Disease outbreak response: why epidemiology plays a central role.

The need to control transboundary animal disease outbreaks is widely recognised, as is the need for evidence-based decisions regarding which control measures to implement. Key data and information are required to inform this evidence base. To ensure effective communication of the evidence, a rapid process of collation, interpretation and translation is required. This paper describes how epidemiology can provide the framework through which relevant specialists can be engaged to this end, and highlights the central role of epidemiologists, with their unique combination of skills, in this process. It provides an example of an evidence team led by epidemiologists, namely the United Kingdom National Emergency Epidemiology Group, which was established to address this need. It then goes on to consider the different strands of epidemiology, the need for a wide multidisciplinary approach, and the importance of training and preparedness activities to facilitate rapid response.

La nécessité de contrôler les foyers de maladies animales transfrontalières est largement reconnue, tout comme celle de fonder la prise de décisions sur des données probantes pour la mise en oeuvre des mesures de contrôle. Afin de documenter cette base d'éléments probants, il est nécessaire d'obtenir un certain nombre de données et d'informations clés. Un processus rapide de collecte, d'interprétation et de traduction des données doit être mis en place afin de communiquer ces éléments probants de manière efficace. Les auteurs décrivent le cadre que l'épidémiologie peut apporter aux chercheurs pour s'engager sur cette voie ; ils soulignent le rôle central des épidémiologistes dans ce processus, grâce au faisceau unique de compétences dont ils disposent. Ils donnent l'exemple d'une équipe animée par des épidémiologistes travaillant sur les données probantes qui a été mise en place spécifiquement pour répondre à ce besoin : le Groupe national d'épidémiologie d'urgence du Royaume-Uni (National Emergency Epidemiology Group). Les auteurs concluent en menant une réflexion sur les différentes branches de l'épidémiologie, le besoin d'une approche pluridisciplinaire large et l'importance des activités de formation et de préparation pour une réponse rapide.

Hay coincidencia general en que hoy resulta imperativo combatir los brotes transfronterizos de enfermedades animales, al igual que es necesario contar con un sólido fundamento de datos factuales para tomar decisiones sobre las medidas de lucha que conviene implantar. Para generar esta base empírica hay que disponer de un conjunto esencial de datos e información y para comunicarla eficazmente se requiere un rápido proceso de recogida, interpretación y traducción. Los autores explican cómo puede la epidemiología constituir el marco de referencia desde el que trabajen para tal fin los distintos especialistas y destacan la función central que cumplen en este proceso los epidemiólogos, gracias a la singular combinación de competencias que presentan. A modo de ejemplo, describen un equipo dedicado al estudio de datos factuales que fue establecido, bajo la dirección de epidemiólogos, justamente para responder a esta necesidad: el Grupo nacional de respuesta epidemiológica a situaciones de emergencia del Reino Unido (National Emergency Epidemiology Group). Por último, tras detenerse en las distintas vertientes de la epidemiología, inciden en la necesidad de abordar la cuestión desde un planteamiento ampliamente pluridisciplinar y en la importancia que revisten las actividades de formación y preparación para facilitar una respuesta rápida.

Experimental simulations of volcanic ash resuspension by wind under the effects of atmospheric humidity.

Ash deposited during volcanic eruptions can be resuspended by wind and become hazardous for health and infrastructure hours to decades after an eruption. Accurate resuspension forecasting requires accurate modelling of the threshold friction velocity of the volcanic particles (Uth*), which is the key parameter controlling volcanic ash detachment by wind. Using an environmental wind tunnel facility this study provides much needed experimental data on volcanic particle resuspension, with the first systematic parameterization of Uth* for ash from the regions Campi Flegrei in Italy and also Eyjafjallajökull in Iceland. In this study atmospheric relative humidity (and related ash moisture content) was systematically varied, from <10% to >90%, which in the case of the Eyjafjallajökull fine ash (<63 µm) produced a twofold increase in Uth*. Using the Campi Flegrei fine ash (<63 µm) an increase in Uth* of only around a factor of 1.5 was observed. Reasonable agreement with force balance resuspension models was seen, which implied an increase in interparticle adhesion force of up to a factor of six due to high humidity. Our results imply that, contrary to dry conditions, one single modelling scheme may not satisfy the resuspension of volcanic ash from different eruptions under wet conditions.

