Arrested development and the histotropic phase of Ascaridia galli in the chicken

Studies on 300 worm-free chickens infected with Ascaridia galli indicated that the histotropic phase is a normal part of the life cycle and that it involves both second- and third-stage larvae. The duration of the histotropic phase was dose-dependent. At low dose rates (50 eggs) it occurred from days 3 to 16 and was terminated abruptly by the third ecdysis. At high dose rates (2000 eggs) it was prolonged until at least day 54, because third-stage larvae became arrested in their development and the third ecdysis was delayed. Arrested development of Ascaridia galli was significantly suppressed following treatment of birds with cyclophosphamide, but expulsion of worms was not prevented. This result suggests the involvement of host antibodies in the induction of the arrested state.