C. perfringens (CP) is the causative agent of many enteric diseases in both animals and humans, including necrotic enteritis (NE) in broilers, a disease characterized by necrosis and inflammation of the small intestine. In addition to NetB toxin, other virulence factors essential for NE disease development have been identified, although their function remains unknown. This project focusses on the early stages of NE pathogenesis with great interest in CP colonization. The expression of two virulence genes, encoding putative chitinases, is upregulated during the first stages of the pathogenesis. In WP1, the importance of these enzymes during colonization and infection will be assessed using in vivo models. Since chitin is not present in the broiler intestine, these chitinases have to carry out an alternative function. We hypothesize that intestinal mucus layer is key in facilitating CP colonization. The mucus-altering potential of chitinases will be assessed in WP2, together with its impact on CP proliferation and binding. Furthermore, we hypothesize that the parasite Eimeria, a predisposing factor to NE, is able to induce mucus secretion or alter mucus composition. This mucus-altering potential and its impact on CP colonization will be assessed in WP3. In summary, a thorough knowledge of the early stages of NE pathogenesis, with regard to the impact of both CP and Eimeria spp. on the mucus layer, is key in better understanding the disease, eventually guiding novel research.