Comparative analysis of the susceptibility of Aedes aegypti and Japanese Aedes albopictus to all dengue virus serotypes

Mosquito populations originating from nonendemic areas have the potential to transmit recently emerging Japanese encephalitis virus genotype IV

Japanese encephalitis virus (JEV) genotype IV (GIV) is one of the least common and most neglected genotypes worldwide, having been identified only on a few Indonesian islands until it was recently found to be the cause of outbreaks that occurred in several Australian states in early 2022. Given the limited availability of information, the vector range for JEV GIV remains unknown; thus, understanding this range could prove invaluable for future prevention efforts in new areas. Herein, we experimentally exposed four mosquito colonies originated from various countries with no previous reports of GIV to JEV GIV strain 19CxBa-83-Cv, which was isolated from Culex vishnui Theobald collected in Bali in 2019. At 7 and 14 days post-JEV GIV exposure through a membrane feeding method, mosquito bodies, head-wings-legs, and saliva were harvested for infection, dissemination, and transmission efficiency analyses. The results showed robust transmission efficiencies of the virus by Culex tritaeniorhynchus Giles (∼74%) and Aedes albopictus Skuse (∼52%) from Japan, followed by Culex quinquefasciatus Say from Vietnam (∼35%) and Culex pipiens form molestus from Turkey (∼18%). Although significant differences were observed, we found that the four mosquito species could transmit JEV GIV. The efficiency of biological transmission of this restricted genotype by mosquitoes from various origins suggests that these mosquito species could support localized transmission if the genotype were introduced to their respective areas. This study emphasizes the importance of remaining vigilant and continuing arbovirus surveillance in all locations.

Comprehensive intra-host infection kinetics reveals high arbo-orthoflavivirus transmission potential by neglected vector species, Aedes scutellaris

BACKGROUND

Dengue virus (DENV) and Zika virus (ZIKV) are primarily transmitted by Aedes mosquitoes. As most studies on vector competence have focused on Aedes aegypti and Aedes albopictus while neglecting other Aedes species, it is possible that the transmission risks might be underestimated. It is necessary to examine additional species that could potentially serve as competent vectors. This is particularly important considering the potential expansion of their geographical range due to climate change or species-specific vector reduction interventions.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, we examined the infection kinetics and transmission potential of Aedes scutellaris from Thailand, comparing to Ae. aegypti and Ae. albopictus. Our findings demonstrated that Ae. scutellaris and Ae. albopictus had lower rates of midgut infection compared to Ae. aegypti due to smaller blood meal sizes during feeding. However, once the infection has established Ae. scutellaris exhibited efficient replication of ZIKV and DENV1-4 in the midguts, secondary organs, and salivary glands. Notably, Ae. scutellaris had a low salivary gland escape barrier, with comparable transmissibility as Ae. aegypti when inoculated with the same viral load.

CONCLUSION

This study highlights the potential of Ae. scutellaris as a vector for DENV and ZIKV and emphasizes the importance of considering neglected mosquito species in arbovirus transmission and surveillance efforts.

(Re)Emerging Arboviruses of Public Health Significance in the Brazilian Amazon

Brazil is one of the most important countries globally in regard to arboviral disease ecology and emergence or resurgence. Unfortunately, it has shouldered a majority of arboviral disease cases from Latin America and its rich flora, fauna (including arthropod vectors), and climate have contributed to the vast expansion of multiple arboviral diseases within its borders and those that have expanded geographically outside its borders. Anthropogenic landscape changes or human-mediated changes such as agriculture, deforestation, urbanization, etc. have all been at play within the country in various locations and can also be attributed to arboviral movement and resurgence. This review describes a brief history of landscape changes within the country and compiles all the known information on all arboviruses found within Brazil (endemic and imported) that are associated with human disease and mosquitoes including their original isolation, associated vertebrate animals, associated mosquitoes and other arthropods, and human disease symptomology presentations. This information is crucial as the Western Hemisphere is currently experiencing multiple arbovirus outbreaks, including one that originated in the Brazilian Amazon. Understanding which arboviruses are and have been circulating within the country will be pertinent as anthropogenic landscape changes are consistently being perpetrated throughout the country, and the occurrence of the next arbovirus epidemic will be a matter of when, not if.

