Background The Asian tiger mosquito, Aedes albopictus , an increasingly relevant arboviral vector, has spread worldwide. However, currently available tools are limited in terms of effective monitoring of vector populations and accurate determination of the extent of viral transmission, especially before and during outbreaks. Therefore, it is essential to develop novel monitoring and surveillance tools, particularly those that target adult mosquitoes and enhance the trapping efficiency for Ae. albopictus . Methods A variety of human body odorants associated with different types of mosquito olfactory receptors were selected, and their attractiveness to Ae. albopictus was tested by a four-arm olfactometer. The optimal compatibility and proportion of the odorants, Mix-5, was observed via orthogonal design analyses. The attractiveness of Mix-5 to Ae. albopictus in the laboratory was assessed using Mosq-ovitraps and Electric Mosquito Killers. In the field, the effectiveness of generic BG-Lure, Mix-5 and a control treatment was compared with a baited Biogents Sentinel trap (BGS-trap) using a Latin square design. Results In the olfactometer experiments, the attractiveness of the selected candidate compounds at varying dilutions was poor when the individual compounds were used alone. The optimal combination, Mix-5, was generated based on orthogonal design analyses. In the laboratory, the average numbers of female Ae. albopictus mosquitoes attracted by the synthetic odorant blend Mix-5 were 27.00 and 27.50, compared with 12.00 and 14.83 for the control, when using Mosq-ovitraps and Electric Mosquito Killers, respectively. In the field, the average number of Ae. albopictus female mosquitoes trapped by Mix-5 was 9.67 females/trap, whereas the average numbers for BG-Lure and the control were 7.78 and 4.47, respectively. The lure also played an important role in attracting Culex quinquefasciatus mosquitoes, and the average numbers of Cx. quinquefasciatus female mosquitoes attracted by Mix-5, BG-Lure and the control were 18.78, 25.11 and 12.22, respectively. Conclusions A human odor-based bait blend was developed and exhibited enhanced effectiveness at attracting Ae. albopictus This blend can be used to monitor and trap dengue vector mosquitoes in Chinese cities. Electronic supplementary material The online version of this article (10.1186/s13071-019-3646-x) contains supplementary material, which is available to authorized users.

Aedes (Stegomyia) albopictus, also known as the Asian tiger mosquito, is a mosquito which originated in Asia. In recent years, it has become increasingly rampant throughout the world. This mosquito can transmit several arboviruses, including dengue, Zika and chikungunya viruses, and is considered a public health threat. Despite the urgent need of genome engineering to analyze specific gene functions, progress in genetical manipulation of Ae. albopictus has been slow due to a lack of efficient methods and genetic markers. In the present study, we established targeted disruptions in two genes, kynurenine hydroxylase (kh) and dopachrome conversion enzyme (yellow), to analyze the feasibility of generating visible phenotypes with genome editing by the clustered regularly interspaced short palindromic repeats (CRISPR) / CRISPR‐associated protein 9 (Cas9) system in Ae. albopictus. Following Cas9 single guide RNA ribonucleoprotein injection into the posterior end of pre‐blastoderm embryos, 30%–50% of fertile survivors produced alleles that failed to complement existing kh and yellow mutations. Complete eye and body pigmentation defects were readily observed in G1 pupae and adults, indicating successful generation of highly heritable mutations. We conclude that the CRISPR/Cas9‐mediated gene editing system can be used in Ae. albopictus and that it can be adopted as an efficient tool for genome‐scale analysis and biological study.

BACKGROUND Aedes albopictus is the primary vector of mosquito‐borne diseases, including dengue and chikungunya, in China. The management of vector mosquitoes is the primary strategy for the control of such infectious diseases. The gravid Ae. albopictus prefers to skip‐oviposit its eggs into different small water containers, and the management of these breeding places is critical for mosquito control. Bacillus thuringiensis subspecies Israelensis (Bti) is a useful biological larvicide, but the effective period of the currently available commercial product is relatively short. This study aimed to develop a long‐lasting formulation of Bti to control the dengue vector mosquito Ae. albopictus. RESULTS Water‐soluble polyethylene glycols and water‐insoluble hexadecanol were mixed with Bti to develop the long‐lasting formulation Bti‐BLOCK, based on the solid dispersion technique. The controlled release of Bti‐BLOCK and its effect on Ae. albopictus were assayed in the laboratory and in the field. The results showed that Bti toxins were slowly released from Bti‐BLOCK into the water and maintained at an effective dose for at least 6 months. Bti‐BLOCK caused high mortality during the immature stage (>90%) and achieved full inhibition during pupation (100%). The efficacy lasted at least 12 weeks in the laboratory and 6 weeks in the field. Furthermore, we confirmed an 89% reduction in Ae. albopictus density and a reduction in the R0 of dengue to a low‐risk level after 6 months of open‐field interventions. CONCLUSIONS We developed a long‐lasting biological larvicide, Bti‐BLOCK, which displayed very good efficacy in the control of the dengue vector mosquito Ae. albopictus.

