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Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 8/5/2013 Publication Date: 11/1/2013 Citation: Leymaster, K.A., Chitko-McKown, C.G., Clawson, M.L., Harhay, G.P., Heaton, M.P. 2013. Effects of TMEM154 haplotypes 1 and 3 on susceptibility to ovine progressive pneumonia virus following natural exposure in sheep. Journal of Animal Science. 91(11):5114-5121. Interpretive Summary: Ovine progressive pneumonia (OPP) is an incurable, slow-acting, wasting disease that affects sheep production in many countries. It is one of the most costly sheep diseases in the United States due to a 20% decrease in production and premature removal of infected sheep from flocks. A gene that affects susceptibility to OPP infection was studied. Sheep with either one or two copies of an unfavorable form of the gene had infection rates of 33% compared to 9% for other sheep. Sheep producers can use DNA information to make their flocks genetically less susceptible to disease. Eradication of the disease will improve health of sheep and increase profits for producers. Technical Abstract: Small ruminant lentiviruses (SRLV) adversely affect production and well-being of sheep and goats throughout much of the world. The SRLVs, including ovine progressive pneumonia virus (OPPV) in North America, cause lifetime infections and management procedures to eradicate or reduce disease prevalence are costly. Variants of ovine transmembrane protein 154 gene (TMEM154) affect susceptibility to OPPV. The primary experimental objective was to estimate additive and dominance effects of TMEM154 haplotypes 1 and 3 on susceptibility to OPPV infection following natural exposure. A group of 187 trial lambs was born and raised by mature, infected ewes to ensure natural exposure to OPPV. Parents of trial lambs were heterozygous for haplotypes 1 and 3, producing lambs with diplotypes 1 1, 1 3, and 3 3. A group of 20 sentinel lambs was born and raised by mature, uninfected ewes that were diplotype 1 1. Sentinel lambs had diplotypes 1 1 and 1 3, being sired by the same set of rams as trial lambs. Trial and sentinel lambs were comingled during the experiment. Lambs were weaned at 60 d of age, bled 1 wk after weaning, and thereafter at intervals of 4 or 5 wk until 9 mo of age when infection status was determined by use of a competitive enzyme-linked immunosorbent assay. Only 1 sentinel lamb became infected. Infection status of trial lambs was analyzed using logistic regression procedures to account for the binary nature of infection status and random effects of sires. Effects of sex, type of birth, type of rearing, age of dam, breed type of dam, and sires were not detected (P > 0.20). Infection status was affected by diplotype of lamb (P = 0.005), with additive (P = 0.002) and dominance (P = 0.052) effects identified. Predicted probabilities of infection for lambs with diplotypes 1 1, 1 3, and 3 3 were 0.094, 0.323, and 0.346, respectively. Confidence intervals for probabilities of infection for diplotypes 1 3 and 3 3 were similar, but distinct from diplotype 1 1. These results are consistent with complete dominance of haplotype 3 relative to haplotype 1. The probability of infection at 9 mo of age averaged 3.56 times greater for lambs with either diplotype 1 3 or 3 3 compared to lambs with diplotype 1 1. Genetic susceptibility to OPPV infection can be reduced by selection to increase the frequency of haplotype 1, resulting in a greater proportion of lambs with diplotype 1 1. |
