Cultivation of the third-stage larvae of Necator americanus in vitro

When filariform larvae of Necator americanus, enclosed within the second sheath, were cultured in various semi-defined media, the best larval development was achieved in Waymouth's MB 752/1 with 20% foetal calf serum (FCS). In this medium, most of the filariform larvae cast off the second sheath and developed into third-stage larvae with provisional buccal capsules and some larvae developed further; 26% were fourth stage after 49 days of culture. Of several supplements tested, only FCS supported such development and no further development occurred if the medium was further supplemented with human red blood cells, liver extract, intestinal extract or tryptose phosphate broth. Larval development stopped at or before early third stage in Eagle's Basal Medium, F-12, NCTC 135 and L-15, even when these media were supplemented with FCS.