The effect of artificial light at night (ALAN) on the characteristics of diapause of Aedes albopictus.

BACKGROUND: Recently, the effect of artificial light at night (ALAN) on the physiology and behavior of insects has gradually attracted the attention of researchers and has become a new research topic. Aedes albopictus is an important vector that poses a great public health risk. Further studies on the diapause of Ae. albopictus can provide a basis for new vector control, and it is also worth exploring whether the effect of ALAN on the diapause of Ae. albopictus will provide a reference for the prevention and control of infectious diseases mediated by Ae. albopictus. METHODS: In this study, we experimentally studied the diapause characteristics of different geographical strains of Ae. albopictus under the interference of ALAN, explored the effect of ALAN on the diapause of Ae. albopictus and explored the molecular mechanism of ALAN on the diapause process through RNA-seq. RESULTS: As seen from the diapause incidence, Ae. albopictus of the same geographic strain showed a lower diapause incidence when exposed to ALAN. The differentially expressed genes (DEGs) were mainly enriched in signaling and metabolism-related pathways in the parental females and diapause eggs of the ALAN group. CONCLUSIONS: ALAN inhibits Ae. albopictus diapause. In the short photoperiod induced diapause of Ae. albopictus in temperate strain Beijing and subtropical strain Guangzhou, the disturbance of ALAN reduced the egg diapause rate and increased the egg hatching rate of Ae. albopictus, and the disturbance of ALAN also shortened the life cycle of Ae. albopictus eggs after hatching.

The predicted potential distribution of Aedes albopictus in China under the shared socioeconomic pathway (SSP)1-2.6.

Aedes albopictus (Skuse) (Diptera: Culicidae) is one of the 100 most invasive species in the world and represents a significant threat to public health. The distribution of Ae. albopictus has been expanding rapidly due to increased international trade, population movement, global warming and accelerated urbanization. Consequently, it is very important to know the potential distribution area of Ae. albopictus in advance for early warning and control of its spread and invasion. We randomly selected 282 distribution sites from 27 provincial-level administrative regions in China, and used the GARP and MaxEnt models to analyze and predict the current and future distribution areas of Ae. albopictus in China. The results showed that the current range of Ae. albopictus in China covers most provinces such as Yunnan and Guizhou Provinces, and the distribution of Ae. albopictus in border provinces such as Tibet, Gansu and Jilin Provinces tend to expand westwards. In addition, the potential distribution area of Ae. albopictus in China will continue to expand westwards due to future climate change under the SSP126 climate scenario. Furthermore, the results of environmental factor filtering showed that temperature and precipitation had a large effect on the distribution probability of Ae. albopictus.

Population genetic characteristics of Aedes aegypti in 2019 and 2020 under the distinct circumstances of dengue outbreak and the COVID-19 pandemic in Yunnan Province, China.

