The Israeli Salmonella surveillance programme for pullet and layer farms during the study period
Under the surveillance scheme for Salmonella that started in June 2017 and continued throughout the entire period of the dataset, layer farms were sampled every 15 weeks from the moment the flock reaches an age of 22 to 24 weeks. Pullet farms were sampled approximately one week prior to the distribution of pullets to layer farms. The general surveillance scheme aimed to include all pullet and layer farms. Samples were taken by inspectors from either the Israeli Veterinary Services (IVS) or the Egg and Poultry Board (EPB). On each sampling occasion, IVS inspectors usually took 2 pairs of drag swabs, 2 pairs of dust swabs from walls and equipment and one dust sample, while EPB inspectors usually took 2 pairs of drag swabs. If present, Salmonella serovars were identified to the group level according to the Kauffman-White scheme by the EPB laboratory. Isolates of groups B or D were further identified to the serovar level by the Salmonella National Reference Laboratory of the Israeli Ministry of Health. Farms testing positive for Salmonella serovars Enteritidis and/or Typhimurium were culled and thoroughly cleaned and disinfected. Repopulation of these farms was only allowed after drag swabs from the empty houses tested negative for all Salmonella serovars.
Farm characteristics
Hens were caged on the vast majority of layer farms (97.5%) and free-ranging on the remainder of farms. Farm size varied widely (less than 100 to 255,000), and the median size was around 2,900. The number of houses per farm varied from 1 to 6, but the vast majority of farms contained only one house (97.9%).
Production cycle
Production cycles on farms that did not test positive for the targeted Salmonella strains lasted on average 18.2 weeks for pullets and 95.4 weeks for layers. The number of houses per farm varied from 1 to 6, but the vast majority of farms contained only one house (97.9%). For farms that had several houses, the production cycle always started at the same date in all houses (same flock in all houses).
Available data
Sampling date were available for a total of 1,842 layer farms and 56 pullet farms during the period from early June 2017 to early April 2019. Three data files are available. All data fields in these files are described in the separate code book file, but here follows a summary of their content:
- File “20230907 SamplingDate.txt” contains sampling data and includes a.o the following fields:
· farm type
· flock identifier
· the sampling date
· sample type
· number of samples by type
· date test result
· test result
- File “20230907 BetweenFarmDistanceMatrix.txt” contains information about the between-farm distance in kilometers.
- File “20230907 FlockData.txt” describes the start and closing date of production cycles.
These files can be linked via the farm and/o flock identifier fields.
Data restrictions
The raw data in its original form could not be published, since it contains information that has been classified as sensitive by the Israeli government. Therefore, firstly, only the information required for the analyses in the Epi-Risk project could be published. Secondly, Instead of reporting farm locations, we therefore provide a matrix with the distance between anonymised farms in kilometers. Finally, we replaced the original farm, flock and sample identifiers by new anonymised ones.
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