Longitudinal study of Salmonella infection in four Italian farrow-to finish swine herds

Abstract

A longitudinal study of Salmonella enterica infection was carried out in 4 Italian farrow-to-finish swine herds. In each herd 5 litters were randomly selected and in each litter 6 piglets ear tagged. Thus, on each farm 30 pigs were included in the study. Individual blood samples were collected for serologic examination at weaning from all piglets and in the same day from all sows 1n the farrowing unit. Piglets were bled again at approximately 60, 90, 150, 210 and 270 days of life with the last blood sample collected at slaughtering. In one herd, in which the duration of productive cycle was about 12 months, the last blood samples was collected at 350 days of life. 5 pen pooled faecal samples were collected from each herd for bacteriological examination with the same time schedule of blood samples. At slaughtering mesenteric lymph nodes were collected from each ear tagged pig. Sera-prevalence (cutoff S/P ratio 0,25) in sows varied from 93,8% to 100%. In all herds sera-prevalence in piglets showed a similar profile with complete decline of maternal antibodies at day 60 and clear sera-conversion between day 90 and day 150. The peak of sera-prevalence was observed between day 210 and day 270. Sera-prevalence at slaughtering varied from 66% to 100%. Salmonella was isolated from faecal samples in 3 out of 4 herds. No Salmonella was isolated from mesenteric lymph nodes at slaughter in 2 herds. Culture prevalence from mesenteric lymph nodes in the other herds was respectively 3,3% and 30%. This longitudinal study provides original information about epidemiological dynamics of Salmonella enterica infection in Italian swine herds in consideration of the typical longer fattening cycles