Prevalence and correlates of recent injecting drug use among gay and bisexual men in Australia: Results from the FLUX study.

BACKGROUND: While illicit drug use is prevalent among gay and bisexual men (GBM) in Australia, little is known about the factors associated with injecting drug use among GBM. METHODS: The Following Lives Undergoing Change (FLUX) study is a national, online prospective observational cohort investigating drug use among Australian GBM. Eligible participants were men living in Australia who were aged 16.5 years or older, identified as gay or bisexual or had sex with at least one man in the last year. We examined baseline data for associations between socio-demographic and behavioural characteristics and recent (last six months) injecting using log-binomial regression. RESULTS: Of 1995 eligible respondents, 206 (10.3%) reported ever injecting drugs and 93 (4.7%) had injected recently, most commonly crystal (91.4%) and speed (9.7%). Among recent injectors, only 16 (17.2%) reported injecting at least weekly; eight (8.6%) reported recent receptive syringe sharing. Self-reported HIV and HCV prevalence was higher among recent injectors than among other participants (HIV: 46.2% vs 5.0%, p < .001; HCV: 16.1% vs. 1.2%, p < .001). Recent injecting was associated with lifetime use of more drug classes (adjusted prevalence ratio (APR) = 1.31, 95% Confidence Interval (95%CI) 1.21-1.41), longer time since initiating party drug use (APR = 1.02, 95%CI 1.01-1.04), greater numbers of sex partners (2-10 sex partners: APR = 3.44, 95%CI 1.45-8.20; >10 sex partners: APR = 3.21, 95%CI 1.30-7.92), group sex (APR = 1.42, 95%CI 1.05-1.91) and condomless anal intercourse with casual partners (APR = 1.81, 95%CI 1.34-2.43) in the last six months. CONCLUSIONS: Observed associations between injecting and sexual risk reflect a strong relationship between these practices among GBM. The intersectionality between injecting drug use and sex partying indicates a need to integrate harm reduction interventions for GBM who inject drugs into sexual health services and targeted sexual health interventions into Needle and Syringe Programs.

Danish VISA-A questionnaire with validation and reliability testing for Danish-speaking Achilles tendinopathy patients.

The VISA-A questionnaire has proven to be a valid and reliable tool for assessing severity of Achilles tendinopathy (AT). The aim was to translate and cross-culturally adapt the VISA-A questionnaire for a Danish-speaking AT population, and subsequently perform validity and reliability tests. Translation and following cross-cultural adaptation was performed as translation, synthesis, reverse translation, expert review, and pretesting. The final Danish version (VISA-A-DK) was tested for reliability on healthy controls (n = 75) and patients (n = 36). Tests for internal consistency, validity, and structure were performed on 71 patients. VISA-A-DK showed good reliability for patients (r = 0.80 ICC = 0.79) and healthy individuals (r = 0.98 ICC = 0.97). Internal consistency was 0.73 (Cronbach's alpha). The mean VISA-A-DK score in AT patients was 51 [47-55]. This was significantly lower than healthy controls with a score of 93 (90-95). Criterion validity was considered good when comparing the scores of the Danish version with the original version in both healthy individuals and patients. VISA-A-DK is a valid and reliable instrument and has shown compatible to the original version in assessment of AT patients. VISA-A-DK is a useful tool in the assessment of AT, both in research and in a clinical setting.

Adolescent chronic pain and association to perinatal factors: linkage of Birth Registry data with the Young-HUNT Study.

BACKGROUND: The aim of this study was to examine the associations of birthweight, gestation and 5-min Apgar score with self-reported chronic nonspecific pain in a large, unselected adolescent population. METHODS: The third population-based Nord-Trøndelag Health Study (HUNT) included 8200 adolescents aged 13-19 years, constituting 78.2% of adolescents in Nord-Trøndelag County. In the target age group, 13-18 years, data on pain frequency from 10 localizations were available from 7373 adolescents. Chronic nonspecific pain was defined as pain at least once a week during the last 3 months, not related to any known disease or injury. Chronic multisite pain was defined as chronic pain in at least three localizations, and chronic daily pain was defined as chronic pain almost every day. Perinatal data were retrieved from the Medical Birth Registry of Norway, and data were available for 7120 of the 7373 adolescents. Covariates included adolescent and maternal general health measures from the HUNT study. RESULTS: We found no consistent association between preterm birth and chronic pain and no clear association between birthweight and chronic pain complaints in adolescence. Post-term birth in boys and a low 5-min Apgar score in both sexes tended to increase the reporting of chronic pain in adolescence. CONCLUSIONS: Perinatal factors, and especially preterm birth and low birthweight, did not seem to have a major impact on pain complaints in adolescence.

