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Joyner C.,Georgia Southern University | Joyner C.,Emory University | Mills M.K.,Georgia Southern University | Mills M.K.,Kansas State University | And 2 more authors.
PLoS ONE | Year: 2013

House flies associate with microbes throughout their life history. Bacteria ingested by adult flies enter the alimentary canal and face a hostile environment including antimicrobial defenses. Because the outcome of this interaction impacts bacterial survival and dissemination, our primary objective was to understand the temporospatial dynamics of fly-bacteria associations. We concurrently examined the temporospatial fate of GFP-expressing Pseudomonas aeruginosa (GFP-P. aeruginosa) in the house fly alimentary canal along with antimicrobial peptide (AMP) expression. Motile, viable GFP-P. aeruginosa were found in all regions of the alimentary canal and were culturable throughout the observation period (2-24 h). A significant decrease in recoverable bacteria occurred between 2 and12 h, followed by an increase between 12 and 24 h. qRT-PCR analysis showed expression of the AMPs cecropin, diptericin, and defensin both locally (gut) and systemically. Furthermore, mRNA of all AMPs were expressed throughout gut tissues, with some tissue-specific temporal variation. Interestingly, fluctuation in recoverable P. aeruginosa was associated with AMP protein expression in the gut (immunofluorescent signal detection), but not with mRNA (qRTPCR). In regards to vector competence, flies excreted GFP-P. aeruginosa throughout the 24 h period, serving as both reservoirs and disseminators of this bacterium. Collectively, our data show flies can harbor and disseminate P. aeruginosa, and that the interactions of fly defenses with bacteria can influence vector competence. Source


Xue L.,Kansas State University | Cohnstaedt L.W.,Center for Grain and Animal Health Research | Scott H.M.,Kansas State University | Scoglio C.,Kansas State University
PLoS ONE | Year: 2013

Rift Valley fever is a vector-borne zoonotic disease which causes high morbidity and mortality in livestock. In the event Rift Valley fever virus is introduced to the United States or other non-endemic areas, understanding the potential patterns of spread and the areas at risk based on disease vectors and hosts will be vital for developing mitigation strategies. Presented here is a general network-based mathematical model of Rift Valley fever. Given a lack of empirical data on disease vector species and their vector competence, this discrete time epidemic model uses stochastic parameters following several PERT distributions to model the dynamic interactions between hosts and likely North American mosquito vectors in dispersed geographic areas. Spatial effects and climate factors are also addressed in the model. The model is applied to a large directed asymmetric network of 3,621 nodes based on actual farms to examine a hypothetical introduction to some counties of Texas, an important ranching area in the United States of America. The nodes of the networks represent livestock farms, livestock markets, and feedlots, and the links represent cattle movements and mosquito diffusion between different nodes. Cattle and mosquito (Aedes and Culex) populations are treated with different contact networks to assess virus propagation. Rift Valley fever virus spread is assessed under various initial infection conditions (infected mosquito eggs, adults or cattle). A surprising trend is fewer initial infectious organisms result in a longer delay before a larger and more prolonged outbreak. The delay is likely caused by a lack of herd immunity while the infection expands geographically before becoming an epidemic involving many dispersed farms and animals almost simultaneously. Cattle movement between farms is a large driver of virus expansion, thus quarantines can be efficient mitigation strategy to prevent further geographic spread. Source


Xue L.,Kansas State University | Scott H.M.,Kansas State University | Cohnstaedt L.W.,Center for Grain and Animal Health Research | Scoglio C.,Kansas State University
Journal of Theoretical Biology | Year: 2012

