Studies on the arrested development of Haemonchus contortus in sheep—I. The induction of arrested development

Blitz N. M. and Gibbs H. C. 1972. Studies on the arrested development of Haemonchus contortus in sheep—I. The induction of arrested development. International Journal for Parasitology, 2: 5–12. Cultures consisting primarily of Haemonchus contortus were established monthly on pasture and under constant conditions for 10 days, and subsequently dosed to worm-free lambs between June and October. Equivalent low levels of arrested development were noted in lambs infected with larvae from these two regimes. In lambs infected with laboratory cultured larvae subsequently aged on pasture during September, and lambs infected naturally at that time, virtually all H. contortus were arrested. This resembles diapause, and is possibly triggered by autumnal environmental conditions acting on the infective larvae.