis for the future elimination of malaria in the whole country.

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

Background Robust malaria vector surveillance is essential for optimally selecting and targeting vector control measures. Sixty-two vector surveillance sites were established between 2005 and 2008 by the national malaria surveillance program in China to measure Anopheles sinensis human biting rates. Using these data to determine the primary ecological drivers of malaria vector human biting rates in malaria epidemic-prone regions of China will allow better targeting of vector control resources in space and time as the country aims to eliminate malaria. Methods We analyzed data from 62 malaria surveillance sentinel sites from 2005 to 2008. Linear mixed effects models were used to identify the primary ecological drivers for Anopheles sinensis human biting rates as well as to explore the spatial-temporal variation of relevant factors at surveillance sites throughout China. Results Minimum semimonthly temperature (β = 2.99; 95% confidence interval (CI) 2.07- 3.92), enhanced vegetation index (β =1.07; 95% CI 0.11–2.03), and paddy index (the percentage of rice paddy field in the total cultivated land area of each site) (β = 0.86; 95% CI 0.17–1.56) were associated with greater An. Sinensis human biting rates, while increasing distance to the nearest river was associated with lower An. Sinensis human biting rates (β = −1.47; 95% CI −2.88, −0.06). The temporal variation (σt02=1.35) in biting rates was much larger than the spatial variation (σs02=0.83), with 19.3% of temporal variation attributable to differences in minimum temperature and enhanced vegetation index and 16.9% of spatial variance due to distance to the nearest river and the paddy index. Discussion Substantial spatial-temporal variation in An. Sinensis human biting rates exists in malaria epidemic-prone regions of China, with minimum temperature and enhanced vegetation index accounting for the greatest proportion of temporal variation and distance to nearest river and paddy index accounting for the greatest proportion of spatial variation amongst observed ecological drivers. Conclusions Targeted vector control measures based on these findings can support the ongoing malaria elimination efforts in China more effectively.

Students’ awareness of malaria at the beginning of national malaria elimination programme in China

BackgroundIn the battle against malaria in China, the rate of elementary and high school students’ awareness on malaria knowledge is an important index for malaria elimination, but only rare data is available. This study aimed to investigate the level of malaria awareness in students at elementary and high schools in malaria endemic areas of China, and to provide the baseline information for the malaria elimination.MethodsThis cross-sectional survey was conducted in 20 different malaria-endemic provinces in the first year of China’s National Malaria Elimination Programme (NMEP). A structured questionnaire was administrated to students at elementary and high schools enrolled. A total of 44,519 questionnaires were effective while 1,220 were excluded because of incomplete survey responses.ResultsMore than 60% of students were aware of malaria, but only 9,013 of them answered correctly to all five questions, and there were still 1,862 students unaware of malaria. There were significant differences of the awareness of malaria among different age groups, between male and female, between two different education levels.DiscussionThe study reveals that students at elementary and high school levels did not have adequate knowledge of malaria about biology, pathogenicity, transmitting vectors and preventive methods and so on at the beginning of NMEP in China. Further emphasis should be paid on health education campaigns in China to increase students’ public awareness of malaria about vector control, treatment, prevention.

Anopheles Vectors in Mainland China While Approaching Malaria Elimination

China is approaching malaria elimination; however, well-documented information on malaria vectors is still missing, which could hinder the development of appropriate surveillance strategies and WHO certification. This review summarizes the nationwide distribution of malaria vectors, their bionomic characteristics, control measures, and related studies. After several years of effort, the area of distribution of the principal malaria vectors was reduced, in particular for Anopheles lesteri (synonym: An. anthropophagus) and Anopheles dirus s.l., which nearly disappeared from their former endemic regions. Anopheles sinensis is becoming the predominant species in southwestern China. The bionomic characteristics of these species have changed, and resistance to insecticides was reported. There is a need to update surveillance tools and investigate the role of secondary vectors in malaria transmission.

Biology, Bionomics and Molecular Biology of Anopheles sinensis Wiedemann 1828 (Diptera: Culicidae), Main Malaria Vector in China

China has set a goal to eliminate all malaria in the country by 2020, but it is unclear if current understanding of malaria vectors and transmission is sufficient to achieve this objective. Anopheles sinensis is the most widespread malaria vector specie in China, which is also responsible for vivax malaria outbreak in central China. We reviewed literature from 1954 to 2016 on An. sinensis with emphasis on biology, bionomics, and molecular biology. A total of 538 references were relevant and included. An. sienesis occurs in 29 Chinese provinces. Temperature can affect most life-history parameters. Most An. sinensis are zoophilic, but sometimes they are facultatively anthropophilic. Sporozoite analysis demonstrated An. sinensis efficacy on Plasmodium vivax transmission. An. sinensis was not stringently refractory to P. falciparum under experimental conditions, however, sporozoite was not found in salivary glands of field collected An. sinensis. The literature on An. sienesis biology and bionomics was abundant, but molecular studies, such as gene functions and mechanisms, were limited. Only 12 molecules (genes, proteins or enzymes) have been studied. In addition, there were considerable untapped omics resources for potential vector control tools. Existing information on An. sienesis could serve as a baseline for advanced research on biology, bionomics and genetics relevant to vector control strategies.