Michele T. Guerin

A farm-level study of risk factors associated with the colonization of broiler flocks with Campylobacter spp. in Iceland, 2001 – 2004

BackgroundFollowing increased rates of human campylobacteriosis in the late 1990s, and their apparent association with increased consumption of fresh chicken meat, a longitudinal study was conducted in Iceland to identify the means to decrease the frequency of broiler flock colonization with Campylobacter. Our objective in this study was to identify risk factors for flock colonization acting at the broiler farm level.MethodsBetween May 2001 and September 2004, pooled caecal samples were obtained from 1,425 flocks at slaughter and cultured for Campylobacter. Due to the strong seasonal variation in flock prevalence, analyses were restricted to a subset of 792 flocks raised during the four summer seasons. Flock results were collapsed to the farm level, such that the number of positive flocks and the total number of flocks raised were summed for each farm. Logistic regression models were fitted to the data using automated and manual selection methods. Variables of interest included manure management, water source and treatment, other poultry/livestock on farm, and farm size and management.ResultsThe 792 flocks raised during the summer seasons originated from 83 houses on 33 farms, and of these, 217 (27.4%) tested positive. The median number of flocks per farm was 14, and the median number of positive flocks per farm was three. Three farms did not have any positive flocks. In general, factors associated with an increased risk of Campylobacter were increasing median flock size on the farm (p ≤ 0.001), spreading manure on the farm (p = 0.004 to 0.035), and increasing the number of broiler houses on the farm (p = 0.008 to 0.038). Protective factors included the use of official (municipal) (p = 0.004 to 0.051) or official treated (p = 0.006 to 0.032) water compared to the use of non-official untreated water, storing manure on the farm (p = 0.025 to 0.029), and the presence of other domestic livestock on the farm (p = 0.004 to 0.028).ConclusionLimiting the average flock size, and limiting the number of houses built on new farms, are interventions that require investigation. Water may play a role in the transmission of Campylobacter, therefore the use of official water, and potentially, treating non-official water may reduce the risk of colonization. Manure management practices deserve further attention.

On-farm comparison of keel fracture prevalence and other welfare indicators in conventional cage and floor-housed laying hens in Ontario, Canada

The objective of this study was to compare the flock-level prevalence of healed keel bone fractures and to benchmark other indicators of well-being in laying hens housed in conventional cages and single-tier floor housing systems at several points during the production period. Commercial farms in Ontario, Canada, that housed hens in cages (n=9) or floor barns (n=8) were included. Flocks were beak-trimmed brown hens of various strains. Each flock was visited at 20, 35, 50, and 65 wk of age. At each visit, 50 hens were weighed, palpated for healed keel fractures, and feather scored over 4 areas of the body. Data were collected from the farm records on cumulative mortality. Keel fracture prevalence was higher in floor-housed flocks compared to cage-housed flocks (48.3±0.04% vs. 24.8±0.03%; P<0.001). The majority of keel fractures occurred by 50 wk. Cumulative mortality tended to be higher in floor-housed flocks compared to cage-housed flocks (2.13±0.42% vs. 1.29±0.19%; P=0.078). Mean BW was lower (1,827±28.8 g vs. 1,888±26.8 g; P=0.02) yet more uniform (CV of BW 9.43±0.40% vs. 10.10±0.32%; P<0.001) in floor-housed flocks compared to cage-housed flocks. Feather condition was not affected by housing system type (P=0.618), although it declined with age (P<0.001). Individual hen factors assessed using Pearson partial correlations indicated that hens with fractures were heavier at 65 wk in both housing types (P<0.05) and that heavier hens housed on the floor had better feather scores (P<0.001) from 35 wk onward. Floor-housed hens with fractures had lower feather scores at 35 wk (P<0.05) but not at 50 or 65 wk. Housing hens in single-tier floor systems increased the flock-level prevalence of keel fractures and resulted in a lower, yet more uniform, BW compared to hens in conventional cages under commercial conditions in Ontario. Benchmarking welfare indicators from alternative housing systems for laying hens is important to ensure that progress is made in improving their well-being.

Temperature-related risk factors associated with the colonization of broiler-chicken flocks with Campylobacter spp. in Iceland, 2001-2004.