Introduction: Since Aedes aegypti invaded Yunnan Province in 2002, its total population has continued to expand. Shi et al. used microsatellite and mitochondrial molecular markers to study the Ae. aegypti populations in Yunnan Province in 2015 and 2016, found that it showed high genetic diversity and genetic structure. However, there are few studies on the population genetic characteristics of Ae. aegypti in Yunnan Province under different levels of human intervention. This study mainly used two common types of molecular markers to analyze the genetic characteristics of Ae. aegypti, revealing the influence of different input, prevention and control pressures on the genetic diversity and structure of this species. Understanding the genetic characteristics of Ae. aegypti populations and clarifying the diversity, spread status, and source of invasion are essential for the prevention, control and elimination of this disease vector. Methods: We analyzed the genetic diversity and genetic structure of 22 populations sampled in Yunnan Province in 2019 and 17 populations sampled in 2020 through nine microsatellite loci and COI and ND4 fragments of mitochondrial DNA. In 2019, a total of 22 natural populations were obtained, each containing 30 samples, a total of 660 samples. In 2020, a total of 17 natural populations were obtained. Similarly, each population had 30 samples, and a total of 510 samples were obtained. Results: Analysis of Ae. aegypti populations in 2019 and 2020 based on microsatellite markers revealed 67 and 72 alleles, respectively. The average allelic richness of the populations in 2019 was 3.659, while that in 2020 was 3.965. The HWE analysis of the 22 populations sampled in 2019 revealed significant departure only in the QSH-2 population. The 17 populations sampled in 2020 were all in HWE. The average polymorphic information content (PIC) values were 0.546 and 0.545, respectively, showing high polymorphism. The average observed heterozygosity of the 2019 and 2020 populations was 0.538 and 0.514, respectively, and the expected average heterozygosity was 0.517 and 0.519, showing high genetic diversity in all mosquito populations. By analyzing the COI and ND4 fragments in the mitochondrial DNA of Ae. aegypti, the populations sampled in 2019 had a total of 10 COI haplotypes and 17 ND4 haplotypes. A total of 20 COI haplotypes were found in the populations sampled in 2020, and a total of 24 ND4 haplotypes were obtained. STRUCTURE, UPGMA and DAPC cluster analyses and a network diagram constructed based on COI and ND4 fragments showed that the populations of Ae. aegypti in Yunnan Province sampled in 2019 and 2020 could be divided into two clusters. At the beginning of 2020, due to the impact of COVID-19, the flow of goods between the port areas of Yunnan Province and neighboring countries was reduced, and the sterilization was more effective when goods enter the customs, leading to different immigration pressures on Ae. aegypti population in Yunnan Province between 2019 and 2020, the source populations of the 2019 and 2020 populations changed. Mantel test is generally used to detect the correlation between genetic distance and geographical distance, the analysis indicated that population geographic distance and genetic distance had a moderately significant correlation in 2019 and 2020 (2019: p < 0.05 R2 = 0.4807, 2020: p < 0.05 R2 = 0.4233). Conclusion: Ae. aegypti in Yunnan Province maintains a high degree of genetic diversity. Human interference is one reason for the changes in the genetic characteristics of this disease vector.

Transcriptome Analysis of Response to Zika Virus Infection in Two Aedes albopictus Strains with Different Vector Competence.

Zika virus (ZIKV), which is mainly transmitted by Aedes albopictus in temperate zones, can causes serious neurological disorders. However, the molecular mechanisms that influence the vector competence of Ae. albopictus for ZIKV are poorly understood. In this study, the vector competence of Ae. albopictus mosquitoes from Jinghong (JH) and Guangzhou (GZ) Cities of China were evaluated, and transcripts in the midgut and salivary gland tissues were sequenced on 10 days post-infection. The results showed that both Ae. albopictus JH and GZ strains were susceptible to ZIKV, but the GZ strain was more competent. The categories and functions of differentially expressed genes (DEGs) in response to ZIKV infection were quite different between tissues and strains. Through a bioinformatics analysis, a total of 59 DEGs that may affect vector competence were screened-among which, cytochrome P450 304a1 (CYP304a1) was the only gene significantly downregulated in both tissues of two strains. However, CYP304a1 did not influence ZIKV infection and replication in Ae. albopictus under the conditions set in this study. Our results demonstrated that the different vector competence of Ae. albopictus for ZIKV may be determined by the transcripts in the midgut and salivary gland, which will contribute to understanding ZIKV-mosquito interactions and develop arbovirus disease prevention strategies.

Replication and transmission of West Nile virus in simulated overwintering adults of Culex pipiens pallens (Diptera: Culicidae) in China.

West Nile virus is perhaps the widest distributed arbovirus globally, being maintained in nature by transmission among ornithophagic Culex mosquitoes and a wide-variety of birds. A factor contributing to the success of the WNV invasion is the ability of the virus to successfully overwinter. Experimental studies on the preservation and transmission of West Nile virus by Culex pipiens pallens under simulated overwintering conditions have shown that Cx. p. pallens has a preservative effect on West Nile virus under low-temperature conditions. After the temperature rises, the virus reproduces rapidly and can spread to susceptible animals while the mosquitos feed on blood. This research is of great significance for exploring how West Nile virus enters new areas and how the cycle of transmission is maintained China.

