Reducing IMHA in Cocker Spaniels Requires Early Recognition
Few Cocker Spaniel owners recognize the signs of immune-mediated hemolytic anemia (IMHA), though the breed has an increased risk for developing the fast-acting, potentially fatal illness. A disease in which a dog’s immune system attacks and destroys the oxygen-carrying red blood cells, IMHA is a major cause of severe anemia.
Not only is it difficult for owners to realize when their dog suffers from IMHA, it can be costly and challenging to treat. This was the case for Christine Erickson of East Bethel, Minnesota. When her 5 ½-year-old agility pro “Bumper” (MACH4 Livingston’s Legendary Bippity Boppity Bumper) looked listless on the agility course doing what he loved, she knew something wasn’t right. Ranked among the Top 10 agility Cocker Spaniels, Bumper usually raced through the course.
“Since ticks are prevalent in this area, at first I thought the problem was a tick-borne disease or even allergies,” Erickson says. “That evening, when Bumper showed no interest in eating or drinking and his gums were pale yellow, I knew it meant a trip to the veterinarian the next day.”
The veterinarian examined Bumper and ran a complete blood count (CBC) test, blood chemistry analysis and blood smear evaluation. The tests showed a low red blood cell count, and the cells had an abnormal shape and size. As is common in dogs with IMHA, the red blood cells were clumped together. This occurs when a coating on antibodies produced by the immune system causes the cells to stick together. The immune system produces antibodies that attach to oxygen-carrying red blood cells and “tag” them for destruction by macrophages, or white blood cells.
Bumper was Erickson’s third Cocker Spaniel. She had never heard of IMHA and neither had the breeder. “It was four days on a roller coaster and in the end, we lost Bumper,” she says. “I learned a whole lot about this disease in a short time and spent a considerable amount of money treating it as well.”
“Not every owner is prepared for the costs associated with treating IMHA,” says Dr. Rob Lyerla, grants chair for the American Spaniel Club Foundation. “Treatment can be very expensive, and unfortunately, there’s no guarantee it will be successful. Dogs that survive the initial crisis face the risk of relapse down the road and the potential for complications related to having a chronically depressed immune system.”
Dr. Lyerla says the American Spaniel Club Foundation recently supported research sponsored by the AKC Canine Health Foundation at Iowa State University and Cornell University to learn more about IMHA and the genetics that make Cocker Spaniels prone to developing it. “The survival rate is considerably better now than it once was, but we need to make more Cocker Spaniel breeders and owners aware of the disease,” he says.
Early recognition of IMHA can mean the difference between life and death. Prompt diagnosis and treatment are key to stopping the destruction of red blood cells, stabilizing a dog and allowing the red blood cells to regenerate.
Lethargy is the most common sign of IMHA due to anemia and oxygen starvation that results from the destruction of healthy blood cells. The lethargy is pronounced and has a rapid onset, making it quite noticeable. Hemoglobin in the urine indicates a breakdown of red blood cells. Jaundice from bilirubin, a byproduct of red blood cell destruction, accumulates and can cause yellowing of the skin and whites of the eyes. Pale white or yellow gums also are a visible sign. The heart can be affected, and dogs with advanced disease may collapse from lack of oxygen.
Owners noticing these rapidly presenting signs in their dogs should seek treatment immediately. For many, that means a trip to the emergency room, possible blood transfusions, overnight stays, and watching the clock for signs of improvement.
A Common Immune-Mediated Disease
Immune-mediated hemolytic anemia is one of the most common immune-mediated disease in dogs. Primary IMHA, the type affecting Cocker Spaniels, accounts for about three-quarters of cases in North America. Considered idiopathic, or having no known cause, primary IMHA is a complex polygenic disorder that likely involves several genes plus environmental triggers.
Secondary IMHA is caused by a reaction to another illness, medications or toxins from snakebites or bee stings. It may occur in dogs battling cancer, such as lymphosarcoma, leukemia or hemangiosarcoma, or when a dog has a blood parasite that causes an abnormal immune reaction. Many tick-borne organisms can induce IMHA.
Destruction can be extravascular (outside the blood vessels) or intravascular (inside the bloodstream). Extravascular destruction, which occurs in the spleen or liver, has a more favorable prognosis because the hemoglobin released by the destroyed cells is engulfed by macrophages, or white blood cells, rather than being released into the bloodstream.
When the destruction is intravascular, the released hemoglobin endangers a dog’s kidney function. Regardless of the site of destruction, massive inflammation can affect multiple organ systems, and blood clotting can cause organ failure or death.
