Salivary factor LTRIN from Aedes aegypti facilitates the transmission of Zika virus by interfering with the lymphotoxin-ß receptor.

Pathogens have co-evolved with mosquitoes to optimize transmission to hosts. Mosquito salivary-gland extract is known to modulate host immune responses and facilitate pathogen transmission, but the underlying molecular mechanisms of this have remained unknown. In this study, we identified and characterized a prominent 15-kilodalton protein, LTRIN, obtained from the salivary glands of the mosquito Aedes aegypti. LTRIN expression was upregulated in blood-fed mosquitoes, and LTRIN facilitated the transmission of Zika virus (ZIKV) and exacerbated its pathogenicity by interfering with signaling through the lymphotoxin-ß receptor (LTßR). Mechanically, LTRIN bound to LTßR and 'preferentially' inhibited signaling via the transcription factor NF-κB and the production of inflammatory cytokines by interfering with the dimerization of LTßR during infection with ZIKV. Furthermore, treatment with antibody to LTRIN inhibited mosquito-mediated infection with ZIKV, and abolishing LTßR potentiated the infectivity of ZIKV both in vitro and in vivo. This study provides deeper insight into the transmission of mosquito-borne diseases in nature and supports the therapeutic potential of inhibiting the action of LTRIN to disrupt ZIKV transmission.

An improved alphaviruses-specific RT-qPCR facilitates monitoring and prevention of alphaviruses.

Molecular surveillance is vital for monitoring arboviruses, often employing genus-specific quantitative reverse-transcription polymerase chain reaction (RT-qPCR). Despite this, an overlooked chikungunya fever outbreak occurred in Yunnan province, China, in 2019 and false negatives are commonly encountered during alphaviruses screening practice, highlighting the need for improved detection methods. In this study, we developed an improved alphaviruses-specific RT-qPCR capable of detecting chikungunya virus, eastern equine encephalitis virus, western equine encephalitis virus, Venezuelan equine encephalitis virus, Sindbis virus, Mayaro virus, and Ross River virus with high sensitivity and specificity. The assay identified three chikungunya virus-positive cases out of 188 sera retrospectively. Later genetic characterization suggested that imported cases from neighboring countries may be responsible for the neglected chikungunya fever outbreak of 2019 in Yunnan. Our findings underscore the value of improved alphaviruses-specific RT-qPCR in bolstering alphaviruses surveillance and informing preventive strategies.

Epidemiological and clinical characteristics of the chikungunya outbreak in Ruili City, Yunnan Province, China.

Chikungunya fever is an acute infectious disease caused by the chikungunya virus (CHIKV) that is characterized by fever, rash, and joint pain. CHIKV has infected millions of people in Africa, Asia, America, and Europe since it re-emerged in the Indian Ocean region in 2004. Here, we report an outbreak of Chikungunya fever that occurred in Ruili of Yunnan Province, a city located on the border between China and Myanmar, in September 2019. The outbreak lasted for three months from September to December. Overall, 112 cases were confirmed by a real-time reverse-transcription polymerase chain reaction in the Ruili People's Hospital, and they showed apparent temporal, spatial, and population aggregation. Among them, 91 were local cases distributed in 19 communities of Ruili City, and 21 were imported cases. The number of female patients was higher than that of male patients, and most patients were between 20 and 60 years old. The main clinical manifestations included joint pain (91.96%), fever (86.61%), fatigue (58.04%), chills (57.14%), rash (48.21%), headache (39.29%), and so forth. Biochemical indexes revealed increased C-reactive protein (63.39%), lymphopenia (57.17%), increased hemoglobin (33.04%), neutrophilia (28.57%), and thrombocytopenia (16.07%). Phylogenetic analysis of the complete sequences indicated that the CHIKV strains in this outbreak belonged to the Indian Ocean clade of the East/Central/South African genotype. We speculated that this chikungunya outbreak might be caused by CHIKV-infected persons returning from Myanmar, and provided a reference for the formulation of effective treatment and prevention measures.

Survey of malaria vectors on the Cambodia, Thailand and China-Laos Borders.

