Transmission Potential of Zika Virus by Aedes aegypti (Diptera: Culicidae) and Ae. mediovittatus (Diptera: Culicidae) Populations From Puerto Rico

Larval competition between the invasive Aedes aegypti (Diptera: Culicidae) and the Caribbean endemic Aedes mediovittatus (Diptera: Culicidae) from Puerto Rico, USA

Competition between mosquito species during the larval phase is a well-established mechanism structuring container mosquito communities, with invasive species often outperforming natives. We assessed the competitive outcome between 2 species that occur on the island of Puerto Rico, the historic invasive Aedes aegypti (L.) and the endemic Aedes mediovittatus (Coquillett) (Diptera: Culicidae). Trials were conducted under intra- and interspecific densities crossed with 2 amounts of 4 different leaf types serving as detrital resources for developing larvae; leaf types were representative of either urban or rural locations. Response variables included survival, male and female mass and development time, and a composite index of population growth (λ'). We also measured tannin levels in detrital environments, a secondary metabolite that can negatively influence mosquito development and survival. The co-occurrence of Ae. aegypti and Ae. mediovittatus generally did not affect survival or population growth of Ae. mediovittatus, however the converse was not true. Specifically, Ae. aegypti suffered lower survival and lower population growth in the presence of Ae. mediovittatus compared to when it was alone. Tannin concentrations did not correspond to competitive outcomes, as the highest tannin levels occurred under the detrital conditions where mosquitoes had highest growth and survival, with no evidence of differences between urban or rural leaf types. This is the first study to quantify the competitive outcomes between these species, both of which are part of the dengue transmission cycle on the island, and our findings suggest that Ae. mediovittatus is capable of outcompeting Ae. aegypti under some resource environments.

Transcriptome analysis of Aedes aegypti midgut and salivary gland post-Zika virus infection

This study aimed to investigate the transcriptomic changes in the midgut and salivary glands of Aedes aegypti mosquitoes infected with Zika virus (ZIKV), in order to explore the molecular mechanisms underlying the interaction between the virus and the mosquito vector. Aedes aegypti from Jiegao (JG) and Mengding (MD) in China were experimentally infected with ZIKV, and the midgut and salivary gland tissues were collected at 2-, 4- and 6 days post-infection (dpi). High-throughput sequencing was performed to analyze the transcriptomic changes between ZIKV-infected and non-infected Ae. aegypti midgut and salivary gland tissues. Bioinformatics tools were employed for further analysis of the transcriptomic data. The expression levels of 8 significantly differentially expressed genes (DEGs) were validated using RT-qPCR. A conjoint analysis of small RNA-seq and mRNA-seq was performed to screen interactional miRNA-mRNA pairs during ZIKV infection. Using the Search Tool for the Retrieval of Interacting Genes, we constructed a protein-protein interaction network of genes and subsequently identified hub genes. The most significant transcriptional changes in Ae. aegypti occurred at 2 dpi. On 2, 4 and 6 dpi, 11 genes showed significant changes in both the midgut and salivary glands of the same mosquito strain, while 25 genes exhibited significant changes in the same tissue between the JG and MD strains. The expression tendencies of 8 DEGs obtained by RNA-Seq were similar to those detected by RT-qPCR. Furthermore, we individually identified 10 hub genes in the midgut and salivary glands. Based on previous miRNA research, we discovered the involvement of 9 miRNAs in the regulation of these hub genes. Our findings demonstrate that Ae. aegypti exhibit distinct transcriptomic changes in response to ZIKV infection. The identification of the hub genes and their regulatory miRNAs provides valuable insights into the molecular mechanisms underlying ZIKV infection in mosquitoes. This study contributes to a better understanding of the pathogen-vector interactions and may aid in the development of targeted strategies for ZIKV control.

Secondary vectors of Zika Virus, a systematic review of laboratory vector competence studies

BACKGROUND

After the unprecedented Zika virus (ZIKV) outbreak in the western hemisphere from 2015-2018, Aedes aegypti and Ae. albopictus are now well established primary and secondary ZIKV vectors, respectively. Consensus about identification and importance of other secondary ZIKV vectors remain. This systematic review aims to provide a list of vector species capable of transmitting ZIKV by reviewing evidence from laboratory vector competence (VC) studies and to identify key knowledge gaps and issues within the ZIKV VC literature.