Our objective was to identify temperature-related risk factors associated with the colonization of broiler-chicken flocks with Campylobacter spp. in Iceland, with an underlying assumption that at minimum ambient temperatures, flies (Musca domestica) play a role in the epidemiology and seasonality of Campylobacter. At slaughter, pooled caecal samples were obtained from 792 flocks that hatched between March 15 and September 15 each year from 2001 to 2004, and cultured for Campylobacter. Daily temperature data (average, maximum and minimum temperatures) were obtained from the Icelandic Meteorological Office. We determined the closest weather station to each farm using ArcGIS 9. We then used logistic-regression models (with a random-effects term for farm) to examine associations between flock positivity and temperature-related predictors. The overall prevalence of Campylobacter was 27.4%, and the month with the highest prevalence (54.4%) was August. The final model included cumulative degree-days (CDD) above an average temperature of 4.4 degrees C and the presence of 1 or more days below a maximum temperature of 8.9 degrees C (threshold below which fly activity was expected to be substantially reduced and egg laying was not expected to occur) during the period 2-4 weeks (i.e. days 8-28) before slaughter. Below 79 CDD, the risk of flock Campylobacter colonization was generally low. Between 79 and 139 CDD, the risk increased gradually, but was lower for flocks raised during periods with 1 or more days <8.9 degrees C than flocks raised without days <8.9 degrees C. The risk increased sharply under conditions of high CDD (>139) and when the maximum temperature remained >8.9 degrees C during the period 2-4 weeks before slaughter.

Flock Prevalence of Exposure to Avian Adeno-Associated Virus, Chicken Anemia Virus, Fowl Adenovirus, and Infectious Bursal Disease Virus Among Ontario Broiler Chicken Flocks

SUMMARY Samples from 231 randomly selected commercial broiler chicken flocks in Ontario were tested at slaughter for exposure to chicken anemia virus (CAV), fowl adenovirus (FAdV), and infectious bursal disease virus (IBDV). Fifteen blood samples per flock were collected and analyzed for the presence of antibodies against CAV, FAdV, and IBDV by ELISA or agar gel immunodiffusion test. Fifteen cecal tonsils and cloacal swabs per flock were analyzed for the presence of CAV, FAdV, and IBDV by PCR. The prevalence of exposure to avian adeno-associated virus (AAAV) was estimated by a PCR test on a subset of FAdV–PCR-positive samples from 178 flocks. Genotypes of FAdV and IBDV were identified on a subset of isolates (n  =  353 and 45, respectively). The flock-level period prevalence of exposure to AAAV, CAV, FAdV, and IBDV during grow-out were 88.76% (95% CI: 84.08–93.45%), 77.06% (95% CI: 71.59–82.52%), 96.54% (95% CI: 94.16–98.91%), and 48.92% (95% CI: 42.42–55.41%), respectively. Results of a multivariable logistic regression model showed a significant association of exposure to FAdV with exposure to AAAV (OR  =  18.57, 95% CI: 3.67–93.86, P  =  0.004) but not with exposure to CAV (P  =  0.7752) or exposure to IBDV (P  =  0.2274). Pathogenic FAdV genotypes (FAdV-02, FAdV-08, and FAdV-11) constituted 39.38% of the isolates. The most-common IBDV genotypes identified were IBDV NC171 (60%) and IBDV 05SA8 (28.89%). This is the first large-scale study to estimate the baseline flock prevalence of exposure to AAAV, CAV, FAdV, and IBDV in commercial broiler flocks in Canada. Potentially pathogenic genotypes of FAdV and IBDV that can guide vaccine development and disease control efforts in Ontario were identified. RESUMEN Prevalencia de la exposición a virus adeno-asociados aviares, al virus de la anemia infecciosa y al virus de la enfermedad infecciosa de la bolsa de Fabricio en parvadas de pollo de engorde en Ontario. Se analizaron muestras de 231 parvadas de pollos de engorde comerciales seleccionados aleatoriamente en Ontario recolectadas durante el procesamiento, para determinar la exposición al virus de la anemia infecciosa (CAV), a adenovirus aviares (FAdV) y para el virus de la enfermedad infecciosa de la bolsa (IBDV). Se recolectaron y analizaron quince muestras por parvada para detectar la presencia de anticuerpos contra el virus de la anemia, adenovirus aviar y virus de la enfermedad de Gumboro mediante ELISA o por la prueba de inmunodifusión en gel de agar. Se analizaron quince muestras de tonsilas cecales e hisopos cloacales por parvada para detectar la presencia de los tres virus por PCR. Se estimó la prevalencia de la exposición a virus aviares adeno-asociados (AAAV) mediante una prueba de PCR en un subconjunto de muestras positivas a la presencia de adenovirus aviares por PCR de 178 parvadas. Los genotipos de adenovirus aviares y del virus de Gumboro se identificaron en un subconjunto de los aislados (n =  353 y 45, respectivamente). El nivel de prevalencia en la parvada a la exposición contra virus adeno asociados, de anemia del pollo y de Gumboro durante el periodo de engorde fueron de 88.76% (Intervalo de confianza del 95%: 84.08 al 93.45%), 77.06 % (IC del 95%: 71.59 al 82.52 %), 96.54 % (IC del 95%: 94.16 al 98.91 %) y 48.92 % (IC del 95%: 42.42 al 55.41 %), respectivamente. Los resultados de un modelo de regresión logística multivariable mostraron una asociación significativa de la exposición a adenovirus aviares con la exposición a los virus adeno asociados (OR  =  18.57, IC del 95%: 3.67 a 93.86, P  =  0.0005), pero no con la exposición a la al virus de la anemia (P  =  0.7752) o con la exposición al virus de Gumboro (P  =  0.2274). Los genotipos patógenos de adenovirus (FAdV-02, FAdV-08, y FAdV-11) constituyeron el 39.38 % de los aislamientos. Los genotipos de Gumboro más comúnmente identificados fueron NC171 (60 %) y IBDV 05SA8 (28.89 %). Este es el primer estudio a gran escala para estimar la línea base de la prevalencia en parvadas a la exposición con virus adeno-asociados aviares, al virus de la anemia, a adenovirus aviares y al virus de la enfermedad de Gumboro en parvadas comerciales en Canadá. Se identificaron genotipos potencialmente patógenos de adenovirus y de Gumboro que pueden guiar los esfuerzos para el desarrollo de vacunas y el control de enfermedades en Ontario.