BACKGROUND: Anopheles maculatus, Anopheles minimus and Anopheles dirus are the major vectors of malaria transmission in the Greater Mekong Subregion (GMS). The malaria burden in this region has decreased significantly in recent years as all GMS countries progress towards malaria elimination. It is necessary to investigate the Anopheles diversity and abundance status and assess the Plasmodium infection rates to understand the malaria transmission potential of these vector species in GMS countries to guide the development of up-to-date vector control strategies and interventions. METHODS: A survey of mosquitoes was conducted in Stung Treng, Sainyabuli and Phongsaly Provinces on the Cambodia-Laos, Thailand-Laos and China-Laos borders, respectively. Mosquito collection was done by overnight trapping at sentinel sites in each province. After morphological identification, the 18S rRNA-based nested-PCR was performed to detect malaria parasites in the captured Anopheles mosquitoes. RESULTS: A total of 18 965 mosquitoes comprising of 35 species of 2 subgenera (Subgenus Anopheles and Subgenus Cellia) and 4 tribes (Tribes Culicini, Aedini, Armigerini and Mansoniini) were captured. Tribe Culicini accounted for 85.66% of captures, followed by Subgenus Anopheles (8.15%). Anopheles sinensis dominated the Subgenus Anopheles by 99.81%. Plasmodium-infection was found in 25 out of the 1 683 individual or pooled samples of Anopheles. Among the 25 positive samples, 19, 5 and 1 were collected from Loum, Pangkhom and Siem Pang village, respectively. Eight Anopheles species were found infected with Plasmodium, i.e., An. sinensis, Anopheles kochi, Anopheles vagus, An. minimus, Anopheles annularis, Anopheles philippinensis, Anopheles tessellatus and An. dirus. The infection rates of Plasmodium falciparum, Plasmodium vivax and mixture of Plasmodium parasite species were 0.12% (2/1 683), 1.31% (22/1 683) and 0.06% (1/1 683), respectively. CONCLUSIONS: Overall, this survey re-confirmed that multiple Anopheles species carry malaria parasites in the international border areas of the GMS countries. Anopheles sinensis dominated the Anopheles collections and as carriers of malaria parasites, therefore may play a significant role in malaria transmission. More extensive investigations of malaria vectors are required to reveal the detailed vector biology, ecology, behaviour, and genetics in GMS regions in order to assist with the planning and implementation of improved malaria control strategies.

Molecular phylogeny of Anopheles nivipes based on mtDNA-COII and mosquito diversity in Cambodia-Laos border.

BACKGROUND: Few studies have been conducted to investigate the distribution of mosquito vectors and the population structure of secondary vectors in the border region of Cambodia-Laos. The aim of this work was to study the mosquito diversity and molecular phylogeny of secondary vectors, i.e., Anopheles nivipes in this area. METHODS: 1440 adult mosquitoes were trapped in the Cambodia-Laos border. mtDNA-COII were amplified and sequenced from 53 An. nivipes DNA samples. Together with COII sequences deposited in GenBank, a total of 86 COII sequences were used for examining population variations, genetic differentiation, spatial population structure, population expansion, and gene flow patterns. RESULTS: The adult mosquitoes were classified into 5 genera and 27 species in this border region. The predominant genera were Culex (60.07%, 865/1440) and Anopheles (31.25%, 450/1440), and the major Anopheles species were An. nivipes (73.56%, 331/450) and Anopheles maculatus (14.22%, 64/450). Based on sequences analysis of COII, a high level of genetic differentiation was reported in two Northwest India (Cheema and Bathinda, Punjab) and Cambodia-Laos (Siem Pang, Stung treng) populations (FST = 0.97824, 0.97343, P < 0.05), as well as lower gene flow (Nm = 0.01112, 0.01365) in the An. nivipes populations. Phylogenetic analysis and SAMOVA revealed a gene barrier restricting gene flow among three An. nivipes populations. Mantel test suggested a significant correlation between geography and gene distance in all An. nivipes populations (Z = 44,983.1865, r = 0.5575, P = 0.0070). Neutrality test and Mismatch distribution revealed a recent population expansion of An. nivipes in the Cambodia-Laos population. CONCLUSIONS: Anopheles nivipes was one of the major Anopheles species in the Cambodia-Laos border. Based on sequences analysis of COII, a genetic barrier between Cambodia-Laos and two Indian populations was found, and a recent population expanding or selecting of An. nivipes occurred in the Cambodia-Laos population, suggesting that COII might be an effective marker for describing the molecular phylogeny of An. nivipes. Further investigation and continuous surveillance of An. nivipes are warranted in this region.

Evolutionary analysis of a newly isolated Banna virus strain from Yunnan, China.

