Human health impact of Salmonella contamination in imported soybean products: A semiquantitative risk assessment

The objectives of our study were to estimate the number of reported cases of human salmonellosis in Denmark that can be attributed to the occurrence of Salmonella in soy-based animal feed and to assess whether certain serotypes can be considered of less importance to human health. The assessment was based on a comparison of Salmonella serotypes isolated from feedstuffs, swine, cattle, and humans, primarily collected through the Danish Salmonella surveillance programs, supplemented with international data sources. The results are presented in three different forms: a qualitative assessment of all serotypes isolated from animal feed and/or food-producing animals based on their detection in humans; a semiquantitative ranking of serotypes by the apparent differences in their public health impact; and an estimate of the number of reported cases of human salmonellosis that can be attributed to the occurrence of Salmonella in soy-based animal feed. Salmonella isolates included in this study belonged to 91 distinct serotypes. Of the 82 serotypes found in both production animals and humans, 45 were also found in feed. In the period from 1999 to 2003, 14.4% of reported human infections were caused by serotypes also isolated from animal feed. Based on a modified version of a previously published risk model, we estimated that up to 1.7% of the total number of reported human cases and 2.1% of domestically acquired infections in the period 1999-2003 could be attributed to feedborne serotypes acquired through the consumption of Danish pork and beef. We concluded that more than 90% of serotypes have the potential, if they occur in feedstuffs, for infecting humans via production animals or foods of animal origin.