Uptake of hepatitis C treatment among people who inject drugs attending Needle and Syringe Programs in Australia, 1999-2011.

The majority of new and existing cases of hepatitis C virus (HCV) infection occur among people who inject drugs (PWID). Despite safe and efficacious HCV antiviral therapy, uptake remains low in this population. This study examined trends in HCV treatment uptake among a large national sample of PWID attending Australian Needle and Syringe Programs between 1999 and 2011. Annual cross-sectional sero-surveys conducted among PWID since 1995 involve completion of a self-administered questionnaire and provision of a dried blood spot for HCV antibody testing. Multivariate logistic regression identified variables independently associated with HCV treatment uptake among 9478 participants with both self-reported and serologically confirmed prior HCV infection. Between 1999 and 2011, the proportion currently receiving treatment increased from 1.1% to 2.1% (P < 0.001), while the proportion having ever received treatment increased from 3.4% to 8.6% (P < 0.001). Men were significantly more likely than women to have undertaken HCV treatment (P = 0.002). Among men, independent predictors of HCV treatment uptake were homosexual identity and older age; among women, independent predictors included homosexual identity and an incarceration history. Despite increases in HCV treatment among Australian PWID between 1999 and 2011, uptake remains low. Strategies are required to increase the proportion of PWID assessed and treated for HCV infection to address the increasing burden of disease. Specific approaches that target women may also be warranted. Continued surveillance of HCV treatment uptake among PWID will be important to monitor the roll-out of simple, safe and more effective HCV treatments expected to be available in the future.

C-reactive protein triggers calcium signalling in human neutrophilic granulocytes via FcγRIIa in an allele-specific way.

C-reactive protein (CRP) binds to Fcγ-receptors, FcγRIIa (CD32) with high affinity and to FcγRIa (CD64) with low affinity. The binding to CD32 has been shown to be allele specific, that is, it binds to R/R131 but not to H/H131. Little is known about the cooperation of CRP and neutrophilic granulocytes (PMNs) in inflammatory reactions. The purpose of the present study was to examine CRP signalling in human PMNs, and whether this signalling is also allele specific. Cytosolic calcium of PMN was measured in a single-cell digital imaging system. Receptor expression and polymorphism were studied by real-time RT-PCR, flow cytometry and standard PCR. C-reactive protein induced cytosolic calcium signals in PMNs from homozygote R/R131 donors, but not in PMNs from heterozygote R/H131 donors. However, after the heterozygote PMNs had been incubated with IFN-γ (100 U/ml) for 2 h, both the proportion of cells responding and the size of the CRP-induced calcium signals increased. IFN-γ increased mRNA expression of CD64 about fivefold and surface protein expression of CD64 about fourfold. The calcium signal elicited by CRP was augmented by PMN adhesion to fibronectin, but almost totally abrogated by sphingosine kinase inhibitors. The signals were partly dependent on calcium influx. In conclusion, calcium signalling instigated by CRP in human PMN is FcγRIIa allele specific, as R/R131 responded to CRP, whereas R/H131 did not. However, increased expression of FcγRIa (CD64), stimulated by IFN-γ, can augment calcium signalling by CRP in low-responders. This suggests that the state of the PMNs, as well as the genetic origin, affect sensitivity for CRP.

Characteristics and comparative performance of direct culture, direct PCR and enumeration methods for detection and quantification of Campylobacter spp. in broiler caeca.

