Home and hub: pet trade and traditional medicine impact reptile populations in source locations and destinations.

The pet trade and Traditional Chinese Medicine (TCM) consumption are major drivers of global biodiversity loss. Tokay geckos (Gekko gecko) are among the most traded reptile species worldwide. In Hong Kong, pet and TCM markets sell tokay geckos while wild populations also persist. To clarify connections between trade sources and destinations, we compared genetics and stable isotopes of wild tokays in local and non-local populations to dried individuals from TCM markets across Hong Kong. We found that TCM tokays are likely not of local origin. Most wild tokays were related to individuals in South China, indicating a probable natural origin. However, two populations contained individuals more similar to distant populations, indicating pet trade origins. Our results highlight the complexity of wildlife trade impacts within trade hubs. Such trade dynamics complicate local legal regulation when endangered species are protected, but the same species might also be non-native and possibly damaging to the environment.

Surveillance of Rodent Pests for SARS-CoV-2 and Other Coronaviruses, Hong Kong.

We report surveillance conducted in 217 pestiferous rodents in Hong Kong for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We did not detect SARS-CoV-2 RNA but identified 1 seropositive rodent, suggesting exposure to a virus antigenically similar to SARS-CoV-2. Potential exposure of urban rodents to SARS-CoV-2 cannot be ruled out.

Low Transmission of Chikungunya Virus by Aedes aegypti from Vientiane Capital, Lao PDR

In 2012−2013, chikungunya virus (CHIKV) was the cause of a major outbreak in the southern part of Lao People's Democratic Republic (Lao PDR). Since then, only a few imported cases, with isolates belonging to different lineages, were recorded between 2014 and 2020 in Vientiane capital and few autochthonous cases of ECSA-IOL lineage were detected in the south of the country in 2020. The CHIKV epidemiological profile contrasts with the continuous and intensive circulation of dengue virus in the country, especially in Vientiane capital. The study's aim was to investigate the ability of the local field-derived Aedes aegypti population from Vientiane capital to transmit the Asian and ECSA-IOL lineages of CHIKV. Our results revealed that, for both CHIKV lineages, infection rates were low and dissemination rates were high. The transmission rates and efficiencies evidenced a low vector competence for the CHIKV tested. Although this population of Ae. aegypti showed a relatively modest vector competence for these two CHIKV lineages, several other factors could influence arbovirus emergence such as the longevity and density of female mosquitoes. Due to the active circulation of CHIKV in Southeast Asia, investigations on these factors should be done to prevent the risk of CHIKV emergence and spread in Lao PDR and neighboring countries.

Recent African strains of Zika virus display higher transmissibility and fetal pathogenicity than Asian strains.

The global emergence of Zika virus (ZIKV) revealed the unprecedented ability for a mosquito-borne virus to cause congenital birth defects. A puzzling aspect of ZIKV emergence is that all human outbreaks and birth defects to date have been exclusively associated with the Asian ZIKV lineage, despite a growing body of laboratory evidence pointing towards higher transmissibility and pathogenicity of the African ZIKV lineage. Whether this apparent paradox reflects the use of relatively old African ZIKV strains in most laboratory studies is unclear. Here, we experimentally compare seven low-passage ZIKV strains representing the recently circulating viral genetic diversity. We find that recent African ZIKV strains display higher transmissibility in mosquitoes and higher lethality in both adult and fetal mice than their Asian counterparts. We emphasize the high epidemic potential of African ZIKV strains and suggest that they could more easily go unnoticed by public health surveillance systems than Asian strains due to their propensity to cause fetal loss rather than birth defects.

Enhanced Zika virus susceptibility of globally invasive Aedes aegypti populations.

The drivers and patterns of zoonotic virus emergence in the human population are poorly understood. The mosquito Aedes aegypti is a major arbovirus vector native to Africa that invaded most of the world's tropical belt over the past four centuries, after the evolution of a "domestic" form that specialized in biting humans and breeding in water storage containers. Here, we show that human specialization and subsequent spread of A. aegypti out of Africa were accompanied by an increase in its intrinsic ability to acquire and transmit the emerging human pathogen Zika virus. Thus, the recent evolution and global expansion of A. aegypti promoted arbovirus emergence not solely through increased vector-host contact but also as a result of enhanced vector susceptibility.

Risk of arbovirus emergence via bridge vectors: case study of the sylvatic mosquito Aedes malayensis in the Nakai district, Laos.

Many emerging arboviruses of global public health importance, such as dengue virus (DENV) and yellow fever virus (YFV), originated in sylvatic transmission cycles involving wild animals and forest-dwelling mosquitoes. Arbovirus emergence in the human population typically results from spillover transmission via bridge vectors, which are competent mosquitoes feeding on both humans and wild animals. Another related, but less studied concern, is the risk of 'spillback' transmission from humans into novel sylvatic cycles. We colonized a sylvatic population of Aedes malayensis from a forested area of the Nakai district in Laos to evaluate its potential as an arbovirus bridge vector. We found that this Ae. malayensis population was overall less competent for DENV and YFV than an urban population of Aedes aegypti. Olfactometer experiments showed that our Ae. malayensis colony did not display any detectable attraction to human scent in laboratory conditions. The relatively modest vector competence for DENV and YFV, combined with a lack of detectable attraction to human odor, indicate a low potential for this sylvatic Ae. malayensis population to act as an arbovirus bridge vector. However, we caution that opportunistic blood feeding on humans by sylvatic Ae. malayensis may occasionally contribute to bridge sylvatic and human transmission cycles.

