Global genomics of Aedes aegypti unveils widespread and novel infectious viruses capable of triggering a small RNA response.

The mosquito Aedes aegypti is a prominent vector for arboviruses, but the breadth of mosquito viruses that infects this specie is not fully understood. In the broadest global survey to date of over 200 Ae. aegypti small RNA samples, we detected viral small interfering RNAs (siRNAs) and Piwi interacting RNAs (piRNAs) arising from mosquito viruses. We confirmed that most academic laboratory colonies of Ae. aegypti lack persisting viruses, yet two commercial strains were infected by a novel tombus-like virus. Ae. aegypti from North to South American locations were also teeming with multiple insect viruses, with Anphevirus and a bunyavirus displaying geographical boundaries from the viral small RNA patterns. Asian Ae. aegypti small RNA patterns indicate infections by similar mosquito viruses from the Americas and reveal the first wild example of dengue virus infection generating viral small RNAs. African Ae. aegypti also contained various viral small RNAs including novel viruses only found in these African substrains. Intriguingly, viral long RNA patterns can differ from small RNA patterns, indicative of viral transcripts evading the mosquitoes' RNA interference (RNAi) machinery. To determine whether the viruses we discovered via small RNA sequencing were replicating and transmissible, we infected C6/36 and Aag2 cells with Ae. aegypti homogenates. Through blind passaging, we generated cell lines stably infected by these mosquito viruses which then generated abundant viral siRNAs and piRNAs that resemble the native mosquito viral small RNA patterns. This mosquito small RNA genomics approach augments surveillance approaches for emerging infectious diseases.

Pyrethroid insecticides in urban catch basins: A potential secondary contamination source for urban aquatic systems.

Pesticide contamination is a threat to many aquatic habitats, and runoff from residential homes is a major contributor of these chemicals in urban surface streams and estuaries. Improved understanding of their fate and transport can help identify areas of concern for monitoring and management. In many urban areas, runoff water congregates in numerous underground catch basins before draining into the open environment; however, at present essentially no information is available on pesticide presence in these systems. In this study, we collected water samples from a large number of underground urban catch basins in different regions of California during the active pest management season to determine the occurrence and profile of the widely used pyrethroid insecticides. Detectable levels of pyrethroids were found in 98% of the samples, and the detection frequency of individual pyrethroids ranged from no detection for fenpropathrin to 97% for bifenthrin. In the aqueous phase, total pyrethroid concentrations ranged from 3 to 726 ng/L, with a median value of 32 ng/L. Pyrethroids were found to be enriched on suspended solids, with total concentrations ranging from 42 to 93,600 ng/g and a median value of 2,350 ng/g. In approximately 89% of the samples, whole water concentrations of bifenthrin were predicted to have toxic units >1 for sensitive aquatic invertebrates. The high detection frequency of bifenthrin and overall pyrethroid concentrations, especially for particle-bound residues, suggest that underground urban catch basins constitute an important secondary source for extended and widespread contamination of downstream surface waters by pesticides such as pyrethroids in urban regions.

Field Evaluation of a Redesigned Oviposition Trap to Monitor Gravid Invasive Aedes Mosquitoes in a Suburban Environment.

Oviposition cup traps (OCT) are commonly used to detect gravid invasive Aedes mosquitoes. Employing OCT during hot summer months or over broad geographic areas is labor intensive because the water in these small-volume traps must be frequently replenished to maintain their attractiveness to mosquitoes. We developed low-cost and simple-to-build oviposition bucket traps (OBT) that attract mosquitoes for more than 1 wk. Comparison of adjacently placed OCT and OBT in the city of Madera, CA, showed OBT captured significantly more Ae. aegypti eggs per trap-night relative to the OCT (8.8 ± 2.6 and 4.1 ± 1.1, respectively; paired t-test, P = 0.0076), and a significantly greater proportion of OBT contained Ae. aegypti eggs relative to OCT (83% of OBT and 65% of OCT; Fisher's exact test, P = 0.0214). The results suggest that OBT can collect larger quantities of Ae. aegypti eggs relative to OCT while potentially offering greater flexibility in scheduling trap inspections.