Grass Fed Beef Sheds E Coli
Summary
This report aims to describe in detail the temporal dynamics of E. coli O157 shedding and risk factors for shedding in a grass-fed beef herd. During a 9-month flow, 23 beef cows were sampled twice a week (58 sampling points) and E. coli O157 was enumerated from faecal samples. Isolates were screened past PCR for presence of rfbDue east, stx 1 and stx 2 . The prevalence per sampling day ranged from 0% to 57%. This study demonstrates that many members of the herd were concurrently shedding E. coli O157. Occurrence of rainfall (P < 0·01), feeding silage (P < 0·01) and lactating (P < 0·01) were found to be predictors of shedding. Moving cattle to a new paddock had a negative result on shedding. This approach, based on short-interval sampling, confirms the known variability of shedding inside a herd and highlights that loftier shedding events are rare.
INTRODUCTION
Infection with Escherichia coli O157 in humans is uncommon simply potentially fatal [Reference Pennington1]. The organism is a common commensal in the gastrointestinal tract of cattle [Reference Nataro and Kaperii]. A great deal of enquiry on E. coli O157 in cattle has been completed in the last 30 years [Reference Arthurthree–Reference Meng, Doyle and Buchanan5], although it is uncertain whether this has resulted in lower rates of human being illness. No decrease in reported clinical cases with Due east. coli O157 has been noted in Scotland over the terminal x years [Reference Pearce6] and foodborne outbreaks yet often occur in many countries. Whether humans become infected through foodborne or environmental pathways, cattle faeces are considered the chief source of infection [Reference Chapmanseven]. Therefore agreement the dynamics of shedding of this organism in cattle and the factors that influence shedding are priorities for improving the prevention of homo infection.
East. coli O157 is invariably detected in cattle populations that are subjected to sufficient sampling and testing. However, the prevalence of East. coli O157 within herds is variable, with estimates ranging from 0·7% to 28% in the Usa [Reference Elder8, Reference LeJeuneix], 3·4–21·8% in the Britain [Reference Pearce6] and i·9–13% in Commonwealth of australia [Reference Cobbold and Desmarchelierten, Reference Feganxi]. While some studies have described peaks in prevalence during belatedly leap, summer and early autumn [Reference Barkocy-Gallagher12, Reference Heuvelink13], others, all carried out in Peachy Great britain, report a lack of convincing seasonal pattern [Reference Ellis-Iversen14, Reference Smith, Paiba and Ellis-Iversen15]. Thus, whether or non shedding is a seasonal miracle is uncertain. In addition to variation in location, which may drive differences, most studies have not sampled for a sufficient length of time to allow them to conclude whether peaks in prevalence are office of an ongoing cyclical pattern or are simply a manifestation of the particular period of observation.
Describing the epidemiology of E. coli O157 in cattle is challenging because of the cost and inconvenience of measuring the concentration of the pathogen in faeces. Intermittent patterns of shedding have been shown in calves [Reference Robinson16, Reference Widiasih17], simply trivial is known virtually the shedding pattern of live adult beef cattle. This is specially so for pasture-based production systems which are not well represented in the literature. While a few longitudinal studies have been performed in developed beef cattle [Reference Smith, Paiba and Ellis-Iversen15, Reference Arthurxviii–Reference LeJeune22], data describing the shedding patterns of private animals that have been repeatedly sampled at short time intervals (<7 days) are missing. Nearly longitudinal studies used fortnightly or monthly sampling intervals during a 3- to 12-calendar month menstruum [Reference Arthur18, Reference Cobbold19, Reference Lahti21]. Some studies have assessed the concentration of E. coli O157 in faeces and several others featured repeated observations on the same animals [Reference Smith, Paiba and Ellis-Iversen15, Reference Arthur18, Reference Cobbold19, Reference Lahti21]. A study that combines these aspects of repeated sampling and enumeration just with the repetition occurring at curt fourth dimension intervals volition provide new and potentially useful information well-nigh shedding of E. coli O157 by cattle.