Wolbachia infection in field-collected Aedes aegypti in Yunnan Province, southwestern China.

Background: Wolbachia is gram-negative and common intracellular bacteria, which is maternally inherited endosymbionts and could expand their propagation in host populations by means of various manipulations. Recent reports reveal the natural infection of Wolbachia in Aedes Aegypti in Malaysia, India, Philippines, Thailand and the United States. At present, none of Wolbachia natural infection in Ae. aegypti has been reported in China. Methods: A total of 480 Ae. aegypti adult mosquitoes were collected from October and November 2018 based on the results of previous investigations and the distribution of Ae. aegypti in Yunnan. Each individual sample was processed and screened for the presence of Wolbachia by PCR with wsp primers. Phylogenetic trees for the wsp gene was constructed using the neighbour-joining method with 1,000 bootstrap replicates, and the p-distance distribution model of molecular evolution was applied. Results: 24 individual adult mosquito samples and 10 sample sites were positive for Wolbachia infection. The Wolbachia infection rate (IR) of each population ranged from 0 - 41.7%. The infection rate of group A alone was 0%-10%, the infection rate of group B alone was 0%-7.7%, and the infection rate of co-infection with A and B was 0-33.3%. Conclusions: Wolbachia infection in wild Ae. aegypti in China is the first report based on PCR amplification of the Wolbachia wsp gene. The Wolbachia infection is 5%, and the wAlbA and wAlbB strains were found to be prevalent in the natural population of Ae. aegypti in Yunnan Province.

Genetic Diversity and Population Genetic Structure of Aedes albopictus in the Yangtze River Basin, China.

Aedes albopictus is an indigenous primary vector of dengue and Zika viruses in China. Understanding the population spatial genetic structure, migration, and gene flow of vector species is critical to effectively preventing and controlling vector-borne diseases. The genetic variation and population structure of Ae. albopictus populations collected from 22 cities along the Yangtze River Basin were investigated with nine microsatellite loci and the mitochondrial CoxI gene. The polymorphic information content (PIC) values ranged from 0.534 to 0.871. The observed number of alleles (Na) values ranged from 5.455 to 11.455, and the effective number of alleles (Ne) values ranged from 3.106 to 4.041. The Shannon Index (I) ranged from 1.209 to 1.639. The observed heterozygosity (Ho) values ranged from 0.487 to 0.545. The FIS value ranged from 0.047 to 0.212. All Ae. albopictus populations were adequately allocated to three clades with significant genetic differences. Haplotype 2 is the most primitive molecular type and forms 26 other haplotypes after one or more site mutations. The rapid expansion of high-speed rail, aircraft routes and highways along the Yangtze River Basin have accelerated the dispersal and communication of mosquitoes, which appears to have contributed to inhibited population differentiation and promoted genetic diversity among Ae. albopictus populations.

Fine-scale genetic structure and wolbachia infection of aedes albopictus (Diptera: Culicidae) in Nanjing city, China.

