The effect of genetic factors on the vulval flap of Ostertagia ostertagi.

Michel J. F., Lancaster M. B. &; Hong C. 1976. The effect of genetic factors on the vulval flap of Ostertagia ostertagi. International Journal for Parasitology6: 83–86. Ostertagia ostertagi, selected according to the form of the vulval flap, were implanted into calves and larvae cultured from the faeces. Larvae obtained in this way were administered to groups of susceptible calves and to groups of calves sensitized by previous infection. Examination of worms recovered post mortem showed that the incidence of worms with reduced flaps was smaller among the progeny of worms with fully developed flaps than among the progeny of worms in which the flap was greatly reduced or absent. This difference was, however, much smaller than that between the worms from sensitized and from susceptible calves.