In this written report 23 cattle were intensively studied over 9 months while managed in a temperate grazing system. They were repeatedly assessed at 3- to seven-24-hour interval intervals for the presence and concentration of E. coli O157 in faeces. The overall objective was to draw in particular the temporal dynamics of Eastward. coli O157 shedding in private cattle managed on pasture and to identify possible gamble factors for shedding of this pathogen.
METHODS
Beef herd characteristics
A longitudinal study was performed from 4 Oct 2012 to 20 June 2013. The study subjects comprised 23 primiparous and multiparous Hereford cattle pastured at Charles Sturt Academy's beef farm, located at Wagga Wagga, NSW, Commonwealth of australia (latitude 35° Southward, longitude 147° East). Rainfall is distributed relatively evenly at 48 mm/calendar month. Average daily minimum and average daily maximum temperatures for summer are 16·ii °C and 31·2 °C and for winter two·7 °C and 12·5 °C, respectively. From October to 28 March the cattle were sampled twice a week, which was reduced to once a calendar week during the months of Apr, May, and June because of a reduction in the number of cattle shedding (⩽1 beast per 24-hour interval) on 3 sampling occasions in the terminal weeks of March.
During the report period the cattle were grazed on different paddocks, varying between 3·five ha and vii ha in area, according to the availability of grass, herd nutritional requirements and environmental direction considerations. The cattle were fed cereal and ryegrass silage every Monday, Wednesday and Fri when no fresh grass was bachelor, starting from thirty Dec 2012, and continuing until the last sampling day (Fig. 2). The herd was used biweekly in March and bimonthly in April and May by veterinary students of the university for teaching purposes. Twenty-1 cows and heifers calved in July 2012, including 2 pairs of twins, resulting in 23 calves at foot and nursing until weaning on 24 January 2013. Thus the calves were only present for function of the study menses.
Ethical standards
The use of animals in this report was approved by Charles Sturt University Animal Care and Ethics Commission Protocol number 12/060.
Sample collection
Animals
A minimum of 10 yard of faeces were nerveless from each cow past rectal palpation or during defecation while the cows were restrained in a crush in the cattle yards. For each cow a new disposable sleeve glove was used and each faecal sample was individually placed into a Whirl-Pak handbag (Nasco, Australia). Transportation occurred on ice inside 2 h of the first sample existence taken and samples were processed straight upon arrival at the laboratory.
Rectal temperature, faecal score and hide contamination were recorded for each cow at every sampling. Rectal temperature was measured after the faecal catch was taken. Faecal score was categorized from i to four (runny/loose/soft/dry) [23] and hide contamination from one to 5 (make clean and dry/slightly dirty/dirty/very muddy/extremely muddied and wet) [24]. Weight (kg) and body status score (score 1–five) [25] were recorded every 14 days. The first author undertook all sampling and data recording.
Environment
Rainfall (mm in 24 h prior to sampling), ambience temperature (mean °C in 24 h prior to sampling), day length (hours between sunrise and dusk on the day of sampling), humidity (% relative humidity at 09:00 hours) and hours of vivid sunshine (bright sunshine in the 24 h to midnight prior to sampling) were obtained for each day throughout the report from the Bureau of Meteorology (BOM). Rainfall data was obtained from the BOM weather station located <2 km from the herd location, while all other data was retrieved from the BOM weather station located <fifteen km away. The quantity and quality of the pastures were recorded every 14 days. Quantity was measured by assessing the average height, using methods described by Morris & Kenyon [Reference Morris and Kenyon26]. Quality was determined past the stage of pasture growth, e.g. short actively growing vegetative pasture (80%), tall actively growing vegetative pasture (75–lxxx%), early on flowering (70–75%) or late flowering (65–lxx%). Contamination of drinking water with Eastward. coli O157 was analysed congruent with the pasture estimates. Water samples, from all drinking-h2o troughs in the paddock used at the time of sampling, were collected into 120 ml sterile containers (Sarstedt, Australia), directly transported to the laboratory and analysed together with the faecal samples.
