Assessing the reliability of innovative criteria to certify that cattle are non-Persistently Infected (non-PI) with the Bovine Viral Diarrhoea Virus (BVDV).

Persistently Infected (PI) animals play a central role in the transmission of BVDV infection between cattle herds. Thus, promoting the certification of non-PI animals is a relevant approach for improving control, as it contributes to securing the trade. The objectives of this study were: i) to assess the reliability of diverse certification criteria, and ii) to identify risk factors for erroneous certification. To do so, the proportion of animals wrongly certified as non-PI on the basis of tests performed after the certification date, was calculated for each criterion. The data used were collected in herds located in Brittany, involved in either a clearance process for those that were infected, or in a surveillance process for herds that were BVDV-free. A total of 23 criteria were defined by combining the technical characteristics of the tests (individual vs. pool; single vs. repeated; direct vs. indirect tests), and some pathogenic characteristics of BVDV infection. Overall, the rates of wrongly-certified animals were low (mean: 1.3 10-4). Direct and indirect criteria had equivalent performances. Heifers from birth, and even foetuses in the last third of gestation, are certified, provided that the herd to which they belong has been free of BVDV for more than 2.5 years. The risk for wrong certification increased in the case of PIs present in the herd or its surroundings. The simplicity of the output-based approach described here, and the excellent performance of indirect criteria relying on serological monitoring of BTM, make it particularly interesting, as its use could facilitate trade between countries.

Modelling the effects of assimilable nitrogen addition on fermentation in oenological conditions.

Alcoholic fermentation in oenological conditions is a biological process carried out under significant physiological constraints: deficiency of nitrogen and other nutriments (vitamins, lipids …) and different stresses (pH and osmotic). In literature, few models have been proposed to describe oenological fermentations. They focused on the initial conditions and did not integrate nitrogen addition during the fermentation process which is a widespread practice. In this work, two dynamic models of oenological fermentation are proposed to predict the effects of nitrogen addition at two different timings: at the beginning of the process and during the fermentation experiment. They were validated and compared against existing models showing an accurate fit to experimental data for CO2 release and CO2 production rate.

Risque zoonotique : médecins généralistes et vétérinaires sont-ils prêts à collaborer ?

INTRODUCTION: Zoonotic risk is a major public health concern that should be addressed through close collaboration between veterinarians and physicians. Yet the few studies available in this field highlight the absence of such collaboration and point to organizational and cultural constraints as explanatory factors. None of them have investigated potential psychosocial determinants. METHODS: This qualitative study is a comparative exploration of veterinarians' and physicians' relationship to zoonotic risk and interprofessional collaboration. Individual exploratory interviews were held with fourteen practicing veterinarians and ten general practitioners - all of whom were French. Their different perceptions of zoonotic risk and collaboration were described by means of a thematic analysis. The social representations of each profession with regard to the other were investigated using attitudinal analyses. RESULTS: Collaboration between general practitioners and veterinarians is commonly perceived as non-existent. The main limiting factors on collaboration are: first, greater psychosocial involvement with regard to zoonotic risk among veterinarians than among general practitioners, due to differences in the degree of exposure to these diseases and in the expertise and values regarding the human-nature relationship; second, contrasting assessments of the others' profession (social desirability), evidenced in veterinarians' negative representations of general practitioners who, conversely, deem veterinarians to be particularly competent; and, thirdly, different perceptions of collaboration (social utility), as a keen interest in collaboration is witnessed among veterinarians, whereas general practitioners see it as only moderately useful. CONCLUSION: It is essential to promote places where physicians and veterinarians can meet locally, so that perceptions of zoonotic risk can evolve, particularly among physicians, along with veterinarians' beliefs about and attitudes towards them.

Risk of seropositivity to Coxiella burnetii in humans living in areas with endemically infected cattle: No way for specific prevention.

