Lavender Foal Syndrome
Encyclopedia
Lavender Foal Syndrome, also called Coat Color Dilution Lethal is a genetic disease that affects newborn foal
s of Arabian horse
bloodlines. Cases reported in peer-reviewed veterinary literature are entirely of foals descended from a number of "Egyptian Arabian" or Egyptian-related bloodline groups. However, in Australia a few breeders of Crabbet-related lines have also had foals affected by LFS. Lavender foal syndrome should be considered in any weak newborn Arabian or part-Arabian foal, particularly if it has some degree of "Egyptian" breeding, if the foal cannot stand, if other signs of neurological problems are present, and especially if they have a light coat coloring.
Research into the genetics of LFS has been conducted at the University of California, Davis
and Cornell University
in the United States, the University of Queensland
in Australia and the University of Pretoria
in South Africa. In November, 2009, Cornell University announced that a DNA
test has been developed to detect carriers of LFS. Simultaneouly, the University of Pretoria also announced that they had developed a DNA
test. Testing is now available at Cornell, Pretoria, Queensland and in New South Wales.
foals because grays are born a dark color and lighten with age. It is also different from roan
, because the hair is of a uniform shade, not of intermingled light and dark hairs.
Foals with LFS are unable to stand, and sometimes cannot even attain sternal recumbency (to roll from their side to lie upright, resting on the sternum, a precursor position to standing). They may lay with their necks arched back, make paddling motions with their legs, and often have seizures. They are usually euthanized within a few days of birth. There is no cure. In some cases, the mare
may also have difficulty foaling, though foaling difficulties are not the cause of the condition.
. When a horse is heterozygous for the gene, it is a carrier, but perfectly healthy and has no symptoms at all. If two carriers are bred together, however, classic Mendelian genetics indicate that there is a 25% chance of any given mating producing a foal that is homozygous for the gene, and hence affected by the disease. It is theorized, though not yet tested, that LFS may also be somehow linked to another genetic disease that affects Egyptian-related Arabians, juvenile epilepsy. This theory has been raised because of a small number of horses who have produced both LFS and epileptic foals.
LFS is one of six genetic diseases known to affect horses of Arabian bloodlines. There are genetic diseases that affect other horse breeds, including different coat dilution lethals, such as lethal white syndrome
. In addition, the color white
in horses, when created by certain alleles of "dominant white" (W) gene, may possibly be fatal if homozygous.
Foal
A foal is an equine, particularly a horse, that is one year old or younger. More specific terms are colt for a male foal and filly for a female foal, but these terms are used until the horse is age three or four. When the foal is nursing from its dam , it may also be called a suckling...
s of Arabian horse
Arabian horse
The Arabian or Arab horse is a breed of horse that originated on the Arabian Peninsula. With a distinctive head shape and high tail carriage, the Arabian is one of the most easily recognizable horse breeds in the world. It is also one of the oldest breeds, with archaeological evidence of horses...
bloodlines. Cases reported in peer-reviewed veterinary literature are entirely of foals descended from a number of "Egyptian Arabian" or Egyptian-related bloodline groups. However, in Australia a few breeders of Crabbet-related lines have also had foals affected by LFS. Lavender foal syndrome should be considered in any weak newborn Arabian or part-Arabian foal, particularly if it has some degree of "Egyptian" breeding, if the foal cannot stand, if other signs of neurological problems are present, and especially if they have a light coat coloring.
History and research
The condition has been recognized since mid- to late- 1950s.Research into the genetics of LFS has been conducted at the University of California, Davis
University of California, Davis
The University of California, Davis is a public teaching and research university established in 1905 and located in Davis, California, USA. Spanning over , the campus is the largest within the University of California system and third largest by enrollment...
and Cornell University
Cornell University
Cornell University is an Ivy League university located in Ithaca, New York, United States. It is a private land-grant university, receiving annual funding from the State of New York for certain educational missions...
in the United States, the University of Queensland
University of Queensland
The University of Queensland, also known as UQ, is a public university located in state of Queensland, Australia. Founded in 1909, it is the oldest and largest university in Queensland and the fifth oldest in the nation...
in Australia and the University of Pretoria
University of Pretoria
The University of Pretoria is a multi campus public research university located in Pretoria, the administrative and de facto capital of South Africa...
in South Africa. In November, 2009, Cornell University announced that a DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
test has been developed to detect carriers of LFS. Simultaneouly, the University of Pretoria also announced that they had developed a DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
test. Testing is now available at Cornell, Pretoria, Queensland and in New South Wales.
