Migration of the Infective larvae of Sheep Gastrointestinal Nematodes

Abstract

The migration of infective larvae of nematodes of the genera Haemonchus, Ostertagia, Trichostrongylus and Chabertia on herbage in the soil was studied under laboratory conditions on three artificially seeded grass plots with different methods of irrigation. The capacity for vertical migration was found to be the highest, i.e. up to 27 cm, in infective larvae of Trichostrongylus spp. Most of the infective larvae of this nematode were found in the herbage 6-15 cm above the soil surface. The rate of vertical migration is proportional to the moisture of the herbage. During 3 hours of watering the herbage, infective larvae were found 12-15 cm above the soil surface, whereas within 4 hours of dessication of the herbage the larvae were concentrated maximally up to 4 cm from the soil surface. Infective larvae of H. contortus, Trichostrongylus spp. and Chabertia ovina migrated horizontally to a maximal distance of 21 cm from the middle of the faeces sample established on grass irrigated twice a day. Infective larvae of the above nematode species occurred only sporadically in soil in the depth of 2 cm; only in one case were infective larvae of Ostertagia spp. found in a depth of 7 cm.