Background: Aedes albopictus is an indigenous primary vector of dengue and Zika viruses in China. Wolbachia is a gram-negative and common intracellular bacteria, which is maternally inherited endosymbionts and could expand their propagation in host populations by means of various manipulations. Compared with research on the dispersion of Ae. albopictus at the macrospatial level (mainly at the country or continent level), little is known about its variation and Wolbachia infection at the microspatial level, which is essential for its management. Meanwhile, no local cases of dengue fever have been recorded in the history of Nanjing, which implies that few adulticides have been applied in the city. Thus, the present study examines how the Ae. albopictus population varies and the Wolbachia infection status of each population among microspatial regions of Nanjing City. Methods: The genetic structure of 17 Aedes albopictus populations collected from urban, urban fringe, and rural regions of Nanjing City was investigated based on 9 microsatellite loci and the mitochondrial coxI gene. The Wolbachia infection status of each population was also assessed with Wolbachia A- and Wolbachia B-specific primers. Results: Nine out of 58 tested pairs of microsatellite markers were highly polymorphic, with a mean PIC value of 0.560, and these markers were therefore chosen for microsatellite genotyping analysis. The Na value of each Ae. albopictus population was very high, and the urban area populations (7.353 ± 4.975) showed a lower mean value than the urban fringe region populations (7.866 ± 5.010). A total of 19 coxI haplotypes were observed among 329 Ae. albopictus individuals via haplotype genotyping, with the highest diversity observed among the urban fringe Ae. albopictus populations (Hd = 0.456) and the lowest among the urban populations (Hd = 0.277). Each Ae. albopictus population showed significant departure from HWE, and significant population expansion was observed in only three populations from the urban (ZSL), urban fringe (HAJY), and rural areas (HSZY) (p < 0.05). Combined with DAPC analysis, all the Ae. albopictus populations were adequately allocated to two clades with significant genetic differences according to population structure analysis, and the best K value was equal to two. AMOVA results showed that most (96.18%) of the genetic variation detected in Ae. albopictus occurred within individuals (FIT = 0.22238, p < 0.0001), while no significant positive correlation was observed via isolation by distance (IBD) analysis (R 2 = 0.03262, p = 0.584). The TCS network of all haplotypes showed that haplotype 1 (H1) and haplotype 4 (H4) were the most frequent haplotypes among all populations, and the haplotype frequency significantly increased from urban regions (36.84%) to rural regions (68.42%). Frequent migration was observed among Ae. albopictus populations from rural to urban regions via the urban fringe region, with four direct migration routes between rural and urban regions. Furthermore, Wolbachia genotyping results showed that most of the individuals of each population were coinfected with Wolbachia A and Wolbachia B. The independent infection rate of Wolbachia A was slightly higher than that of Wolbachia B, and no significant differences were observed among different regions. Conclusion: In the microspatial environment of Nanjing City, the urban fringe region is an important region for the dispersion of Ae. albopictus populations between rural and urban areas, and Wolbachia A and Wolbachia B coinfection is the most common Wolbachia infection status in all Ae. albopictus populations among different regions.

Screening and analysis of immune-related genes of Aedes aegypti infected with DENV2.

Dengue virus type Ⅱ (DENV2) is a primary serotype responsible for the dengue fever epidemic, and Aedes aegypti is the main DENV2 vector. Understanding the Aedes aegypti immune mechanism against DENV2 is the basis for research on immune blockade in mosquitoes. Some preliminary studies lack validation in the literature, so this study was performed to further study and validate the potential target genes to provide a further basis for screening key target genes. We screened 51 genes possibly related to Aedes aegypti infection and immunity from the literature for further verification. First, bioinformatic methods such as GO, KEGG and PPI analysis were used, and then RT-qPCR was used to detect the changes in mRNA expression in the midguts and salivary glands of Aedes aegypti infected with DENV2.Bioinformatic analysis showed that mostly genes of the glucose metabolism pathway and myoprotein were influenced. In salivary glands, the Gst (xa) and Toll (xb) expression levels were significantly correlated with DENV2 load (y, lg[DENV2 RNA copies]), y = -3436xa+0.2287xb+3.8194 (adjusted R2 = 0.5563, F = 9.148, PF = 0.0045). In midguts, DENV2 load was significantly correlated with the relative Fba(R2 = 0.4381, t = 2.497, p < 0.05, df = 8), UcCr(R2 = 0.4072, t = 2.344, p < 0.05, df = 8) and Gbps1(R2 = 0.4678, t = 2.652, p < 0.05, df = 8) expression levels, but multiple regression did not yield significant results. This study shows that genes related to glucose metabolism and muscle proteins contribute to the interaction between Aedes aegypti and dengue virus. It was confirmed that SAAG-4, histone H4, endoplasmin, catalase and other genes are involved in the regulation of DENV2 infection in Aedes aegypti. It was revealed that GST and Toll in salivary glands may have antagonistic effects on the regulation of DENV2 load. Fba, UcCr and Gbps1 in the midgut may increase DENV2 load. These study results further condensed the potential target gene range of the Aedes aegypti immune mechanism against DENV2 infection and provided basic information for research on the Aedes aegypti in vivo blockade strategy against DENV2.