Banna virus (BAV) is a typical arbovirus whose infection is associated with fever and viral encephalitis. The whole genome of BAV is composed of 12 RNA segments. BAVs, which have been divided into three genotypes (A, B, and C) based on phylogenetic analysis of segment 12 or segment 9, are currently undergoing rapid evolution. Recent studies have shown that BAV variation can exceed intraspecific limits and generate novel viruses. In the current study, a new BAV strain, named 113c5, was isolated from Culex tritaeniorhynchus and found to be a member of genotype A2 based on phylogenetic analysis of segments 9 and 12. The complete genome sequence of the new BAV strain described in the current study might contribute to the surveillance of evolutionary characteristics of BAVs.

Epidemiologic Analysis of Efforts to Achieve and Sustain Malaria Elimination along the China-Myanmar Border.

Malaria cases have dramatically declined in China along the Myanmar border, attributed mainly to adoption of the 1-3-7 surveillance and response approach. No indigenous cases have been reported in China since 2017. Counties in the middle and southern part of the border area have a higher risk for malaria importation and reestablishment after elimination.

Axl Deficiency Promotes the Neuroinvasion of Japanese Encephalitis Virus by Enhancing IL-1α Production from Pyroptotic Macrophages.

Japanese encephalitis virus (JEV) is a flavivirus that causes Japanese encephalitis (JE), which has an unclear pathogenesis. Despite vaccination, thousands of deaths attributed to JE are reported annually. In this study, we report that mice deficient for Axl, a receptor tyrosine kinase that plays multiple roles in flaviviral infection, displayed greater mortality upon JEV infection. The effect of Axl deficiency on JEV infection was mediated by markedly elevated serum interleukin-1α (IL-1α) levels, which devastated the blood-brain-barrier and promoted viral neuroinvasion within 24 h postinfection. Using an in situ infection model, we showed that dead macrophages were the primary source of observed increased serum IL-1α levels. Axl deficiency enhanced cell death and caused pyroptosis in 80% of JEV-infected macrophages by disrupting phosphatidylinositol 3-kinase (PI3K)-Akt signaling. Intriguingly, the primary effector released by pyroptotic macrophages in our model was IL-1α rather than IL-1ß. Finally, we assessed the effect of an IL-1α antagonist and demonstrated that it effectively prevented the incidence of JE. Our results indicate that Axl plays a protective role in JEV infection, identify IL-1α released by pyroptotic macrophages as a crucial factor promoting JEV neuroinvasion, and suggest that an IL-1α antagonist may be a candidate for JE therapy.IMPORTANCE Japanese encephalitis virus (JEV) is a mosquito-borne flavivirus that causes Japanese encephalitis (JE), the most commonly diagnosed viral encephalitis worldwide. The fatality rate of JE is 20%, and nearly half of the surviving patients develop neuropsychiatric sequelae. Axl is a receptor tyrosine kinase that plays multiple roles in flaviviral infections. Currently, the involvement of Axl in JEV infection remains enigmatic. In this study, we demonstrate that Axl impedes the pathogenesis of severe JE in mice by maintaining blood-brain-barrier (BBB) integrity and restricting viral neuroinvasion. Furthermore, serum IL-1α is a key mediator of this process and is primarily released by JEV-infected pyroptotic macrophages to elicit BBB breakdown, while an IL-1α antagonist can effectively reduce the incidence of severe JE. Our work uncovers the protective role of Axl in antagonizing severe JE and shows that the use of an IL-1α antagonist may be a promising tactic to prevent severe JE.

Seven decades towards malaria elimination in Yunnan, China.