METHODS

A search was performed until 15th March 2022 on the Cochrane Library, Lilacs, PubMed, Web of Science, WHOLIS and Google Scholar. The search strings included three general categories: 1) "ZIKA"; 2) "vector"; 3) "competence", "transmission", "isolation", or "feeding behavior" and their combinations. Inclusion and exclusion criteria has been predefined and quality of included articles was assessed by STROBE and STROME-ID criteria.

FINDINGS

From 8,986 articles retrieved, 2,349 non-duplicates were screened by title and abstracts,103 evaluated using the full text, and 45 included in this analysis. Main findings are 1) secondary vectors of interest include Ae. japonicus, Ae. detritus, and Ae. vexans at higher temperature 2) Culex quinquefasciatus was not found to be a competent vector of ZIKV, 3) considerable heterogeneity in VC, depending on the local mosquito strain and virus used in testing was observed. Critical issues or gaps identified included 1) inconsistent definitions of VC parameters across the literature; 2) equivalency of using different mosquito body parts to evaluate VC parameters for infection (mosquito bodies versus midguts), dissemination (heads, legs or wings versus salivary glands), and transmission (detection or virus amplification in saliva, FTA cards, transmission to neonatal mice); 3) articles that fail to use infectious virus assays to confirm the presence of live virus; 4) need for more studies using murine models with immunocompromised mice to infect mosquitoes.

CONCLUSION

Recent, large collaborative multi-country projects to conduct large scale evaluations of specific mosquito species represent the most appropriate approach to establish VC of mosquito species.

Interspecies Isobaric Labeling-Based Quantitative Proteomics Reveals Protein Changes in the Ovary of Aedes aegypti Coinfected With ZIKV and Wolbachia

Zika is a vector-borne disease caused by an arbovirus (ZIKV) and overwhelmingly transmitted by Ae. aegypti. This disease is linked to adverse fetal outcomes, mostly microcephaly in newborns, and other clinical aspects such as acute febrile illness and neurologic complications, for example, Guillain-Barré syndrome. One of the most promising strategies to mitigate arbovirus transmission involves releasing Ae. aegypti mosquitoes carrying the maternally inherited endosymbiont bacteria Wolbachia pipientis. The presence of Wolbachia is associated with a reduced susceptibility to arboviruses and a fitness cost in mosquito life-history traits such as fecundity and fertility. However, the mechanisms by which Wolbachia influences metabolic pathways leading to differences in egg production remains poorly known. To investigate the impact of coinfections on the reproductive tract of the mosquito, we applied an isobaric labeling-based quantitative proteomic strategy to investigate the influence of Wolbachia wMel and ZIKV infection in Ae. aegypti ovaries. To the best of our knowledge, this is the most complete proteome of Ae. aegypti ovaries reported so far, with a total of 3913 proteins identified, were also able to quantify 1044 Wolbachia proteins in complex sample tissue of Ae. aegypti ovary. Furthermore, from a total of 480 mosquito proteins modulated in our study, we discuss proteins and pathways altered in Ae. aegypti during ZIKV infections, Wolbachia infections, coinfection Wolbachia/ZIKV, and compared with no infection, focusing on immune and reproductive aspects of Ae. aegypti. The modified aspects mainly were related to the immune priming enhancement by Wolbachia presence and the modulation of the Juvenile Hormone pathway caused by both microorganism’s infection.

Mosquitoes (Diptera: Culicidae) on the islands of Puerto Rico and Vieques, U.S.A

We conducted an island-wide survey of the Caribbean islands Puerto Rico and Vieques, U.S.A. during late 2018 and early 2019 to document the current richness of mosquitoes (Diptera: Culicidae). We used a combination of larval surveys and adult trapping using baited CDC light traps and BG-Sentinel traps across 41 of the 78 municipalities. We collected 9 genera, 12 subgenera, and 31 species, which when combined with past studies yields 44 species on the islands. We also note species occurrences across habitat types and elevations from around the islands. One new record, Aedes (Ochlerotatus) obturbator Dyar and Knab, is noted. However we found no evidence of the presence of Aedes albopictus (Skuse), an invasive found throughout the Caribbean, or Aedes (Fredwardsius) vittatus (Bigot), an exotic species recently reported in the Dominican Republic and Cuba. Habitat associations and information regarding the medical importance of species are also included. Given that the islands often experience outbreaks of several arboviruses, obtaining a complete picture of the species present is of high importance.