Survival and Replication of Zika Virus in Diapause Eggs of Aedes Albopictus From Beijing, China.

Zika virus (ZIKV) has emerged as a globally important arbovirus. The virus is primarily transmitted to humans through the bite of an infective Aedes albopictus in temperate area. Vertical transmission of ZIKV by Ae. albopictus is determined and has been suggested to be a means by which the virus could persist in nature. Ae. albopictus undergoes a well-characterized photoperiodic diapause. Viruses are harbored by overwintering mosquitoes in diapause that contributes to the resurgence of vertebrate diseases in the following spring, yet little is known about the impact of diapause on the regulation of viral replication and survival. The purpose of this study is to determine that Ae. albopictus in Beijing are highly susceptible to ZIKV (92.3%), and viable virus is passed to their organs of progeny via vertical transmission. Moreover, diapause eggs (diapause incidence 97.8%) had significantly lower minimum infection rates and filial infection rates of the first gonotrophic cycle than those of the second gonotrophic cycle in the short-day photoperiod group. Regarding the development of diapause eggs, the minimum infection rates and ZIKV RNA copy number increased significantly, suggesting that virus RNA replication occurred in the diapause eggs. Meanwhile, eggs from the ZIKV-infected mosquitoes had a significantly lower hatching rate compared with uninfected mosquitoes, implying an intriguing interaction between diapause eggs and virus. The findings here suggest that vertical transmission of ZIKV from diapause eggs to progeny may have a critical epidemiological role in the dissemination and maintenance of ZIKV circulating in the vector.

The Potential Vector Competence and Overwintering of West Nile Virus in Vector Aedes Albopictus in China.

West Nile virus (WNV) is an arbovirus, which causes widespread zoonotic disease globally. In China, it was first isolated in Jiashi County, Kashgar Region, Xinjiang in 2011. Determining the vector competence of WNV infection has important implications for the control of disease outbreaks. Four geographical strains of Aedes Albopictus (Ae. Albopictus) in China were allowed to feed on artificial infectious blood meal with WNV to determine the infection and transmission rate. The results indicated that four strains of Ae. Albopictus mosquitoes could infect and transmit WNV to 1- to 3-day-old Leghorn chickens. The infection rates of different strains were ranged from 16.7 to 60.0% and were statistically different (χ2 = 12.81, p < 0.05). The highest infection rate was obtained from the Shanghai strain (60.0%). The transmission rates of Ae. Albopictus Shanghai, Guangzhou, Beijing, and Chengdu strains were 28.6, 15.2, 13.3, and 6.7%, respectively. Furtherly, the results reveal that Ae. Albopictus Beijing strain infected orally can transmit WNV transovarially even the eggs are induced diapausing. The study confirmed that WNV could survive in the diapause eggs of Ae. Albopictus and could be transmitted to progeny after diapause termination. This is of great significance for clarifying that the WNV maintains its natural circulation in harsh environments through inter-epidemic seasons.

Vector competence of Aedes aegypti and screening for differentially expressed microRNAs exposed to Zika virus.

BACKGROUND: Zika virus (ZIKV) is transmitted to humans primarily by Aedes aegypti. Previous studies on Ae. aegypti from Jiegao (JG) and Mengding (MD) in Yunnan province, China have shown that these mosquitoes are able to transmit ZIKV to their offspring through vertical transmission, indicating that these two Ae. aegypti strains pose a potential risk for ZIKV transmission. However, the vector competence of these two Ae. aegypti strains to ZIKV has not been evaluated and the molecular mechanisms influencing vector competence are still unclear. METHODS: Aedes aegypti mosquitoes from JG and MD were orally infected with ZIKV, and the infection rate (IR), dissemination rate (DR), transmission rate (TR) and transmission efficiency (TE) of these two mosquito strains were explored to evaluate their vector competence to ZIKV. On 2, 4 and 6 days post-infection (dpi), the small RNA profiles between ZIKV-infected and non-infected Ae. aegypti midgut and salivary gland tissues were compared to gain insights into the molecular interactions between ZIKV and Ae. aegypti. RESULTS: There were no significant differences in the IR, DR, TR and TE between the two Ae. aegypti strains (P > 0.05). However, ZIKV RNA appeared 2 days earlier in saliva of the JG strain, which indicated a higher competence of the JG strain to transmit ZIKV. Significant differences in the microRNA (miRNA) expression profiles between ZIKV-infected and non-infected Ae. aegypti were found in the 2-dpi libraries of both the midgut and salivary gland tissues from the two strains. In addition, 27 and 74 miRNAs (|log2 fold change| > 2) were selected from the miRNA expression profiles of ZIKV-infected and non-infected midgut and salivary gland tissues from the JG and MD strains, respectively. CONCLUSIONS: Our results provide novel insights into the ZIKV-mosquito interactions and build a foundation for future research on how miRNAs regulate the vector competence of mosquitoes to this arbovirus.