Rift Valley fever virus (RVFV) has been expanding its geographical distribution with important implications for both human and animal health. The emergence of Rift Valley fever (RVF) in the Middle East, and its continuing presence in many areas of Africa, has negatively impacted both medical and veterinary infrastructures and human morbidity, mortality, and economic endpoints. Furthermore, worldwide attention should be directed towards the broader infection dynamics of RVFV, because suitable host, vector and environmental conditions for additional epidemics likely exist on other continents; including Asia, Europe and the Americas. We propose a new compartmentalized model of RVF and the related ordinary differential equations to assess disease spread in both time and space; with the latter driven as a function of contact networks. Humans and livestock hosts and two species of vector mosquitoes are included in the model. The model is based on weighted contact networks, where nodes of the networks represent geographical regions and the weights represent the level of contact between regional pairings for each set of species. The inclusion of human, animal, and vector movements among regions is new to RVF modeling. The movement of the infected individuals is not only treated as a possibility, but also an actuality that can be incorporated into the model. We have tested, calibrated, and evaluated the model using data from the recent 2010 RVF outbreak in South Africa as a case study; mapping the epidemic spread within and among three South African provinces. An extensive set of simulation results shows the potential of the proposed approach for accurately modeling the RVF spreading process in additional regions of the world. The benefits of the proposed model are twofold: not only can the model differentiate the maximum number of infected individuals among different provinces, but also it can reproduce the different starting times of the outbreak in multiple locations. Finally, the exact value of the reproduction number is numerically computed and upper and lower bounds for the reproduction number are analytically derived in the case of homogeneous populations. © 2012 Elsevier Ltd. Source


Zhang H.,University of Wyoming | Harpster M.H.,University of Wyoming | Park H.J.,University of Wyoming | Johnson P.A.,University of Wyoming | Wilson W.C.,Center for Grain and Animal Health Research
Analytical Chemistry | Year: 2011

A model paramagnetic nanoparticle (MNP) assay is demonstrated for surface-enhanced Raman scattering (SERS) detection of DNA oligonucleotides derived from the West Nile virus (WNV) genome. Detection is based on the capture of WNV target sequences by hybridization with complementary oligonucleotide probes covalently linked to fabricated MNPs and Raman reporter tag-conjugated gold nanoparticles (GNPs) and the subsequent removal of GNP-WNV target sequence-MNP hybridization complexes from solution by an externally applied magnetic source. Laser excitation of the pelleted material provided a signature SERS spectrum which is diagnostic for the reporter, 5,5′- dithiobis(succinimidy-2-nitrobenzoate) (DSNB), and restricted to hybridization reactions containing WNV target sequences. Hybridizations containing dilutions of the target oligonucleotide were characterized by a reduction in the intensification of the spectral peaks accorded to the SERS signaling of DSNB, and the limit of detection for target sequence in buffer was 10 pM. Due to the short hybridization times required to conduct the assay and ease with which reproducible Raman spectra can be acquired, the assay is amenable to adaptation within a portable, user-friendly Raman detection platform for nucleic acids. © 2010 American Chemical Society. Source


Arakane Y.,Kansas State University | Arakane Y.,Chonnam National University | Lomakin J.,University of Kansas | Gehrke S.H.,University of Kansas | And 7 more authors.
PLoS Genetics | Year: 2012

Insect cuticle is composed primarily of chitin and structural proteins. To study the function of structural cuticular proteins, we focused on the proteins present in elytra (modified forewings that become highly sclerotized and pigmented covers for the hindwings) of the red flour beetle, Tribolium castaneum. We identified two highly abundant proteins, TcCPR27 (10 kDa) and TcCPR18 (20 kDa), which are also present in pronotum and ventral abdominal cuticles. Both are members of the Rebers and Riddiford family of cuticular proteins and contain RR2 motifs. Transcripts for both genes dramatically increase in abundance at the pharate adult stage and then decline quickly thereafter. Injection of specific double-stranded RNAs for each gene into penultimate or last instar larvae had no effect on larval-larval, larval-pupal, or pupal-adult molting. The elytra of the resulting adults, however, were shorter, wrinkled, warped, fenestrated, and less rigid than those from control insects. TcCPR27-deficient insects could not fold their hindwings properly and died prematurely approximately one week after eclosion, probably because of dehydration. TcCPR18-deficient insects exhibited a similar but less dramatic phenotype. Immunolocalization studies confirmed the presence of TcCPR27 in the elytral cuticle. These results demonstrate that TcCPR27 and TcCPR18 are major structural proteins in the rigid elytral, dorsal thoracic, and ventral abdominal cuticles of the red flour beetle, and that both proteins are required for morphogenesis of the beetle's elytra. Source

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