Detection and enumeration of Campylobacter spp. in broiler chicken flocks are key components of research and surveillance studies aimed at reducing Campylobacter infections in people. Direct culture of caecal contents onto selective agar is the typical method used to confirm flock colonisation. Modified charcoal cefoperazone deoxycholate agar (mCCDA) is commonly used for this method, although alternative selective media have been used. Additionally, PCR methods to detect Campylobacter DNA from caecal contents may provide a rapid alternative. However comparative performance data for these methods is limited and therefore required to ensure optimal detection methods for this sample type. In this study, 306 broiler caeca were tested for Campylobacter using direct culture on mCCDA, Skirrows and Preston agars and two real-time PCR methods, one specific for mapA/ceuE regions and another for the flaA gene region. Additionally, the suitability of spread plating and spiral plating methods for enumeration of Campylobacter and the impact of sample storage were assessed. This study confirmed modified CCDA as an optimal media for detection of Campylobacter in broiler caeca. It was significantly more sensitive than Skirrows or Preston agars. This study also demonstrated that the mapA/ceuE PCR had excellent agreement with culture on mCCDA and is a genuine alternative method. Spread plating and spiral plating methods were suitable for enumeration although spiral plating appeared more sensitive for stored samples (72 h). A 1 log reduction in viable Campylobacters was observed in stored samples, therefore storage effects should be considered for quantitative studies with broiler caeca.

Persistent environmental reservoirs on farms as risk factors for Campylobacter in commercial poultry.

Campylobacter is the most common known source of human bacterial enteritis in the developed world and poultry is considered the main source. Broilers often become colonized with Campylobacter during rearing, and then contaminate the farm environment. The objective of this study was to identify Campylobacter-positive environmental reservoirs on farms, as these pose a risk to broiler flocks becoming colonized with Campylobacter. We considered the temporal aspects of exposure and colonization. A longitudinal study monitored six conventional rearing farms over 2 years. The broiler flocks, catchers' equipment, vehicles, shed surrounds, shed entrance, other equipment, farm entrance, other animals, puddles, dead birds, mains water and drinkers were systematically sampled 2-4 times per flock. A multivariable generalized estimating equation model was used to assess associations between contaminated environmental sites and colonized broiler flocks. The associations were adjusted for confounders and other known risk factors. To further assess temporality of contamination, the sequence of contamination of the different environmental sites and the flocks was established. Contaminated shed entrances and anterooms, contaminated drinkers and shedding of Campylobacter by other animals such as cattle, dogs, wildlife and rodents were significantly associated with positive flocks. The reservoir of 'other animals' was also the reservoir most commonly positive before the flock became colonized. The other sites usually became contaminated after the flock was colonized.

Husbandry risk factors associated with subclinical coccidiosis in young cattle.

This paper describes an observational longitudinal study of cattle farms in England and Wales, which aimed to identify management practices associated with the presence of Eimeria spp. infection in young cattle. Thirty cattle farms situated in England and Wales were selected and one group of more than 20 young cattle aged 5-18 months of age was monitored on each farm. Three variables were identified as significantly associated with status in a multivariable model. The odds of finding Eimeria spp. were lower on farms that kept sheep on the same premises as the cattle, as was an increase in the maximum age within the sampled group. The latter probably reflects the development of post-infection immunity within the sampled animals. Good water-trough hygiene protected against Eimeria spp. oocyst excretion, with the odds of detection being higher on farms where it was reported that the water troughs were not cleaned and emptied more than once per month. The value of frequent emptying and cleaning of water troughs in reducing the exposure of calves to Eimeria spp. and thus lowering the impact of coccidiosis, both clinical and subclinical should be communicated to cattle farmers.

Risk factors for transmission of foot-and-mouth disease during an outbreak in southern England in 2007.

During an outbreak of foot-and-mouth disease (FMD) in southern England in 2007, a case-control study was conducted to identify risk factors for infection and to investigate the relative impact of risk factors on transmission between the infected farms. Seven of the eight case farms in the outbreak and 22 control farms participated. Data were collected via questionnaires and subjected to comparative statistical analysis. Case farms were further classified as primary or secondary according to the likely source of infection during the study. On primary case farms, it was plausible that infection had been introduced directly from the original source. On secondary case farms, FMD infection was more likely to have originated from another infected premises. Calving occurred more frequently on case farms than on control farms during the risk period, and the two primary case farms had a larger proportion of youngstock than the other farms. Secondary case farms (n=5) had a higher composite environmental risk score and a lower biosecurity score than control farms.

Influence of season and geography on Campylobacter jejuni and C. coli subtypes in housed broiler flocks reared in Great Britain.

