Evans Syndrome in Dogs

Dogs, like humans, can suffer from a wide range of health issues, including autoimmune disorders. One such condition is Evans Syndrome, a rare and complex immune disorder that affects a dog's blood cells. While relatively uncommon, Evans Syndrome can have serious consequences for affected dogs. In this article, we will explore what Evans Syndrome is, its causes, symptoms, diagnosis, and available treatment options.

What is Evans Syndrome?

Evan's syndrome is a form of IMHA in dogs where the red blood cells and platelets are destroyed by the immune system. It is a rare autoimmune disorder in dogs. This disorder occurs when a dog's immune system mistakenly targets and destroys its red blood cells (erythrocytes) and platelets (thrombocytes). These blood cells play crucial roles in transporting oxygen and clotting blood, respectively, so their destruction can lead to severe health problems.

Is Evans Syndrome in Dogs Common？

Not very common. IMHA can affect both dogs and cats, but typically middle-aged dogs are more susceptible.  In dogs that have secondary IMHA due to disease, spayed females are more commonly affected.  There is some evidence of genetic predisposition in Cocker Spaniels and Miniature Schnauzers. Roughly 60% of dogs with IMHA will also experience ITP (Evans Syndrome).

Symptoms of Evans Syndrome

Dogs with Evans syndrome are usually critically ill. If you’re noticing symptoms of Evans syndrome, you need to get your pet to an emergency veterinarian as soon as possible. The symptoms of Evans Syndrome can vary in severity and may include:

• Lethargy: Affected dogs may appear weak, tired, and unwilling to engage in normal activities.
• Pale Gums and Mucous Membranes: Hemolytic anemia can lead to pale gums, lips, and other mucous membranes in the mouth.
• Jaundice (Yellowing of the Skin and Eyes): The breakdown of red blood cells can result in the release of bilirubin, leading to jaundice.
• Fever: Some dogs with Evans Syndrome may develop a fever.
• Bleeding: Thrombocytopenia can lead to bleeding tendencies, which might manifest as nosebleeds, bleeding gums, or bruising.
• Weakness: Due to the anemia and decreased oxygen-carrying capacity of the blood, dogs may exhibit weakness and exercise intolerance.
• Lack of Appetite: Dogs with Evans Syndrome may lose interest in eating.
• Enlarged Spleen: An enlarged spleen (splenomegaly) is sometimes observed.
• Frequent Urination: Some dogs may urinate more frequently than usual.

What Causes Evans Syndrome in Dogs?

Your dog may have no known underlying cause of Evans syndrome, which is called primary or idiopathic Evans syndrome. This form of the syndrome is considered idiopathic, meaning that it occurs without a clear identifiable reason. It is thought to be related to an overactive immune system, where the body's immune cells mistakenly attack and destroy its own blood cells. The exact cause of primary Evans syndrome is not well understood and is often diagnosed through exclusion.

Some potential causes or triggers for secondary Evans syndrome include:

• Infection: Infections, especially those transmitted by ticks (such as Lyme disease) or other pathogens, can sometimes trigger an autoimmune response that leads to Evans syndrome.
• Cancer: Certain cancers, particularly hematological malignancies like lymphoma, can lead to secondary Evans syndrome. In these cases, the cancer cells can disrupt the normal functioning of the immune system, leading to autoimmune reactions.
• Recent Vaccination: While rare, there have been reported cases of Evans syndrome occurring after vaccination. It's important to note that the benefits of vaccination typically outweigh the risk of such rare side effects.
• Medications: Some medications, including certain antibiotics and anticonvulsants, have been associated with secondary Evans syndrome in rare cases. The mechanism by which these medications trigger the syndrome is not fully understood.

Is Evans Syndrome in Dogs Fatal?

Yes, it is fatal, and it is worth noting that early diagnosis and treatment can significantly improve the chances of a positive outcome. While some dogs with Evans Syndrome can respond well to treatment and go on to live relatively normal lives, others may have a more difficult course and may experience life-threatening complications. Early diagnosis and treatment can significantly improve the chances of a positive outcome. 

What is the Survival Rate of Evans Syndrome in Dogs?

The survival rate of dogs with Evans Syndrome can vary widely and is influenced by several factors, including the severity of the condition, the dog's overall health, the response to treatment, and how quickly the condition was diagnosed and treated. Some studies report that Evans syndrome has a mortality rate of around 30 percent, while some hospitals report a less than 10 percent mortality rate. Around 40 percent of cases will experience recurrence or relapse when medications are withdrawn, indicating the importance of long-term management of Evans syndrome in dogs. Survival depends heavily on the treatability of the underlying cause and rapid initiation of treatment.

Diagnosis

Diagnosing Evans Syndrome in dogs requires a thorough examination by a veterinarian. Diagnostic steps may include:

• Complete Blood Count (CBC): A CBC helps determine the levels of red blood cells, white blood cells, and platelets in the dog's blood.
• Blood Smear: A blood smear can reveal abnormal cell shapes or sizes and provide clues about the underlying cause.
• Bone Marrow Aspiration: In some cases, a bone marrow aspiration may be necessary to assess the bone marrow's ability to produce blood cells.
• Other Tests: Additional tests, such as serology to check for underlying infections or autoimmune disorders, may be conducted.