Dispersal patterns and population genetic structure of Aedes albopictus (Diptera: Culicidae) in three different climatic regions of China.

BACKGROUND: Aedes albopictus is an indigenous primary vector for dengue and Zika viruses in China. Compared with its insecticide resistance, biology and vector competence, little is known about its genetic variation, which corresponds to environmental variations. Thus, the present study examines how Ae. albopictus varies among different climatic regions in China and deciphers its potential dispersal patterns. METHODS: The genetic variation and population structure of 17 Ae. albopictus populations collected from three climatic regions of China were investigated with 11 microsatellite loci and the mitochondrial coxI gene. RESULTS: Of 44 isolated microsatellite markers, 11 pairs were chosen for genotyping analysis and had an average PIC value of 0.713, representing high polymorphism. The number of alleles was high in each population, with the ne value increasing from the temperate region (3.876) to the tropical region (4.144). Twenty-five coxI haplotypes were detected, and the highest diversity was observed in the tropical region. The mean Ho value (ca. 0.557) of all the regions was significantly lower than the mean He value (ca. 0.684), with nearly all populations significantly departing from HWE and displaying significant population expansion (p value < 0.05). Two genetically isolated groups and three haplotype clades were evaluated via STRUCTURE and haplotype phylogenetic analyses, and the tropical populations were significantly isolated from those in the other regions. Most genetic variation in Ae. albopictus was detected within populations and individuals at 31.40 and 63.04%, respectively, via the AMOVA test, and a relatively significant positive correlation was observed among only the temperate populations via IBD analysis (R2 = 0.6614, p = 0.048). Recent dispersions were observed among different Ae. albopictus populations, and four major migration trends with high gene flow (Nm > 0.4) were reconstructed between the tropical region and the other two regions. Environmental factors, especially temperature and rainfall, may be the leading causes of genetic diversity in different climatic regions. CONCLUSIONS: Continuous dispersion contributes to the genetic communication of Ae. albopictus populations across different climatic regions, and environmental factors, especially temperature and rainfall, may be the leading causes of genetic variation.

Vertical Transmission of Zika Virus by Jiegao and Mengding Aedes aegypti (Diptera: Culicidae) Strains in Yunnan Province in China.

Zika virus (ZIKV) is a mosquito-borne pathogen classified in the genus Flavivirus of the family Flaviviridae. Vertical transmission is considered to be the primary way to maintain some arboviruses under adverse natural conditions, which play a critical epidemiological role in arbovirus spread and maintenance. Aedes aegypti is the primary vector for ZIKV. In this study, we demonstrated vertical transmission in two Ae. aegypti strains from Jiegao (JG) and Mengding (MD) in the border area of Yunnan province. The minimum infection rate of F1 adult progeny from JG Ae. aegypti strain was significantly higher than that of MD Ae. aegypti strain in the second gonotrophic cycle (1:14.29 and 1:200, respectively, p < 0.05). The cytopathic effect was observed in C6/36 cells after infection of ZIKV isolated from the progeny. The results suggest that Ae. aegypti mosquitoes from JG and MD play potential roles in ZIKV spread and maintenance. Therefore, more adult and eggs control methods should be implemented to control mosquitoes if a Zika epidemic occurs.