Management
Management variables that changed during the period of report were recorded. This included feeding of supplements, artificial insemination, joining with a balderdash, weaning of calves, spread of fertilizer on the pastures, relocation to other paddocks, medical treatments and vaccinations. The dates of veterinarian teaching classes (teaching of moo-cow handling, hook trimming and casting) were recorded.
Sample processing
Faecal samples
X grams of faeces from each sample were homogenized in ninety ml of sterile buffered peptone water (BPW) (Oxoid, Australia). For each homogenized broth 100 μl was plated direct on sorbitol MacConkey+5-bromo-4-chloro-3-indolyl-b-d-glucuronide agar (Oxoid) containing cefixime (0.05 mg/l) and potassium tellurite (ii.5 mg/50) (Oxoid) (CT-SMAC+BCIG) and incubated for 18–24 h at 37 °C for direct civilization [Reference Okrend, Rose and Lattuada27]. Each homogenized broth was incubated at 37 °C for 6 h [Reference Dunn, Keen and Thompson28]. The enriched broth was stored at 4 °C until immunomagnetic separation (IMS) was performed the adjacent twenty-four hours.
Confirmation and storage
After incubation of the CT-SMAC+BCIG plates, all plates were screened for non-sorbitol fermenting and β-glucuronidase-negative colonies (harbinger-coloured colonies). Upwards to ten doubtable colonies were tested using an E. coli O157 latex test (Oxoid) to confirm the colonies as O157 or otherwise [Reference Cernicchiaro29]. When positive colonies on direct culture plates were establish, the number of colony-forming units (c.f.u.) was counted and the c.f.u./g of faeces estimated subsequently bookkeeping for the dilution factor. Pure isolates were stored at −lxxx °C in BPW with 20% glycerol for later analysis past polymerase concatenation reaction (PCR).
Water samples
The water samples were filtered with cellulose nitrate membrane filters with pore size 0.2 μm (Bio-Rad, Commonwealth of australia). The entire filters were added to ninety ml sterile BPW, directly plated and enriched as described for the faecal samples.
IMS
For all faecal and water samples that were negative after direct plating, manual IMS was performed. Two ml of each enriched sample was centrifuged for 2 min at 52 yard prior to IMS. A 24-well plate was set up with 20 μl of anti Eastward. coli O157 immunomagnetic beads (Invitrogen, Australia). I one thousand μ50 of the supernatant of each enriched centrifuged sample was transferred to a well [Reference Fegan11] and thoroughly mixed with the beads on a gyratory mixer (Ratek, Australia) for i h. The plate was so placed on a magnet for 2 min to immobilize the chaplet afterwards which the enrichment solution was removed while the plate remained on the magnet. Later removing the plate from the magnet, the beads were washed in g μl of phosphate buffered saline (PBS) (MP Biomedicals, Australia) with 0·05% Tween 20 (Sigma, Commonwealth of australia) (PBST). The solution was mixed for 2 min and placed back on the magnet for two min to immobilize the chaplet. Again the wash solution was removed and the launder step repeated. After the second wash the chaplet were removed from the magnet and re-suspended in 100 μfifty PBST. The resulting solution was carve up and inoculated onto CT-SMAC + BCIG plates and incubated for 18–24 h at 37 °C [Reference Feganxi, Reference Dunn, Keen and Thompson28].
