Lethal White Overo Syndrome
What is LWOS?
The foals are born after an 11 month gestation and look to be a normal foal. They are all white, with blue eyes, but internally they are non functioning. Most foals will die within 72 hours. They don't develop a functioning intestinal system. The Meconium (first stool) ends up impacted high in intestines and will not appear. They will show signs of colic (stomach ache) and will need to be euthanized. Necropsies show that they have a pale, underdeveloped colon, underdeveloped digestive system, internal obstructions, and lack of nerves that allow the intestines to move the material through the intestines.
LWO effects two physical traits: Pigment and Enteric nerve cells. This suggests that early in the syndrome it was related to an important embryonic tissue (neural crest). Stem cells --> go to nerve cells, and melanocytes --> pigments.
The mutation is in the middle of the endothelia receptor type B (EDNRB) gene when it is homozygous lle ll8 lys (OO). Carriers of the gene Frame Overo's are (nO). It is a TC>AG mutation that changes Isoleucine --> Lysine of the EDNRB protein.
This is a problem because there is no treatment for these horses. Surgery to bypass the intestinal damage was never successful due to the extensive nature of the lesions. There are a lot of myths as to what horses carry the gene. People don't tend to know a whole lot about this disorder unless they are a huge breeder. To the backyard horse owner who wants a foal, most of the time they dont know and they may breed to the wrong stud and end up with a non save able foal. It is also a problem as it is a big money loss. To the people who spend the money to breed to the stud, feed the mare while in gestation and then the vet bills the foal will have.
Genotypes of LWO
Phenotypes of LWO
This is a horse that does not carry the LWO gene.
This horse carries one of the genes.
This is a Lethal White Foal, that has both of the LWO genes.
My Opinion on Eradication
- Santsch, Elizabeth. "Overo Lethal White Syndrome." The Horse. The Horse, 1 June 2001. Web. 23 Apr 2013. <http://www.thehorse.com/(F(M8dwSybN626amw5f0dLFuG9-UfhjONST4HUDeB-oDFPlRzZN8i_XP8yqqb6zW1lOCzg2XdyCqRIsGM9uN0nbfY092i2d1dQhreJX4sAzupw5TeKpX1OsMr0oiGZqy3OxPu_iLE1Y7KSIvF569Ky8vLBfLiSMn3nQpfB0j1o3djXf3NJqa1h9uIvNNN7U2X6BiPfA9A2))/articles/12685/overo-lethal-white-syndrome>.
- Santschi, Elizabeth. "Overo Lethal White Syndrome in the Horse." American Association of Equine Practitioners. AAEP, 16 Jun 2002. Web. 23 Apr 2013. <www.aaep.org/health_articles_view.php?id=55>.
- "LWO - Lethal White Overo Testing." Animal Genetics. Animal Genetics, n.d. Web. 23 Apr 2013. <www.animalgenetics.us/LWO.htm>.
- Bowditch, Karen. "Overo Lethal White Syndrome in the Horse." Equine Exchange. University of Saskatchewan, n.d. Web. 23 Apr 2013. <http://equineexchange.net/FINALThesis.pdf>.
- Walker, Dawn. "Lethal Whites - A Light at the End of the Tunnel." American Paint Horse Association. APHA, n.d. Web. 23 Apr 2013. <http://my.apha.com/breed/geneticsarticles/lethal-whites-1>.
- "Overo Lethal White Syndrome." College of Veterinary Medicine. Kansas State University, 13 Feb 2008. Web. 23 Apr 2013. <http://www.vet.k-state.edu/depts/vhc/equine/medicine/overo.htm>.
- Dvrotsus, Paul, Elizabeth Santschi, and James Mickelson. "The Impact of the Mutation Causing Overo Lethal White Syndrome on White Patterning in Horses." IVIS. IVIS, n.d. Web. 23 Apr 2013.
- "Overo Lethal White Syndrome." Bringing Light to HYPP - Equine Genetics. N.p., n.d. Web. 23 Apr 2013. <http://www.bringinglighttohypp.org/learn-about-owls/81-overo-lethal-white-syndrome>.