House-level risk factors associated with the colonization of broiler flocks with Campylobacter spp. in Iceland, 2001 – 2004

BackgroundThe concurrent rise in consumption of fresh chicken meat and human campylobacteriosis in the late 1990s in Iceland led to a longitudinal study of the poultry industry to identify the means to decrease the frequency of broiler flock colonization with Campylobacter. Because horizontal transmission from the environment is thought to be the most likely source of Campylobacter to broilers, we aimed to identify broiler house characteristics and management practices associated with flock colonization. Between May 2001 and September 2004, pooled caecal samples were obtained from 1,425 flocks at slaughter and cultured for Campylobacter. Due to the strong seasonal variation in flock prevalence, analyses were restricted to a subset of 792 flocks raised during the four summer seasons. Logistic regression models with a farm random effect were used to analyse the association between flock Campylobacter status and house-level risk factors. A two-stage process was carried out. Variables were initially screened within major subsets: ventilation; roof and floor drainage; building quality, materials and repair; house structure; pest proofing; biosecurity; sanitation; and house size. Variables with p ≤ 0.15 were then offered to a comprehensive model. Multivariable analyses were used in both the screening stage (i.e. within each subset) and in the comprehensive model.Results217 out of 792 flocks (27.4%) tested positive. Four significant risk factors were identified. Campylobacter colonization was predicted to increase when the flock was raised in a house with vertical (OR = 2.7), or vertical and horizontal (OR = 3.2) ventilation shafts, when the producers boots were cleaned and disinfected prior to entering the broiler house (OR = 2.2), and when the house was cleaned with geothermal water (OR = 3.3).ConclusionThe increased risk associated with vertical ventilation shafts might be related to the height of the vents and the potential for vectors such as flies to gain access to the house, or, increased difficulty in accessing the vents for proper cleaning and disinfection. For newly constructed houses, horizontal ventilation systems could be considered. Boot dipping procedures should be examined on farms experiencing a high prevalence of Campylobacter. Although it remains unclear how geothermal water increases risk, further research is warranted to determine if it is a surrogate for environmental pressures or the microclimate of the farm and surrounding region.

Incidence, distribution, seasonality, and demographic risk factors of Salmonella Enteritidis human infections in Ontario, Canada, 2007–2009