BACKGROUND: Yunnan Province was considered the most difficult place in China for malaria elimination because of its complex malaria epidemiology, heterogeneous ecological features, relatively modest economic development, and long, porous border with three malaria endemic countries: Lao People's Democratic Republic, Myanmar, and Viet Nam. METHODS: Academic publications and grey literature relevant to malaria elimination in Yunnan covering the period from 1950 until 2020 inclusive were considered. The following academic indexes were searched: China Science Periodical Database, China National Knowledge Infrastructure Database, and MEDLINE. Grey literature sources were mainly available from the National Institute of Parasitic Diseases (NIPD), the Chinese Center for Diseases Control and Prevention, and the Yunnan Institute of Parasitic Diseases (YIPD). RESULTS: A malaria elimination campaign in the 1950-1960s, based mainly on mass administration of antimalarial drugs and large-scale vector control, reduced morbidity and mortality from malaria and interrupted transmission in some areas, although elimination was not achieved. Similar strategies were used to contain outbreaks and a resurgence of disease during the 1970s, when malaria services were discontinued. From the 1980s, malaria incidence declined, despite the challenges of large numbers of mobile and migrant populations and an unstable primary health care system in rural areas following economic transformation. Launch of the national malaria elimination programme in 2010 led to adoption of the '1-3-7' surveillance and response strategy specifying timely detection of and response for every case, supported by the establishment of a real-time web-based disease surveillance system and a new primary health care system in rural areas. Border malaria was addressed in Yunnan by strengthening the surveillance system down to the lowest level, cross-border collaboration with neighbouring countries and non-governmental organizations, and the involvement of other sectors. CONCLUSIONS: Seven decades of work to eliminate malaria in Yunnan have shown the importance of political commitment, technically sound strategies with high quality implementation, a robust surveillance and response system at all levels, community participation and effective management of border malaria. The experiences and lessons learned from elimination remain important for prevention re-establishment of malaria transmission in the Province.

Intensive surveillance, rapid response and border collaboration for malaria elimination: China Yunnan's ''3 + 1''strategy.

BACKGROUND: Eliminating malaria and preventing re-establishment of malaria transmission in border areas requires universal coverage of malaria surveillance and a rapid response to any threats (i.e. malaria cues) of re-establishing transmission. MAIN TEXT: Strategy 1: Intensive interventions within 2.5 km-wide perimeter along the border to prevent border-spill malaria. The area within 2.5 km along the international border is the travel radius of anopheline mosquitoes. Comprehensive interventions should include: (1) proactive and passive case detection, (2) intensive vector surveillance, (3) evidence-based vector control, and (4) evidence-based preventative treatment with anti-malarial drugs. Strategy 2: Community-based malaria detection and screening of migrants and travellers in frontier townships. Un-permitted travellers cross borders frequently and present in frontier townships. Maintenance of intensified malaria surveillance should include: (1) passive malaria detection in the township hospitals, (2) seek assistance from villager leaders and health workers to monitor cross border travellers, and refer febrile patients to the township hospitals and (3) the county's Centre for Disease Control and Prevention maintain regular proactive case detection. Strategy 3: Universal coverage of malaria surveillance to detect malaria cues. Passive detection should be consolidated into the normal health service. Health services personnel should remain vigilant to ensure universal coverage of malaria detection and react promptly to any malaria cues. Strategy + 1: Strong collaborative support with neighbouring countries. Based on the agreement between the two countries, integrated control strategies should be carried out to reduce malaria burden for both countries. There should be a clear focus on the border areas between neighbouring countries. CONCLUSION: The 3 + 1 strategy is an experience summary of border malaria control and elimination, and then contributed to malaria elimination in Yunnan's border areas, China. Nevertheless, Yunnan still has remaining challenges of re-establishment of malaria transmission in the border areas, and the 3 + 1 strategy should still be carried out.

Effectiveness of joint 3 + 1 malaria strategy along China-Myanmar cross border areas.

