Modelling the epidemiology of Verocytotoxin-producing <i>Escherichia coli</i> serogroups in young calves

Liu, W. C.; Jenkins, Claire; Shaw, Darren; Matthews, Louise; Pearce, Michael; Low, J. C.; Gunn, George J.; Smith, H. R.; Frankel, Gad; Woolhouse, Mark

doi:10.1017/s0950268804003644

Cited by 11 publications

(12 citation statements)

References 12 publications

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“…Although this may due in part to an increased probability of detection using IMS at higher concentrations, this finding is in agreement with reports in the literature of persistent high shedders (greater than 10 4 CFU g K1 ; Liu et al 2005). It has been suggested that removing 'super-shedders' would be the most effective control strategy for reducing on-farm prevalence of E. coli O157 (Matthews et al 2006).…”

Section: Discussionsupporting

confidence: 90%

Quantifying within- and between-animal variation and uncertainty associated with counts of Escherichia coli O157 occurring in naturally infected cattle faeces

Robinson

Brown

Wright

et al. 2008

J. R. Soc. Interface.

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Cattle faeces are considered the most important reservoir for human infection with Escherichia coli O157. We have previously described shedding of E. coli O157 in the faeces of naturally infected cattle cohorts. However, the data require further investigation to quantify the uncertainty and variability in the estimates previously presented. This paper proposes a method for analysing both the presence and the quantity of E. coli O157 in cattle faecal samples, using two isolation procedures, one of which enumerates E. coli O157. The combination of these two measurements, which are fundamentally different in nature and yet measuring a common outcome, has necessitated the development of a novel statistical model for ascertaining the contribution of the various components of variation (both natural and observation induced) and for judging the influence of explanatory variables. Most of the variation within the sampling hierarchy was attributable to multiple samples from the same animal. The contribution of laboratory-level variation was found to be low. After adjusting for fixed and random effects, short periods of increased intensity of shedding were identified in individual animals. We conclude that within-animal variation is greater than between animals over time, and studies aiming to elucidate the dynamics of shedding should focus resources, sampling more within than between animals. These findings have implications for the identification of persistent high shedders and for assessing their role in the epidemiology of E. coli O157 in cattle populations. The development of this non-standard statistical model may have many applications to other microbial count data.

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Section: Discussionsupporting

confidence: 90%

Quantifying within- and between-animal variation and uncertainty associated with counts of Escherichia coli O157 occurring in naturally infected cattle faeces

Robinson

Brown

Wright

et al. 2008

J. R. Soc. Interface.

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“…The best set of parameter values is the one with the highest probability of reproducing the data. Following our previous approach [23], we are required to define some properties of the data to allow comparison between model output and the observed data. These are : (1) the number of positive infections, which is the number of samples that tested positive for a particular VTEC serogroup using a particular detection method ; (2) the infection week, which is the number of weeks during which at least one sample tested positive ; and (3) the number of animals that ever tested positive for a particular serogroup.…”

Section: Basic Model and Parameter Estimationmentioning

confidence: 99%

Modelling the epidemiology and transmission of Verocytotoxin-producingEscherichia coliserogroups O26 and O103 in two different calf cohorts

et al. 2007

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Mathematical models are constructed to investigate the population dynamics of Verocytotoxin-producing Escherichia coli (VTEC) serogroups O26 and O103 in two different calf cohorts. We compare the epidemiological characteristics of these two serogroups within the same calf cohort as well as the same serogroups between the two calf cohorts. The sources of infection are quantified for both calf cohort studies. VTEC serogroups O26 and O103 mainly differ in the rate at which calves acquire infection from sources other than infected calves, while infected calves typically remain infectious for less than 1 week regardless of the serogroups. Fewer than 20% of VTEC-positive samples are the result of calf-to-calf transmission. PFGE typing data are available for VTEC-positive samples to further subdivide the serogroup data in one of the two calf cohort studies. For serogroup O26 but not O103, there is evidence for unequal environmental exposure to infection with different PFGE types.

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“…Mathematical models have been used to inform the design and impact of interventions [12][13][14], understand transmission dynamics in dairy [15,16] and beef [17,18] production systems, and determine the key processes that drive infection dynamics [16,19]. To date, much of the modelling has been carried out by constructing and simulating from mechanistic models [16] and, fitting these models to experimental infection data [20] or cross-sectional data on prevalence and concentration of E. coli O157:H7 in cattle faeces [19].…”

Section: Introductionmentioning

confidence: 99%

‘Super' or just ‘above average'? Supershedders and the transmission of Escherichia coli O157:H7 among feedlot cattle

Spencer

Besser

Cobbold

et al. 2015

J. R. Soc. Interface.

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Supershedders have been suggested to be major drivers of transmission of Escherichia coli O157:H7 (E. coli O157:H7) among cattle in feedlot environments, despite our relatively limited knowledge of the processes that govern periods of high shedding within an individual animal. In this study, we attempt a data-driven approach, estimating the key characteristics of high shedding behaviour, including effects on transmission to other animals, directly from a study of natural E. coli O157:H7 infection of cattle in a research feedlot, in order to develop an evidence-based definition of supershedding. In contrast to the hypothesized role of supershedders, we found that high shedding individuals only modestly increased the risk of transmission: individuals shedding over 10 3 cfu g 21 faeces were estimated to pose a risk of transmission only 2.45 times greater than those shedding below that level. The data suggested that shedding above 10 3 cfu g 21 faeces was the most appropriate definition of supershedding behaviour and under this definition supershedding was surprisingly common, with an estimated prevalence of 31.3% in colonized individuals. We found no evidence that environmental contamination by faeces of shedding cattle contributed to transmission over timescales longer than 3 days and preliminary evidence that higher stocking density increased the risk of transmission.

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Modelling the epidemiology of Verocytotoxin-producing Escherichia coli serogroups in young calves

Cited by 11 publications

References 12 publications

Quantifying within- and between-animal variation and uncertainty associated with counts of Escherichia coli O157 occurring in naturally infected cattle faeces

Quantifying within- and between-animal variation and uncertainty associated with counts of Escherichia coli O157 occurring in naturally infected cattle faeces

Modelling the epidemiology and transmission of Verocytotoxin-producingEscherichia coliserogroups O26 and O103 in two different calf cohorts

‘Super' or just ‘above average'? Supershedders and the transmission of Escherichia coli O157:H7 among feedlot cattle

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