While wild-type BALB/c mice accordingly cleared parasites within 6–9 days of infection, parasite presence was prolonged in the small intestine of MIF-deficient (Mif−/−) animals with higher egg outputs (Fig. 1a) and a failure to promptly expel either of two strains of N. brasiliensis, a mouse-adapted strain, passaged in mice (Fig. 1b), or the conventional rat-passaged strain (Fig. 1c), respectively; indeed a small number of adult worms were still present in Mif−/− mice 12 days post-infection (data not shown). Here, MIF is linked to infection.