Clinical signs
The condition gets its name because most, though not all, affected foals are born with a unique coat color dilution that lightens the tips of the coat hairs, or even the entire hair shaft. The color has variously been described as a silver sheen, a dull lavender, a pale, dull pinkish-gray or pale chestnut. This dilution differs from grayGray (horse)
Gray or grey is a coat color of horses characterized by progressive silvering of the colored hairs of the coat. Most gray horses have black skin and dark eyes; unlike many depigmentation genes, gray does not affect skin or eye color Their adult hair coat is white, dappled, or white intermingled...
foals because grays are born a dark color and lighten with age. It is also different from roan
Roan (horse)
Roan is a horse coat color pattern characterized by an even mixture of colored and white hairs on the body, while the head and "points"—lower legs, mane and tail—are more solid-colored. The roan pattern is dominantly-inherited, and is found in many horse breeds...
, because the hair is of a uniform shade, not of intermingled light and dark hairs.
Foals with LFS are unable to stand, and sometimes cannot even attain sternal recumbency (to roll from their side to lie upright, resting on the sternum, a precursor position to standing). They may lay with their necks arched back, make paddling motions with their legs, and often have seizures. They are usually euthanized within a few days of birth. There is no cure. In some cases, the mare
Mare (horse)
A mare is an adult female horse or other equine.In most cases, a mare is a female horse over the age of three, and a filly is a female horse age three and younger. However, in Thoroughbred horse racing, a mare is defined as a female horse more than four years old; in harness racing a mare is a...
may also have difficulty foaling, though foaling difficulties are not the cause of the condition.
Inheritance
Lavender foal syndrome is most commonly thought to be created by a recessive geneDominance relationship
Dominance in genetics is a relationship between two variant forms of a single gene, in which one allele masks the effect of the other in influencing some trait. In the simplest case, if a gene exists in two allelic forms , three combinations of alleles are possible: AA, AB, and BB...
. When a horse is heterozygous for the gene, it is a carrier, but perfectly healthy and has no symptoms at all. If two carriers are bred together, however, classic Mendelian genetics indicate that there is a 25% chance of any given mating producing a foal that is homozygous for the gene, and hence affected by the disease. It is theorized, though not yet tested, that LFS may also be somehow linked to another genetic disease that affects Egyptian-related Arabians, juvenile epilepsy. This theory has been raised because of a small number of horses who have produced both LFS and epileptic foals.
LFS is one of six genetic diseases known to affect horses of Arabian bloodlines. There are genetic diseases that affect other horse breeds, including different coat dilution lethals, such as lethal white syndrome
Lethal white syndrome
Lethal white syndrome , also called overo lethal white syndrome , lethal white overo , and overo lethal white foal syndrome , is an autosomal genetic disorder most prevalent in the American Paint Horse...
. In addition, the color white
White (horse)
White horses are born white and stay white throughout their life. White horses may have brown, blue, or hazel eyes. "True white" horses, especially those that carry one of the dominant white genes, are rare...
in horses, when created by certain alleles of "dominant white" (W) gene, may possibly be fatal if homozygous.
Additional information
- Goodwin-Camplglio, Lisa. "Genetic Disorders in Arabian Horses" Current Research Projects. 'World Arabian Horse Organization, September 2008.
- Page P, Parker R, Harper C, Guthrie A, Neser J. "Clinical, clinicopathologic, postmortem examination findings and familial history of 3 Arabians with lavender foal syndrome." J Vet Intern Med. 2006 Nov-Dec;20(6):1491-4. Department of Companion Animal Clinical Studies Faculty of Veterinary Science, University of Pretoria, Onderstepoort, South Africa. PMID: 17186871