Monitoring of Lawsonia intracellularis in breeding herd gilts.

In modern pig production, proliferative enteropathy is a common cause of diarrhoea and poor growth in young animals. This study aimed to determine the possible spread of Lawsonia intracellularis through the sale of replacement gilts and the possibility to protect the herds by adequate biosecurity measures. This was achieved by repeated sampling of 50 gilts in an infected multiplying herd, from the last day in the farrowing pen and until sale. Further, 60 gilts sold from this herd were tested during their stay in quarantine in a recipient herd. To confirm freedom from infection, 100 growing pigs in the recipient herd were also tested. Individual faecal (n=748) and blood (n=728) samples were analysed by PCR and ELISA, respectively. Transmission of L. intracellularis from the sows to their offspring was not demonstrated. However, the possible transmission between herds by replacement gilts was demonstrated. Peak shedding occurred at 12 and 15 weeks of age, and single animals were also PCR-positive at 24-36 weeks of age in the multiplying herd and in the quarantine in the recipient herd. Further, the possible occurrence of chronically infected carrier animals was suggested. Although L. intracellularis is widely spread, it appears possible to avoid the transmission between herds by employing adequate biosecurity measures. Thus, it would be advisable to establish herd profiles in breeding herds to avoid the selling of infected animals as well as to establish the health status of the recipient herd. Further, the health status of the recipient herds should be known. Copyright 2009 Elsevier B.V. All rights reserved.