Susceptibility of Armigeres subalbatus Coquillett (Diptera: Culicidae) to Zika virus through oral and urine infection.

BACKGROUND: Zika virus (ZIKV) disease outbreaks have been occurring in South America since 2015, and has spread to North America. Because birth defects and cases of Guillain Barré have been associated with infection with ZIKV, this has drawn global attention. ZIKV is generally considered an Aedes-transmitted pathogen. The transmission of ZIKV through blood by Aedes mosquito bites has been recognized as the major transmission route. However, it is not clear whether there are other transmission routes that can cause viral infection in mosquitos. The aim of the present study is to describe the susceptibility of Armigeres subalbatus, which often develop in human waste lagoons, to ZIKV, through oral infection in adult mosquitoes and urine infection in larvae. METHODOLOGY/PRINCIPAL FINDINGS: Five-day-old female Ar. subalbatus ingested infectious blood meals containing ZIKV. After 4, 7, and 10 days of ingesting infectious blood meals, ZIKV could be detected in the midguts, salivary glands, ovaries, and collected saliva of mosquitoes. The ZIKV infection rate (IR) on day 10 reached 40% in salivary glands and 13% in saliva, indicating that these mosquitoes were able to transmit ZIKV. In addition, ZIKV infection was also discovered in mosquito ovaries, suggesting the possibility of vertical transmission of virus. Moreover, Ar. subalbatus transmitted ZIKV to infant mice bitten by infectious mosquitoes. In a second experiment, 1st-instar larvae of Ar. subalbatus were reared in water containing ZIKV and human urine. After pupation, pupae were placed in clean water and transferred to a mosquito cage for emergence. Although ZIKV RNA was detected in all of the larvae tested, ZIKV was not detected in the saliva of any adult Ar. subalbatus. Considering that there are more uncontrollable factors in nature than in the laboratory environment, the possibility that the virus is transmitted to adult mosquitoes via larvae is very small period. CONCLUSIONS/SIGNIFICANCE: Adult Ar. subalbatus could be infected with ZIKV and transmit ZIKV through mosquito bites. Therefore, in many rural areas in China and in undeveloped areas of other Asian countries, the management of human waste lagoons in the prevention and control of Zika disease should be considered. Corresponding adjustments and modifications should also be made in prevention and control strategies against ZIKV.

Potential Vector Competence of Mosquitoes to Transmit Baiyangdian Virus, a New Tembusu-Related Virus in China.

A new duck Tembusu-related flavivirus, Baiyangdian virus (BYDV), caused duck egg-drop syndrome in China. The rapid spread, unknown transmission routes, and zoonotic nature, raise serious concern about BYDV as a potential threat to human health. The study provides the first evaluation on the vector competence of Culex and Aedes mosquitoes to transmit BYDV in China. The results show that Culex tritaeniorhynchus, Culex pipiens pallens, Culex pipiens quinquefasciatus, and Aedes albopictus can become infected with BYD-1 virus (BYDV-1) on different days after oral infection. Although the viral copies in Ae. albopictus was higher than that in Cx. p. quinquefasciatus at 13 days postinfection (χ2 = 10.385, p = 0.016), there was no significant differences between infection rates of four mosquito species (χ2 = 3.98, p = 0.137). In transmission experiment, healthy ducks were infected after being bitten by virus-positive mosquitoes and BYDV-1 disseminated to and replicated in the duck brains. These findings verified the potential role of Cx. p. quinquefasciatus and Cx. tritaeniorhynchus as vectors of BYDV-1. BYDV-1 was also detected in salivary gland of Cx. p. pallens, which indicated that this virus could be transmitted by mosquitoes. These results provide evidence for the role of Culex mosquitoes in the transmission cycles involving BYDV-1 and avian hosts in China.

RNA interference of odorant receptor CquiOR114/117 affects blood-feeding behavior in Culex quinquefasciatus.