Treatment for Dogs with Evans Syndrome

Treatment for Evans Syndrome typically involves a combination of therapies aimed at managing the autoimmune response, addressing anemia and thrombocytopenia, and providing supportive care. Here are some of the common components of treatment:

• Hospitalization: Severely affected dogs may require hospitalization to stabilize their condition. This can include intravenous (IV) fluids to address dehydration and support overall health.
• Blood Transfusions: In cases of severe anemia and thrombocytopenia, blood transfusions may be necessary to restore red blood cell and platelet levels.
• Immunosuppressive Medications: Steroids, such as dexamethasone or prednisone, are often used to suppress the overactive immune response that is causing the destruction of red blood cells and platelets.
• Other Immunosuppressive Drugs: In some cases, additional immunosuppressive medications like azathioprine or cyclosporine may be prescribed to help control the immune system.
• Antibiotics: If an infection is suspected or confirmed, antibiotics may be prescribed to treat the infection. This is important because infections can trigger or exacerbate the autoimmune response.
• Tick-Borne Disease Coverage: If your dog has an infection, specific antibiotics will be started. Some veterinarians may prescribe doxycycline as a precaution, even if tick-borne disease testing is negative, to cover all potential sources of infection. 

Overall, early diagnosis and prompt treatment are essential for improving the prognosis of dogs with Evans Syndrome. 

How to Prevent Evans Syndrome in Dogs?

Evans Syndrome in dogs is an autoimmune disorder, and like most autoimmune diseases, it cannot be entirely prevented because it is caused by the dog's own immune system mistakenly attacking its own cells. However, you can take steps to help reduce the risk of Evans Syndrome and provide your dog with the best overall health:

• Keeping your dog up-to-date on vaccinations and scheduling regular veterinary check-ups is crucial. Vaccinations can protect your dog from various infectious diseases that could potentially trigger autoimmune responses or other health problems. Your veterinarian can advise you on the appropriate vaccination schedule based on your dog's age, breed, and lifestyle.
• Use tick and flea preventatives recommended by your veterinarian to protect your dog from these parasites and the diseases they may carry.
• Some dog breeds may have a genetic predisposition to autoimmune diseases, including Evans Syndrome. If you are considering getting a dog, research the breed's health history and consider adopting from reputable breeders who prioritize health screening.

What is the active ingredient in dog dewormers?

Common active ingredients found in tick repellents for dogs include:

• Fipronil: Fipronil is a common active ingredient in many topical tick-repellent products for dogs. It works by affecting the nervous system of ticks and other parasites.
• Imidacloprid: Imidacloprid is an insecticide that can be found in some spot-on treatments for dogs. It works by affecting the nervous system of ticks and fleas.
• Pyrethroids: Some tick repellents contain pyrethroids like cypermethrin and deltamethrin. These chemicals are effective at repelling and killing ticks but should be used with caution, especially in households with cats, as they can be toxic to cats.

It's essential to read the product label and follow the manufacturer's instructions when using tick repellents for dogs. Additionally, consult with your veterinarian to choose the most suitable tick prevention product for your dog, taking into consideration your dog's age, size, health, and any potential interactions with other medications or products. 

What dog breeds are more prone to autoimmune diseases?

• German Shepherd: German Shepherds are known to have a higher risk of developing immune-related disorders such as immune-mediated hemolytic anemia (IMHA) and exocrine pancreatic insufficiency (EPI).
• Irish Setter: Irish Setters are more prone to autoimmune disorders like autoimmune hemolytic anemia (AIHA).
• Doberman Pinscher: This breed is known to have an increased risk of developing certain autoimmune conditions, including hypothyroidism and von Willebrand's disease, which is not strictly an autoimmune disease but involves an immune system component.
• Boxer: Boxers are more susceptible to certain autoimmune skin conditions, including pemphigus complex.
• Collie: Collies, including Rough Collies and Border Collies, may have a genetic predisposition to certain autoimmune conditions, including dermatomyositis.
• Beagle: Beagles are at a higher risk for immune-mediated polyarthritis, which affects the joints.
• Cocker Spaniel: Autoimmune diseases such as immune-mediated hemolytic anemia (IMHA) and autoimmune thyroiditis are more common in Cocker Spaniels.
• Poodle: Poodles are known to be susceptible to certain autoimmune skin conditions, including sebaceous adenitis.

Can A Dog Recover from Evans Syndrome?

The initial days following a diagnosis of Evans Syndrome pose the highest risk, with the possibility that not all patients will respond favorably to intensive treatment. However, for those patients who successfully endure the initial days of treatment and are subsequently discharged from the hospital, the long-term prognosis is generally positive. Nevertheless, vigilant monitoring remains essential.

Conclusion

Evans Syndrome is a rare but potentially life-threatening autoimmune disorder in dogs. Understanding its causes, symptoms, and treatment options is crucial for dog owners and veterinarians alike. If you suspect your dog may be suffering from Evans Syndrome, seek immediate veterinary attention to provide the best possible care and improve their chances of recovery.