The prevalence of Lawsonia intracellularis in swine herds in Poland

Proliferate enteropathy (PE) is an enteric disease that occurs primarily in weaning and fattening pigs. Various publications have noted that the percentage of infected herds in agriculturally developed countries is as high as 30-50%. The disease is widespread in swine and results mainly in growth-rate losses and increased feed efficiency. The aim of the study was to perform an epidemiological survey on Polish pig farms in order to discover the prevalence of herds infected with L. intracellularis. Biological material for laboratory investigations was collected from 54 pig farms (36 farrow-to-finish, 8 breeding and 10 fattening herds). A number of pigs in all the farms surveyed showed clinical symptoms characteristic for PE. The size of the herds differed, with the smallest herd having 10 and the biggest 2,540 sows. The number of pigs in fattening farms also varied. The smallest had an annual production of 2500 fatteners and the largest - 23 000 animals. Biosecurity measures were disregarded,: and "all in all out" procedures were not applied. Weaning time differed throughout the farms and varied between 24-42 days. Faecal samples were taken directly from each animal and kept in refrigerated storage for further examinations. The sampled pigs were selected amongst those showing possible signs of the disease (poor growth, diarrhoea). A total of 957 faecal samples were collected to find the genetic material of L. intracellularis. Total DNA was extracted from the faeces which had been taken from the weaned piglets and fatteners having diarrhoea by using the Genomic DNA Prep Plus (R) kit (Helicionus, A&A Biotechnology). Five micro liters of DNA were amplified by one tube nested - PCR technique, using two sets of PCR primers, which consisted of 20 - base pair (bp) oligonucleotides corresponding to 319 bp and 270 bp regions of p78 L. intracellularis sequence. The results indicated that 10 fattening farms were infected with L. intracellularis. Herds in 7 out the 8 breeding farms 7 (87,5%) were susceptible to infection. 23 (63,8%) out of a total of 36 farrow-to-finish farms were found to be positive. Small farms, which counted less then 50 sows, were negative for L. intracellularis. The highest percentage of positive faecal samples (84,2%) was found in fattening farms. An average of 30,8 % of pigs were infected in farrow-to-finish farms. The lowest percentage of infected animals was noted in nucleus herds (19,7%). Adding growth promoters to the feed did not significantly influence the presence of the infections in the farms. No evidence of the acute form of ileitis (Porcine haemorrhage enteropathy - PHE) was found to be present or confirmed in any of the investigated farms. Most PE-infected herds in Poland revealed a chronic form of the disease. An epidemiological study showed that distribution of L. intracellularis infections is widespread within populations of Polish swine herds.