What is Combined Immunodeficiency Disease?
Combined immunodeficiency disease is an abnormality in the immunity of the cells and the production of antibodies. This disease typically happens in Arabian foals, and is characterized by the thymus being abnormal. The thymus is the organ that is responsible for production of immune cells.
Combined immunodeficiency disease affects the horses by having a lacking number of two types of cells that fight harmful substances and invaders, known as T cells and B cells. The disease is progressive in the foals and is life-threatening.
This inherited disease is only witnessed in Arab horses, either purebred or partly-bred. Unfortunately, this disease is very severe, and many foals succumb to the disease within half a year. There is no treatment.
This recessive disorder requires both the dam and sire to have one or more copies of the gene to pass to the foal. If the foal is born with only one defective copy of the gene, he is considered to be a carrier of the disease.
Combined immunodeficiency disease, also known as SCID or CID, is an untreatable disease that affects the immune system, leaving the horse highly susceptible to many illnesses and infections. This genetic disease occurs in Arabian foals.
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Symptoms of Combined Immunodeficiency Disease in Horses
Symptoms of this disease are the same as many other illnesses, so intense testing and examination are important to rule out other conditions. Symptoms include:
- Increased and high temperature
- Respiratory distress
- Infections and illnesses that last a long time
- Illnesses that become worse over time
Other immune-deficiency diseases can occur in horses. These immune-deficiency diseases can be hereditary, as SCID, or acquired in other ways. Other types of immune deficiency disorders include:
- Immunoglobulin deficiency
- Allergies, such as milk allergies
- Anaphylactic shock
- Sweet Itch
- Immune-mediated hemolytic anemia
- Immune-mediated thrombocytopenia
- Hypersensitivity pneumonitis
Causes of Combined Immunodeficiency Disease in Horses
Arabian horses and horses crossbred with Arabian horses can be affected by this disease. Causes include:
- The SCID (Severe Combined Immunity Disease) gene mutation is present
- The horse is homozygous for SCID
- The cells of the horse have no immunity and are unable to fight infection
Diagnosis of Combined Immunodeficiency Disease in Horses
If your horse is having any of the above symptoms, make an appointment with your veterinarian. Your veterinarian will perform a complete physical examination. He will also ask you about his symptoms, when they began, the severity, and about his health history.
If your horse is an Arabian foal, or a crossbreed, then your veterinarian may choose to perform a DNA test. This will be conducted by a cheek swab or through blood testing. This is the only definitive measure that your veterinarian can do to check for Combined Immunodeficiency Disease. While only two to three percent of Arabian horses have the gene mutation, due to your horse’s symptoms, this test may be performed once your medical professional has ruled out any other disorders.
If your horse is affected, the test will show two copies of the gene and will be homozygous for the disease. If your horse is a carrier, the test will show the normal genes (alleles) and the combined immunodeficiency disease gene in the horse’s DNA. The carrier horse will also be heterozygous for the disease.
Treatment of Combined Immunodeficiency Disease in Horses
Unfortunately, there is no treatment for this disease. Horses generally succumb to the disease within six months or are euthanized with the owner’s consent.
Recovery of Combined Immunodeficiency Disease in Horses
Euthanasia is always very difficult for any horse owner. Many owners choose this option in the final stages or when they see that their loved one is suffering. It is important to purchase from a reputable breeder if you plan on investing in another Arabian foal. Knowing the bloodlines and knowing if the mother and father have been genetically tested (with negative results) will allow your horse and you to enjoy a wonderful and healthy life together.