Geographical and seasonal variation in the incidence and prevalence of Campylobacter jejuni and C. coli in housed broiler flocks reared in Great Britain in 2004 to 2006 was investigated in this study. Ceca (30) from 797 flocks, not subject to prior partial depopulation and reared on 211 farms, were examined individually for the presence of Campylobacter spp. The best-fitting climatic factors explained approximately 46% of the prevalence of Campylobacter-colonized flocks at slaughter and consisted of a combination of temperature at slaughter, number of sunshine hours in placement month, and millimeters of rainfall in placement month. Positive flocks were more likely to be slaughtered between June and November than during the rest of the year and to be reared in northern Great Britain than in central or southern Great Britain. C. jejuni was identified in approximately 90% of flocks, and C. coli was present in 10% of flocks. The most common clonal complexes identified in 226 isolates typed by multilocus sequence typing (MLST) were ST-45, ST-21, ST-574, ST-443, and ST-828. Flocks slaughtered at the same time were more likely to have similar complexes, and ST-45 had a seasonal pattern, with the highest prevalence in June, and was also more likely to be present in flocks reared in northern Great Britain.

Q fever outbreak in Cheltenham, United Kingdom, in 2007 and the use of dispersion modelling to investigate the possibility of airborne spread.

We describe the investigation of an outbreak of Q fever in the town of Cheltenham, England. The outbreak was detected in June 2007, and prospective and retrospective case finding identified 30 confirmed or probable human cases. The investigation identified windborne spread of Coxiella burnetii from nearby sheep farms as the most likely source of infection. A telephone survey was conducted to identify risk practices at local farms. Subsequently the atmospheric dispersion model NAME was used to identify whether air from the identified farms with high risk practices had been carried into Cheltenham town centre during the risk period. Three high risk farms were identified and the modelling showed that air from all of these farms was carried over Cheltenham in the estimated risk period. The investigation resulted in an information campaign to farmers and production of improved advice for livestock farmers on reducing the risks of transmitting Q fever to humans.

Longitudinal study to investigate VTEC O157 shedding patterns in young cattle.

Individual animal samples were collected from ten VTEC O157 positive farms approximately monthly over 11months to investigate the shedding of VTEC O157 by youngstock. VTEC O157 was isolated from 7.7% of the 6266 samples and 28.9% of the 1383 animals. On six of the farms VTEC O157 was isolated at multiple visits from several animals, whereas the remaining four farms had one or two positive animals at any one visit, with VTEC isolated from a maximum of four visits. A total of 92 animals were positive more than once (up to four sampling occasions) with a maximum of four negative samples between positive isolations. The results reveal a large variation in individual animal shedding patterns; the proportion of shedding animals on positive farms; and over time within the same farm. The lack of consistent shedding restricts the ability to target potential interventions to specific positive animals/groups or herds.

Long-term high-physiological-dose growth hormone reduces intra-abdominal fat in HIV-infected patients with a neutral effect on glucose metabolism.

OBJECTIVES: The aim of the study was to investigate the effect of long-term high-physiological-dose recombinant human growth hormone (rhGH) therapy on fat distribution and glucose metabolism in HIV-infected patients. METHODS: Forty-six HIV-infected Caucasian men on highly active antiretroviral therapy (HAART), with an age range of 21-60 years and no significant comorbidity, were included in this randomized, placebo-controlled, double-blind, single-centre trial. Twenty-eight subjects were randomized to 0.7 mg/day rhGH, and 18 subjects to placebo, administered as daily subcutaneous injections between 1 and 3 pm for 40 weeks. Endpoints included changes in visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), limb fat mass, percentage of limb fat, plasma lipids, insulin resistance and glucose tolerance. RESULTS: VAT and trunk fat mass decreased significantly in the GH group compared with the placebo group [-19 cm(2) (-11%) vs. 12 cm(2) (6%), P=0.03, and -548 g (-9%) vs. 353 g (6%), P<0.01, respectively]. The beneficial fat redistribution in the GH group occurred without concomitant changes in subcutaneous fat at the abdomen or extremities. rhGH therapy was well tolerated. Insulin resistance, glucose tolerance, and total plasma cholesterol and triglycerides did not significantly change during intervention. CONCLUSIONS: Daily 0.7 mg rhGH treatment for 40 weeks reduced abdominal visceral fat and trunk fat mass in HIV-infected patients. This treatment appeared to be safe with respect to glucose tolerance and insulin sensitivity.

Verocytotoxigenic Escherichia coli O157 in animals on public amenity premises in England and Wales, 1997 to 2007.

