Isolation of Salmonella serotypes from feces of pigs raised in a multiple-site production system

Objective - To determine the prevalence and serotypes of Salmonella organisms in feces of pigs raised in a modern, multiple-site production system. Design - Cross-sectional study of prevalence. Sample Population - Swine housed on 7 farms (1 gilt development farm, 2 breeding farms, 1 nursery farm, and 3 finishing farms) that formed a multiple-site production system. Procedure - Fecal samples were obtained from 792 pigs (96 to 202/farm) and submitted for bacteriologic culture of Salmonella organisms. Results - Salmonellae were isolated from pigs on all 7 farms and from 95 of 792 (12%) fecal samples. Prevalence ranged from 3.4% at the gilt development farm to 18 and 22% at the breeding farms. Serotypes identified were Salmonella derby, S typhimurium var. Copenhagen, S heidelberg, S typhimurium, S mbandaka, S worthington, and S tennessee. No single serotype was not isolated from all the farms of the production system and the most prevalent serotypes at the 3 finishing farms (S typhimurium or S typhimurium var. Copenhagen) were not isolated from the breeding or nursery farms. Clinical Implications - Upstream infection (pigs infected before arriving at finishing farms) appears to be an unimportant source of Salmonella infection of finished hogs in multiple-site systems. High prevalence of Salmonella shedding in breeding animals suggests that food products derived from culled breeding livestock may be an important source of foodborne disease.