New hydroepidemiological models of indicator organisms and zoonotic pathogens in agricultural watersheds
► We model E. coli and Campylobacter in idealized agricultural watersheds. ► Results are characterised by four fundamental dimensionless quantities. ► Efficacy of agricultural best management practices is predicted ► Post-BMP stream concentration reductions are greater for Campylobacter cf. E. coli....
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Published in | Ecological modelling Vol. 222; no. 13; pp. 2093 - 2102 |
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Main Authors | , |
Format | Journal Article |
Language | English |
Published |
Amsterdam
Elsevier B.V
10.07.2011
Elsevier |
Subjects | |
Online Access | Get full text |
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Summary: | ► We model
E. coli and
Campylobacter in idealized agricultural watersheds. ► Results are characterised by four fundamental dimensionless quantities. ► Efficacy of agricultural best management practices is predicted ► Post-BMP stream concentration reductions are greater for
Campylobacter cf.
E. coli. ► Under this model, farms can attain
Campylobacter sterility.
Simple analytical models are derived to assess how a series of cattle animal farms affect the transport and fate of an indicator organism (
Escherichia coli) and a zoonotic pathogen (
Campylobacter) in a stream. Separate steady-state mass-balance models are developed and solved for the ultimate minimum and maximum concentrations for the two organisms. The
E. coli model assumes that the organism is ubiquitous and abundant in the animals’ digestive tracts. In contrast, a simple dose–response model is employed to relate the
Campylobacter prevalence to drinking water drawn from the stream. Because faecal indicators are commonly employed to assess the efficacy of best management practice (BMP) interventions, we also employ the models to assess how BMPs impact pathogen levels. The model provides predictions of (a) the relative removal efficacy for
Campylobacter and (b) the prevalence of
Campylobacter infection among farm animals after implementation of BMPs. Dimensionless numbers and simple graphs are developed to assess how prevalence is influenced by a number of factors including animal density and farm spacing. A significant outcome of this model development is that the numerous dimensional input and parameter variables are reduced to a group of just four dimensionless
Campylobacter-related quantities, characterizing: animal density; in-stream attenuation; animal-to-animal transmission; and infection recovery. Calculations reveal that for some constellations of these four quantities there can be a greater-than-expected benefit in that the proportional reduction of stream
Campylobacter concentrations post-BMP can substantially exceed the proportional reduction of concentrations of
E. coli in that stream. In addition, a criterion for system sterility (i.e., the conditions required for the farm infection rate to decrease with downstream distance) is derived. |
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Bibliography: | http://dx.doi.org/10.1016/j.ecolmodel.2011.04.008 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0304-3800 1872-7026 |
DOI: | 10.1016/j.ecolmodel.2011.04.008 |