PCR
All isolates were screened past PCR for the presence of rfbE, which encodes the E. coli O157 serotype [Reference Wang, Clifford and Frankthirty], and for the virulence genes stx 1 and stx 2 [Reference Paton and Paton31] (Table ane). Colony PCR was performed on samples, using OneTaq Dna polymerase (New England Biolabs, USA). A multiplex PCR analysis was gear up for detection of the in a higher place-mentioned genes using a multiplex PCR plus kit (Qiagen, Australia). Thermocycling was performed in a Bio-Rad S1000 Thermal Cycler (Bio-Rad) post-obit the cycling weather condition from Paton & Paton [Reference Paton and Paton31]. PCR products were then visualized on a 2% agarose gel containing SYBR Condom DNA gel stain (Invitrogen).
Table one. Primers used for detection of E. coli O157 genes
Descriptive analysis
Graphical analysis was performed to appraise relationships between the probability of cattle shedding Eastward. coli O157 and a range of animal and environmental variables. Data describing each individual animate being'due south shedding status at each sampling point was summarized for the herd to give the observed proportion of cattle shedding East. coli O157. These proportions were then fitted to a cubic spline model to provide a smoothed curve (and accompanying 95% confidence interval) defining the probability of shedding through time and providing a footing for visually assessing the relationship between diverse factors (animal, environment, management) and the occurrence of shedding (Figs 3–5). The graph displaying probability of shedding through fourth dimension was annotated with the timing of central direction events such every bit motion to new paddocks, weaning, vaccination and handling (Fig. 2).
Statistical assay
Herd level
Trend in the proportion of animals testing positive to E. coli O157 on each sampling 24-hour interval was estimated by a cubic spline model. Visual assessment of this curve, overlaid with animal, environment and direction variables, was performed to explore any putative associations in the get-go instance. Visual analysis of this curve revealed that 1 pocket-size and three substantial discrete peaks in shedding occurred over the period nether study. The three events with estimated peak proportion of herd shedding at >20% were described as a 'herd-shedding event' and defined equally the catamenia where the estimated probability of shedding exceeded 0·ane. Reassessing the data in light of herd-shedding events allowed all sampling points (days on which sampling occurred) to be classified as occurring within six discrete events comprised of three shedding events alternate with three non-shedding events.
Generalized linear mixed models were used to assess whether variation in each animal, environmental and management variable at each sampling betoken could exist associated with a period of time identified previously equally a 'herd-shedding event'. For beast-level variables [hide contamination score, faecal consistency score, trunk weight, body condition score, rectal temperature, pregnancy status (Y = 1/Due north = 0) and lactating (Y = 1/N = 0)], the animal-level variable was specified as the outcome, while herd-shedding consequence (Y/N) was included as a fixed consequence. The effect number (1–half dozen) and moo-cow identifier (1–23) inside each event were estimated as random furnishings reflecting the nested sampling construction of observations within cows within events. For management and environmental variables taken at the herd level [movement betwixt paddocks (Y = i/Northward = 0), feeding of silage (Y = i/N = 0), handled by students (Y = 1/Northward = 0), calves at foot (Y = one/North = 0), quality and quantity of the pasture, rainfall, humidity, temperature, hours of bright sunshine and day length] herd-shedding event was estimated as a fixed effect and event number as a random outcome. These model structures were adopted in order to account for the inclusion of herd-specific random effects and to permit for more biologically meaningful estimation of coefficients. Goose egg hypothesis significance tests for the stock-still effects were conducted by adding of the assay of variance table for each model. Least squares estimates and standard errors of boilerplate responses nether each shedding upshot class were calculated from each model.
Individual animal level
Logistic regression analysis was used to explore the effect of potential beast-, environmental- and management-level take a chance factors on individual animal shedding. Start, univariable analyses were performed. Variables with P < 0·05 were jointly analysed using a forrad selection process in multiple regressions. Every bit repeated observations of individual animals may not be independent, a random effect of cow identifier was included.
Based on the estimated counts from faecal samples, animals were categorized as negative, low-level (<103 c.f.u./g) or high-level (⩾10iii c.f.u./g) shedders of E. coli O157. These data were analysed by using a generalized linear model with presence of a high shedding every bit the binomial outcome, low shedding as a fixed effect and cow identifier as a random effect.
