In E. tenella infection, an increase in intestinal permeability at day 5 post-infection (pi) associated with an increase in CLDN1 and claudin-2 (CLDN2) and a decrease in occludin (OCLN), E-cadherin and tight junction protein-1 (Pham et al., 2021), reflects an alteration in the integrity of the intestinal barrier, potentially favoring secondary infections by opportunistic pathogens. The gene discussed is CLDN2; the disease is infection.