Spatio-temporal patterns of an anthrax outbreak in white-tailed deer, Odocoileus virginanus, and associated genetic diversity of Bacillus anthracis.

BACKGROUND: Anthrax, a soil-borne zoonosis caused by the bacterium Bacillus anthracis, is enzootic in areas of North America with frequent outbreaks in west Texas. Despite a long history of study, pathogen transmission during natural outbreaks remains poorly understood. Here we combined case-level spatio-temporal analysis and high resolution genotyping to investigate anthrax transmission dynamics. Carcass locations from a single white-tailed deer, Odocoileus virginanus, outbreak were analyzed for spatial clustering using K-function analysis and directionality with trend surface analysis and the direction test. RESULTS: The directionalities were compared to results of high resolution genotyping. The results of the spatial clustering analyses, combined with deer movement data, suggest anthrax transmission events occur within limited spatial areas, with carcass locations occurring within the activity space of adjacent cases. The directionality of the outbreak paralleled adjacent dry river beds. Isolates from the outbreak were represented by a single genotype based on multiple locus variable number tandem repeat analysis (MLVA); four sub-genotypes were identified using single nucleotide repeat (SNR) analysis. CONCLUSIONS: Areas of high transmission agreed spatially with areas of higher SNR genetic diversity; however, SNRs did not provide clear evidence of linear transmission. Overlap of case home ranges provides spatial and temporal support for localized transmission, which may include the role of necrophagous or hematophagous flies in outbreaks in this region. These results emphasize the need for active surveillance and prompt cleanup of anthrax carcasses to control anthrax both during outbreaks and between seasons.

Does the Internet represent a sexual health risk environment for young people?

This study examined sexual risk behaviors/outcomes among college students with online partners only, offline partners only, and both online/offline partners. Students with both online/offline partners were more likely to report sexually transmitted diseases, unintended pregnancy, and more vaginal/oral sex partners. Sex with online partners was not riskier than sex with offline partners.

Predicting the Geographic Distribution of the Bacillus anthracis A1.a/Western North American Sub-Lineage for the Continental United States: New Outbreaks, New Genotypes, and New Climate Data.

Bacillus anthracis, the causative pathogen of anthrax, is a spore-forming, environmentally maintained bacterium that continues to be a veterinary health problem with outbreaks occurring primarily in wildlife and livestock. Globally, the genetic populations of B. anthracis include multiple lineages, and each may have different ecological requirements and geographical distributions. It is, therefore, essential to identify environmental associations within lineages to predict geographical distributions and risk areas with improved accuracy. Here, we model the ecological niche and predict the geography of the most widespread sublineage of B. anthracis in the continental United States using updated MERRA-derived (Modern Era Retrospective analysis for Research and Applications; the NASA atmospheric data reanalysis of satellite information with multiple data products) bioclimate variables (i.e., MERRAclim data) and updated soil variables. We filter the occurrence data associated with the A1.a/Western North American sub-lineage of B. anthracis from historical anthrax outbreaks using the multiple-locus variable-number tandem repeat system. In addition, we also incorporate recent cases associated with B. anthracis A1.a sub-lineage from 2008 to 2012 in Montana, Colorado, and Texas. Our results provide the predicted distribution of the A1.a sub-lineage of B. anthracis for the United States with better predictive accuracy and higher spatial resolution than previous estimates. Our prediction serves as an improved disease risk map to better inform anthrax surveillance and control in the United States, particularly the Dakotas and Montana where this sub-lineage is persistent.

The necrophagous fly anthrax transmission pathway: empirical and genetic evidence from wildlife epizootics.

Early studies confirmed Bacillus anthracis in emesis and feces of flies under laboratory conditions, but there is little empirical field evidence supporting the roles of flies in anthrax transmission. We collected samples during outbreaks of anthrax affecting livestock and native and exotic wildlife on two ranches in West Texas (2009-2010). Sampling included animal carcasses, maggots, adult flies feeding on or within several meters of carcasses, and leaves from surrounding vegetation. Microbiology and PCR were used to detect B. anthracis in the samples. Viable B. anthracis and/or PCR-positive results were obtained from all represented sample types. Genetic analysis of B. anthracis samples using multilocus variable number tandem repeat analysis (MLVA) confirmed that each ranch represented a distinct genetic lineage. Within each ranch, we detected the same genotype of B. anthracis from carcasses, maggots, and adult flies. The results of this study provide evidence supporting a transmission cycle in which blowflies contaminate vegetation near carcasses that may then infect additional browsing animals during anthrax outbreaks in the shrubland environment of West Texas.

Ecological niche modeling of Bacillus anthracis on three continents: evidence for genetic-ecological divergence?

We modeled the ecological niche of a globally successful Bacillus anthracis sublineage in the United States, Italy and Kazakhstan to better understand the geographic distribution of anthrax and potential associations between regional populations and ecology. Country-specific ecological-niche models were developed and reciprocally transferred to the other countries to determine if pathogen presence could be accurately predicted on novel landscapes. Native models accurately predicted endemic areas within each country, but transferred models failed to predict known occurrences in the outside countries. While the effects of variable selection and limitations of the genetic data should be considered, results suggest differing ecological associations for the B. anthracis populations within each country and may reflect niche specialization within the sublineage. Our findings provide guidance for developing accurate ecological niche models for this pathogen; models should be developed regionally, on the native landscape, and with consideration to population genetics. Further genomic analysis will improve our understanding of the genetic-ecological dynamics of B. anthracis across these countries and may lead to more refined predictive models for surveillance and proactive vaccination programs. Further studies should evaluate the impact of variable selection of native and transferred models.