Experimental cross-infections of Haemonchus placei (Place, 1893) in sheep and cattle

To examine effects on biology and morphology, Haemonchus placei infections were propagated in cattle or sheep and infective larvae were introduced int o the same or opposite host. Ovine source larvae had a geometric mean (GM) prepatent period of 26.5 days regardless of host species, compared to 30.6 days for bovine source larvae regardless of host species. Similarly, ovine source H. placei had a higher GM percentage establishment versus bovine sou rce larvae (9.6% versus 3.4%) regardless of host species. The patent daily egg count for ovine source versus bovine source H. placei was 109.1 versus 50.0 FEC regardless of host species. Mean spicule length for ovine source H . placei was 492.5 mum while bovine source measured 496.5 mum Mean female t ail length for ovine source H. placei was 586.5 and 589.5 mum for bovine so urce H. placei. Using synlophe morphology, all worms that were measured wer e identified as H. placei. Sixty-three percent of females examined for vulv ar flap morphology had knob-like vulvar flaps while the remaining 37% had l inguiform vulvar flaps. (C) 2001 Elsevier Science B.V. All rights reserved.