Q fever, a zoonotic disease caused by Coxiella burnetii, is endemic among cattle in Western France. However, studies assessing the risk of human infection in such areas are lacking to date, while they may provide information about key specific preventive actions which could be advised to the human populations living with or close to cattle. Therefore, we conducted a cross-sectional study in two departments of Western France during the 2017/18 winter in order to explore possible risk factors for seropositivity among two distinct populations, i) an occupational risk group, that is, the cattle farmers, and ii) the general adult population (approached by blood donors). Sera were collected in 176 cattle farmers and 347 blood donors respectively, and tested for phase I and II antibodies using an indirect immunofluorescence antibody assay. Each participant was asked to fill in a questionnaire containing socio-demographic characteristics, occupational and non-occupational risk exposure. Identified risk factors were: in the general population, working in contact with ruminants, comparatively to any other activity (OR = 4.41; 95% CI: [1.59-6.55]); among farmers, managing an itself infected cattle herd (OR = 3.20; 95% CI: [1.59-6.55]). No other controllable risk factor (lifestyle, outdoor activities, proximity to pets and livestock animals, occupational practices) was here evidenced. In areas with endemically infected cattle, human exposure to Coxiella burnetii is to some extent unavoidable. This strengthens the need for physicians' awareness of the symptoms of Q fever and the appropriateness of general biosecurity measures, especially among at-risk groups living there.

Local characteristics associated with higher prevalence of ESBL-producing Escherichia coli in community-acquired urinary tract infections: an observational, cross-sectional study.

OBJECTIVES: The prevalence of ESBL-producing Escherichia coli (ESBL-E. coli) in community-acquired urinary tract infections (UTI) has been increasing worldwide since 2000, but with large geographical variations. The aim of this study was to determine whether the ESBL-E. coli rate in urine samples from individuals with community-acquired UTI was associated with the local socio-economic, environmental, agricultural and healthcare characteristics. METHODS: This was a cross-sectional study in western France using data on antibiotic susceptibility of E. coli isolated from urine samples of individuals with community-acquired UTI analysed in non-hospital laboratories from 2015 to 2017. The ESBL-E. coli rate was calculated for each laboratory. Data on socio-economic characteristics, human antibiotic consumption, hospital bed density, animal farming density and percentage of agricultural land and surface water were retrieved at the municipality level and aggregated by study area. Their association with ESBL-E. coli prevalence was quantified using multivariate linear regression models with a backward selection. RESULTS: From 358 291 E. coli isolates from urine samples tested in 92 laboratories, the mean ESBL-E. coli prevalence for the study period was 3.30%. In an adjusted model, the ESBL-E. coli rate was significantly (P < 0.05) and positively associated with the local percentage of people >65 years old, third-generation cephalosporin use (DDD/1000 inhabitants), number of hospital beds/km2, poultry density, pig density and percentage of agricultural land. Lower deprivation was associated with a higher ESBL-E. coli rate. CONCLUSIONS: Several anthropogenic factors (primary care, hospitals and animal farming) are associated with the local ESBL-E. coli rate in community-acquired UTI. These results could contribute to improve risk management, including identification of at-risk patient groups.

Risk Factors of Extended-Spectrum Beta-Lactamases-Producing Escherichia coli Community Acquired Urinary Tract Infections: A Systematic Review.

PURPOSE: The prevalence of extended-spectrum beta-lactamase-producing Escherichia coli (ESBL-EC) has been increasing worldwide since the early 2000s. E. coli is found in 70-90% of community-acquired urinary tract infections (CA-UTIs). We performed a systematic literature review to determine the risk factors for CA-UTI caused by ESBL-EC. METHODS: We searched the MEDLINE, Cochrane Library, Embase and Web of Science databases without language or date restriction up to March 2019. Two independent reviewers selected studies with quantified risk factors for CA-UTI due to ESBL-EC, and assessed their quality using the Newcastle-Ottawa Scale. RESULTS: Among the 5,597 studies identified, 16 observational studies (n=12,138 patients) met the eligibility criteria. The included studies were performed in various countries, and 14/16 were published after 2012. The most relevant risk factors for CA-UTI due to ESBL-EC identified were prior use of antibiotics (odds ratio (OR) from 2.2 to 21.4), previous hospitalization (OR: 1.7 to 3.9), and UTI history (OR: 1.3 to 3.8). Two risk factors were related to environmental contamination: travelling abroad, and swimming in freshwater. CONCLUSION: Our findings could allow adapting empiric antibiotic treatments according to the patient profile. Further studies are needed to quantify the relationships between CA-UTI due to ESBL-EC and the environment.

