Lawsonia intracellularis is the bacterium responsible for the condition known as Equine Proliferative Enteropathy (EPE) which affects weanlings and yearlings primarily. As the name suggests, this disease causes a thickening of the intestine resulting in protein loss through the gut. Affected animals may show signs of dullness, colic, diarrhoea, weight loss and filling of the lower legs. This bacterium cannot be cultured in the laboratory as it only grows inside living cells, therefore, PCR testing is required to detect the DNA of the organism in faeces.