A number of laboratories have reported that IL-25 is induced by infection with, and required for immunity to, the nematode Nippostrongylus brasiliensis, a rat parasite that briefly infects immune-competent mice (Fallon et al., 2006; Fort et al., 2001; Hurst et al., 2002; Zhao et al., 2010), as well as the nematodes Heligmosomoides polygyrus (Pei et al., 2016), Trichuris muris (Owyang et al., 2006) and Trichinella spiralis (Angkasekwinai et al., 2013). Here, IL25 is linked to infection.