Effects on milk quantity and composition associated with extruded linseed supplementation to dairy cow diets.

Enhanced milk composition can improve human health. The composition of milk determines its nutritional and market value. Therefore, in almost all pricing schemes the economic benefits obtained from raw milk sales are influenced by the milk yield and composition. The objective of this retrospective study was to quantify the average effects of supplementing extruded linseed, rich in α-linolenic acid, to dairy cows on milk yield and milk fat and protein content under field conditions. The study included test day records performed on cows from 1294 dairy herds during the period from 2008 to 2015 that were supplied at least 4 times with extruded linseed deliveries. Exposure statuses were defined according to the time sequence and the amount of extruded linseed distributed in the herd. The unexposed population was composed of cows being in a herd period when extruded linseed was not offered. In a linear dose-response relationship, every 100 g increase in exposure to EL was associated with an increased milk yield from 0.11 to 0.14 kg/day, decreased milk fat from 0.06 to 0.13 g/kg and decreased milk protein from 0 to 0.02 g/kg, according to the cow parity. This study provides information on the associations between estimated intakes of EL and milk production and composition using a large database obtained from commercial dairy herds.

Spread of Coxiella burnetii between dairy cattle herds in an enzootic region: modelling contributions of airborne transmission and trade.

Q fever, a worldwide zoonotic disease caused by Coxiella burnetii, is a looming concern for livestock and public health. Epidemiological features of inter-herd transmission of C. burnetii in cattle herds by wind and trade of cows are poorly understood. We present a novel dynamic spatial model describing the inter-herd regional spread of C. burnetii in dairy cattle herds, quantifying the ability of airborne transmission and animal trade in C. burnetii propagation in an enzootic region. Among all the new herd infections, 92% were attributed to airborne transmission and the rest to cattle trade. Infections acquired following airborne transmission were shown to cause relatively small and ephemeral intra-herd outbreaks. On the contrary, disease-free herds purchasing an infectious cow experienced significantly higher intra-herd prevalence. The results also indicated that, for short duration, both transmission routes were independent from each other without any synergistic effect. The model outputs applied to the Finistère department in western France showed satisfactory sensitivity (0.71) and specificity (0.80) in predicting herd infection statuses at the end of one year in a neighbourhood of 3 km around expected incident herds, when compared with data. The model developed here thus provides important insights into the spread of C. burnetii between dairy cattle herds and paves the way for implementation and assessment of control strategies.

Evaluation of Two PCR Tests for Coxiella burnetii Detection in Dairy Cattle Farms Using Latent Class Analysis.

Different tests performed on bulk tank milk samples (BTM) are available to determine the C. burnetii status of herds. However, these tests, which are based on the detection of either antibodies directed against C. burnetii (ELISA) or bacterial DNA (PCR), have limitations. A currently disease-free herd infected in the past may continue to test positive with ELISA due to the persistence of antibodies in animals that were infected and that subsequently cleared the infection. Infectious herds can also be misclassified using PCR because of the absence of bacteria in the BTM when the test is performed. Recently, PCR has been used for bacterial DNA detection in the farm environment, which constitutes the main reservoir of C. burnetii. The objectives of this study were to assess and compare the sensitivities and specificities of one commonly used PCR test in BTM (PCR BTM) and of a PCR applied to environmental samples (PCR DUST) in dairy cattle farms. BTM and dust samples were collected (using environmental swabs) in 95 herds. The evaluation of the performance of the 2 tests was conducted using latent class models accounting for within herd disease dynamics. Parameter estimation was carried out using MCMC, within a Bayesian framework. Two types of priors were used for the specificity of PCR DUST. A model with a uniform prior on 0-1 fitted the data better than a model with a uniform prior on 0.95-1. With the best model PCR DUST had a lower sensitivity than PCR BTM (0.75 versus 0.83) and a specificity of 0.72. The moderately low value for the specificity of PCR DUST suggests that the presence of bacteria on farm is not always associated with persistent infections and shedding of bacteria in milk.

Using animal performance data to evidence the under-reporting of case herds during an epizootic: application to an outbreak of bluetongue in cattle.

