By Dr. Laura Hady
Similar to humans, pets have an immune system that helps prevent and fight infectious diseases. Pets have both innate immunity and acquired immunity. The first line of attack on invaders is innate immunity, which is present at birth. Acquired immunity is the body’s learned recognition of an invader called an antigen. This is the basis for vaccines, which enable the body to effectively activate a more specific defense against a disease when exposed to it.
A problem arises when an “incorrect” signal is sent to these cells and the body starts to attack your pet’s normal cells, causing the body to function abnormally. This is an immune related disease. Below are just some of these diseases and information about them.
- Pemphigus foliaceus is when the body attacks the skin cells, causing crusts and ulcers to form on the nose, ear tips, and near the mouth in dogs and cats. A skin biopsy is needed to confirm the diagnosis because the crusts can look like a bacterial infection. Steroids and other immunosuppressive drugs are involved in treatment. Pemphigus can go into remission, but flareups can occur throughout a pet’s life. System lupus erythematosus (SLE) can also affect the skin, appearing as pemphigus foliaceus, so blood tests are needed to confirm a diagnosis.
- Immune-mediated hemolytic anemia is where the body attacks the red blood cells of dogs. Symptoms include weakness, decreased appetite, increased breathing rate, dark stool, and yellow-tinged skin, gums, or eyes. A physical exam may show a fever, low red blood cell counts, increased white cell counts, elevated liver enzymes, and blood in the urine. Other specialized tests may be needed to rule out infectious diseases and cancer. Your veterinarian may also ask about travel history and exposure to infections, as pets may develop these diseases after an infection. Hospitalization is often needed until the patient is stabilized and eating again. Treatment includes steroids, immunosuppressives, and in some cases, blood transfusions. Thirty percent to 70% of dogs survive, but this disease does recur up to 15% of the time.
- Immune-mediated thrombocytopenia affects the platelets of the blood, which aid in stopping bleeding. Dogs with this disease will seem weak and may not want to eat. They may experience bruising of the skin, pale gums, and bleeding from a simple scratch, or even spontaneous bleeding if the platelets get too low. Diagnosis and treatment is similar to the immune-mediated anemia with comparable survival rates, but the possible recurrence rate is from 9%-39%.
- Inflammatory bowel disease can result in the body attacking its intestinal cells. Diarrhea is the most reported symptom. Fecal testing and lab work should be done to rule out other causes of vomiting and diarrhea. Biopsy of several areas of the intestine gives the definitive diagnosis. Life-long treatment of steroids, probiotics, and diet change may be required for both cats and dogs.
- Vaccines can help protect a pet by either presenting a weakened version of the pathogen (modified live) or a killed pathogen. This allows the body to “see” a pathogen that is not going to cause a disease, yet form a memory of the disease so it knows later to fight against it if exposed. An example of a modified live vaccine is the distemper, parvo, adenovirus, parainfluenza combination for dogs. An example of a killed virus is the rabies vaccine for both dogs and cats. Vaccine reactions affect less than 1% of animals but can be scary if you see your pet experience symptoms. The spectrum of vaccine reactions includes soreness at the injection site, fevers, hives, facial swelling, vomiting and diarrhea, difficulty breathing, and very rarely, collapse. Emergency care is needed for these situations. A discussion with your family veterinary staff should help you know which vaccines are needed for your pet’s age, risk of exposure in their environment, and potential travel.
While immune mediated diseases can be life threatening, the best step is to get your pet in for an exam when they start to experience some of the mentioned symptoms. Your family veterinary staff can guide you through what tests are required based on the animal’s history and exams. Some pets will require lifelong monitoring and treatment, but most do well if the diseases are diagnosed and treated in the early stages.
