Estimation of the risk of Salmonella shedding by finishing pigs using a logistic model obtained from a survey

An analytic epidemiological survey was carried out in 105 French farms to identify factors associated with Salmonella shedding by finishing pigs. This study gave out a list of 7 risk factors using a logistic model. The aim of the present survey was to validate this model on a second sample of batches of pigs in order to estimate their Salmonella status. The validation study was carried out from April 2003 to August 2005 on 64 finishing pig batches distinct from those used originally to generate the logistic model. In each farm, Salmonella shedding of a batch of pigs at the end of the finishing phase was assessed using swabs as described in the analytical study. Questionnaires were filled in with the farmer to collect data related to management routines. Blood samples from10 growing and 10 finishing pigs were taken to assess sanitary risk factors: status vs Lawsonia intracellularis and Porcine Respiratory Coronavirus. Salmonella contamination status of a finishing room before loading, a further identified risk factor, was tested by environmental swabbing procedure. The estimated risk with the standard error, of Salmonella shedding was calculated using the logistic model and compared to the bacteriological Salmonella status of each batch. Several thresholds are proposed and sensitivity, specificity, positive and negative predictive values related to each cut-off value were calculated. A cut-off value of 0.34 maximised both sensitivity (76.9%) and specificity (68.6%) of the model. Whatever the threshold, the accuracy of the Salmonella non-shedding predicted status is better than the Salmonella shedding predicted status. In a bacteriological sampling programme, this model could be a useful tool to identify batches with low risk of Salmonella shedding and to focus attention on those getting a high probability for being positive

Study of Salmonella contamination of pig slurry in France

A study was carried out from April 2003 to August 2005 In 69 French pig farms to detect Salmonella contaminated pig batches and to assess the level of contamination of their slurry. In each herd, a batch of finishing pigs was included in the survey. In the selected room, Salmonella shedding was assessed using swabs method, pools of faecal material and 4 litres of slurry stored in the pit below the pigs. All samples were analysed for the presence of Salmonella enlerica in a classical bacteriological four-step protocol. Quantification of Salmonella was performed in pools of faecal material and slurry samples according to the most probable number method. Using the swabbing procedure, 20.3% of the batches tested Salmonella positive at the end of the finish1ng phase and 11 .6 % according to the pools of faeces (8/69). Quantification of Salmonella 1n faeces could be performed 1n 6 out of 8 pos1tive batches with levels ranging from 2.4 to 350 Salmonella/gram. The slurry of 11 .8% of the batches (8/68) was found to be Salmonella contaminated. A quantification was achieved in 3 of them Levels of less than 11 0 Salmonellalml were found. The study Indicates that pig slurry may be contammated by Salmonella enterica. However, the percentage of pos1tive samples was rather low and Salmonella could only be detected 1n slurry stored 1n the pit under the slatted floor of moderately or highly shedding batches. Since storage without introduction of new fresh slurry is known to reduce Salmonella surv1val, the probability of spreading the bactena in the environment IS expected to be low as far as adequate storage conditions are applied

Enquête nationale de prévalence du virus de l'hépatite E dans le réservoir porcin

National audienc

Enquête nationale de prévalence du virus de l hépatite E dans le réservoir porcin

National audienc

Enquête nationale de prévalence du virus de l'hépatite E dans le réservoir porcin

National audienc

Authorship Statement

National audienc

Estimation of the risk of Salmonella shedding by finishing pigs using a logistic model obtained from a survey

An analytic epidemiological survey was carried out in 105 French farms to identify factors associated with Salmonella shedding by finishing pigs. This study gave out a list of 7 risk factors using a logistic model. The aim of the present survey was to validate this model on a second sample of batches of pigs in order to estimate their Salmonella status. The validation study was carried out from April 2003 to August 2005 on 64 finishing pig batches distinct from those used originally to generate the logistic model. In each farm, Salmonella shedding of a batch of pigs at the end of the finishing phase was assessed using swabs as described in the analytical study. Questionnaires were filled in with the farmer to collect data related to management routines. Blood samples from10 growing and 10 finishing pigs were taken to assess sanitary risk factors: status vs Lawsonia intracellularis and Porcine Respiratory Coronavirus. Salmonella contamination status of a finishing room before loading, a further identified risk factor, was tested by environmental swabbing procedure. The estimated risk with the standard error, of Salmonella shedding was calculated using the logistic model and compared to the bacteriological Salmonella status of each batch. Several thresholds are proposed and sensitivity, specificity, positive and negative predictive values related to each cut-off value were calculated. A cut-off value of 0.34 maximised both sensitivity (76.9%) and specificity (68.6%) of the model. Whatever the threshold, the accuracy of the Salmonella non-shedding predicted status is better than the Salmonella shedding predicted status. In a bacteriological sampling programme, this model could be a useful tool to identify batches with low risk of Salmonella shedding and to focus attention on those getting a high probability for being positive.</p

Study of Salmonella contamination of pig slurry in France

A study was carried out from April 2003 to August 2005 In 69 French pig farms to detect Salmonella contaminated pig batches and to assess the level of contamination of their slurry. In each herd, a batch of finishing pigs was included in the survey. In the selected room, Salmonella shedding was assessed using swabs method, pools of faecal material and 4 litres of slurry stored in the pit below the pigs. All samples were analysed for the presence of Salmonella enlerica in a classical bacteriological four-step protocol. Quantification of Salmonella was performed in pools of faecal material and slurry samples according to the most probable number method. Using the swabbing procedure, 20.3% of the batches tested Salmonella positive at the end of the finish1ng phase and 11 .6 % according to the pools of faeces (8/69). Quantification of Salmonella 1n faeces could be performed 1n 6 out of 8 pos1tive batches with levels ranging from 2.4 to 350 Salmonella/gram. The slurry of 11 .8% of the batches (8/68) was found to be Salmonella contaminated. A quantification was achieved in 3 of them Levels of less than 11 0 Salmonellalml were found. The study Indicates that pig slurry may be contammated by Salmonella enterica. However, the percentage of pos1tive samples was rather low and Salmonella could only be detected 1n slurry stored 1n the pit under the slatted floor of moderately or highly shedding batches. Since storage without introduction of new fresh slurry is known to reduce Salmonella surv1val, the probability of spreading the bactena in the environment IS expected to be low as far as adequate storage conditions are applied.</p

Risk factors associated with the presence of hepatitis E virus in livers and seroprevalence in slaughter-age pigs: a retrospective study of 90 swine farms in France

International audienceThe frequency of sporadic cases of hepatitis E in humans in developed countries has increased in recent years. The consumption of raw or undercooked pig liver-based products has been identified as an important source of human infection. The question of possible massive human exposure to this zoonotic agent has been raised by the high prevalence of hepatitis E virus (HEV) in swine herds. However, little is known about the epidemiology of HEV on pig farms. A retrospective study, based on a previous prevalence study of 185 farms, was conducted on 90 farms located in Western France, randomly selected from this database, to identify factors associated with the presence of HEV in pig livers and HEV seroprevalence in slaughter-age pigs. At least one HEV RNA-positive liver was found in 30% of the sampled farms while seroprevalence in slaughter-age pigs at the farm level reached almost 75%. Different factors were associated with the two conditions. The risk of having HEV-positive livers was increased by early slaughter, genetic background, lack of hygiene measures and surface origin of drinking water. High HEV seroprevalence was associated with mingling practices at the nursery stage and hygiene conditions. These results can be used to determine on-farm measures to reduce within-farm HEV spread and infection of slaughter-age pigs