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Auto-Immune Hemolitic Anemia

 

What Is IMHA?

   Auto-immune hemolitic anemia (AIHA) is a life-threatening immune system disorder.  The immune system is designed to attack and kill germs, viruses and other foreign material within the body, but with AIHA, the immune system produces antibodies that attack and kill the body's own red blood cells.  These antibodies are supposed to be a defense against illness and germs which are harmful to the body, but with this disease, the system goes haywire and the antibodies target and attack the animalís own red blood cells.   The destruction of the dog's red blood cells leads to anemia.  As the disease progresses and more red blood cells are destroyed, the body is unable to produce an adequate supply of replacement red blood cells and the dog begins to show signs of disease.  Clinical signs of AIHA are most often gradual and progressive, but some pets may suffer a sudden, acute hemolytic crisis.  Symptoms may include signs of oxygen deprivation, jaundice, fever, pale mucous membranes and heart murmur.

   The normal life span of a circulating red blood cell is about 4 months.  The number of red blood cells is usually maintained at a constant level because new red blood cells are always being made.  New red blood cells usually replace the old red blood cells as they are destroyed and removed from circulation by the white blood cells.  Anemia develops when the level of red blood cells is decreased to a point where the bone marrow is unable to produce an adequate number of new red blood cells to compensate for the ones that are destroyed.

   Red blood cells carry oxygen to tissues throughout the body.  If the body is unable to produce enough new, oxygenated red blood cells to compensate for the decrease in oxygen transport, the body's organs and tissue can suffer serious and irreparable damage.  If the balance of red blood cells isn't corrected in a reasonable amount of time, the animal will not survive. 

   As of this time, the cause(s) of AIHA are largely unknown.  In most instances there is no indication of why the immune system, which is designed to protect the animal, suddenly targets its weapons against the animal itself.  There is some indication that certain breeds may have  a genetic predisposition for AIHA.  Some Cocker and Springer Spaniels, Poodles, Lhasa Apsos, Shih Tzus and Old English Sheepdogs are believed to have this predisposition.  AIHA can appear in any breed however, and is more common in animals 3 to 8 years of age and in females rather than males. 

  There are several non-genetic factors that may play a role in the development of AIHA.  This problem can occur as a symptom of some types of cancer and other underlying autoimmune disorders, such as systemic lupus erythematosis.   Certain bacterial or viral infections may trigger autoimmune reactions.  It is also believed that some drugs (antibiotics, analgesics, etc.) as well as viral antigens found in modified-live vaccines can induce AIHA.    There is some evidence from several new studies that dogs may not need vaccinations every year and that over-vaccination can, in some breeds and instances, contribute to auto-immune disorders.

   AIHA can progress rapidly to a life-threatening situation and can prove fatal even when the dog receives prompt, appropriate treatment.   If you ever believe there is the slightest chance your dog could be suffering from AIHA, you should seek immediate veterinary care as this is the dog's only chance of survival.


SYMPTOMS

  • Pallor of mucous membranes
  • Fever
  • Tiring easily, weakness
  • Lethargy, depression
  • Yellow tinged gums or whites of the eyes
  • Dark or dark yellow urine
  • Enlarged spleen  

Diagnosis

   Your vet may run some or all of the tests below to diagnose or rule out AIHA:

Complete history and medical examination.  He will need information on all medications the dog has received, date of last vaccinations and any available information about the color of urine and stool.
CBC - "Complete blood count".  CBC is a count of the number and types of red blood cells, white blood cells and platelets in a given amount of blood.   CBC is actually a label for a number of tests, rather  than a single test.  (See CBC for detailed information on a complete blood count and a compiled list of "normal" CBC counts.)
Coombs test - Blood test for evidence of immune reaction to the blood.  This blood test confirms an AIHA diagnosis.  Unfortunately this is not an exceedingly accurate test, many AIHA positive dogs will test negative.
Kansas State University College of Veterinary Medicine has developed a more accurate test for dogs suspected of having AIHA.
Serum biochemical profile - Will help identify factors that might cause anemia.
Urinalysis - Another source to identify possible causes of anemia.
Saline agglutination test - Blood test to check clumping together of red blood cells.
Ultrasound examinations, x-rays, blood tests for infectious diseases or other diagnostic procedures  could be necessary for some patients to help rule out other causes of anemia or to help identify triggering condition(s) that contributed to the development of IMHA.

