Submitted to: World Association for the Advancement of Veterinary Parasitologists
Publication Type: Abstract Only
Publication Acceptance Date: 1/10/1999
Publication Date: N/A
Citation: Gasbarre, L.C., Leighton, E.A. 1999. Genetic resistance to gastrointestinal nematodes of cattle [abstract]. World Association for the Advancement of Veterinary Parasitologists.
Technical Abstract: Gastrointestinal nematodes remain a serious constraint on the efficient raising of cattle throughout the world. Although there are several safe and efficacious anthelmintics in widespread use, changing environmental and consumer concerns coupled with the potential for anthelmintic resistance requires that adjuncts to current control procedures be developed. One means to supplement current control programs is to use hos genetics to reduce parasite transmission, thus requiring less intensive anthelmintic use. Cattle identical across their major histocompatibility complex were secondarily bred for enhanced or diminished resistance to GI nematodes. Offspring were challenged by natural exposure over a 4 month period to pastures containing Ostertgia ostertagi, Cooperia oncophora, and Nematodirus helvetianus. Calves were extensively monitored both immunologically and parasitologically throughout the test period, and selected calves were killed to accurately asess parasite burdens. Immunit to the parasites can be manifested either as reduced numbers of worms or as reduced fecundity of the females (heritibility - 0.3). Bulls with increased risk of producing susceptible (non-responder) calves can be identified. Fecal EPG are a poor indicator of Ostertagia numbers, and in calves serum pepsinogen levels are more accurate. Genetic resistance in cattle functions differently than that reported in sheep and likely involves different immune effector mechanisms, due to the dominance of Ostertagia in this parasite-host system. Host genetics can be used to substantially reduce transmission of GI nematodes in cattle.