Fusarium begoniae metabolites: a promising larvicidal, pupicidal potential, histopathological alterations and detoxifications enzyme profiles of medically important mosquito vector Aedes aegypti, Culex quinquefasciatus and Anopheles stephensi

Endophytic fungal molecules have the potential to be a cost-effective chemical source for developing eco-friendly disease-controlling pharmaceuticals that target mosquito-borne illnesses. The primary aims of the study were to identify the fungus Fusarium begoniae larvicidal ability against Aedes aegypti, Culex quinquefasciatus, and Anopheles stephensi. The ethyl acetate extract demonstrated lethal concentrations that kill 50% of exposed larvae (LC50) and 90% of exposed larvae (LC90) for the 1st to 4th instar larvae of An. stephensi (LC50 = 54.821, 66.525, 68.250, and 73.614; LC90 = 104.56, 138.205, 150.415, and 159.466 μg/mL), Cx. quinquefasciatus (LC50 = 64.981, 36.505, 42.230, and 36.514; LC90 = 180.46, 157.105, 140.318, and 153.366 μg/ mL), and Ae. aegypti (LC50 = 74.890, 33.607, 52.173, and 26.974; LC90 = 202.56, 162.205, 130.518, and 163.286 μg/mL). Mycelium metabolites were evaluated for their pupicidal activity towards Ae. aegypti (LC50 = 80.669, LC90 = 119.904), Cx. quinquefasciatus (LC50 = 70.569, LC90 = 109.840), and An. stephensi (LC50 = 73.269, LC90 = 110.590 μg/mL). The highest larvicidal activity was recorded at 300 µg/mL, with 100% mortality against first and second-instar larvae of Cx. quinquefasciatus. Metabolite exposure to larvae exhibited several abnormal behavioral changes. The exposure to F. begoniae metabolite, key esterases such as acetylcholinesterase, α-and-β-carboxylesterase, and acid and alkaline phosphatase activity significantly decreased compared to control larvae. The outcomes of the histology analysis revealed that the mycelium metabolites-treated targeted larvae had a disorganized abdominal mid and hindgut epithelial cells. The is first-hand information on study of ethyl-acetate-derived metabolites from F. begoniae tested against larvae and pupae of Ae. aegypti, Cx. quinquefasciatus and An. stephensi. Bio-indicator toxicity findings demonstrate that A. nauplii displayed no mortality.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-04061-z.

Evaluation of long-term preservation methods for viral RNA in mosquitoes at room temperature

Mosquitoes are important vectors of various pathogenic viruses. Almost all viruses transmitted by mosquitoes are RNA viruses. Therefore, to detect viral genes, mosquito samples must be kept at low temperatures to prevent RNA degradation. However, prolonged transport from the field to laboratory can pose challenges for temperature control. The aim of this study was to evaluate methods for preserving viral RNA in mosquito bodies at room temperature. Virus-infected mosquito samples were immersed in ethanol, propylene glycol, and a commercially available nucleic acid preservation reagent at room temperature, and viral RNA stability was compared. As a result, for the two RNA viruses (San Gabriel mononegavirus and dengue virus 1) subjected to this experiment, no significant decrease in the viral RNA was observed for at least eight weeks after immersion in the reagents, and the amount of RNA remaining was equivalent to that of samples stored at - 80 °C. These results indicate that immersion storage in these reagents used in this study is effective in preserving viral RNA in mosquitoes under room temperature conditions and is expected to be implemented in epidemiologic surveillance that is not limited by the cold chain from the field to the laboratory.

Rapid detection of West Nile and Dengue viruses from mosquito saliva by loop-mediated isothermal amplification and displaced probes

Arthropod-borne viruses are major causes of human and animal disease, especially in endemic low- and middle-income countries. Mosquito-borne pathogen surveillance is essential for risk assessment and vector control responses. Sentinel chicken serosurveillance (antibody testing) and mosquito pool screening (by RT-qPCR or virus isolation) are currently used to monitor arbovirus transmission, however substantial time lags of seroconversion and/or laborious mosquito identification and RNA extraction steps sacrifice their early warning value. As a consequence, timely vector control responses are compromised. Here, we report on development of a rapid arbovirus detection system whereby adding sucrose to reagents of loop-mediated isothermal amplification with displaced probes (DP-LAMP) elicits infectious mosquitoes to feed directly upon the reagent mix and expectorate viruses into the reagents during feeding. We demonstrate that RNA from pathogenic arboviruses (West Nile and Dengue viruses) transmitted in the infectious mosquito saliva was detectable rapidly (within 45 minutes) without RNA extraction. Sucrose stabilized viral RNA at field temperatures for at least 48 hours, important for transition of this system to practical use. After thermal treatment, the DP-LAMP could be reliably visualized by a simple optical image sensor to distinguish between positive and negative samples based on fluorescence intensity. Field application of this technology could fundamentally change conventional arbovirus surveillance methods by eliminating laborious RNA extraction steps, permitting arbovirus monitoring from additional sites, and substantially reducing time needed to detect circulating pathogens.