Genotype-level variation in lifetime breeding success, litter size and survival of sheep in scrapie-affected flocks.
Five different sheep flocks with natural outbreaks of scrapie were examined to determine associations between individual performance (lifetime breeding success, litter size and survival) and scrapie infection or PrP genotype. Despite different breed composition and forces of infection, consistent patterns were found among the flocks. Regardless of the flock, scrapie-infected sheep produced on average 34 % fewer offspring than non-scrapie-infected sheep. The effect of scrapie on lifetime breeding success appears to be a function of lifespan as opposed to fecundity. Analysis of litter size revealed no overall or genotype differences among the five sheep flocks. Survival, however, depends on the individual's scrapie status (infected or not) and its PrP genotype. Susceptible genotypes appear to perform less well in lifetime breeding success and life expectancy even if they are never affected with clinical scrapie. One possible explanation for these results is the effect of pre-clinical scrapie. Additional evidence supporting this hypothesis is discussed.
Chase-Topping
Margo E
ME
Centre for Tropical Veterinary Medicine (CTVM), Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Roslin, Midlothian EH25 9RG, UK.
Kruuk
Loeske E B
LEB
Institute of Cell, Animal and Population Biology, University of Edinburgh, Edinburgh EH9 3JT, UK.|Centre for Tropical Veterinary Medicine (CTVM), Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Roslin, Midlothian EH25 9RG, UK.
Lajous
Daniel
D
Institut National de la Recherche Agronomique, Station d'Amélioration Génétique des Animaux, BP 27, 31326 Castanet-Tolosan Cedex, France.
Touzeau
Suzanne
S
Institut National de la Recherche Agronomique, Unité de Mathématiques et Informatique Appliquées, 78352 Jouy-en-Josas Cedex, France.
Matthews
Louise
L
Centre for Tropical Veterinary Medicine (CTVM), Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Roslin, Midlothian EH25 9RG, UK.
Simm
Geoff
G
Sustainable Livestock Systems Group, Scottish Agricultural College, Bush Estate, Penicuik, Midlothan EH26 0PH, UK.
Foster
James D
JD
Institute for Animal Health, Neuropathogenesis Unit, Ogston Building, West Mains Road, Edinburgh EH9 3JF, UK.
Rupp
Rachel
R
Institut National de la Recherche Agronomique, Station d'Amélioration Génétique des Animaux, BP 27, 31326 Castanet-Tolosan Cedex, France.
Eychenne
Francis
F
Institut National de la Recherche Agronomique, Station d'Amélioration Génétique des Animaux, BP 27, 31326 Castanet-Tolosan Cedex, France.
Hunter
Nora
N
Institute for Animal Health, Neuropathogenesis Unit, Ogston Building, West Mains Road, Edinburgh EH9 3JF, UK.
Elsen
Jean-Michel
JM
Institut National de la Recherche Agronomique, Station d'Amélioration Génétique des Animaux, BP 27, 31326 Castanet-Tolosan Cedex, France.
Woolhouse
Mark E J
MEJ
Centre for Tropical Veterinary Medicine (CTVM), Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Roslin, Midlothian EH25 9RG, UK.
D000818:Animals; D001947:Breeding; D004196:Disease Outbreaks; D005260:Female; D014644:Genetic Variation; D005838:Genotype; D008098:Litter Size; D011328:Prions / Q000235:genetics*; D012608:Scrapie / Q000453:epidemiology / Q000235:genetics / Q000401:mortality; D012757:Sheep Diseases / Q000453:epidemiology / Q000235:genetics / Q000401:mortality; D034561:Sheep, Domestic / Q000378:metabolism / Q000502:physiology*; D015996:Survival Rate
D011328:Prions