A peridomestic Aedes malayensis population in Singapore can transmit yellow fever virus.

The case-fatality rate of yellow fever virus (YFV) is one of the highest among arthropod-borne viruses (arboviruses). Although historically, the Asia-Pacific region has remained free of YFV, the risk of introduction has never been higher due to the increasing influx of people from endemic regions and the recent outbreaks in Africa and South America. Singapore is a global hub for trade and tourism and therefore at high risk for YFV introduction. Effective control of the main domestic mosquito vector Aedes aegypti in Singapore has failed to prevent re-emergence of dengue, chikungunya and Zika viruses in the last two decades, raising suspicions that peridomestic mosquito species untargeted by domestic vector control measures may contribute to arbovirus transmission. Here, we provide empirical evidence that the peridomestic mosquito Aedes malayensis found in Singapore can transmit YFV. Our laboratory mosquito colony recently derived from wild Ae. malayensis in Singapore was experimentally competent for YFV to a similar level as Ae. aegypti controls. In addition, we captured Ae. malayensis females in one human-baited trap during three days of collection, providing preliminary evidence that host-vector contact may occur in field conditions. Finally, we detected Ae. malayensis eggs in traps deployed in high-rise building areas of Singapore. We conclude that Ae. malayensis is a competent vector of YFV and re-emphasize that vector control methods should be extended to target peridomestic vector species.

Cell-Fusing Agent Virus Reduces Arbovirus Dissemination in Aedes aegypti Mosquitoes In Vivo.

Aedes aegypti mosquitoes are the main vectors of arthropod-borne viruses (arboviruses) of public health significance, such as the flaviviruses dengue virus (DENV) and Zika virus (ZIKV). Mosquitoes are also the natural hosts of a wide range of viruses that are insect specific, raising the question of their influence on arbovirus transmission in nature. Cell-fusing agent virus (CFAV) was the first described insect-specific flavivirus, initially discovered in an A. aegypti cell line and subsequently detected in natural A. aegypti populations. It was recently shown that DENV and the CFAV strain isolated from the A. aegypti cell line have mutually beneficial interactions in mosquito cells in culture. However, whether natural strains of CFAV and DENV interact in live mosquitoes is unknown. Using a wild-type CFAV isolate recently derived from Thai A. aegypti mosquitoes, we found that CFAV negatively interferes with both DENV type 1 and ZIKV in vitro and in vivo For both arboviruses, prior infection by CFAV reduced the dissemination titer in mosquito head tissues. Our results indicate that the interactions observed between arboviruses and the CFAV strain derived from the cell line might not be a relevant model of the viral interference that we observed in vivo Overall, our study supports the hypothesis that insect-specific flaviviruses may contribute to reduce the transmission of human-pathogenic flaviviruses.IMPORTANCE The mosquito Aedes aegypti carries several arthropod-borne viruses (arboviruses) that are pathogenic to humans, including dengue and Zika viruses. Interestingly, A. aegypti is also naturally infected with insect-only viruses, such as cell-fusing agent virus. Although interactions between cell-fusing agent virus and dengue virus have been documented in mosquito cells in culture, whether wild strains of cell-fusing agent virus interfere with arbovirus transmission by live mosquitoes was unknown. We used an experimental approach to demonstrate that cell-fusing agent virus infection reduces the propagation of dengue and Zika viruses in A. aegypti mosquitoes. These results support the idea that insect-only viruses in nature can modulate the ability of mosquitoes to carry arboviruses of medical significance and that they could possibly be manipulated to reduce arbovirus transmission.

New records and updated checklist of mosquitoes (Diptera: Culicidae) from Lao People's Democratic Republic, with special emphasis on adult and larval surveillance in Khammuane Province.

A list of mosquitoes from the Nakai Nam Theun National Protected Area along the Nam Theun, Nam Mon, Nam Noy, and Nam On rivers, Nakai District, Khammuane Province, Lao People's Democratic Republic (Lao PDR) is presented. Fifty-four mosquito taxa were identified, including 15 new records in the Lao PDR. A fragment of the mtDNA cytochrome c oxidase subunit I (COI) gene, barcode region, was generated for 34 specimens, and together with four specimens already published, it represented 23 species in eight genera. In addition, an updated checklist of 170 mosquito taxa from Lao PDR is provided based on field collections from Khammuane Province, the literature, and specimens deposited in the Smithsonian Institution, National Museum of Natural History (SI-NMNH), Washington, DC, U.S.A. This paper provides additional information about the biodiversity of mosquito fauna in Lao PDR.