Cryopreservation of Infective Third-Stage Larvae of Trichostrongylus axei and T. colubriformis

Trichostrongylus axei and T. colubriformis infective third-stage larvae were frozen and stored for varying periods at -170 C: 10 to 80 days for T. axei and 10 to 38 days for T. colubriformis. Thawed, surviving larvae were used to infect rabbits. Survival percentages changed little between worms stored for the period of the test. Larvae surviving freezing, storage, and thawing were as infective as nonfrozen larvae in rabbits. Several benefits could be gained from longterm storage of nematode infective larvae. The considerable expenditure of time, labor, and funds to continually maintain monospecific isolates in culture animals would be reduced and the risk of accidental contamination would be minimized. Moreover, many monospecific isolates with particular genetic characteristics could be set aside for future study. Various accounts concerning the ability of nematodes to survive the effects of subzero temperatures date back as far as Spallanzini (1776). Since then, sufficient evidence from various workers (Weinman and McAllister, 1947; Anderson and Levine, 1968; Muller, 1970) has accumulated to indicate that cryopreservation of nematodes is feasible and could be an important and useful laboratory procedure. Therefore, the following study on cryoCopyright © 2011, The Helminthological Society of Washington OF WASHINGTON, VOLUME 39, NUMBER 1, JANUARY 1972 141 Table 1. Percentages of larvae surviving cryopreservation and numbers of nematode parasites recovered from infected rabbits. Worms recovered from rabbits Larvae T. axci T. colubriformis