THE RELATION BETWEEN SALMONELLA OCCURRENCE IN SOWS AND PIGLETS: A LONGITUDINAL STUDY

1. GHENT UNIVERSITY Department of Veterinary Public Health and Food Safety, Department of Reproduction, Obstetrics, and Herd Health Faculty of Veterinary Medicine, Ghent University THE RELATION BETWEEN SALMONELLA OCCURRENCE IN SOWS AND PIGLETS: A LONGITUDINAL STUDY Nollet N., Dewulf J., Houf K., De Zutter L., de Kruif A., Maes D. Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium Summary The aim of the present study was to investigate the relationship between Salmonella occurrence in sows and their offspring. In 3 Belgian farrow-to-finish herds, 3 groups of 34, 40 and 32 sows, resp. were selected and individually sampled during late gestation and lactation. From each of the sows, 3 piglets were randomly selected and sampled on 4 occasions. The relative risk ratio (RR) for a litter to be culture positive given the respective sow was seropositive during lactation was 0.25 (0.09-0.93). Piglets originating from Salmonella excreting sows during late gestation or lactation did not have a significant higher risk for Salmonella excretion during the nursery period (RR=0.52 (0.00-1.90)). The direct role of the sow in the transmission of Salmonella to her offspring could not be demonstrated in the present study. Introduction Pork is a major source for human salmonellosis. A lot of research has been focused on the routes of infection of Salmonella in finishing pigs, and the environment is believed to play an important role in the infection of pigs. Salmonella shedding can also be detected in sows, and the sow might play a prominent role in the direct transmission of Salmonella to her offspring. The aim of the present study was to investigate the relationship between Salmonella occurrence in sows and in their offspring. Materials and Methods • Herds: • 3 Belgian farrow-to-finish herds, subclinically Salmonella infected • 1 group per herd of 34, 40 and 32 sows resp. – same expected farrowing date • 3 piglets per sow • Sows: • Faecal samples: late gestation - lactation • Blood samples: late gestation - lactation • Faecal samples / rectal swabs: qualitative Salmonella isolation • Blood samples: indirect mix-ELISA (Idexx Inc.)  Salmonella antibodies • Relative risk ratios (RR) • Multinomial parametric bootstrapping (@risk 4.5)  exact 95% C.I. • Piglets: • Rectal swabs: • day before and 7 days after weaning • halfway nursery period • day before moving to growing unit • Blood samples: • day before weaning • halfway nusery period • day before moving to growing unit Results and Discussion • Sow seropositive during lactation  significant lower risk for pigs to excrete Salmonella during nusery period (*) • Sow excreting Salmonella during late gestation or lactation  no higher risk for pigs excreting Salmonella during nursery period • Similar results in Beloeil et al. (2003); Kranker et al. (2003) • Maternal antibodies may protect pigs during the first weeks of life • Salmonella excretion during nursery period probably caused by horizontal transmission, triggered by weaning stress Conclusion The role of the sow in the direct transmission of Salmonella from the sows to their offspring could not be demonstrated in the present study. Further research analysing genetic similarities between Salmonella isolates of sows and piglets is going on. Cited references can be obtained from the first author.