The odorant receptors (ORs) play a critical role for mosquitoes in the identification of blood-feeding hosts and other physiological processes. The OR8 subfamily in mosquitoes has been shown to be strongly involved in the detection the mammalian host associated odor, 1-octen-3-ol. CquiOR114/117 has been shown to be an orthologous OR8 in Culex quinquefasciatus Say. In this study, the expression of CquiOR114/117 in the different developmental stages of Cx. quinquefasciatus was detected by the amplification of CquiOR114/117 with real-time fluorescence quantitative polymerase chain reaction (PCR). RNA interference (RNAi) technology was used to interfere with the expression of CquiOR114/117 in females to observe the blood-feeding behavior change. The results showed that the expression level of CquiOR114/117 in the egg-to-pupa stage was significantly lower than that in the adult stage and that the expression level of the female mosquitoes peaked on the third day after emergence. The expression of CquiOR114/117 was significantly decreased in the 2-6 days after the injection of dsRNA compared with the control groups. The analysis of the blood-feeding behavior showed a significant positive correlation between CquiOR114/117 expression and the engorgement rate of the mosquitoes. CquiOR114/117 is speculated to have an effect on the blood-feeding behavior of Cx. quinquefasciatus.

Vector Competence and Vertical Transmission of Zika Virus in Aedes albopictus (Diptera: Culicidae).

Zika virus (ZIKV) is an emerging mosquito-borne pathogen belonging to the genus Flavivirus of the family Flaviviridae. Aedes albopictus is widely distributed in China. However, little is known about the vector competence of Ae. albopictus in China. The present study presents the oral susceptibility and vector competence of Ae. albopictus Guangzhou strain to ZIKV. Additionally, vertical transmission of ZIKV is described. The results demonstrated the susceptibility of local Ae. albopictus mosquitoes to ZIKV with an extrinsic incubation period of 6 days. Disseminated infection was observed in Ae. albopictus starting on day 2 postinfection (PI). Starting on day 6 PI, the saliva of Ae. albopictus exhibited ZIKV infection, and the transmission rate was 36.4%. Vertical transmission was observed during the first gonotrophic cycle. The minimum infection rate was observed in third-to-fourth instar larvae.

Vector Mosquito Ecology and Japanese Encephalitis Virus Genotype III Strain Detection from Culex tritaeniorhynchus and Pig in Huaihua, China.

The Japanese encephalitis virus (JEV), a mosquito-borne zoonotic pathogen, is the major cause of viral encephalitis worldwide. An investigation of mosquito species diversity, JEV infection rate, and seasonal population fluctuations of Culex tritaeniorhynchus in Huaihua County, Hunan Province, China, revealed the distribution of vector mosquito populations and genotypes and molecular characteristics of current, common JEV strains in this region. Research on mosquito species diversity in different habitats in Huaihua revealed that local community composition was relatively simple, including five species from four genera (two Culex spp., one Anopheles sp., one Aedes sp., and one Armigeres sp.). Cx. tritaeniorhynchus was clearly the dominant species comprising 94.2-98.6% of all specimens and was always the most common species captured in paddy fields, pigpens, and human dwellings. The seasonal abundance of Cx. tritaeniorhynchus was relatively even, with a single seasonal peak in late August. Two Huaihua JEV strains isolated from the mosquito and pig were highly congruent. The genetic affinities were determined by analyzing capsid/premembrane (C/PrM) and envelope (E) gene variation. The results showed that they were of genotype III and most closely related to the live, attenuated vaccine strains SAl4-14-2 and SA14 and JaGAr01. The Huaihua E protein shares high similarity (mosquito 98.8% and pig 97.6%) at the nucleotide level with the SA14-14-2 vaccine. Although we found that the E gene sequences of the Huaihua JEV mosquito strain and pig strain have 11 and 15 amino acid site substitutions compared with the SAl4-14-2 vaccine, key sites that associated with JEV's antigenic activity and neurovirulence were unchanged. The SA14-14-2 vaccine should therefore be effective in preventing JEV infection in the Huaihua region.

Correction to: The polymorphism and geographical distribution of knockdown resistance of adult Anopheles sinensis populations in eastern China.

Please be advised that since publication of the original article [1] the authors have flagged that they omitted to provide the up-to-date version of Fig. 1 and, as such, the wrong version of Fig. 1 is present in the article.