Immune Mediated Hemolytic Anemia (IMHA) is one of the most common causes of regenerative anemia in dogs. It is a life threatening disease that affects some of the most popular breeds of dogs such as the Miniature Schnauzer, Collie, Springer Spaniel, Poodle, Bichon Frise, Miniature Pinscher, Spitz and Old English Sheepdog. IMHA can occur in any breed but the American Cocker Spaniel is 12 times more likely than other breeds to develop IMHA.
Recognizing the symptoms of IMHA can mean the difference between life and death for your beloved pet. This article will discuss the specifics of the disease process, treatment and the signs that indicate that your pet needs prompt Veterinary Medical attention.
One of the first things you may notice is lethargy. Your pet seems “droopy.” He has not wanted to play with his favorite toy or she has not greeted family members when they have returned from work or school. You may also notice rapid breathing (tachypnea), or discolored urine (red or amber). Nosebleeds, vomiting, diarrhea or melena (dark tarry stool) can also be seen with this disease. In more severe cases, our pet may seem normal until she collapses.
If your pet displays any of these symptoms, check his gums. The gums of a non-pigmented breed should look just like yours, bright pink and moist. In IMHA, your pet’s gums may be pale pink or almost white. You may notice a yellow color (jaundice) and/or spots that look like bruises. These bruises may be pinpoint (petechiae) or larger dots (ecchymoses) and are indicative of a serious clotting problem from the destruction of platelets (Thrombocytopenia).
If you notice any combination of these symptoms, seek Veterinary Medical attention immediately. IMHA cannot be treated with any over -the- counter medications and delay in treatment may result in serious complications (including death).
Scientists have studied this disease and have identified two types of IMHA, Primary and Secondary. Primary IMHA is caused when the immune system develops antibodies to healthy Red Blood Cells (RBC’s) and starts to destroy them. Secondary IMHA occurs when another disease process alters the proteins on the surface of RBC’s which stimulates the immune system to produce auto-reactive antibodies and destroy these altered red blood cells.
The cause of Primary IMHA is not known. Cancer, some infectious disease, and administration of certain drugs haven been shown to cause Secondary IMHA.
Infectious disease agents that have been implicated in the development of IMHA include some Tick-borne diseases; (Babesiosis, Haemobartonellosis, Anaplasmosis); Salmonella (a common cause of food poisoning), Hookworm and Whipworm infestations.
Some cancers such as Lymphosarcoma, Leukemia, Soft Tissue Sarcoma, Lung cancer (Bronchoalveolar Carcinoma), Mast Cell Tumor and vascular tumors of the spleen have been linked to the development of IMHA presumably through alterations in proteins on the surface of red blood cells.
Inflammatory conditions of the Pancreas, Prostate, and Bladder as well as Systemic Lupus Erythematosis (SLE or Lupus) have led to the development of IMHA. The administration of Levamisole and Griseofulvin (antifungals), Carprofen (NSAID, Rimadyl) and Cephalosporins (antibiotic) have been implicated in some cases of IMHA.
Certain toxins such as Rattlesnake and Bee venom have been known to cause Secondary IMHA in dogs. Recent Vaccination has been noted in many cases of the Secondary IMHA. Mechanisms by which vaccination could cause IMHA are not known but non-specific immune stimulation and exacerbation of pre-existing disease are suspected.
Your Primary Care Veterinarian should be aware of your pet’s medical history but she may not be familiar with your pet’s travel history. Be sure to tell your Veterinarian of recent trips your pet has taken and inform your Primary Care Veterinarian of any medical care that has been provided by another DVM. Providing your Veterinarian with a thorough and detailed history is essential for making a timely and accurate diagnosis.
After your pet has been examined, your Veterinarian will perform a series of tests. Serum Chemistries to assess organ function, a CBC to measure relative numbers of red and white blood cell populations, and a blood smear to observe the blood cells directly. A Urinalysis will measure the amount of hemoglobin (red blood cell protein) being passed in the urine. The Saline Agglutination Test allows for direct observation of the effects of anti-RBC antibodies and confirms the diagnosis of IMHA. Radiographs will be taken to identify enlarged organs or tumors and rule out other conditions that mimic IMHA (i.e. Zinc Toxicity from the ingestion of coins). Your Veterinarian may also test for Tick borne diseases if your pet has recently traveled to certain areas.
Treatment of IMHA is supportive and involves treatment of suspected or confirmed underlying disease. Any medications (see above) that may be causing hemolysis will be discontinued. Antibiotics will be given if Tick bourne diseases are suspected or diagnosed.
Most dogs with IMHA will need a blood transfusion and IV fluids. Dogs tolerate blood transfusions very well and they significantly improve survival. Dogs with no previous history of transfusion or a history of a first transfusion no longer than 5 days before, can receive “Universal Donor” blood products or Oxyglobin (an oxygen carrying solution made from cow’s blood).
Your Veterinarian will also give drugs to suppress the immune system. Steroids (Prednisone, Dexamethasone) are often given in combination with Chemotherapy drugs to produce adequate immunosupression while decreasing undesirable side effects of steroids.
After your pet comes home from the Veterinary Hospital, she will remain on medications on a tapering schedule as directed by your Veterinarian. Regular follow-up visits will be required to monitor the disease’s response to treatment and make adjustments as needed. Some dogs will need lifelong therapy.
In summary, Immune Mediated Hemolytic Anemia (IMHA) is a disease that affects many breeds of dogs but the American Cocker Spaniel is overrepresented. There are two forms of IMHA, Primary and Secondary. The most common signs are weakness, lethargy and pale gums. Some severely affected dogs will collapse with little or no warning. Prompt medical attention is necessary. Be sure to tell your Veterinarian about recent trips or any vaccinations or medications prescribed by another Veterinarian. Treatment is supportive, consisting of blood transfusion, IV fluids, immunosuppressive drugs and antibiotics if needed. Treatment is often long-term and some dogs will need life-long therapy.
This article is dedicated the memory of “Ringo” Peevy.
Adapted from Small Animal Emergency and Critical Care Medicine by Silverstein, D C and Hopper, K.