RESULTS
Descriptive and statistical assay
During the 9-month study period, a full of 1323 faecal samples were collected from 23 Hereford cows over 58 sampling days. Due east. coli O157 was isolated from 168 (12·seven%) samples with 21 (1·vi%) positive on straight enumeration plates and 147 (11·1%) positive only through IMS. The amount of E. coli O157 shed in faeces ranged from <100 to xx 700 c.f.u./g faeces. All cows within the herd shed Eastward. coli O157 at least one time during this written report (Fig. 1). A large variation in the frequency of shedding among animals was identified. East. coli O157 was shed intermittently by all animals and the number of occasions on which an individual cow was identified every bit shedding Eastward. coli O157 ranged betwixt 2 and xv (out of 58 sampling points in total). The maximum number of consecutive sampling points that an animal was found to be positive (by either direct culture or IMS) was seven (three·5 weeks). The prevalence per sampling 24-hour interval ranged from 0% to 56·5% (Fig. 2). Out of 168 isolates screened by PCR, all were positive for the O157 rfb factor, 166 (98·8%) were positive for stx i and stx two , and two (1·2%) were positive for stx 1 only.
Fig. one. Plot of the individual shedding patterns. Samples in which E. coli O157 was detected just by immunomagnetic separation (grayness dots) are represented every bit fifty c.f.u./g for graphical purposes. Sampling points for which enumeration was possible are indicated past blackness dots and samples in which no E. coli O157 was detected are represented by white dots.
Fig. ii. Temporal change in probability of animals shedding E. coli O157 (and 95% conviction intervals), the timing of management variables and the timing of movement of animals betwixt paddocks.
E. coli O157 was isolated from i of 62 water samples that were collected during the report. The isolate identified within h2o tested positive for the O157 rfb, stx i and stx ii genes by PCR. This positive water sample was establish on 11 November 2012 when none of the cows were positive for Eastward. coli O157.
Temporal data on shedding events and management events are shown in Figure ii. This figure shows three distinct peaks in probability of shedding. There was a major acme in mid-summer (mid-Dec to late January), a minor top in fall (late February to mid-March) and a 2d major peak in early winter (late May to belatedly June). None of the management variables appeared to exist associated with whatever of the peaks in shedding.
Time-based change in the probability of shedding is likewise shown in Effigy iii accompanied by the temporal patterns of rainfall and humidity. Although all of the peaks in shedding are immediately preceded past rainfall this can likewise exist said for many periods where shedding was not detected. Thus, descriptive bear witness lone does non support a human relationship between variation in rainfall and the presence or absence of a 'herd-shedding event'. Even so, the generalized linear mixed model showed that rainfall is a risk factor (P = 0·03): the hateful of rainfall in the 24 h prior to sampling during herd-shedding events (iii·iv mm) differed significantly from that for non-shedding events (0·6 mm) (Tabular array 2). Visually, there was no apparent association between humidity and shedding, which was confirmed by statistical analysis.
Fig. 3. Temporal change in probability of animals shedding E. coli O157, rainfall (mm) in the 24 h prior to sampling, and relative humidity (%) at 09:00 hours on the twenty-four hours of sampling.
Tabular array 2. Variables relating animal, management and environmental factors with the mean and standard fault (due south.e.) for shedding vs. non-shedding events and the P value
Temporal change in the probability of shedding in Figure 4 is accompanied by the temporal patterns of temperature, hours of bright sunshine and day length. All three variables showed a like temporal curve. Based on this descriptive bear witness the variation in the environmental variables could non be explained by the presence or absenteeism of a 'herd-shedding event'. This was supported by statistical analysis in which none of these variables was a significant risk cistron (Table ii).
