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Canine Immune- Mediated Hemolytic Anemia - more commonly known as IMHA - is a relatively rare but complex, and potentially life-threatening disorder of the blood. It can affect humans, cats and dogs. While it is not common, because it is a serious, chronic disorder it is something that every pet parent should at least be aware of.
IMHA is a disease of the blood. It causes the immune system to change and the body begins to attack and destroy red blood cells. In most cases, the trigger is never known. The result of this is severe anemia, which means the body now lacks the red blood cells it needs to function and all of its cells become oxygen deprived. Severe anemia can be life-threatening, so immediate treatment is a must.
There can be a number of reasons that a pup - even a young, previously healthy pup - can develop IMHA. To complicate things even further there are two different types of IMHA: primary and secondary.
Primary IMHA, which is the most commonly diagnosed form, has no known cause, but is believed to be genetic in nature.
Secondary IMHA is the 'side effect' of another health condition, vaccination reaction, including cancer, exposure to toxins, Lyme disease, infections and even, occasionally secondary IMHA can develop as the result of a bad reaction to medications.
There are also two different ways IMHA can present itself.
Intravascular IMHA means that red blood cells are destroyed throughout the bloodstream, while in extravascular IMHA they are destroyed within various organs (liver, spleen etc.) only.
Both forms CAN be extremely dangerous IF left untreated.
Secondary IMHA can affect any pet dog, BUT primary IMHA is believed to have a genetic component that is found more frequently in some breeds than others. These breeds include:
Research has also shown that middle-aged to older pets (females are slightly more likely to get autoimmune diseases in general) are often more likely to develop IMHA but no one is quite sure why that is.
IMHA can be hard to pinpoint - for pet parents at least - but as it is a severe form of anemia, there are some telltale signs. They include the following:
Many of these symptoms are also related to other conditions, so they do not indicate for sure if your pup is suffering from IMHA. Time is essential, so if you see any of these signs, don't delay seeing your vet.
DVM Tony Johnson, has this stark message to say about how serious you should take any of these signs of IMHA in your pet dog:
It can happen with remarkable speed – one day your dog is happily snoozing by the fire, the next day your veterinarian is telling you that he’s in a 50:50 battle for his life.
- Tony Johnson, DVM, DACVECC -
If at all in doubt, err on the side of caution and get your pup to the vet as soon as possible, especially as secondary IMHA is usually a sign of another health condition as well.
In order to properly diagnose IMHA, and to identify the underlying causes if it is believed that the condition may be secondary, a number of tests will have to be conducted including the standard blood test known as a packed cell volume (PCV).
Most of these tests will involve complicated bloodwork, as not only will that identify the condition but also reveal how severe it is.
According to Dr. Christopher G. Byers, "one common mistake practitioners can make is not being aggressive enough in identifying any underlying causes, such as neoplasia, that may make the IMHA a secondary disease".
So make sure, you have thoroughly investigated this possibility. This investigation should include an extensive history, infectious disease testing and thorough diagnostic testing. Ultrasound scans and x-rays will also be used to rule out conditions like cancer, and to look for any organ damage that the disease may already have caused.
One of the other tests that a vet should run if gums are yellowed or pale is a packed cell volume blood test to check for hemolytic anemia.
The treatment a pet dog receives for IMHA will vary according to its severity, whether it is primary or secondary and whether OR not another health condition needs to be treated as well.
In most cases, the first treatment administered will be a blood transfusion, so that the pup's red blood cell supply can be quickly replenished. Once that has been achieved, if it can be, then your vet will look at beginning long term immunosuppression, using high doses of steroid medications, to prevent the body from attacking the new red blood cells that have been introduced via blood transfusion and the new red blood cells that will need to grow from them.
If there is a secondary health condition present, which is the most common situation, then that will have to be treated as well.
So to summarize, when looking at IMHA treatment there are three main goals the therapy treatment achieves:
1) Bring the condition under control
2) Address the underlying cause if any for the IMHA, if detected
3) Suppress the immune system to stop its attack on the red blood cells.
Dogs that receive treatment are on medication for several months. Steroids like prednisone are the cornerstone of immunosuppresive therapy.
Additional immunosuppressive drugs, antibiotics, and anticoagulant drugs include: cyclosporine, famotidine, melatonin, doxycycline and aspirin are the typical initial treatment regimen for dogs with confirmed IMHA in which no underlying primary disease is found (idiopathic IMHA).
The prognosis for dogs diagnosed with IMHA varies significantly. If the episode was secondary, managing the underlying cause can increase their survival odds significantly. If the IMHA is primary the pup will need to be on immunosuppressive drugs for the rest of their lives, and that will leave them open to contracting infections more easily than other pups. For pet dogs that respond quickly to immunosuppressive therapy and do not require repeated blood transfusions, the prognosis can be good.
Follow-up care generally includes repeat labwork and physical exams.
Sadly, about one dog in five will have a relapse at some point.
Pet parents do have to be prepared for the fact that if their pup is diagnosed with primary IMHA they will need to be treated for it for life, and their general health will need to be constantly monitored as well, as their immune system will have to be drug suppressed so that their own bodies do not begin attacking their red blood cells again.
Unfortunately data shows that 60-75% of IMHA cases do NOT have apparent causes.
Vaccines have the greatest protective effects in the young. Although, there is some thinking that vaccination can trigger IMHA but reports have been conflicting. This however remains controversial as some studies show an association with recent vaccination and others show none.
Because the real cause of primary IMHA is not really understood there is really nothing that can be done to prevent it, other than to ensure your younger dog gets his vaccinations early on.
A lot of pet owners are very angry at this auto immune disease, how fast it attacks and the lack of available treatments.
The good news is that there have been a number of recent research breakthroughs and veterinary medicine for IMHA is improving every day.
In the case of secondary IMHA, some of the possible causes can be prevented to a certain extent. Try to keep your pet away from toxins, including household chemicals, and, to help minimize the risk of Lyme Disease don't walk your pup in long grasses and always check him for ticks when you come in after time spent outside, especially if you live in the Northeastern United States.
Share Your Experience: Have a story about this common autoimmune disease in your pet dog? What sorts of things caused this onset? And if you opted for therapy treatment for IMHA for your dog, what were your experiences? Anything you can tell us to watch out for or advice you can give is very welcome.
If you are concerned about your pet, visit or call your veterinarian – he/she is your best resource to ensure the health and well-being of your dog. This information is for informational purposes only and is not meant as a substitute for the professional advice of, or diagnosis or treatment by, your veterinarian with respect to your pet.