Genetic Disorders
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Equine CA or Cerebellar Abiotrophy, found almost solely in the Arabian horse bloodlines, is a neurological, genetic condition. Most foals appear normal and show no sign of cerebellar abiotrophy at birth but noticeable symptoms usually appear around four months of age. There are some cases where the first symptoms of cerebellar abiotrophy appeared in foals only a few days old or horses over a year.Cerebellar abiotrophy develops when the neurons recognized as Purkinje cells, located in a region of the brain called the cerebellum, start to die off shortly after birth. It affects a horse's coordination and balance under six months of age but because of the gradual onset of CA symptoms, caretakers or owners often do not notice any physical problems in affected horses until they are much older. A horse without Purkinje cells has no sense of distance and space. [...]
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Club foot is a lack of the attachment of the coffin bone in the hoof that results in varying degrees of malformation of the hoof as well as the stride of the affected horse. Club foot is almost always on one of the front feet, but very rarely on both. About a fifth of the time club foot may be seen on a hind foot, but typically these cases are much less severe.The coffin bone in the horse's hoof is responsible for giving the exterior hoof its uniform shape, as well as allowing the horse to carry its weight normally distributed throughout movement. The coffin bone is actually in three separate segments, and club foot is noted when the lowest segment, or third phalange, is twisted and out of proper positioning. [...]
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Although congenital hepatic fibrosis is more commonly seen in other species of mammals including humans, it is occasionally seen in one breed of horses, and that is the Swiss Freiberger horse. In research tests, all of the reported cases of congenital hepatic fibrosis within the breed can be directly linked back to offspring and decedents of one stallion named Wigar, thereby confirming that the condition is hereditary. Since the condition does not occur in every foal born in the line, researches have determined that it is a recessive autosomal gene that causes the condition.Congenital hepatic fibrosis is present at birth and results in a thickening and altering of the tissues of the liver. Typically in most affected horses the condition is progressive, fatal and non-treatable with the liver enlarging significantly and large cysts developing throughout the organ. Since the liver is responsible for filtering and detoxifying the blood, when a malfunction in the liver occurs the results are very serious and usually fatal. [...]
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Cow hock is a term used to describe a particular formation or conformation of the hindquarters of a horse. The hock is the joint that is between the cannon bone and the gaskin on the hind leg, it is the point at which the leg bends towards the back before it drops straight down to the fetlock. The hock is roughly equivalent to a human elbow in that it bends forward rather than backwards like our knees do.The term cow hock simply means that the horse's hocks turn in towards each other rather than staying parallel. If you look at a cow you will notice that their hocks turn in, hence the name. Many breeders prefer a horse to be very slightly cow hocked, especially in gaited breeds where it adds a somewhat rolling movement to the hindquarters. Most horses will have a slight turning in at the point of the hock, which will cause no soundness problems nor will it affect the horse's performance in any way. [...]
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Cryptorchidism occurs when one or both of the testicles in a colt do not descend into the scrotum. This condition can occur in the male of any species, but it is often noted in specific lines of horses, so it is likely to have a genetic or inherited component. When a colt's testicle or testicles do not descend the colts is called a ridgling or rig, or may also be known as a high flanker if the testicle is located just above the scrotum under the skin.In all male fetuses the testicles are first developed in the abdominal cavity, then at about the second week of development they move down through the inguinal canal, through two sets of inguinal rings, into the scrotum. The rings are muscular areas that help to move the testicles down into the scrotum. In some male fetuses, through hormonal, mechanical and developmental reasons either one or both of the testicles do not move into the correct location. [...]
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Just like any type of mammal, the horse depends on the spine and skeleton to support the body, and the spinal chord and the brain to send impulses through the skeleton and muscles to move. In conditions that are known as degenerative disorders there are either toxins, injuries, infections, genetic conditions or other forms of diseases that cause the natural functioning of the skeleton or nervous systems to degenerate or break down over time. Once these conditions are present, unless noticed and treated very early on there is likely to be permanent and non-reversable damage that will affect the horse throughout his or her life, even if the condition is managed. [...]
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Many people incorrectly think that Miniature Horses and the Falabella breed are actually dwarf horses, which is false. Miniature horses and Falabellas are bred to be small and through selective breeding have developed into their own breeds that breed true to small, usually well-conformed horses. However, it is true that dwarf horses have been used in the development of the Miniature Horses bred by disreputable breeders resulting in a greater likelihood of dwarf offspring from Miniature Horses. This short cut to developing the smallest possible Miniature Horses has had disastrous results. Falabella horses, only being bred by one family, have had fewer problems with dwarfism as the breeding herd was comprehensively managed. Full sized or "normal sized" horses of any breed will very rarely produce a dwarf offspring, but this is extremely uncommon. Some pony breeds, especially in remote areas of the world where the breeds have been very isolated and have inbred continually, dwarfism is a serious concern to the continuation of the breed. [...]
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Dyscoria is a distortion or irregular development of the pupil of the eye that leads to vision problems as the pupil may not dilate and expand correctly in changing light environments. In horses dyscoria is most commonly noted in breeds that are part of the gaited horses bred in the Rocky Mountain areas of the United States. These breeds include the Rocky Mountain Pleasure Horse, Kentucky Mountain and crosses between these breeds. This condition can also be found in dogs and humans.Most horses with dyscoria also have an eye condition known as ASD or anterior segment dysgenesis. This condition causes an irregular formation of the front parts of the eye that is genetically linked but often not serious. It is not progressive and does not become more pronounced as the horse matures, in fact many horses have such mild symptoms of the condition that it is not known unless an ophthalmologic examination is completed by a vet. Diagnosis of dyscoria is done by applying drops of mydriatic drug that causes normal pupils to dilate. The pupil with dyscoria will not dilate normally and will confirm diagnosis of the condition. [...]
