Modeling the risk of salmonellosis from consumption of pistachios produced and consumed in the United States

The risk of salmonellosis from consumption of pistachios produced and consumed in the U.S. was assessed through quantitative microbial risk assessment. Data on Salmonella prevalence and concentration on pistachios, nut crop volume, storage times and temperatures during processing and handling, and reductions during storage or from roasting were derived from laboratory experiments, published literature, and industry expert opinion. Uncertainty was analyzed via what-if scenarios for Salmonella prevalence, concentration, storage reduction, treatment variability, portion of crop treated, and increased consumption. The estimated U.S. incidence of salmonellosis when 100% of pistachios were exposed to a 4 ± 0 log reduction treatment averaged 1.4 cases per billion servings, or <1 case/year, without considering Salmonella decline during storage. Including Salmonella decline during storage reduced the salmonellosis estimates approximately 10-fold. The predicted arithmetic mean number of cases associated with individual 500,000-kg storage silos, contaminated at the highest observed levels, ranged from 5 to 530 when the product was consumed untreated, but was reduced to below 1 case per silo when a 4 ± 0 log reduction treatment was applied. Assuming a uniform 4-log reduction treatment is applied to 100% of the crop and there is no decline of Salmonella during storage, the assessment indicates the following: 10-fold increases in either Salmonella prevalence or concentration, 2-fold increases in both prevalence and concentration, or consumption of >0.05% of untreated product volume yield an arithmetic mean risk of >1 case/year.