It is well documented that susceptibility to worm infection is largely dictated by the host immune system response against parasitic infection; CD4+ T helper cell 2 (Th2) responses mount a targeted immune response which leads to rapid worm expulsion, whereas if the host mounts a CD4+ T helper cell 1 response against whipworm infection, the host experiences chronic infections with low worm burdens (Else et al., 1992). The gene discussed is CD4; the disease is trichuriasis.