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United States Department of Agriculture

Agricultural Research Service

Title: Using Host Genomics to Control Nematode Infections

Authors
item Gasbarre, Louis
item Sonstegard, Tad
item Van Tassell, Curtis
item Araujo, Ricardo - USDA BELTSVILLE

Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 7, 2004
Publication Date: October 1, 2004
Citation: Gasbarre, L.C., Sonstegard, T.S., Van Tassell, C.P., Araujo, R. 2004. Using host genomics to control nematode infections. Veterinary Parasitology 125, pp. 155-161.

Interpretive Summary: Transmission of cattle GI nematodes can be reduced by identification and management of the few individuals responsible for most of the eggs seeding pastures. To identify the genes coding for parasite resistance we developed a closed-pedigree herd of Angus cattle containing 343 parasite-challenged calves derived from 43 sire families. Parasite challenge consisted of a 4-6 month exposure on pastures that harboring the most common nematode pathogens in Northern climates. To characterize the genome of each animal we used 248 microsatellite markers. Measures of resistance to the parasites included: the mean and peak number of parasite eggs passed in the feces, the parasite egg profile, and final serum pepsinogen which measures tissue damage in the stomach. A sophisticated statistical program called Genoprobe was used to calculate probability of allele inheritance for each cell division in the in the herd, was used to determine inheritance probabilities which were then used to identify regions of the genome that contains genes affecting resistance to the parasites. Factors controlled for in the analysis included sex of calf, age of dam at calving, age of calf, calving season, and sire. Genomic regions influencing parasite resistance were identified on bovine chromosomes, 2, 3, 5, 6, 14, and 15 for EPG, and on chromosomes 3, 11, and 18 for serum pepsinogen. We have also developed a 409 gene microarray to identify immune system-related genes showing different levels of expression in resistant or susceptible animals. These data are being combined with current studies involving validation and fine mapping of the genomic regions to identify the genetic basis for GI nematode resistance in cattle.

Technical Abstract: Transmission of cattle GI nematodes can be reduced by identification and management of the few individuals responsible for most of the eggs seeding pastures. To identify the genes coding for parasite resistance we developed a closed-pedigree Angus population containing 343 parasite-challenged calves derived from 43 sire families. Parasite challenge consisted of a 4-6 month exposure on pastures harboring Ostertagia and Cooperia. Genotypying involved 248 microsatellite markers and 432 animals: the parasite-challenged animals, their parents, and historic sires from the extended pedigree. Phenotypic traits analyzed were mean and peak EPG, the EPG profile, and final serum pepsinogen. GenoProb, a program based on multilocus iterative allelic peeling to calculate probability of allele inheritance for each meiosis in the pedigree, was used to determine inheritance probabilities which were then used to identify quantitative trait loci (QTL) on the bovine chromosomes. Models for analysis included sex of calf, age of dam at calving, age of calf, calving season, and sire. In a sire family model, within-sire regression was calculated based on the probability of inheriting 1of the 2 marker alleles from the sire. QTL were identified on bovine chromosomes, 2, 3, 5, 6, 14, and 15 for EPG, and on chromosomes 3, 11, and 18 for serum pepsinogen. We have also developed a 409 gene microarray to identify immune system-related genes showing different levels of expression in resistant or susceptible animals. These data are being combined with current studies involving validation and fine mapping of the QTL to identify the genetic basis for GI nematode resistance in cattle.

Last Modified: 8/1/2014