Preserving viable infective stages of chicken ascarids under laboratory conditions facilitates the maintenance of characterized nematode strains for research purposes. We investigated the survivability of Ascaridia galli eggs exposed to low temperatures and the cryoprotectant dimethyl sulfoxide (DMSO). Two egg developmental stages (unembryonated or fully embryonated) were stored at 4°C, –20°, or –80°C in sterile water or with 5% and 10% DMSO for 1, 2, 4, or 8 weeks. Egg survival was assessed by morphology following post-storage incubation in 0.1 N H2SO4 at 26°C for unembryonated eggs or with a viability dye exclusion test of hatched larvae for the embryonated eggs. The results revealed that neither DMSO nor the hardy chitinous eggshell protected eggs from freezing damage, and not a single egg survived even for 1 week of storage at –20° or –80°C. DMSO at 10% significantly reduced (P < 0.0001) overall egg survival and embryonation capacity with increasing storage time at 4°C compared to water alone. For both egg developmental stages, egg survival was maintained in 5% DMSO at a rate similar to that in water alone. Unembryonated A. galli eggs survived refrigeration better than embryonated eggs with larval viability declining linearly at almost a double rate in the latter (9.75%/week) compared to the former (5.64 %/week). We conclude that DMSO is unlikely to provide cryoprotection for A. galli eggs and also causes concentration-dependent toxicity with increasing exposure time. Furthermore, survival during refrigeration is better for unembryonated than embryonated eggs.