Following the emergence of the Bluetongue virus serotype 8 (BTV-8) in France in 2006, a surveillance system (both passive and active) was implemented to detect and follow precociously the progression of the epizootic wave. This system did not allow a precise estimation of the extent of the epizootic. Infection by BTV-8 is associated with a decrease of fertility. The objective of this study was to evaluate whether a decrease in fertility can be used to evidence the under-reporting of cases during an epizootic and to quantify to what extent non-reported cases contribute to the total burden of the epizootic. The cow fertility in herds in the outbreak area (reported or not) was monitored around the date of clinical signs. A geostatistical interpolation method was used to estimate a date of clinical signs for non-reported herds. This interpolation was based on the spatiotemporal dynamic of confirmed case herds reported in 2007. Decreases in fertility were evidenced for both types of herds around the date of clinical signs. In non-reported herds, the decrease fertility was large (60% of the effect in reported herds), suggesting that some of these herds have been infected by the virus during 2007. Production losses in non-reported infected herds could thus contribute to an important part of the total burden of the epizootic. Overall, results indicate that performance data can be used to evidence the under-reporting during an epizootic. This approach could be generalized to pathogens that affect cattle's performance, including zoonotic agents such as Coxiella burnetii or Rift Valley fever virus.

Relative contributions of neighbourhood and animal movements to Coxiella burnetii infection in dairy cattle herds.

Q fever in dairy cattle herds occurs mainly after inhalation of contaminated aerosols generated from excreta by shedder animals. Propagation of Coxiella burnetii, the cause of the disease between ruminant herds could result from transmission between neighbouring herds and/or the introduction of infected shedder animals in healthy herds. The objective of this study were (i) to describe the spatial distribution C. burnetii-infected dairy cattle herds in two different regions: the Finistère District in France (2,829 herds) and the island of Gotland in Sweden (119 herds) and (ii) to quantify and compare the relative contributions of C. burnetii transmission related to neighbourhood and to animal movements on the risk for a herd to be infected. An enzyme--linked immunosorbent assay was used for testing bulk tank milk in May 2012 and June 2011, respectively. Only one geographical cluster of positive herds was identified in north-western Finistère. Logistic regression was used to assess the association of risk for a herd to test positively with local cattle density (the total number of cattle located in a 5 km radius circle) and the in-degree (ID) parameter, a measure of the number of herds from which each herd had received animals directly within the last 2 years. The risk for a herd to test positively was higher for herds with a higher local cattle density [odds ratio (OR) = 2.3, 95% confidence interval (CI) = 1.6-3.2, for herds with a local density between 100 and 120 compared to herds with a local density 60]. The risk was also higher for herds with higher IDs (OR = 2.3, 95% CI = 1.6-3.2, for herds with ID 3 compared to herds that did not introduce animals). The proportion of cases attributable to infections in the neighbourhood in high-density areas was twice the proportion attributable to animal movements, suggesting that wind plays a main role in the transmission.

Vaccination using phase I vaccine is effective to control Coxiella burnetii shedding in infected dairy cattle herds.

The effectiveness of the vaccination of dairy cows combined or not with antibiotics (i.e. oxytetracycline) to control Coxiella burnetii (Cb) shedding at herd level was investigated in 77 Q fever clinically affected herds. In addition to nulliparous heifers' vaccination, one out of the four following medical strategies was randomly assigned to dairy cows in each herd: vaccination (using a phase I vaccine) alone, vaccination combined with oxytetracycline, oxytetracycline alone or nothing. Their effectiveness to reduce Cb load in quarterly samples of bulk tank milk (BTM) and of pooled milk of primiparous (MP) was assessed through logistic hierarchical models. A significant reduction in Cb load was observed in herds where the vaccination of ≥80% of dairy cows was implemented; whereas the use of antibiotics was uneffective. Our findings support the interest of a whole vaccination strategy and provide evidence for decreasing the use of antibiotics in dairy cattle herds.

Dairy goat demography and Q fever infection dynamics.

