Autoimmune diseases are increasingly prevalent in dogs and have genetic and environmental triggers. Here’s what you should be aware of.
If you were unlucky enough to catch a cold or the flu this past winter, you know firsthand how the health of your immune system can make all the difference between a speedy recovery and an illness that drags on for weeks. The immune system in both people and animals plays an essential role in maintaining the body’s overall general health and resistance to disease. But sometimes, things go wrong with the immune system. Both genetic and environmental factors can cause or “trigger” immune dysfunction, leading to either immune deficiency – or immune stimulation, also called autoimmune disease.
Immunity against self
Immune competence is provided and maintained by two cellular systems in the body that involve a type of white blood cell called lymphocytes. These cells have specialized immune functions, including those of the circulating blood or humoral immune system derived from B-lymphocytes or B-cells (from the bone marrow); and a cellular or cell-mediated immune system derived from T-lymphocytes or T-cells (from the thymus gland).
The term “autoimmunity” literally means immunity against self. It’s caused by an immune-mediated reaction to self-proteins or antigens (i.e. failure of self-tolerance). Susceptibility to autoimmune disease has a genetic basis in humans and animals. Numerous viruses, bacteria, chemicals, toxins and drugs have been implicated as the triggering environmental agents in susceptible individuals.
This mechanism operates most often by a process known as “molecular mimicry” – when a foreign substance mimics a body component so that antibodies are raised against both of them. The resultant autoimmune diseases reflect the sum of the genetic and environmental factors involved. Autoimmunity is most often mediated by T-cells or their dysfunction. As stated in a landmark review: “perhaps the biggest challenge in the future will be the search for the environmental events that trigger self-reactivity” (Sinha, Lopez and McDevitt, Science, 248: 1380, 1990).
Genetically-based autoimmune diseases
The list of documented heritable autoimmune disorders in humans and animals is alarming, and continues to grow as we damage and pollute our environment.
• Endocrine – thyroid (thyroiditis), adrenal (Addison’s disease), pancreatic (diabetes)
• Hematologic – erythrocyte (AIHA, IMHA), platelet (IMTP), leukocyte
• Muscle – myasthenia gravis, masticatory muscle myositis, polymyositis, dermatomyositis
• Eye – keratoconjunctivitis sicca, uveitis, pannus, uveodermatologic syndrome (VKH)
• Skin – pemphigus disorders, systemic lupus erythematosus, vitiligo
• Neurologic – immune-complex meningoencephalitis
• Renal – immune-complex glomerulonephritis, systemic lupus erythematosus (SLE)
• