Malaria is a life-threatening disease caused by Plasmodium parasites,which are transmitted to people through the bites of female Anopheles mosquitoes. The mainstay of current malaria control programs relies on insecticides to control vector mosquito population density and antimalarial drugs to treat infections. However,the emergence and increasing spread of mosquito insecticide resistance and parasite drug resistance have stalled the progress against malaria over the past few years,and call for new intervention strategies. Impeding malaria parasite infection in the vector Anopheles mosquito is a novel strategy to block malaria transmission at the source. The strategy of symbiotic control, using gut microbiota to inhibit parasite development in the mosquito midgut, has been regarded as a promising way to thwart malaria transmission. In this paper the development of symbiotic control including paratransgenesis during the past two decades has been summarized and the future direction of this promising malaria-control strategy has been discussed.

Malaria is a major vector-borne disease transmitted by the bite of Anopheles mosquito,which has caused a heavy disease, economical and social burden to China. After long-term effective malaria control and elimination actions,China was officially granted a malaria-free certification by the World Health Organization (WHO) in June 30, 2021. From "Eliminate the four pests to prevent diseases" initiated by the Patriotic Health Campaign Committee in the early years of the founding of the people’s Republic of China,to the integrated mosquito management strategy in the 1980s, to the sustainable vector management proposed in 2004,and then to Anopheles control of the epidemic spot in the stage of malaria elimination,the Anopheles control strategies and techniques in China have been evolved and innovated with stratified sustainable Anopheles control in the past 70 years,which has played a key role in malaria elimination in China. At present,there are still severe challenges and great pressure in controlling the risk of re-transmission caused by malaria importation and maintaining the malaria-free in China. It is necessary to continue to carry out sustainable control of Anopheles in China,and share the stratified sustainable Anopheles control strategies and practical experience for actively participating in the global action to eliminate malaria,so as to contribute Chinese efforts to realizing the vision of a Malaria-Free world and a community of common health for mankind.

The mosquitoes in the genus Anopheles are important disease vector, with 8 subgenera and 480 species known worldwide and 2 subgenera and 62 species in China, and are the unique genus of human malaria vector. The malaria still kills hundreds of thousands of people worldwide each year, with most of them being children under the age of five. China has made a decisive achievement in malaria control, and announced the elimination of local malaria transmission in China. The achievement has been granted by World Health Organization; however there are still imported cases every year. The elimination of malaria stems from effective vector control, as well as basic and applied scientific research relate Anopheles. With the change of climate and environment, the main malaria transmission vector species and their biological and ecological features are also potentially changing, and the surveillance and control of vectors remain an important issue that needs attention. In this paper, the taxonomic and phylogenetic studies of Anopheles, the ecology and transmission capability of the major malaria vectors, and the surveillance and control of Anopheles in China are reviewed, in order to provide a useful reference for the control of vector mosquitoes and related infectious diseases.

Objective To determine the genetic variation and structure of Anopheles lesteri populations in China using microsatellite loci, and to explore the factors affecting population genetic differentiation. Methods Adult mosquitoes were captured using a sucking tube. An. lesteri was identified based on morphology and rDNA ITS2. Genescan was performed in 9 microsatellite loci. Based on the fragment length polymorphism of microsatellite DNA, genetic diversity within and between populations were calculated. Structure software was used to estimate cluster number and effective population size. Results A total of 216 An. lesteri adults were identified in 17 collection sites, which were pooled into 9 populations for analysis. The mean number of alleles in the populations of An. lesteri ranged from 3.22 to 7.44, the mean expected heterozygosity and the observed heterozygosity were 0.48-0.71 and 0.33-0.47, respectively. The pairwise fixation index ranged from -0.01 to 0.25 (mean, 0.13). The variation within populations (86.55%) was greater than variation between populations (13.45%) that was positively correlated with geographic distance. Structure software showed that An. lesteri populations could be divided into cluster I (populations from Guangdong and Liaoning provinces of China) and cluster II (populations from Hainan, Hubei, Henan, Yunnan, and Sichuan provinces of China, and South Korea). Conclusion The genetic variation of An. lesteri populations in China mainly exists among individuals, with moderate variation levels, and the genetic structure of populations follows the isolation-by-distance model. An. lesteri belongs to two gene pools. Yunnan population was the original gene pool, which gradually migrated to east and north of China and led to the appearance of individuals in the second gene pool.

Objective To investigate the differences in the microbial composition in Anopheles sinensis and water in larvae breeding site. Methods An. sinensis adults were collected from Jiading district, Shanghai, China and divided into unfed (A) and fed (B) groups. Water samples were collected from paddy fields in the same area (W). Metagenomic DNA was extracted and the 16S rDNA V4 region was subjected to Illumina Miseq high-throughput sequencing. The sequence number and operational taxonomic units (OTUs) were used for statistical analysis of the composition and abundance of microflorae, the richness and diversity of bacterial communities, and changes in bacterial composition across communities, which were compared with the microbial composition in An. sinensis larvae (L). Results The numbers of high-quality sequences and clustered OTUs were 129 056/2 622.5 (A), 171 734/3 324.5 (B), and 225 890.5/2 997 (W), respectively. The clustered OTUs were assigned to 20 phyla, 144 families, and 295 genera. The bacterial richness as indicated by Chao1 index was in the order of B>W>A. The bacterial diversity was B>W>A (Simpson index) or A>B>W (Shannon index). The dominant bacteria in fed and unfed adults were Proteobacteria and Firmicutes, and the abundant genera were Acinetobacter (A, 41.35%; B, 25.71%) and Pantoea (A, 10.85%; B, 12.70%). Asaia was the most abundant (40.85%) in fed adults. In paddy field water, the dominant bacteria were Firmicutes, Bacteroides, and Proteobacteria. The genera with >10.00% abundances were Desulfosporosinus (24.19%), Flectobacillus (19.48%), Flavobacterium (15.27%), Pseudomonas (12.19%), and Alkalibacter (10.28%). As shown by the t test, the numbers of phyla with statistical differences between A, B, and L were 1 (B/A), 9 (L/A), and 9 (W/A). Principal component analysis showed similar bacterial diversity among samples in the same group, and heatmap showed that W and L clustered into one clade, while B and A into another clade. Conclusion An. sinensis adults are dominated by Acinetobacter, Pantoea, and Asaia. The composition of bacteria in paddy field water is similar to those in larvae living in the water as well as fed and unfed female mosquitos.