Between 2007 and 2009, the largest human Q fever epidemic ever described occurred in the Netherlands. The source was traced back to dairy goat farms, where abortion storms had been observed since 2005. Since one putative cause of these abortion storms is the intensive husbandry systems in which the goats are kept, the objective of this study was to assess whether these could be explained by herd size, reproductive pattern and other demographic aspects of Dutch dairy goat herds alone. We adapted an existing, fully parameterized simulation model for Q fever transmission in French dairy cattle herds to represent the demographics typical for Dutch dairy goat herds. The original model represents the infection dynamics in a herd of 50 dairy cows after introduction of a single infected animal; the adapted model has 770 dairy goats. For a full comparison, herds of 770 cows and 50 goats were also modeled. The effects of herd size and goat versus cattle demographics on the probability of and time to extinction of the infection, environmental bacterial load and abortion rate were studied by simulation. The abortion storms could not be fully explained by demographics alone. Adequate data were lacking at the moment to attribute the difference to characteristics of the pathogen, host, within-herd environment, or a combination thereof. The probability of extinction was higher in goat herds than in cattle herds of the same size. The environmental contamination was highest within cattle herds, which may be taken into account when enlarging cattle farming systems.

Effectiveness of vaccination and antibiotics to control Coxiella burnetii shedding around calving in dairy cows.

Effectiveness of phase 1 vaccine, combined or not with tetracycline, to control Coxiella burnetii vaginal shedding at calving in cows was assessed through a 13 months study in 22 Q fever clinically affected commercial dairy herds. Four medical strategies implemented at herd level but randomly assigned to cows (vaccination, vaccination and tetracycline, tetracycline, nothing) were compared. There was no significant interaction effect between vaccination and antibiotherapy. Tetracycline used once at drying off was associated with a lower risk of being detected shedder at calving (OR=0.40, CI 95% [0.21-0.75]), but had no significant effect on the bacterial load shed. Vaccination did not significantly prevent shedding but was significantly (OR=0.15, CI 95% [0.03-0.85]) associated with lower bacterial load shed. Thus, vaccination using a phase 1 vaccine and antibiotherapy using tetracycline is associated with a decrease in shedding in dairy cows and could contribute to reduce the bacterial load generated in the environment. To the best of our knowledge, this is the first study providing useful information for evidenced-based and rational use of medical strategy combining antibiotic and vaccination in infected dairy cattle herds.

A Vegetation Index qualifying pasture edges is related to Ixodes ricinus density and to Babesia divergens seroprevalence in dairy cattle herds.

Babesia divergens, transmitted by the tick Ixodes ricinus, is the main agent of bovine piroplasmosis in France. This Apicomplexa often is present in asymptomatic carriers; however, clinical cases are rare. While numerous factors are known to influence tick density, no risk factor of contact with B. divergens has been identified for cattle. Our study aimed to explore whether a Vegetation Index could serve as an indirect indicator of within-herd B. divergens seroprevalence. In February 2007, blood samples were taken from all of the cows in 19 dairy cattle herds in Western France and IFAT serology was performed individually to measure B. divergens seroprevalence. The following spring, I. ricinus nymphs were collected by drag sampling along transects on the vegetation of each farm's pasture perimeters. Tick density was related significantly to a Vegetation Index (V.I., ranging from 1 to 5) that took into account the abundance of trees and bushes on the edge of pastures: most ticks (57%) were found in transects with the highest V.I. (covering 15% of the explored surface in the study area). At the farm level, the proportion of transects presenting I. ricinus nymphs was significantly related to B. divergens seroprevalence: the farms with more than 15% of transects with I. ricinus had a significantly higher risk of high seroprevalence. The proportion of pasture perimeters where the V.I.=5 also was significantly related to B. divergens seroprevalence: the farms where more than 20% of transects had a V.I.=5 had a significantly higher risk of high seroprevalence. Given that the Vegetation Index is a steady indicator of the potential I. ricinus density in the biotope, we recommend that the risk of high B. divergens seroprevalence in cows be evaluated using this tool rather than drag samplings.

Genetic instability of Campylobacter coli in the digestive tract of experimentally infected pigs.