Fig. iv. Temporal change in probability of animals shedding E. coli O157, hateful ecology temperature (°C) in the 24 h to 09:00 hours, bright sunshine (hours) in the 24 h to midnight prior to sampling, and day length on the day of sampling.
Fourth dimension-based change in the probability of shedding is shown in Figure five together with the temporal patterns of the individual creature variables: body weight, faecal consistency and hide contamination. Visually, at that place was no apparent association between any of the three variables and the probability of shedding East. coli O157. Statistical analysis of the animal variables in a generalized linear mixed model showed that neither the variation in live weight nor in faecal consistency was associated with the presence or absence of a 'herd-shedding event' (Table 2). The boilerplate level of hide contamination score during shedding events (one·4) did differ from non-shedding events (1·7) (P = 0·04).
Fig. 5. Temporal change in probability of animals shedding Due east. coli O157, mean torso weight, mean faecal score, and hateful hide contagion score, accompanied by the information for each private animal.
Univariable analysis to explore potential take chances factors associated with individual animal shedding resulted in eight variables that were jointly analysed using multiple regression. The final logistic model is shown in Table 3. Iv variables remained in the final model. In gild of statistical significance the risk factors were: feeding of silage (P < 0·01), lactating (P < 0·01), rainfall in the calendar week prior to sampling (P < 0·01) and movement between paddocks (P = 0·04).
Table 3. Final model from multiple regression on individual animal level
In full, E. coli O157 was isolated from 168 samples on 38 of the 58 sampling days. Analysis showed that the presence of a high-level shedder was significantly (P = 0·04) associated with a college proportion of low-shedding animals on the aforementioned day (odds ratio 1·3, standard error 0·14).
DISCUSSION
The current study focused on the temporal dynamics of E. coli O157 shedding in adult grass-fed beef cattle. Although marked variation of shedding between and within individuals occurred, an obvious pattern in shedding over fourth dimension was identified. The outstanding feature of the variation in the probability of shedding was the iii distinctive peaks indicating the herd experienced discrete shedding events where many animals were concurrently shedding, referred to every bit synchronization of shedding. Previous studies have reported peaks of shedding in summer and early on autumn, which is in agreement with the first ii peaks in shedding in the current study; however, the third peak of shedding occurred in wintertime. Virtually longitudinal studies performed previously sampled merely once a month [Reference Arthur18, Reference Kondo20], which merely provides rough information on temporal shedding patterns within a herd. Our findings suggest that if more frequent sampling had been used in before studies, e.g. twice a week, a dissimilar seasonal blueprint might have been detected. Moreover, with the use of individual brute data it is evident that the synchronization of shedding in cows is accompanied by a marked elevation in the concentration of the pathogen in faeces. This indicates that shedding at high levels does not occur independently of other animals shedding low levels of the same pathogen inside the herd. Previous studies accept besides observed an association between the presence of a high-level shedder in the herd and a loftier proportion of low shedders [Reference Chase-Topping32, Reference Low33]. Whether high-level shedding is the cause of low-level Eastward. coli O157 shedding, or vice versa, is non known.
Intermittent shedding patterns have besides been reported previously in calves [Reference Robinson16, Reference Widiasih17]. However, in this study very few cattle shed at high levels and the elapsing was very short. Robinson and colleagues [Reference Robinson16] observed animals shedding at high levels for extended periods merely this study looked at a grouping of calves purposely selected because they were known to be shedding. The current study is unique because it studies shedding and non-shedding animals in item over time in a natural setting. There are two other notable explanations for the lower frequency in high-level shedding and the lower concentrations found in this report compared to other studies. One is an effect due to the historic period of the animals, since younger animals (aged 2–6 months) are associated with a higher prevalence of Due east. coli O157 than adults [Reference Paiba34]. Second, the majority of previous studies involved feedlot cattle, where the high density of housing is likely to increase fauna-to-creature transmission [Reference Jeon35], compared to animals at pasture. Next to this, E. coli O157 in cattle faeces is not evenly distributed and its density can vary betwixt sites in a faecal pat [Reference Pearce36], which might influence the concentration of the organism.