BACKGROUND: Cross-border malaria in Laiza City of Myanmar seriously affected Yingjiang County of China and compromised reaching the goal of malaria elimination by 2020. Since 2017, a pilot project on 3 + 1 strategy of joint cross-border malaria prevention and control was carried out for building a malaria buffer in these border areas. Here, 3 were the three preventive lines in China where different focalized approaches of malaria elimination were applied and + 1 was a defined border area in Myanmar where the integrated measures of malaria control were adopted. METHODS: A 5-year retrospective analysis (2015 to 2019) was conducted that included case detection, parasite prevalence and vector surveillance. Descriptive statistics was used and the incidence or rates were compared. The annual parasite incidence and the parasite prevalence rate in + 1 area of Myanmar, the annual importation rate in Yingjiang County of China and the density of An. minimus were statistically significant indictors to assess the effectiveness of the 3 + 1 strategy. RESULTS: In + 1 area of Myanmar from 2015 to 2019, the averaged annual parasite incidence was (59.11 ± 40.73)/1000 and Plasmodium vivax accounted for 96.27% of the total confirmed cases. After the pilot project, the annual parasite incidence dropped 89% from 104.77/1000 in 2016 to 12.18/1000 in 2019, the microscopic parasite prevalence rate dropped 100% from 0.34% in 2017 to zero in 2019 and the averaged density of An. Minimus per trap-night dropped 93% from 1.92 in June to 0.13 in September. The submicroscopic parasite prevalence rate increased from 1.15% in 2017 to 1.66% in 2019 without significant difference between the two surveys (P = 0.084). In Yingjiang County of China, neither indigenous nor introduced case was reported and 100% cases were imported from Myanmar since 2017. The averaged annual importation rate from 2015 to 2019 was (0.47 ± 0.15)/1000. After the pilot project, the annual importation rate dropped from 0.59/1000 in 2016 to 0.28/1000 in 2019 with an overall reduction of 53% in the whole county. The reduction was 67% (57.63/1000 to 18.01/1000) in the first preventive line, 52% (0.20/1000 to 0.10/1000) in the second preventive line and 36% (0.32/1000 to 0.22/1000) in the third preventive line. The averaged density of An. Minimus per trap-night in the first preventive line dropped 94% from 2.55 in June to 0.14 in September, without significant difference from that of + 1 area of Myanmar (Z value = - 1.18, P value = 0.24). CONCLUSION: The pilot project on 3 + 1 strategy has been significantly effective in the study areas and a buffer zone of border malaria was successfully established between Laiza City of Myanmar and Yingjiang County of China.

Genetic polymorphism of merozoite surface proteins 1 and 2 of Plasmodium falciparum in the China-Myanmar border region.

BACKGROUND: Malaria is a major public health problem in the China-Myanmar border region. The genetic structure of malaria parasite may affect its transmission model and control strategies. The present study was to analyse genetic diversity of Plasmodium falciparum by merozoite surface proteins 1 and 2 (MSP1 and MSP2) and to determine the multiplicity of infection in clinical isolates in the China-Myanmar border region. METHODS: Venous blood samples (172) and filter paper blood spots (70) of P. falciparum isolates were collected from the patients of the China-Myanmar border region from 2006 to 2011. The genomic DNA was extracted, and the msp1 and msp2 genes were genotyped by nested PCR using allele-specific primers for P. falciparum. RESULTS: A total of 215 P. falciparum clinical isolates were genotyped at the msp1 (201) and msp2 (204), respectively. For the msp1 gene, MAD20 family was dominant (53.49%), followed by the K1 family (44.65%), and the RO33 family (12.56%). For the msp2 gene, the most frequent allele was the FC27 family (80.93%), followed by the 3D7 family (75.81%). The total multiplicity of infection (MOI) of msp1 and msp2 was 1.76 and 2.21, with a prevalence of 64.19% and 72.09%, respectively. A significant positive correlation between the MOI and parasite density was found in the msp1 gene of P. falciparum. Sequence analysis revealed 38 different alleles of msp1 (14 K1, 23 MAD20, and 1 RO33) and 52 different alleles of msp2 (37 3D7 and 15 FC27). CONCLUSION: The present study showed the genetic polymorphisms with diverse allele types of msp1 and msp2 as well as the high MOI of P. falciparum clinical isolates in the China-Myanmar border region.

Complete genome sequence of a novel negevirus isolated from Culex tritaeniorhynchus in China.

A novel negevirus, tentatively named Manglie virus (MaV), was isolated from Culex tritaeniorhynchus from the village of Manglie, Yunnan, China, in August 2011. It was identified by high-throughput sequencing of cell culture supernatants, and the complete genome was sequenced using an Illumina MiSeq sequencer. The complete MaV genome comprised 9,218 nt encoding three hypothetical proteins and had a poly(A) tail. BLASTn analysis showed that the genome had the greatest similarity to Ngewotan virus strain Nepal22, with query coverage of 100% and 79% identity. Genomic and phylogenetic analyses demonstrated that MaV should be considered a novel negevirus.

Molecular characterization and phylogenetic analysis of a dengue virus serotype 3 isolated from a Chinese traveler returned from Laos.