BackgroundIn Canada, surveillance systems have highlighted the increasing trend of Salmonella enterica serovar Enteritidis (S. Enteritidis) human infections. Our study objectives were to evaluate the epidemiology of S. Enteritidis infections in Ontario using surveillance data from January 1, 2007 through December 31, 2009.MethodsAnnual age-and-sex-adjusted incidence rates (IRs), annual and mean age-adjusted sex-specific IRs, and mean age-and-sex-adjusted IRs by public health unit (PHU), were calculated for laboratory-confirmed S. Enteritidis cases across Ontario using direct standardization. Multivariable Poisson regression with PHU as a random effect was used to estimate incidence rate ratios (IRRs) of S. Enteritidis infections among years, seasons, age groups, and sexes.ResultsThe annual age-and-sex-adjusted IR per 100,000 person-years was 4.4 [95% CI 4.0-4.7] in 2007, and 5.2 [95% CI 4.8-5.6] in both 2008 and 2009. The annual age-adjusted sex-specific IRs per 100,000 person-years ranged from 4.5 to 5.5 for females and 4.2 to 5.2 for males. The mean age-adjusted sex-specific IR was 5.1 [95% CI 4.8-5.4] for females and 4.8 [95% CI 4.5-5.1] for males. High mean age-and-sex-adjusted IRs (6.001-8.10) were identified in three western PHUs, one northern PHU, and in the City of Toronto. Regression results showed a higher IRR of S. Enteritidis infections in 2009 [IRR = 1.18, 95% CI 1.06-1.32; P = 0.003] and 2008 [IRR = 1.17, 95% CI 1.05-1.31; P = 0.005] compared to 2007. Compared to the fall season, a higher IRR of S. Enteritidis infections was observed in the spring [IRR = 1.14, 95% CI 1.01-1.29; P = 0.040]. Children 0–4 years of age (reference category), followed by children 5–9 years of age [IRR = 0.64, 95% CI 0.52-0.78; P < 0.001] had the highest IRRs. Adults ≥ 60 years of age and 40–49 years of age [IRR = 0.31, 95% CI 0.26-0.37; P < 0.001] had the lowest IRRs.ConclusionsThe study findings suggest that there was an increase in the incidence of S. Enteritidis infections in Ontario from 2007 to 2008–2009, and indicate seasonal, demographic, and regional differences, which warrant further public health attention.

Keel fracture assessment of laying hens by palpation: inter-observer reliability and accuracy

The objective of this study was to assess the interobserver reliability (agreement) and accuracy of keel palpation for the purpose of detecting old fractures in an end-of-lay flock of commercial laying hens. The low level of invasiveness and the relative speed at which this evaluation can be carried out lends itself well to use in a welfare audit, but only if the results are reliable and accurate from various assessors. The palpation technique first described by Wilkins and others (2004) was used to manually palpate for keel fractures. The technique was modified in that only keel fractures were considered. Eight assessors with varying laying hen experience palpated 100 live ISA Brown hens that had been in lay for 49 weeks. The hens were then euthanased and examined by dissection to establish whether there had been a keel fracture present (yes/no). The accuracy for individual assessors ranged from 87.1 to 96.8 per cent, with a mean of 91.8 per cent among all eight assessors. The interobserver reliability among all eight assessors was moderate (=0.44). Accuracy and κ values were 84.8 per cent and 0.41 for the first 50 hens, and 99.5 per cent and 0.47 for the last 50 hens, respectively, indicating that there was increased accuracy and agreement as the assessors became more experienced at palpation. This level of agreement, and the high level of accuracy, would make this technique an acceptable measure of keel fracture prevalence in a welfare audit.

Evaluating area-level spatial clustering of Salmonella Enteritidis infections and their socioeconomic determinants in the greater Toronto area, Ontario, Canada (2007 – 2009): a retrospective population-based ecological study

BackgroundThere have been only a few region-level ecological studies conducted in Canada investigating enteric infections in humans. Our study objectives were to 1) assess the spatial clustering of Salmonella enterica serotype Enteritidis (S. Enteritidis) human infections in the Greater Toronto Area, and 2) identify underlying area-level associations between S. Enteritidis infection rates and socioeconomic status (SES) indicators that might explain the clustering of infections.MethodsRetrospective data on S. Enteritidis infections from 2007 to 2009 were obtained from Ontario’s reportable disease surveillance database and were grouped at the forward sortation area (FSA) - level. A spatial scan statistic was employed to identify FSA-level spatial clusters of high infection rates. Negative binomial regression was used to identify FSA-level associations between S. Enteritidis infection rates and SES indicators obtained from the 2006 Census of Canada. Global Moran’s I statistic was used to evaluate the final model for residual spatial clustering.ResultsA spatial cluster that included nine neighbouring FSAs was identified in downtown Toronto. A significant positive curvilinear relationship was observed between S. Enteritidis infection rates and FSA-level average number of children at home per census family. Areas with high and areas with low average median family income had higher infection rates than FSAs with medium average median family income. Areas with a high proportion of visible minority population had lower infection rates than FSAs with a medium proportion of visible minority population. The Moran’s I statistic was not significant, indicating that no residual spatial autocorrelation was present after accounting for the SES variables in the final model.ConclusionsOur study demonstrated that FSAs with high and low average median family income, medium proportion of visible minority population, and high average number of children at home per census family had the highest S. Enteritidis infection rates. These areas should be targeted when designing disease control and prevention programs. Future studies are needed in areas with high S. Enteritidis infection rates to identify sources of environmental contamination of the local food supply, to assess food safety practices at local food markets, retail stores, and restaurants, and to identify novel individual-level risk factors.