Objective To investigate the mutations of insecticide resistance-related genes through a sequencing analysis of the target genes of insecticides in Anopheles sinensis collected in Guangyuan of Sichuan province, China, and to provide guidance for the chemical control of An. sinensis in this region. Methods A total of 35 female An. sinensis mosquitoes collected in Jianshe village of Longtan township in Guangyuan of Sichuan province in September 2018 were selected, and genomic DNA was extracted after the abdomen was removed. PCR was used to obtain the gene fragments of acetylcholinesterase (ace), voltage-gated sodium channel (VGSC), and gamma-amino butyric acid receptor Rdl subunit (rdl), and then a sequencing analysis was performed. Results In comparison to the gene sequence of reference species, 20.00% of the 35 An. sinensis mosquitoes had resistance mutations, with a frequency of 5.71% for ace resistance allele (119 S), 7.14% and 1.43% for VGSC resistance alleles (1014F and 1014C), and 14.29% for rdl resistance allele (296S). Although there was a low proportion of An. sinensis mosquitoes with resistance mutations (<20.00%), mutations of multiple target genes were observed in more than 70.00% of the mosquitoes with mutation. Conclusion There is a certain proportion of resistance alleles in this An. sinensis population, with a genetic basis of developing high-level resistance, and the presence of mosquitoes with multiple target gene mutations indicates that this An. sinensis population has the possibility of developing into a multidrug-resistant population.

Objective To investigate the population density of Anopheles vector of malaria after elimination of malaria in Hangzhou, China, and to provide a basis for risk assessment of imported malaria transmission and development of control strategy. Methods Ten districts, counties, or cities in Hangzhou were selected as malaria vector monitoring sites from 2018 to 2019. The density of adult (malaria vector) and larval mosquito populations were monitored by lamp-trapping, human-trapping, and dip survey methods. The data of confirmed cases of vivax malaria in Hangzhou from 2016 to 2020 were collected. The characteristics of malaria vector and epidemic were analyzed. Results A total of 1 686 mosquitoes were captured by lamp-trapping from 2018 to 2019. Of malaria vectors, only An. sinensis (116, 6.88%) was captured in the suburb and rural areas. A total of 834 An. sinensis adults were captured by human-trapping. The density was the highest in late July, which was 0.56 mosquitoe/person-hour in suburb areas and 5.63 mosquitoes/person-hour in rural areas (20.50 mosquitoes/person-hour in Chun'an county). Only 373 An. sinensis larvae were captured by dip survey in rice fields, with the density of 0.70, 0.05, and 0.02 larva/dip in Chun'an county, Tonglu county, and Lin'an district, respectively. The density of larvae was the highest in late July (0.54 larva/dip on average). From 2016 to 2020, 12 imported cases of vivax malaria were reported in Hangzhou, mainly in Yuhang district and Xihu district. The mean time from onset to diagnosis was (7.08±8.24) d. Conclusion An. sinensis is the only malaria vector consistently present in Hangzhou, which is mainly found in rural areas and varies significantly across seasons. Undetected imported cases of vivax malaria still pose a risk of transmission in Hangzhou.

Objective To investigate the distribution of malaria vectors Anopheles after the elimination of malaria in 12 counties and cities in Dali Bai autonomous prefecture (Dali prefecture), Yunnan province, China; to assess the local risk of imported malaria retransmission, and to provide a basis for consolidating local achievements of malaria elimination and formulating local technical schemes for preventing imported malaria retransmission after elimination of malaria. Methods The study was conducted from July to September in 2017. According to the altitude, each county (city) was divided into high, middle, and low stratifications, and one natural village from each stratification was selected as the survey site. The all-night light trapping method and half-night human-bait method were used. One barn or human room in the east, west, south, north, and middle of each survey site was selected as an observation point. The all-night light trapping method was used to catch mosquitoes at each survey site for 3 consecutive nights per month, and the half-night human-bait method was used to catch mosquitoes at each low-altitude survey site once a month. Results A total of 13 species of Anopheles mosquitoes were captured, among which An. sinensis was distributed in all these 12 counties and cities; An. minimus was only caught in Yunlong county; An. kunmingensis was distributed in 7 counties and cities, i.e., Xiangyun county, Jianchuan county, Binchuan county, Heqing county, Eryuan county, Weishan county, and Dali city. The results of all-night light trapping method showed that Xiangyun county had the highest density of Anopheles mosquitoes (164.55 mosquitoes/light·night). The results of half-night human-bait method showed that only Jianchuan county and Heqing county had Anopheles mosquitoes caught, and the densities were 0.72 mosquitoes/net·h and 0.06 mosquitoes/net·h, respectively. Conclusion Considering the imported malaria cases in 2018-2020, Dali city is at risk of retransmission of Plasmodium vivax; Yunlong county is potentially at risk of retransmission of multiple malaria; the other 10 counties are all potentially at risk of retransmission of P. vivax. It is suggested that related departments should keep strengthening the team building for malaria control and the surveillance work of malaria vectors Anopheles.