At the request of the public health authorities, 31 public amenity premises in England and Wales containing animals of various species were investigated for the presence of verocytotoxigenic Escherichia coli (VTEC) O157 between 1997 and 2007, because of putative associations with human cases. VTEC O157 was confirmed in one or more species on 19 (61.3 per cent) of the premises. There were significant associations between the presence of VTEC O157 and the number of species sampled, the size of the enterprise, the presence of young cattle and the presence of adult pigs. E coli O157 was isolated from 305 (17.8 per cent) of 1715 samples taken from all the premises, and verocytotoxin genes were detected by PCR in 184 (98.4 per cent) of 187 representative isolates. On positive premises, the highest mean proportion of positive samples (29.0 per cent) was in cattle, followed by sheep (24.4 per cent), donkeys (14.6 per cent), pigs (14.3 per cent), horses (12.3 per cent) and goats (9.9 per cent). A high proportion of positive samples was obtained from camelid species sampled on three of the premises. The main phage types (PT) were 2 and 21/28, which were those most commonly isolated from human cases during the same period. A single PT was detected on 14 of the 19 positive premises, with up to six different species having the same PT.

Risk factors for Campylobacter colonisation during rearing of broiler flocks in Great Britain.

We investigated the associations between Campylobacter colonisation and management practices and farm characteristics in 603 housed broiler batches originating from 137 farms in Great Britain. All study batches were the initial batch slaughtered from the selected house on enrolled farms. Between 1 and 15 batches were sampled from each farm throughout the study. A total of 34.2% of the batches was Campylobacter positive and multivariable multilevel logistic regression revealed that the risk of Campylobacter colonisation was highest in July (OR=3.4, CI95%:1.8; 6.4), August (OR=3.4, CI95%:1.9; 6.2) and September (OR=3.7, CI95%:1.9; 7.1). Cattle on or adjacent to the farm increased the risk (OR=1.7, CI95%:1.1; 2.7), whereas chlorinated drinking water reduced it (OR=0.5, CI95%:0.2; 0.9). If the first removed batch from the previous flock in the house had been Campylobacter positive, the first batch of the following flock was also more likely to be colonised (OR=3.2, CI95%:2.1; 4.9). This association was more likely due to a persistent risk practice or source of Campylobacter on the farm than a direct carry-over from previous flock.

Factors influencing the presence and concentration of E. coli O157 and E. coli in farm waste on six cattle farms in North-West England.

AIMS: To investigate the factors influencing the presence and burden of Escherichia coli O157 in farm wastes. METHODS AND RESULTS: Wastes from six cattle farms were screened for the presence and concentration of E. coli O157 and E. coli on three occasions over a year and waste management data were collected. Sixty-three of 878 (7.1%) samples were positive for verocytotoxigenic Escherichia coli O157 and 664/875 (75.9%) for E. coli with detectable levels greater in fresh waste than in stored waste, pasture or dirty water. CONCLUSIONS: The turning/stirring of stored waste and the use of more than one store (allowing longer storage times) reduced the proportion of E. coli O157 positive samples. The presence of E. coli O157 significantly reduced from a high prevalence found in fresh faeces and stored waste to lower proportions in dirty water and pasture samples. Escherichia coli O157 was only detected on pasture when waste was spread from contaminated stores the day before sampling. A high prevalence of positive E. coli O157 samples were detected when cattle were re-housed. SIGNIFICANCE AND IMPACT OF THE STUDY: These findings help to support the importance of treating and storing farm waste, as well as providing evidence for the level of dilution of E. coli O157 from fresh waste to recently spread pastures.

Short communication: turbidity as an indicator of Escherichia coli presence in water troughs on cattle farms.

Studies have shown that water-drinking troughs are an important source of Escherichia coli infection on cattle farms, and a study was designed to provide farmers with an easy-to-use tool to monitor trough contamination and help determine when to empty and clean water troughs. A total of 164 water troughs were sampled on 33 cattle farms, and the on-farm turbidity tester results were found to be significantly correlated with laboratory turbidity results. Turbidity was associated with E. coli concentration, although the association was not linear. Emptying the troughs within a week of sampling was shown to reduce the turbidity score, but no linear association between time of emptying and E. coli concentration was discovered. A turbidity score of 4 was set as a cutoff point for when to clean a trough, yielding a sensitivity of 0.94 and a specificity of 0.03 for identifying a level of E. coli concentration that was more likely to contain E. coli O157 (>5,800 cfu/100 mL).