Schmallenberg virus pathogenesis, tropism and interaction with the innate immune system of the host

Schmallenberg virus (SBV) is an emerging orthobunyavirus of ruminants associated with outbreaks of congenital malformations in aborted and stillborn animals. Since its discovery in November 2011, SBV has spread very rapidly to many European countries. Here, we developed molecular and serological tools, and an experimental in vivo model as a platform to study SBV pathogenesis, tropism and virus-host cell interactions. Using a synthetic biology approach, we developed a reverse genetics system for the rapid rescue and genetic manipulation of SBV. We showed that SBV has a wide tropism in cell culture and “synthetic” SBV replicates in vitro as efficiently as wild type virus. We developed an experimental mouse model to study SBV infection and showed that this virus replicates abundantly in neurons where it causes cerebral malacia and vacuolation of the cerebral cortex. These virus-induced acute lesions are useful in understanding the progression from vacuolation to porencephaly and extensive tissue destruction, often observed in aborted lambs and calves in naturally occurring Schmallenberg cases. Indeed, we detected high levels of SBV antigens in the neurons of the gray matter of brain and spinal cord of naturally affected lambs and calves, suggesting that muscular hypoplasia observed in SBV-infected lambs is mostly secondary to central nervous system damage. Finally, we investigated the molecular determinants of SBV virulence. Interestingly, we found a biological SBV clone that after passage in cell culture displays increased virulence in mice. We also found that a SBV deletion mutant of the non-structural NSs protein (SBVΔNSs) is less virulent in mice than wild type SBV. Attenuation of SBV virulence depends on the inability of SBVΔNSs to block IFN synthesis in virus infected cells. In conclusion, this work provides a useful experimental framework to study the biology and pathogenesis of SBV

Mosquito density, macroinvertebrate diversity, and water chemistry in water-filled containers: Relationships to land use

The proliferation of disease-vector mosquitoes has been attributed to the effects of land-use change. We investigated the relationship between land use, macroinvertebrate communities, and water chemistry in water-filled containers in native forest, pasture land, and urban land at two locations (Waikanae and Paraparaumu) in the Kapiti region, New Zealand. Larvae of the endemic Culex pervigilans and exotic Aedes notoscriptus constituted 45.0% and 55.0% of all late-instar mosquito species collected. At Waikanae, fourth instar A. notoscriptus, pupal, and total mosquito densities were higher in native forest than in urban land and pasture land, and pupal density was higher in native forest than in pasture land. At Paraparaumu, fourth instar A. notoscriptus and pupal densities were higher in native forest and urban land than in pasture land. Macroinvertebrate communities in human-modified land uses were dominated by two herbivorous chironomid species, consisted of fewer species, higher densities, and different composition than in native forest. Water chemistry was also associated with land use, with nitrate, nitrite, and acidity higher in native forest at both locations. Fourth instar A. notoscriptus, pupal, and total mosquito densities were negatively associated with non-culicid invertebrate density. Fourth instar A. notoscriptus density was also negatively associated with pH. Fourth instar C. pervigilans density was not significantly related to any water chemistry variables. These results indicate that land-use change may not necessarily lead to higher densities of mosquitoes in larval habitats by altering the associated macroinvertebrate community

Evaluation of two dipping methods for sampling immature Culex and Ochlerotatus mosquitoes (Diptera: Culicidae) from artificial containers

Monitoring changes in populations of immature (larvae and pupae) mosquitoes are fundamental to determining mosquito-borne disease risk. Dipping is the most common method used to sample immature mosquitoes, but it can be biased towards particular species and instars. We aimed to assess the generality of the findings of Mori (1989), who showed that stirring the water of artificial containers gave more consistent and accurate samples of Ochlerotatus togoi compared with conventional dipping without prior stirring.Five water-filled artificial containers were placed in each of pastureland, urbanland, and native forest. These containers were subsequently colonised by Culex pervigilans and O. notoscriptus and were used to compare two dipping methods using a plastic dipper. One method involved removing the container from the field and stirring the water before sampling (destructive sampling), and was compared with a conventional field dipping method without prior stirring (field dipping). Results from this study showed that when comparing samples from the two methods, destructive sampling gave estimates that had very strong and better correlations with absolute counts, and were more accurate and consistent. Field dipping generally underestimated O. notoscriptus, possibly because it did not sample the bottom of the container where Ochlerotatus larvae browse detrital sediments. When using estimates from destructive sampling compared with field dipping, the relationship between mosquito density and land use was more similar to the relationship between absolute counts and land use across all population measures used. The results suggest that destructive sampling may be a more reliable mosquito sampling method than conventional field dipping when studying questions on mosquito ecology

Appendix B. Equation for calculating λ', a composite index of population performance based on r', which estimates the realized per capita rate of population change for each replicate cohort.

Equation for calculating λ', a composite index of population performance based on r', which estimates the realized per capita rate of population change for each replicate cohort

Appendix A. Geographic origin of populations of A. albopictus collected.

Geographic origin of populations of A. albopictus collected

Appendix C. Statistical tables and additional figures.

Statistical tables and additional figures

Linking stormwater Best Management Practices to social factors in two suburban watersheds.

To reduce nutrient pollution in urban watersheds, residents need to voluntarily practice a range of stormwater Best Management Practices (BMPs). However, little is known about the underlying social factors that may act as barriers to BMP implementation. The overall goal of this study was to better understand barriers to BMP implementation by exploring the links among resident demographics, knowledge, and behaviors so that appropriate education can be more effectively developed and targeted. In 2014-2015, a detailed questionnaire was administered door-to-door to 299 randomly selected households in two sub-watersheds of the Chesapeake Bay basin to test relationships among resident demographics, knowledge and attitudes towards water resources and BMPs, and BMP implementation. Multifactor regression models showed that respondents who had greater knowledge of water resources and BMPs lived in households that implemented greater numbers of BMPs. In turn, resident BMP knowledge, or familiarity with BMPs, strongly varied with race and ownership status, with respondents who identified as Caucasian or within a collection of 'Other' races, and who were home owners, having greater BMP knowledge than respondents who identified as African American and who were home renters, respectively. Renters and members of homeowner's associations were also less likely to implement BMPs independent of knowledge, possibly reflecting perceived or real bureaucratic or procedural barriers to good stormwater management. Overall, respondents preferred to receive educational materials on stormwater via pamphlets and YouTube videos. These results suggest that resident ownership status knowledge is important to determining the number of household BMPs, and that education outreach should probably target African American and renting households that have lower BMP knowledge and landlords and administrators of homeowner's associations using well-planned print and video educational media