Campylobacter, a leading cause of food-borne illness worldwide, has a widespread distribution with a broad range of animal hosts and environmental reservoirs. The genetic description of bacterial strains is a powerful tool for epidemiological studies but can be impaired by the high genomic variability of Campylobacter. Our study aimed (i) at investigating the genotypic instability of Campylobacter generated either in vitro by subculturing or after in vivo passage on specific pathogen-free pigs and (ii) at evaluating the suitability of typing methods to detect such variation. Pigs were inoculated per os with three Campylobacter strains (one C. coli originating from pig faeces, one C. jejuni and one C. coli originating from poultry faeces) alone or in mixture and non-inoculated pigs were housed in adjacent pens. Genotypic instability was investigated using both macrorestriction combined with pulsed-field gel electrophoresis analysis (PFGE) and PCR restriction fragment length polymorphism analysis of the flaA gene (flaA PCR-RFLP). No variability in the genetic profile was observed for the three strains maintained through twenty times subculturing events in vitro. Genotypic variability was evidenced in vivo only in pigs inoculated with C. coli of porcine origin, either alone or in a mix, with both genotyping methods. In our study, for one porcine C. coli strain, 13% and 21% of variability were generated in the digestive tract of pigs by PFGE and flaA PCR-RFLP typing methods, respectively. This study is a first approach for a better understanding of the genomic instability of Campylobacter in pig under field conditions.

Modelling the effect of heterogeneity of shedding on the within herd Coxiella burnetii spread and identification of key parameters by sensitivity analysis.

Coxiella burnetii is the bacterium responsible for Q fever, a worldwide zoonosis. Ruminants, especially cattle, are recognized as the most important source of human infections. Although a great heterogeneity between shedder cows has been described, no previous studies have determined which features such as shedding route and duration or the quantity of bacteria shed have the strongest impact on the environmental contamination and thus on the zoonotic risk. Our objective was to identify key parameters whose variation highly influences C. burnetii spread within a dairy cattle herd, especially those related to the heterogeneity of shedding. To compare the impact of epidemiological parameters on different dynamical aspects of C. burnetii infection, we performed a sensitivity analysis on an original stochastic model describing the bacterium spread and representing the individual variability of the shedding duration, routes and intensity as well as herd demography. This sensitivity analysis consisted of a principal component analysis followed by an ANOVA. Our findings show that the most influential parameters are the probability distribution governing the levels of shedding, especially in vaginal mucus and faeces, the characteristics of the bacterium in the environment (i.e. its survival and the fraction of bacteria shed reaching the environment), and some physiological parameters related to the intermittency of shedding (transition probability from a non-shedding infected state to a shedding state) or to the transition from one type of shedder to another one (transition probability from a seronegative shedding state to a seropositive shedding state). Our study is crucial for the understanding of the dynamics of C. burnetii infection and optimization of control measures. Indeed, as control measures should impact the parameters influencing the bacterium spread most, our model can now be used to assess the effectiveness of different control strategies of Q fever within dairy cattle herds.

A side effect of decreased fertility associated with vaccination against bluetongue virus serotype 8 in Holstein dairy cows.

Inactivated virus vaccines have been widely used to control bluetongue after introduction of serotype 8 of the bluetongue virus (BTV) in northern Europe in 2006. To evaluate vaccination, quantitative knowledge of its possible side effects is needed. One current adverse reaction with inactivated vaccines is a rise in body temperature, which could reduce cow reproductive performance. The objective of this study was to quantify a possible side effect of vaccination on fertility before the implantation of the embryo of dairy cows under field conditions. The study was performed on herds that were not exposed to BTV. Fertility was assessed by return-to-service following artificial insemination (AI). Biological assumptions for a possible side effect of vaccination were conception failure and embryonic death. Associations between return-to-service rates and vaccine injections were assessed using mixed-logistic regression models and survival analysis. Two models were considered: a 3-week-return-to-service model comparing cows vaccinated between 3 days before and 16 days after AI and unvaccinated cows (assuming an effect on conception failure or early embryonic death), and a 90-day-return-to-service model comparing cows vaccinated between 3 days before and 42 days after AI and unvaccinated cows (assuming an effect on conception failure, early or late embryonic death). Only cows receiving a second vaccine injection between 2 and 7 days after AI had a significantly higher risk of 3-week-return-to-service (RR=1.19 [1.07-1.33]). This corresponds to an increase of return-to-service by 4 percentage points. A side effect of vaccination could be due to early embryonic death. The slight side effect on fertility associated with vaccination was low compared to effects of BTV-8 exposure on fertility.

Seroprevalence of Q fever in naturally infected dairy cattle herds.