BACKGROUND: Dengue virus (DENV) infection caused by international visitors has become a public health concern in China. Although sporadic imported cases of DENV have been documented in Yunnan, China since 2000, a complete genome sequence of dengue virus serotype 3 (DENV-3) imported from Laos is still not available. Here, we report the first complete genome sequence and genomic characterization of a DENV-3 strain (YNPE3) isolated from a patient returned from Laos. METHODS: Viral isolation from the patient's serum was performed using mosquitoes C6/36 cells. Reverse transcriptase polymerase chain reaction (RT-PCR) was used for identification and serotyping of the virus. The complete sequence was determined by Sanger dideoxy sequencing. Homology analysis was implemented by NCBI-BLAST. Multiple sequence alignment was performed using MegAlign module of the Lasergene 7 software package DNASTAR. MFOLD software was used to predict the RNA secondary structure of 5' untranslated region (UTR) and 3' UTR. Phylogenetic analysis, which was based on envelope gene and complete coding sequence, was performed by Maximum-Likelihood method. RESULTS: RT-PCR analysis confirmed that the virus belonged to dengue virus serotype 3, which was named YNPE3 strain. The full-length genome of the YNPE3 strain was 10,627 nucleotides (nts) with an open reading frame (ORF) encoding 3390 amino acids. Strain YNPE3 shared 98.6-98.8% nucleotide identity with the closely related strains isolated in India (JQ922556, KU216209, KU216208). We observed the deletion of about 40 nts in the 5' UTR and 3' UTR of strain YNPE3, and 11 nts (ACGCAGGAAGT) insertion that was present in the 3' UTR of YNPE3. Compared with prototype strain H87, abundant amino acid substitutions in the YNPE3 strain were observed. Phylogenetic analysis revealed that the YNPE3 strain belonged to genotype III of DENV-3, and that it might be closely related with genotype III strains isolated in Laos and India. CONCLUSIONS: This is the first report of the complete genome sequence and molecular characterization of a DENV-3 isolate imported from Laos. The presented results can further promote disease surveillance, and epidemiological and evolutionary studies of the DENV-3 in Yunnan province of China.

Full-length genome and molecular characterization of dengue virus serotype 2 isolated from an imported patient from Myanmar.

BACKGROUND: Dengue is the most common mosquito-borne infection worldwide and a serious threat to global public health. Sporadic dengue virus serotype 2 (DENV-2) imported cases from Myanmar have been documented almost every year in Yunnan Province of China since 2005. However, the complete genome sequences of DENV-2 isolates imported from Myanmar are not available. METHODS: The full-length genome of the DENV-2 strain (YNPE2), isolated from an imported case from Myanmar in 2013, was identified by the next-generation sequencing. The extreme ends of the viral genome were validated by 5'/3' RACE and Sanger sequencing. Furthermore, phylogenetic, recombination and selection pressure analyses were conducted for the molecular characterization of YNPE2 strain. RESULTS: Whole-genome sequencing revealed that the full-length sequence of YNPE2 strain was 10,724 bases, with an open reading frame encoding for 3391 amino acids. The YNPE2 strain had 99.0% nucleotide identity and 99.8% amino acid identity with two closely related strains, ThD2_0078_01 strain (DQ181797) and DENV-2/TH/BID-V2157/200 strain (FJ639832). The phylogenetic analysis suggested that the YNPE2 strain belonged to Asian I genotype and was likely derived from Thailand strain (DQ181797). Moreover, selection pressure analysis revealed two amino acid sites of the NS4B and NS5 proteins, with important evidence of positive selection. CONCLUSION: This study revealed the first complete genome sequence and molecular characterization of a DENV-2 strain (YNPE2) isolated from an imported case from Myanmar, thus providing a valuable reference genome source for future surveillance, epidemiology and vaccine development of DENV-2 virus in Yunnan, China.

Molecular characterization of an imported dengue virus serotype 4 isolate from Thailand.

The epidemic of dengue virus infections has spread markedly in Yunnan province of China in recent years due to an increase in the number of imported dengue cases. To the best of our knowledge, the present study is the first to report a whole genome sequence and molecular characterization of an imported DENV-4 isolate from Thailand. The current strain, 2013JH285, has an RNA genome of 10,772 nucleotides that shares 99.0% nucleotide and 99.7% amino acid sequence identity with the 2013 Thailand strain CTI2-13. Phylogenetic analysis of the whole genome sequence revealed that the 2013JH285 strain belongs to genotype I of DENV-4. Recombination analysis suggested that the 2013JH285 strain originated from inter-genotypic recombination of DENV-4 strains. The new complete DENV-4 genome sequence reported here might contribute to further understanding of the molecular epidemiology and disease surveillance of DENV-4 in China.

