To test whether Zika virus has adapted for more efficient transmission by Aedes aegypti mosquitoes, leading to recent urban outbreaks, we fed mosquitoes from Brazil, the Dominican Republic, and the United States artificial blood meals containing 1 of 3 Zika virus strains (Senegal, Cambodia, Mexico) and monitored infection, dissemination, and virus in saliva. Contrary to our hypothesis, Cambodia and Mexica strains were less infectious than the Senegal strain. Only mosquitoes from the Dominican Republic transmitted the Cambodia and Mexica strains. However, blood meals from viremic mice were more infectious than artificial blood meals of comparable doses; the Cambodia strain was not transmitted by mosquitoes from Brazil after artificial blood meals, whereas 61% transmission occurred after a murine blood meal (saliva titers up to 4 log10 infectious units/collection). Although regional origins of vector populations and virus strain influence transmission efficiency, Ae. aegypti mosquitoes appear to be competent vectors of Zika virus in several regions of the Americas.

To evaluate the potential role of s (Skuse) as a vector of Zika virus (ZIKV), colonized mosquitoes of low generation number (≤ F5) from Brazil, Houston, and the Rio Grande Valley of Texas engorged on viremic mice infected with ZIKV strains originating from Senegal, Cambodia, Mexico, Brazil, or Puerto Rico. Vector competence was established by monitoring infection, dissemination, and transmission potential after 3, 7, and 14 days of extrinsic incubation. Positive saliva samples were assayed for infectious titer. Although all three mosquito populations were susceptible to all ZIKV strains, rates of infection, dissemination, and transmission differed among mosquito and virus strains. from Salvador, Brazil, were the least efficient vectors, demonstrating susceptibility to infection to two American strains of ZIKV but failing to shed virus in saliva. Mosquitoes from the Rio Grande Valley were the most efficient vectors and were capable of shedding all three tested ZIKV strains into saliva after 14 days of extrinsic incubation. In particular, ZIKV strain DakAR 41525 (Senegal 1954) was significantly more efficient at dissemination and saliva deposition than the others tested in Rio Grande mosquitoes. Overall, our data indicate that, while is capable of transmitting ZIKV, its competence is potentially dependent on geographic origin of both the mosquito population and the viral strain.

Understanding the transmission patterns of West Nile and St. Louis encephalitis viruses (family Flaviviridae, genus Flavivirus, WNV and SLEV) could result in an increased ability to predict transmission risk to humans. To examine transmission patterns between vector and host, we trapped mosquitoes in three Florida counties from June to November 2005 by using chicken-baited lard can mosquito traps. These traps were used to monitor for presence of WNV and SLEV in mosquitoes and subsequent transmission of these viruses to chickens. In total, 166,615 female mosquitoes were sorted into 4,009 pools based on species and bloodfed status, and they were tested for presence of WNV and SLEV. Sera from 209 chickens were tested for WNV and SLEV antibodies. We detected eight WNV-positive Culex nigripalpus Theobald mosquito pools; SLEV was not detected in any pools. Six positive pools were collected in August and September from Duval County, one pool in September from Manatee County, and one pool in November from Indian River County. Of the eight chickens potentially exposed to WNV, antibodies were detected in only one chicken, indicating a low rate of transmission relative to the observed mosquito infection rates. Low virus transmission rates relative to infection rates would suggest that using sentinel chicken seroconversion data as a means of arbovirus surveillance may underestimate the prevalence of WNV in the mosquito population. However, using mosquito infection rates may overestimate the risk of arboviral transmission. A variety of factors might account for the observed low level of transmission including a lack of viral dissemination in mosquito vectors.

Tephritid pests, such as the Mexican fruit fly, Anastrepha ludens (Loew), represent a major threat to fruit production worldwide. In order to control these pests, sterile insect technique is used to suppress and eradicate wild populations. For this control method to be successful, hundreds of millions of flies must be produced weekly in mass rearing facilities. The large quantity of artificial diet and close proximity of flies at various life stages allows bacteria from family Enterobacteriaceae, Bacillaceae, Pseudomonadaceae, and others to multiply and spread more easily. In this study, bacteria with a possible pathogenic effect were isolated from Mexican fruit fly eggs and dead Mexican fruit fly larvae. Two strains of bacteria associated with dead and dying larvae were identified using the 16S rRNA sequence as a species of Morganella. Further sequencing of multiple genes and the entire genomes identified both strains as Morganella morganii. Pathogenicity tests were completed to assess this bacterium as a Mexican fruit fly pathogen. Several measures of pathogenicity including effects on larval and pupal weight, adult percent emergence, and flight ability were measured for the 2 strains of Morganella compared against a control. In all cases, the presence of the Morganella strains significantly reduced all quality control measurements compared to the control. Also, at 10 5 colony forming units per ml or higher levels of inoculum, the presence of Morganella resulted in 100% mortality of larvae. This study illustrates that Morganella morganii is an extremely lethal pathogen of mass reared Mexican fruit flies.

We used a path analysis procedure to examine the influence of environmental effects on the egg hatching response of the container breeding mosquito, Aedes triseriatus. A. triseriatus eggs were collected from 22 different sites across the eastern US, and exposed to repeated hatch stimuli in the laboratory. The resulting data were used to construct hatch indexes for each site. Structural equation modeling was used to discriminate among hypotheses relating to the functional relationships between population hatch trait and local climatic conditions. The results suggest that the delayed hatch pattern is an adaptive bet-hedging strategy that allows the species to manage desiccation risks. The selected model indicates that environmental variables differentially affect the immediate and the delayed, long term hatch patterns. High temperatures directly reduce the number of egg hatching on the first stimulus, but only indirectly affect the delayed hatch pattern. Low precipitation and high variability in precipitation directly increase the delaying pattern. The hatch trait appears to be a critical adaptation that allows the species to occupy a broad range in east North America.