Prevalence of subclinical Salmonella enterica infection in Danish finishing pig herds

Our aim was to determine the Salmonella enterica prevalence in 96 randomly selected Danish pig herds, based on serological examination of blood sample s and bacteriological examination of faecal samples (collected simultaneous ly from the same pens). For comparison, 39 high-seroprevalence herds were i ncluded in the study. The representativeness of the selected herds was asse ssed, based on descriptive statistics of herd size and type. Totals of 1330 pen samples and 6814 blood samples were examined. The results from the meat-juice screening in the Danish S. enterica Control Programme were available for 3372 meat-juice samples from 91 of the 96 ran domly selected herds and 1195 meat-juice samples from 37 of the 39 high-ser oprevalence herds. Of the 96 randomly selected herds, 23 herds had no posit ive pen samples (out of 10), no positive blood samples (out of 50) and no p ositive meat-juice samples (out of approximately 30-40 samples in 6 months) . Ten herds had one or more positive meat-juice samples but were otherwise negative. S. Typhimurium was isolated from 30 of the 39 high-seroprevalence herds. Our conclusions were: (1) The within-herd seroprevalence among the 96 rando mly selected Danish pig herds was low (average within-herd seroprevalence = 2%, maximum = 32%). (2) Among the 39 high-seroprevalence herds (recently a ssigned level 3 in the S. enterica Control Programme), S. enterica was isol ated from 77% of the herds when 10 pen samples were examined bacteriologica lly. (3) Seropositivity tended to be related to the presence of S. Typhimur ium. (C) 2000 Elsevier Science B.V. All rights reserved.