Background Zika virus (ZIKV) and dengue virus (DENV) are closely related flaviviruses primarily transmitted by Aedes mosquitoes. Armigeres subalbatus is an emerging and widely distributed mosquito, and ZIKV has been detected and isolated from it. However, it is not clear whether Ar. subalbatus could be a vector for ZIKV and DENV or not. In this study, we investigated the infection and transmission of Ar. subalbatus to ZIKV and DENV. Methods A line of Ar. subalbatus was isolated from Guangdong, China, and further identified by the mitochondrial cytochrome oxidase subunit 1 (COI) gene. The adults of Ar. subalbatus were fed with blood meal containing ZIKV or DENV-2. At 4, 7, 10, 14, and 21 days post-inoculation (dpi), the infections of ZIKV or DENV-2 in the midguts, ovaries and salivary glands were detected and quantified by RT-PCR and RT-qPCR. To assess the transmissibility, suckling mice were exposed to bites of ZIKV-infected mosquitoes, and ZIKV was detected in brain tissue by RT-qPCR and plaque assays. Furthermore, the larvae of Ar. subalbatus were reared in artificial urine containing ZIKV or DENV-2. The infection rates and viral titers of larvae and adults were analyzed by RT-PCR and RT-qPCR, and the viral distribution in larval tissues was observed by immunohistochemistry. Chi-square test and one-way ANOVA analysis were used for assessing the infection rate and viral titer in varied tissues and different time points, respectively. Results Following oral inoculation, ZIKV but not DENV-2 could be detected in Ar. subalbatus midguts at 4 dpi, ovaries at 7 dpi and salivary glands at 10 dpi. The highest infection rate (IR) of ZIKV was 27.8% in midgut at 7 dpi, 9.7% in ovary and 5.6% in salivary gland at 21 dpi. Eight days after being bitten by ZIKV-positive mosquitoes, ZIKV was detected in three brain tissues out of four suckling mice exposed to bites. ZIKV could be detected in the larvae reared in artificial urine contained ZIKV at a high concentration of 105 pfu/ml and various tissues of adults with a low infection rate (0.70–1.35%). ZIKV could be observed in anal papillae and midgut of larvae at 4 dpi under laboratory conditions. Conclusions ZIKV but not DENV-2 can infect Ar. subalbatus by blood meal and artificial urine, and the infected mosquitoes can transmit ZIKV to suckling mice by bite. From these findings, we can conclude that the Ar. subalbatus isolated from Guangdong province, China, is a potential vector for ZIKV and should therefore be considered in vector control programs to prevent and control of Zika virus disease. Graphical Abstract

Aedes albopictus is the sole vector for various mosquito-borne viruses, including dengue, chikungunya, and Zika. Ecofriendly biological agents are required to reduce the spread of these mosquito-borne infections. Mosquito densoviruses (MDVs) are entomopathogenic mosquito-specific viruses, which can reduce the capacity of isolated vectors and decrease mosquito-borne viral disease transmission. However, their variable pathogenicity restricts their commercial use. In the present study, we developed a series of novel larvicide oil suspensions (denoted Bacillus thuringiensis (Bti) oil, Ae. albopictus densovirus (AalDV-5) oil, and a mixture of AalDV-5+Bti oil), which were tested against Ae. albopictus larvae under experimental semi-field and open-field conditions. The effect of AalDV-5 on non-target species was also evaluated. The combined effect of AalDV-5+Bti was greater than that of individual toxins and was longer lasting and more persistent compared with the laboratory AalDV-5 virus strain. The virus was quantified on a weekly basis by quantitative polymerase chain reaction (qPCR) and was persistently detected in rearing water as well as in dead larvae. Wildtype densovirus is not pathogenic to non-target organisms. The present findings confirm the improved effect of a mixed microbial suspension (AalDV-5+Bti oil) larvicide against Ae. albopictus. The development and testing of these products will enable better control of the vector mosquitoes.