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Most commonly associated with Quarter horse bloodlines, EPSM or Equine Polysaccharide Storage Myopathy is a muscle condition or disease. There are documented occurrences of EPSM in other horses such as American Paint horses, Warm bloods, draft horses, quarter horse crosses, and draft crosses. Evidence shows that in Quarter horses, EPSM is a inheritable disease, but this remains unproven in many other breeds. A horse with Equine Polysaccharide Storage Myopathy has an excessive glycogen buildup or storage in the skeletal muscles due to improper digestion of sugars, starches and carbohydrates found in cereal grains such as barley, corn, and oats.Often, there are very few or very subtle symptoms in the early stages and because of the recent discovery of EPSM, it is often not considered or diagnosed until fairly advanced. [...]
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As with many of the hardest to eradicate genetic conditions Fell Pony Syndrome is linked to an autosomal recessive gene. This means that the condition will only occur if both the dam and the sire have the gene but are only carrying one, not two copies. When the two mate, each contributes one half of the double gene needed, and if both contribute the recessive gene for the syndrome the result is a foal that will only live a few short weeks before dying.Autosomal means that there is one, two-part gene that is responsible for the condition. The foal will inherit one part of the gene from the mother and one part from the father to make the complete gene pair. Since foals with the condition will die and not reproduce, only carriers, adults that have one Fell Pony Syndrome gene and one normal gene, or clear, adults with two normal genes, will continue on in the population. Since horses with only one gene have no visible symptoms of carrying the gene, they can only be detected through careful monitoring and recording of breedings that produce either healthy or unhealthy foals. [...]
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Lavender foal syndrome or LFS is a newly classified genetic condition that exists in the Arabian horse breed. It is caused by an autosomal recessive gene, which means that it is directly inherited from each of the parents. Both the sire and dam must have the recessive gene for LFS and must pass it to the foal in order for the foal to have the defect. A horse, either male or female, that has only one copy of the gene for LFS will not exhibit any signs or problems throughout their life, it will only be their foal, if they are crossed with another LFS recessive horse that will have the risk of being born with the syndrome.The most telling diagnosis of LFS is the unique color of the foal. He or she will be born with a lavender, silver or pinkish tinge to the coat that is different from a gray or roan coloration, it is very abnormal in color. The eyes may also be somewhat bluish to gray in color, but this is often not as noticeable. The mare will usually have troubles during the delivery of the foal and the foal will be unable to stand or move his or her legs. [...]
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As with any animal the horse's liver plays a key role in detoxifying the blood, regulating parts of the metabolic process, as well as storage of nutrients and synthesis of essential chemicals and proteins in the body. The liver is also very important in producing bile, which is necessary for proper digestion.Liver diseases and disorders can occur due to injury, infections, disease, genetic conditions or even toxicity. Depending on the decrease in functioning of the liver the clinical signs of liver problems can range from a jaundiced or yellow appearance to the whites of the eyes to severe causes resulting in rapid death. In mild to moderate cases there will also be colic or digestive problems, swelling of the abdominal area and weight loss, and even central nervous system problems such as staggering, lack of coordination and muscle weakness due to a condition known as hepatic encephalopathy. Depending on the type of onset of the condition these symptoms may be very sudden or may develop slowly over time. [...]
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OAAM is actually the abbreviation for the congenital condition known as Occipital Atlanto-Axial Malformation that occurs almost exclusively in Arabian horses. This condition results in a fusing of the spinal vertebrae in the neck and where the neck and skull join. The results of this lethal condition may initially be mild to debilitating and severe as the foal will have limited movement of the neck throughout its short life. In severe cases paralysis and extreme lack of coordination will also be noted as the foal tries to move.OAAM can be diagnosed when the foal is less than one month old although in some cases it can be weeks before it is identified and diagnosed. In early diagnosed cases it is often very severe as the foal is unable to position his or her head correctly to nurse. The spine has fused so tightly at the base of the skull that they are not able to extend the head into the correct position to access the mare. In addition the foal may not be able to stand or to move once he or she is in the standing position. OAAM will cause the gross motor muscles or the large muscles of the body to lack control resulting in poor if any coordination. [...]
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There are many different types of genetic, infectious, viral and even toxicity issues that can result in permanent or temporary paralysis of horses. Since there are so many possible triggers to a horse's inability to move it is critical to try to decide what has caused the condition before treatment is started. Keeping good records of feeds, pastures, vaccinations as well as contact with other horses or any changes in exercise or behavior prior to the paralysis is essential to help the vet in knowing what the most likely causes are.Paralysis in horses can affect one leg, both front or both back legs or the whole body. Depending on which limbs are affected the paralysis may be severely debilitating or it may be manageable. Temporary paralysis of one back leg may not be a paralysis at all, rather it may be a condition known as locked stifle where a ligament has simply caught on the stifle, preventing the horse from bending the leg. This type of condition is usually corrected by massaging of the stifle and manipulation of the limb to correct the lock. [...]
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Brittle hoof is one of the many horse conditions that both explains as well as labels a health problem. Brittle hoof is exactly what you would think, a condition where the hoof itself, including the horn and the hoof wall or exterior, becomes dry and cracks easily, leading to lameness as well as the chance that fungus and bacteria can get into the hoof.Brittle hoof is common in some breeds, leading researchers to believe that there is a hereditary component to the condition. Breeds that are more prone to brittle hoof include Welsh Ponies and New Forest Ponies, but almost any other type of chunky horse or pony, often described as cobby, can have the condition in their line. Horses that are raised in very wet or soft and moist pastures or areas that are then moved to dry, sandy or stabled conditions with straw or pellets for bedding may also develop the condition, due to the change in the surface that is in contact with the hoof. [...]
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Genetic Disorders
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