Previously, merely Williams et al. [Reference Williams37] identified an association between increasing rainfall and increased shedding of E. coli O157 in calves in Sydney, Australia (a higher rainfall environment compared to the present written report). Rainfall events could conceivably promote shedding by making conditions beneficial for multiplication of the bacteria in the environment, changing pasture conditions to increment exposure of cattle to Eastward. coli O157, or by somehow affecting forage composition and diet leading to alterations in the gut favouring proliferation of E. coli O157. Previous research in other countries has not found a relationship between rainfall and shedding. Still, these studies did not rely on short-interval sampling and were conducted in unlike climates and product systems.
The negative association between hide score and probability of shedding in this written report was unexpected and does not appear to be biologically plausible. It is very probable that this clan is a spurious finding arising from either hazard or measurement fault.
Feeding silage was demonstrated to exist associated with E. coli O157 shedding at the private fauna level. Many studies on diet and E. coli O157 shedding have been performed, often presenting contradictory results. Whether the significant association with silage establish in the present study is due to a direct effect of silage on the microbiome or due to changes in the environment (e.1000. drought) which were the reason for feeding silage, is not known.
Lactating was also positively associated with shedding of the pathogen. This consequence has not been reported in literature earlier. It is possible that stress or hormonal changes influence Due east. coli O157 shedding cattle.
This report found that when animals were moved to another paddock in the week prior to sampling they were less likely to shed E. coli O157. This might have resulted from the absence of fresh faecal pats in a new paddock and reduced Eastward. coli O157 contamination.
The advantage of using a smoothed curve (rather than raw data on animal shedding) is that information technology takes account of dissonance due to sampling variation arising from the small number of individuals, and, at each fourth dimension indicate it uses data from proximal time points to back up the interpretation of probability of shedding [Reference Verbyla38]. In this style, it was possible to avert potential false-positive significant correlations due to chance associations that frequently occur when comparing two time series of events [Reference Aldrich39]. It must be noted that when analysis of variance was practical on score variables, such equally hide contamination score, that these scores should not be seen as 'ranks', simply as proxy measurements for an underlying truthful scale of dirtiness, and averages and standard errors do supply useful information.
Because this study was based on a single herd, care must exist taken when extrapolating estimation to the broader population of cattle. Yet, the major findings are helpful because, for example, they suggest that shedding patterns vary substantially betwixt production systems (e.k. pasture beefiness, dairy, feedlot beef), and that animals inside a herd tin can be synchronized in their shedding (and non-shedding) which may take applied implications for the chance of human exposure to E. coli O157. Moreover, the extent of individual animal variability revealed in this work and in previous studies [Reference Robinson16, Reference Matthewsxl] casts doubt on findings of risk factor and intervention studies where outcomes are based on single assessment of dichotomous shedding status. Findings hither have besides highlighted the lack of precision in the present understanding of shedding patterns in beef cattle and indicate the need to now focus on describing the extent of daily variation in shedding within individual animals.
ACKNOWLEDGEMENTS
The authors admit farm manager Jim Mellor for his cooperation throughout written report, and the assistance of James Stephens and Tony Hobbs (Charles Sturt Academy) in sampling of the animals. We are grateful to Franziska Pilger and Saliya Gurusinghe for technical help and Robert Barlow for supplying E. coli O157 and Stx-positive isolates.
This work was supported by Meat and Livestock Australia Ltd (grant number A.MFS.0247).
DECLARATION OF Involvement
None.
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Source: https://www.cambridge.org/core/journals/epidemiology-and-infection/article/synchronization-of-e-coli-o157-shedding-in-a-grassfed-beef-herd-a-longitudinal-study/1E4A70F2A6732074C7E28944F57228E9
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