Spider lamb syndrome, also known as spider syndromeHereditary chondrodysplasia ("spider syndrome") in a New Zealand Suffolk lamb of American origin., originally published in New Zealand veterinary journal, Volume 43, p.118-22 (1995); by West, DM; Burbidge, H M; Vermunt, J J; Arthur, D G; archived at the International Sheep Research Centre; retrieved July 19, 2012 and more formally as ovine hereditary chondrodysplasia,Developmental progression of the Spider Lamb Syndrome in Small Ruminant Research, Volume 18, Issue 2, Pages 179-184, October 1995, by A.M. Oberbauer, N.E. East, R. Pool, J.D. Rowe, and R.H. BonDurant is a homozygous recessive disorder affecting the growth of cartilage and bone in sheep. The name derives from the limbs of afflicted animals being thin, elongated, and "spider-like".
It is a semilethal trait,Spider Lamb Syndrome: Introduction at UC Davis School of Veterinary Medicine; retrieved July 19, 2012 which is thought to have been first observed in the 1970s,Spider Lamb Syndrome - 1998 Sheep Day Report: The Test for Spider Lamb Syndrome Gene in Sheep at North Dakota State University; by Bert Moore, Wes Limesand and Paul Berg; publisher 1998; retrieved July 19, 2012 and is most common in sheep of the Suffolk and Hampshire breeds.Spider Lamb Syndrome, at the Merck Veterinary Manual; published 2011; retrieved July 19, 2012 These are both black-faced breeds of sheep; the syndrome has never been detected in white-faced breeds.
The syndrome was an economically significant issue for sheep breeders in the 1980s, but with strict testing and breeding programs it has become less common.
The mutation which causes spider lamb syndrome is found on ovine chromosome 6,Localization of the locus causing Spider Lamb Syndrome to the distal end of ovine Chromosome 6, from Mammalian Genome 10, 35–38 (1999); by N.E. Cockett, T.L. Shay, J.E. Beever, D. Nielsen, J. Albretsen, M. Georges, K. Peterson, A. Stephens, W. Vernon, O. Timofeevskaia, S. South, J. Mork, A. Maciulis, T.D. Bunch; archived at the University of Liège; retrieved July 19, 2012 and involves the inactivation of fibroblast growth factor receptor 3.Enhanced skeletal growth of sheep heterozygous for an inactivated fibroblast growth factor receptor 3, Journal of Animal Science, vol. 84 no. 11 2942-2949; by L. B. Smith, M. R. Dally, R. D. Sainz, K. L. Rodrigue and A. M. Oberbauer It has been compared to dwarfism in beef cattle.
Afflicted animals may be visibly deformed at birth and unable to stand, or seemingly normal for the first 4 to 6 weeks of their lives.
Symptoms Symptoms have been observed on fetal lambs as early as by the completion of the second gestational trimester.Developmental progression of the Spider Lamb Syndrome, by A.M. Oberbauer, N.E. East, R. Pool, J.D. Rowe, and R.H. BonDurant; in Small Ruminant Research; Volume 18, Issue 2, October 1995, Pages 179-184 Under normal production circumstances, the lambs usually do not survive past the neonatal period. For this reason, the disease is considered semi-lethal. The disease typically affects the musculo-skeletal system. The clinical signs can include: skeletal abnormalities, twisted or humped spines, facial defects, bent legs, abnormally long legs, flat ribs, and underdeveloped muscles. Due to these symptoms, lambs cannot stand to nurse.
Spider lamb syndrome is untreatable, and in almost all cases, the lambs must be euthanized.
Causes Spider lamb syndrome is caused by a mutation to the gene for fibroblast growth factor receptor 3 (FGFR3), on ovine chromosome 6. FGFR3 is in the tyrosine kinase receptor family and its function is to restrict the proliferation of cartilage at the growth plates of the long bones: regulating ossification (the conversion of cartilage into bone), limiting skeletal elongation, and thereby ensuring that the limbs are the right length.
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