Coxiella burnetii is the causal agent of Q fever, a worldwide spread zoonosis. Prevention of C. burnetii shedding in cattle is critical to control the spread of the pathogen between animals, and from animals to humans. Vaccination with a phase 1 vaccine has been shown to be effective in preventing shedding when implemented in still susceptible animals, even in infected cattle herds. The identification of these animals (dairy cows and nulliparous females) as targets for vaccination consequently is crucial. Hygiene measures conventionally also are implemented, but their relative impact on C. burnetii diffusion remains unknown. The objectives of this study therefore were to (i) describe the distribution of the within-herd apparent seroprevalence among cows and nulliparous females and (ii) to explore the association between management practices and herd characteristics on the one hand, and these seroprevalences on the other. In a sample of 100 naturally and clinically infected dairy herds, blood samples were taken systematically from all nulliparous females (older than 12 months) and cows, and serologically tested. Information on herd characteristics and management practices were collected through a questionnaire filled in by each farmer. The variation in within-herd seroprevalence among cows and the risk for a herd of having at least one seropositive nulliparous female were investigated using multivariate (linear and logistic respectively) regression models. Median within-herd seroprevalence was 0.32 (Q1=0.22; Q3=0.43). We observed a low to null (median=0.01; Q1=0; Q3=0.10) within-herd seroprevalence in nulliparous females contrary to a high value (median=0.42) and variability (Q1=0.28; Q3=0.56) in cows. Only a few herd characteristics and management practices were found to be related to seroprevalence. Within-herd seroprevalence in cows was found to be significantly (P<0.10) higher in herds (i) with a number of cows<46, (ii) with seasonal calving, and (iii) with grazing or contact through the fence with other ruminant herds. The risk of having at least one seropositive nulliparous female was increased in herds (i) with seasonal calving and (ii) where the foetus and/or the placenta of aborted cows were not systematically removed. Our findings support, in addition to the implementation of high level of hygiene measures, the relevance of vaccination (at least in nulliparous females) as a method to control the spread of C. burnetii within an infected herd, as vaccination is effective in susceptible animals and given that nulliparous females are mostly not infected even in infected herds.

Rapid identification and quantification of Campylobacter coli and Campylobacter jejuni by real-time PCR in pure cultures and in complex samples.

BACKGROUND: Campylobacter spp., especially Campylobacter jejuni (C. jejuni) and Campylobacter coli (C. coli), are recognized as the leading human foodborne pathogens in developed countries. Livestock animals carrying Campylobacter pose an important risk for human contamination. Pigs are known to be frequently colonized with Campylobacter, especially C. coli, and to excrete high numbers of this pathogen in their faeces. Molecular tools, notably real-time PCR, provide an effective, rapid, and sensitive alternative to culture-based methods for the detection of C. coli and C. jejuni in various substrates. In order to serve as a diagnostic tool supporting Campylobacter epidemiology, we developed a quantitative real-time PCR method for species-specific detection and quantification of C. coli and C. jejuni directly in faecal, feed, and environmental samples. RESULTS: With a sensitivity of 10 genome copies and a linear range of seven to eight orders of magnitude, the C. coli and C. jejuni real-time PCR assays allowed a precise quantification of purified DNA from C. coli and C. jejuni. The assays were highly specific and showed a 6-log-linear dynamic range of quantification with a quantitative detection limit of approximately 2.5 × 10² CFU/g of faeces, 1.3 × 10² CFU/g of feed, and 1.0 × 10³ CFU/m² for the environmental samples. Compared to the results obtained by culture, both C. coli and C. jejuni real-time PCR assays exhibited a specificity of 96.2% with a kappa of 0.94 and 0.89 respectively. For faecal samples of experimentally infected pigs, the coefficients of correlation between the C. coli or C. jejuni real-time PCR assay and culture enumeration were R² = 0.90 and R² = 0.93 respectively. CONCLUSION: The C. coli and C. jejuni real-time quantitative PCR assays developed in this study provide a method capable of directly detecting and quantifying C. coli and C. jejuni in faeces, feed, and environmental samples. These assays represent a new diagnostic tool for studying the epidemiology of Campylobacter by, for instance, investigating the carriage and excretion of C. coli and C. jejuni by pigs from conventional herds.