Porcine proliferative enteropathy caused by Lawsonia intracellularis

Abstract

Porcine Proliferative enteropathy (PE or ileitis) is an infectious enteric disease caused by the intracellular pathogen Lawsonia intracellularis (LI). PE is endemic in many countries and causes severe economic losses in swine production system worldwide due to reduction of daily weight gain, reduction of feed conversion ratio and due to increase of mortality and swine waste. In Europe, the prevalence of infected farms and infected animals is more than 90% and 40%, respectively. In PE, intestinal mucosa is thickened by uncontrolled proliferation of intestinal crypt cells while secretory cells and absorbent cells are decreased in number because LI prevents their maturation. Diarrhea is the consequence, due to reduced absorption and loss of amino acid and protein in intestinal lumen. Clinical forms are divided into acute (proliferative hemorrhagic enteropathy – PHE) and chronic form (porcine intestinal adenomatosis – PIA). Acute form affects animals from 4 to 12 weeks of age and is characterized by high mortality (>50%) and hemorrhagic diarrhea; chronic form affects swine of 6-20 weeks of age and is characterized by pasty diarrhea. Based on morphological findings, two other forms are reported: necrotic enteritis (NE) and regional ileitis (RI): the first is a chronic form complicated by secondary infection that result in coagulative necrosis of intestinal epithelium; healing of necrotic enteritis lesions results in both thickening of muscular layer of intestinal wall and granulation tissue deposition, both of which are typical findings of RI. Indirect diagnosis (e.g. ELISA) assess the exposure to L. intracellularis while direct diagnosis (PCR, qPCR, IHC) assess the current infection; effective diagnosis is obtained comparing results of quantification of microorganism/g of feces and the detection of L. intracellularis within intestinal lesion. Prophylaxis and control of proliferative enteropathy are based on biosecurity measures combined with strict washing and disinfection measures to reduce environmental contamination. Proper nutrition management helps to ensure the balance of intestinal microflora by the use of highly digestible protein, by correct intake of fiber fraction and with probiotic and prebiotic supplements. To limit subclinical forms of disease, vaccination should replace antibiotic treatments which instead should be reserved only for symptomatic groups of pig.