TREATMENT

   The first steps in treating AIHA are to stabilize the dog and suppress the immune system so that the destruction of the red blood cells can be slowed down or stopped completely.  Your vet will most likely administer high doses of corticosteroids (prednisone) for its anti-inflammatory and immunosuppressive action.   The dosage may vary somewhat (higher), but a general guideline will be about 1 mg per pound of body weight per day divided into 2 daily doses.  This treatment is generally continued until the dog is in remission and then the dosage is slowly decreased over a period of several months until the dog has been successfully weaned off of the medication or has reached the lowest "maintenance" dose that will control the disease. 

   Early withdrawal of the medication could lead to a relapse.  It's important that the dog have a blood test before every medication change and that, if the dog is on more than one medication, there is only one medication change at a time.   Changes should be limited to approximately 25% of the prescribed dosage and should only be attempted once every 3-4 weeks.  

   The above treatment is not successful in some dogs.  Unresponsive cases may require more potent immunosuppressive medication or other therapies in addition to the corticosteroids.  These alternate therapies may include Azathioprine (Imuran), Cyclophosphamide (Cytoxan), intravenous Gamma Globulin, Danazol or Winstrol (anabolic steroids), Cyclosporine or Leflumonide (Arava).  

   Unresponsive cases might also benefit from having a thyroid screening panel run on the dog.  Thyroid issues can be an underlying problem with AIHA positive dogs or it is possible for the disease itself to cause thyroid gland damage.  If the dog does have a thyroid issue, putting it on thyroid medication could improve its recovery.

  It's very important that you discuss with your vet and that you fully understand the side-affects and long-term health risks of your dog's medications and treatment.   Corticosteroid treatments are, in themselves, detrimental to the dog over long periods of time.  Side effects can range from increased drinking and appetite, with more frequent urination and weight gain, vomiting and diarrhea, to muscle wasting, behavior changes, elevated liver enzymes and pancreatitis.   Two serious side affects with Azathioprine are bone marrow suppression and an increase in the susceptibility to infection. 

   As your dog recovers, it's a good idea to keep a close eye on his urine.  This can be an early indicator of further problems.  The urine should be a regular, yellow color.  A brownish color or signs of blood are not normal and you should get in touch with your veterinarian immediately.  If you are having trouble seeing the urine, you can lay down some white paper-towels for the dog to eliminate on or you can try sliding a paper plate under the dog just before it starts to urinate.

    Additionally, if your dog is diagnosed with AIHA, there are a number of other health issues that you should address with your veterinarian.   These can include the need for continuing heartworm and flea/tick preventative and/or yearly vaccinations or worming.   You should be sure and discuss any changes or additions that you would like to make in your dogs health care with your veterinarian BEFORE they are implemented.  Due to the seriousness of this disease, changes that may seem minor or a normal part of his routine care, can end up causing serious set-backs.

PROGNOSIS

   The clinical course of AIHA is different for every dog.  The disease can range from mild in some dogs to fatal in others.  Mortality rates, as a whole, will range from 20%-50% but are generally higher for dogs with very sudden and severe cases of the disease. 

   Secondary complications can also be responsible for complicating recovery or causing death.  Some serious complications of recovery include pulmonary blood clots caused by the release of coagulants into the blood from the breakdown of red blood cells and kidney failure due to kidney damage from fragments of destroyed red blood cells. 

Please feel free to CONTACT US for further information on Cocker Spaniels.

Thanks,

Cindy

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