Zoonoses Action Plan Monitoring Programme: An Investigation of the Sampling Protocol

Abstract

The Zoonoses Action Plan (ZAP) Salmonella Programme was established by the British Pig Executive to monitor Salmonella prevalence in quality-assured British pigs at slaughter by testing a sample of pigs with a meat juice enzyme-linked immunosorbent assay for antibodies against group B and C(1) Salmonella. Farms were assigned a ZAP level (1 to 3) depending on the monitored prevalence, and ZAP 2 or 3 farms were required to act to reduce the prevalence. The ultimate goal was to reduce the risk of human salmonellosis attributable to British pork. A mathematical model has been developed to describe the ZAP sampling protocol. Results show that the probability of assigning a farm the correct ZAP level was high, except for farms that had a seroprevalence close to the cutoff points between different ZAP levels. Sensitivity analyses identified that the probability of assigning a farm to the correct ZAP level was dependent on the sensitivity and specificity of the test, the number of batches taken to slaughter each quarter, and the number of samples taken per batch. The variability of the predicted seroprevalence was reduced as the number of batches or samples increased and, away from the cutoff points, the probability of being assigned the correct ZAP level increased as the number of batches or samples increased. In summary, the model described here provided invaluable insight into the ZAP sampling protocol. Further work is required to understand the impact of the program for Salmonella infection in British pig farms and therefore on human health.

Variation of bacteriologic and serologic Salmonella enterica prevalence between cohorts within finishing swine production farms

“…Different sampling approaches and statistical methods to categorize pig herds have been investigated (Abrahantes, Bollaerts, Aerts, Ogunsanya, & Van der Stede, 2009;Arnold & Cook, 2009;Davies, Heath, Coxon, & Sayers, 2003;Ekeroth, Alban, & Feld, 2003;Snary, Munday, Arnold, & Cook, 2010). However, a consensus still does not exist as to what would be the best approach.…”

Changes in perceptions and motivators that influence the implementation of on-farm Salmonella control measures by pig farmers in England

“…Insufficient information was available to confirm that a lower score in phase 2 indicated a significant reduction in seroprevalence . The accuracy of the score is dependent on the sensitivity and specificity of the test, the number of batches of pigs tested and the number of samples taken per batch (Snary et al, 2010). Nevertheless, the ZNCP scores provided a crude estimate of Salmonella prevalence amongst those farms that supplied pigs to abattoirs that were participating in ZNCP.…”

Stress induced Salmonella Typhimurium recrudescence in pigs coincides with cortisol induced increased intracellular proliferation in macrophages

“…Salmonellosis is one of the most important zoonotic bacterial diseases and pigs are considered as one of the main sources of human salmonellosis [3-6]. Worldwide, Salmonella enterica subspecies enterica serovar Typhimurium ( Salmonella Typhimurium) is the predominant serovar isolated from slaughter pigs [7].…”