Receptivity to malaria in the China-Myanmar border in Yingjiang County, Yunnan Province, China.

BACKGROUND: The re-establishment of malaria has become an important public health issue in and out of China, and receptivity to this disease is key to its re-emergence. Yingjiang is one of the few counties with locally acquired malaria cases in the China-Myanmar border in China. This study aimed to understand receptivity to malaria in Yingjiang County, China, from June to October 2016. METHODS: Light-traps were employed to capture the mosquitoes in 17 villages in eight towns which were categorized into four elevation levels: level 1, 0-599 m; level 2, 600-1199 m; level 3, 1200-1799 m; and level 4, > 1800 m. Species richness, diversity, dominance and evenness were used to picture the community structure. Similarity in species composition was compared between different elevation levels. Data of seasonal abundance of mosquitoes, human biting rate, density of light-trap-captured adult mosquitoes and larvae, parous rate, and height distribution (density) of Anopheles minimus and Anopheles sinensis were collected in two towns (Na Bang and Ping Yuan) each month from June to October, 2016. RESULTS: Over the study period, 10,053 Anopheles mosquitoes were collected from the eight towns, and 15 Anopheles species were identified, the most-common of which were An. sinensis (75.4%), Anopheles kunmingensis (15.6%), and An. minimus (3.5%). Anopheles minimus was the major malaria vector in low-elevation areas (< 600 m, i.e., Na Bang town), and An. sinensis in medium-elevation areas (600-1200 m, i.e., Ping Yuan town). In Na Bang, the peak human-biting rate of An. minimus at the inner and outer sites of the village occurred in June and August 2016, with 5/bait/night and 15/bait/night, respectively. In Ping Yuan, the peak human-biting rate of An. sinensis was in August, with 9/bait/night at the inner site and 21/bait/night at the outer site. The two towns exhibited seasonal abundance with high density of the two adult vectors: The peak density of An. minimus was in June and that of An. sinensis was in August. Meanwhile, the peak larval density of An. minimus was in July, but that of An. sinensis decreased during the investigation season; the slightly acidic water suited the growth of these vectors. The parous rates of An. sinensis and An. minimus were 90.46 and 93.33%, respectively. CONCLUSIONS: The Anopheles community was spread across different elevation levels. Its structure was complex and stable during the entire epidemic season in low-elevation areas at the border. The high human-biting rates, adult and larval densities, and parous rates of the two Anopheles vectors reveal an exceedingly high receptivity to malaria in the China-Myanmar border in Yingjiang County.

Complete genome sequence of Menghai rhabdovirus, a novel mosquito-borne rhabdovirus from China.

Menghai rhabdovirus (MRV) was isolated from Aedes albopictus in Menghai county of Yunnan Province, China, in August 2010. Whole-genome sequencing of MRV was performed using an Ion PGM™ Sequencer. We found that MRV is a single-stranded, negative-sense RNA virus. The complete genome of MRV has 10,744 nt, with short inverted repeat termini, encoding five typical rhabdovirus proteins (N, P, M, G, and L) and an additional small hypothetical protein. Nucleotide BLAST analysis using the BLASTn method showed that the genome sequence most similar to that of MRV is that of Arboretum virus (NC_025393.1), with a Max score of 322, query coverage of 14%, and 66% identity. Genomic and phylogenetic analyses both demonstrated that MRV should be considered a member of a novel species of the family Rhabdoviridae.

Complete genome sequence of Menghai flavivirus, a novel insect-specific flavivirus from China.

Menghai flavivirus (MFV) was isolated from Aedes albopictus in Menghai county of Yunnan Province, China, during an arboviruses screening program in August 2010. Whole genome sequencing of MFV was performed using an Ion PGM™ Sequencer. The complete genome of MFV was 10897 nucleotides in length and encoded a polyprotein and fairly interesting flavivirus orf (FIFO). The polyprotein contained three flavivirus structural proteins (C, prM/M and E) and seven nonstructural proteins. Nucleotide BLAST analysis revealed that the MFV genome showed highest similarity to Xishuangbanna Aedes flavivirus, a novel insect-specific flavivirus recently isolated from the same area. These species shared a query cover of 99%, but only 71% identity, while FIFO showed no similarity with any of the published sequences. Genomic and phylogenetic analyses suggested that MFV was a novel species of the genus Flavivirus. Our findings enrich our understanding of the genetics and prevalence of the family Flaviviridae.