THE RESPONSE OF BREEDING DOES TO NEMATODIASIS - SEGREGATION INTO RESPONDERS AND NONRESPONDERS

Responder and non-responder does were identified from a hock of 95 Sco ttish Cashmere 26-year-old does exposed to natural nematode infection over a 12-month period. Every 5 weeks, the does were faecal sampled fo r worm-egg counts prior to anthelmintic treatment. Responsive and non- responsive individuals were identified on the basis of their cumulativ e faecal egg count (FEC) rankings: the 8 lowest and 8 highest rankings were deemed to be responders and non-responders, respectively. Retros pective analysis showed that the mean egg count of the 8 responders wa s significantly lower than that of the 8 non-responders. The selected responders and non-responders were subsequently housed together with 8 randomly selected does from a control line, and given a mixed trickle challenge with Teladorsagia circumcincta and Trichostrongylus vitrinu s larvae (L3). Mean responder FEC was significantly lower following ar tificial infection than that of non-responder and unselected does. Per ipheral eosinophilia was significantly greater in responders in the fi rst 3 weeks of this infection. On day 60, the infection was terminated with anthelmintic and 7 days later the goats were given a single chal lenge of 50000 T. circumcincta L3. The mean responder worm burden was lower, and exhibited greater evidence of retardation of worm developme nt, than those of non-responder and unselected does. Responders had si gnificantly more mast cells and globule leukocytes post-challenge than did the other 2 groups. These results suggest that under the conditio ns encountered in this experiment, it is possible to segregate goats i nto responders and non-responders using simple parasitological criteri a, as individual responsiveness is a relatively repeatable phenomenon. Copyright (C) 1996 Australian Society for Parasitology. Published by Elsevier Science Ltd.