Cryopreservation of human hookworms.

First-stage larvae (L1) of the human hookworms Ancylostoma duodenale and Necator americanus were frozen over liquid nitrogen after a 1-hr incubation in a cryoprotectant (10% DMSO and 10% dextran). Thawed larvae developed to the infective third stage (L3) on agar plates. In the case of A. duodenale, the larvae were infective to dogs. The infectivity of N. americanus L3 was not tested.