Rearing system affects prevalence of keel-bone damage in laying hens: a longitudinal study of four consecutive flocks

&NA; High flock‐level prevalence of keel‐bone fractures and deviations in laying hens are commonly reported across various housing systems; however, few longitudinal studies exist, especially for furnished and conventional cage systems. Load‐bearing exercise improves bone strength and mineral composition in laying hens and has the potential to reduce keel‐bone damage, especially if exercise is allowed during critical periods of bone growth throughout the pullet rearing phase. The objective of this study was to determine the prevalence of keel‐bone damage in laying hens housed in furnished and conventional cages, and assess whether opportunities for exercise during the pullet rearing phase influenced the prevalence of keel‐bone damage throughout the laying period. Four flock replicates of 588 Lohmann Selected Leghorn‐Lite pullets/flock were reared in either conventional cages (Conv) or an aviary rearing system (Avi) and placed into conventional cages (CC), 30‐bird furnished cages (FC‐S) or 60‐bird furnished cages (FC‐L) for adult housing. Keel‐bone status was determined by palpation at 30, 50, and 70 wk of age. Age (P < 0.001) and rearing system (P < 0.001) had an effect on the presence of keel‐bone fractures. The presence of fractures increased with age, and hens raised in the Avi system had a lower percentage of fractures (41.6% ± 2.8 SE) compared to hens reared in the Conv system (60.3% ± 2.9 SE). Adult housing system did not have an effect on the percentage of keel fractures (P = 0.223). Age had an effect on the presence of deviations (P < 0.001), with deviations increasing with age. Rearing system (P = 0.218) and adult housing system (P = 0.539) did not affect the presence of deviations. Keel fractures and deviations were strongly associated with each other at all ages: 30 wk: (P < 0.001); 50 wk: (P < 0.001); and 70 wk: (P < 0.001). Increased opportunities for exercise provided by an aviary rearing system reduced the prevalence of keel‐bone fractures through the end‐of‐lay.

Risk factors associated with the colonization of Ontario layer chicken flocks with Brachyspira species.

Brachyspira species are frequent colonizers of the gastrointestinal tract in a variety of domestic animals, including birds. In chickens, Brachyspira species are associated with a clinical condition known as avian intestinal spirochetosis (AIS), a disease characterized by chronic diarrhoea, weight loss, low egg production, and faecal-stained eggs. The purpose of this study was to identify risk factors associated with the presence of Brachyspira species in Ontario layer chicken flocks. Pooled faecal samples were collected from 89 flocks from 58 farms between August 2010 and February 2011; 52 flocks were classified as dirty flocks (history of downgrades for dirty eggs) and 37 were classified as clean flocks (no history of downgrades for dirty eggs). A questionnaire related to management, biosecurity practices, and antimicrobial use was administered prior to sample collection. Using real-time polymerase chain reaction; 63.5% of the dirty flocks and 24.3% of the clean flocks were positive for Brachyspira species. A logistic regression model with a random effect for farm showed that the odds of Brachyspira species for flocks ≥ 60 weeks of age were higher than for flocks ≤ 34 weeks (OR=9.3; P=0.014). The odds of Brachyspira species in flocks housed in A-frame cages with manure curtains (OR=20.0; P=0.002) and flocks from multi-age farms (OR=8.5; P=0.001) were higher than for flocks in cage-stacked houses and from single-age farms, respectively. The odds of Brachyspira species for flocks housed in barns ≥ 30 years old was lower than for flocks housed in barns ≤ 14 years old (OR=0.1; P=0.002). The calculated intra-class correlation coefficient was 5.6 × 10(-14); the notably low proportion of variation among farms after the fixed effects were included in the model suggests that the farm-level variable (multi-age farm) included in the final model accounted for most of the farm-to-farm variation in Brachyspira presence. Therefore, it is recommended that strict biosecurity, and between-flock decontamination efforts to reduce the infection pressure, be followed on farms with multiple flocks of different ages to avoid transmission of the bacteria between flocks.