RNA interference is essential to modulating the pathogenesis of mosquito-borne viruses in the yellow fever mosquito Aedes aegypti.

While it has long been known that the transmission of mosquito-borne viruses depends on the establishment of persistent and nonlethal infections in the invertebrate host, specific roles for the insects' antiviral immune pathways in modulating the pathogenesis of viral infections is the subject of speculation and debate. Here, we show that a loss-of-function mutation in the Aedes aegypti Dicer-2 (Dcr-2) gene renders the insect acutely susceptible to a disease phenotype upon infection with pathogens in multiple virus families associated with important human diseases. Additional interrogation of the disease phenotype demonstrated that the virus-induced pathology is controlled through a canonical RNA interference (RNAi) pathway, which functions as a resistance mechanism. These results suggest comparatively modest contributions of proposed tolerance mechanisms to the fitness of A. aegypti infected with these pathogens. Similarly, the production of virus-derived piwi-interacting RNAs (vpiRNAs) was not sufficient to prevent the pathology associated with viral infections in Dcr-2 null mutants, also suggesting a less critical, or potentially secondary, role for vpiRNAs in antiviral immunity. These findings have important implications for understanding the ecological and evolutionary interactions occurring between A. aegypti and the pathogens they transmit to human and animal hosts.

The Aedes aegypti siRNA pathway mediates broad-spectrum defense against human pathogenic viruses and modulates antibacterial and antifungal defenses.

The mosquito's innate immune system defends against a variety of pathogens, and the conserved siRNA pathway plays a central role in the control of viral infections. Here, we show that transgenic overexpression of Dicer2 (Dcr2) or R2d2 resulted in an accumulation of 21-nucleotide viral sequences that was accompanied by a significant suppression of dengue virus (DENV), Zika virus (ZIKV), and chikungunya virus (CHIKV) replication, thus indicating the broad-spectrum antiviral response mediated by the siRNA pathway that can be applied for the development of novel arbovirus control strategies. Interestingly, overexpression of Dcr2 or R2d2 regulated the mRNA abundance of a variety of antimicrobial immune genes, pointing to additional functions of DCR2 and R2D2 as well as cross-talk between the siRNA pathway and other immune pathways. Accordingly, transgenic overexpression of Dcr2 or R2d2 resulted in a lesser proliferation of the midgut microbiota and increased resistance to bacterial and fungal infections.

Predictive model for microclimatic temperature and its use in mosquito population modeling.

Mosquitoes transmit several infectious diseases that pose significant threat to human health. Temperature along with other environmental factors at breeding and resting locations play a role in the organismal development and abundance of mosquitoes. Accurate analysis of mosquito population dynamics requires information on microclimatic conditions at breeding and resting locations. In this study, we develop a regression model to characterize microclimatic temperature based on ambient environmental conditions. Data were collected by placing sensor loggers at resting and breeding locations such as storm drains across Houston, TX. Corresponding weather data was obtained from National Oceanic and Atmospheric Administration website. Features extracted from these data sources along with contextual information on location were used to develop a Generalized Linear Model for predicting microclimate temperatures. We also analyzed mosquito population dynamics for Aedes albopictus under ambient and microclimatic conditions using system dynamic (SD) modelling to demonstrate the need for accurate microclimatic temperatures in population models. The microclimate prediction model had an R2 value of ~ 95% and average prediction error of ~ 1.5 °C indicating that microclimate temperatures can be reliably estimated from the ambient environmental conditions. SD model analysis indicates that some microclimates in Texas could result in larger populations of juvenile and adult Aedes albopictus mosquitoes surviving the winter without requiring dormancy.

Prevalence of Shiga-toxigenic Escherichia coli in House Flies (Diptera: Muscidae) in an Urban Environment.

House flies (Musca domestica L. [Diptera: Muscidae]) can act as a mechanical vector for food-borne pathogens including Shiga toxin-producing Escherichia coli (Migula; Enterobacteriales: Enterobacteriaceae) (STEC) in and around cattle feedlots. The present study assessed the prevalence of STEC in house flies from a restaurant area of a town in northeastern Kansas. Two hundred twenty-four house flies were collected over 10 wk, surface sterilized, individually homogenized, and cultured by a multifaceted approach of direct plating on selective media and an enrichment broth, followed by the immunomagnetic separation. Bacterial isolates were screened for eight serogroups of E. coli: O103, O104, O26, O111, O45, O145, O121, and O157 using multiplex polymerase chain reaction (PCR). Furthermore, O-serogroup-positive isolates were tested for virulence genes stx1, stx2, eae, and ehxA by PCR. The majority (91.5%) of flies carried enteric bacteria, and the mean value of enteric concentration on the modified Possé agar was 6.7 ± 1.1 × 106 colony forming units per fly. Thirty-nine of the 224 flies (17.4%) were positive for one or more E. coli serogroup of interest; with the majority O103 (10.7%), followed by O26 (3.1%), O121 (1.3%), O45 (1.3%), and O104 (0.9%). However, none of the serogroup-positive isolates carried any of the virulence genes tested. Results of our study show that house flies in the urban environment do not carry STEC. Nevertheless, detection of E. coli O-serogroups with the potential to acquire virulence traits indicates that house flies in an urban environment represent a public health risk.

New records of Ornithodoros puertoricensis Fox 1947 (Ixodida: Argasidae) parasitizing humans in rural and urban dwellings, Panama.

The presence of ticks inside human constructions was evaluated in two localities from Colon province (Charco La Piedra and Espinar) and one from Panama province (Ancon, City of Panama). In two of houses, eight people from Charco La Piedra and one from Ancón reported "insect bites," which produced blisters for several weeks. The investigation resulted in the collection of argasid ticks, which were identified by morphology and sequencing the 16s ribosomal RNA gene, and later evaluated for the presence of relapsing fever Borrelia DNA. All ticks were identified as Ornithodoros puertoricensis. While spirochetal DNA was not detected by PCR in the ticks, our report highlights the potential for relapsing fever borreliosis in rural and urban localities in Panama.