Selecting animals with the ability to resist and tolerate interal parasite infections is one of the best long-term strategy for managing internal parasite problems in small ruminants. Parasite resistance (usually quantified by fecal egg counts) is a moderately heritable trait and there is considerable within and between breed variability. Parasite resilience is less heritable, but is more easily estimated on the farm, using the FAMACHA© system and Five Point Check©. There are genetic correlations between fecal egg counts and FAMACHA© scores.


Blueprint for Selecting Parasite Resistant Sheep: A Shepherd's Perspective. Kathy Bielek, Misty Oaks Farm, Wooster, Ohio [Timely Topic, January 2014].

Breed type and resistance: building a parasite-resistant meat goat herd at North Carolina A&T State University. Niki Whitley and Sara Beth Routh, North Carolina A&T State University. [Timely Topic, May 2013].

Building internal parasite resistance in small ruminants: new ATTRA publication focuses on animal selection; Linda Coffey, National Center for Appropriate Technology/Sustainable Agriculture Information Network [Timely Topic, October 2012].

How can artificial insemination (AI) further parasite resistance in sheep? Joan Burke, Stephan Wildeus, Roxanne Newton, and Kathy Bielek [Timely Topic, February 2014].

Impact of selection and breed on resistance. Ken Andries, Kentucky State University [Timely Topic, November 2017]

Resistance: it's a gene frequency thing; Will Getz, Fort Valley State University [Timely Topic, January 2013].

Selection for Parasite Resistance; Joan Burke, Dale Bumpers Small Farm Research Center, USDA-ARS, Booneville, Arkansas [Timely Topic, October 2017].


Stop Selecting Sissy Sheep (and Goats)! Dr. Gareth Bath, University of Pretoria, South Africa [Timely Topic, July 2016]

Conference Proceedings

Genetics of Parasite Resistance in Small Ruminants; David Riley and Lauretta Ngere, Texas A&M University; 10th Anniversary Conference of the American Consortium for Small Ruminant Parasite Control, Fort Valley, Georgia [May 2013].


Practical Breeding for Sheep Resistance and Resilience to Haemonchus Contortus: Trial to Select Haemonchus Contortus Resistant Sheep Unders Summer Rainfall Field Conditions. W4: What Works With Worms Congress, Pretoria, South Africa [2015].

External Links

Genetics of resistance to Haemonchus contortus infections in sheep; H.B. Vanimisetti; M.S. Thesis; Virginia Tech [2003].

Strategies for Genetic Improvement of Parasite Resistance in Sheep. David R. Notter, Virginia Tech.


Fact Sheets

Best Management Practices for Controlling Internal Parasites in Small Ruminants: Genetic Selection: Using Crossbreeding and Estimated Breeding Values. Scott Bowdridge and Andrew Weaver, West Virginia University [March 2019].

Tools for managing internal parasites in small ruminants: animal selection; Linda Coffey; National Center for Appropriate Technology/The National Sustainable Agriculture Information Service (ATTRA) [May 2012].


The use of sheep breeds resistant to internal parasites; J.E. Correa; Alabama Cooperative Extension System [2012].

Journal Articles
Meeting Abstracts

Are Dorper Crossbred Ewes As Tolerant to Intestinal Parasites As St. Croix Or Katahdin Ewes in the Southeastern United States?; J. Burke; Southern Section of the American Society of Animal Science [February 2002].

Are Dorper Crossbred Weaned Lambs As Tolerant to Intestinal Parasites As St. Croix Or Katahdin Lambs in the Southeastern United States?; J. Burke; Southern Section of the American Society of Animal Science [February 2002].

Pasture-raised Katahdin and Katahdin crossbred lambs: growth and parasite resistance; N. Whitley, D. Jackson, D. Cazac, J. Miller, J. Burke, and R. Subburathinam; Southern Section of the American Society of Animal Science.