Anthony Carr, Drmedvet, DACVIM, professor of small animal clinical sciences at the University of Saskatchewan in Canada, has studied IMHA for 20 years. In necropsy studies, he has found that 90 percent of dogs with IMHA had blood clots in various organs. “Inflammation and hemostasis, the process of clotting to stop bleeding, are definitely linked,” Dr. Carr says. “IMHA is a condition of massive inflammation that promotes hemostasis and the formation of clots.”
In an article published in the Journal of Veterinary Internal Medicine in 2002, Dr. Carr was the lead author of research that aimed to identify risk factors for
canine IMHA. Medical records of dogs admitted to the University of Wisconsin Veterinary Medicine Teaching Hospital from 1987 to 1995 were reviewed.
Seventy-two cases of IMHA were included. Among the 28 breeds represented in the study, Cocker Spaniels were the most overrepresented breed. Other breeds at higher risk for IMHA were English Springer Spaniels, Collies, Irish Setters, and Poodles.
Mortality frequently was associated with thromboembolism. A life-threatening acute blood clot that can result in sudden death, thromboembolism often goes to the lungs preventing oxygen from getting into the bloodstream. “Blood transfusions may be needed to buy time until medications can work,” Dr. Carr says.
Confirming a diagnosis of IMHA involves a series of tests. Similar to what Erickson’s dog Bumper underwent, diagnostic testing could include CBC tests, blood chemistry analysis to evaluate organ function and electrolyte levels, and blood smear evaluation to assess the clumping of red blood cells. A Coombs test can help detect antibodies attached to red blood cells. An abdominal ultrasound or radiograph can be performed to check for other causes of anemia, such as cancer in the abdomen. Kidney function and urinary tract infections can be evaluated via urinalysis.
“Cocker Spaniels are the poster children for IMHA,” says Jeanne S. Grim, DVM, who breeds Cocker Spaniels and participates in conformation, obedience, rally, agility, and hunting. “My experience with this disease is that most owners don’t realize the urgency of the condition and how challenging it can be to treat a dog. If you wait 36 hours from the time you realize a dog is acting abnormally to go to the veterinarian, it could be too late.”
Veterinarians use a three-pronged approach to treat IMHA that involves suppressing the immune system, preventing blood clots and treating clinical signs. For immunosuppression, prednisone, a corticosteroid hormone, is the first drug used. Although it is effective, prednisone can affect quality of life, causing side effects such as excessive thirst and urination, panting, gastrointestinal ulcers, and increased susceptibility to infections.
Prednisone may be combined with a second immunosuppressant for better control. Giving a slower-acting drug, such as azathioprine or cyclosporine, provides an added chance to suppress the immune system and allows a dog to be tapered off prednisone sooner while continuing the slower-acting drugs that have fewer side effects. Dogs also may receive low doses of aspirin, heparin or clopidogrel to help prevent blood clots. Other drugs that have been used to treat IMHA when a dog is not responding to more traditional drug therapy include lefluonomide and mycophenolate mofetil.
Dogs that survive the initial crisis of IMHA 60 days or more face the risk of relapse and complications related to having a chronically depressed immune system. About 15 percent are estimated to experience a relapse.
Although no causative gene is expected to be discovered soon linking affected dogs to the complex polygenic disease, better education and awareness of IMHA will surely help increase survival for affected Cocker Spaniels. Dr. Lyerla, of the American Spaniel Club Foundation, is optimistic about the future.
“There is more to be learned about the causes of IMHA and, of course, treatment can possibly improve,” he says. “Importantly, Cocker Spaniel enthusiasts can work together to help get the word out about this disease and help identify dogs in the early hours of IMHA when a difference still can be made.”
Purina thanks Dr. Rob Lyerla, grants chair for the American Spaniel Club Foundation, for helping us to identify this topic for the Cocker Spaniel Update.
Recognizing Signs of IMHA
The signs of immune-mediated hemolytic anemia (IMHA) vary by dog and can be challenging to diagnose, partly due to a lack of familiarity of the disease by breeders and owners. Among the common signs of the condition are:
- Extreme lethargy or weakness
- Pale or yellow gums
- Jaundice of the eyes
- Shallow or rapid breathing
- Fast pulse
- Loss of appetite and weight loss
- Dark orange or brown urine indicating hemoglobin in the urine
- Black feces due to hemorrhage of the gastrointestinal tract
- Collapse due to a lack of oxygen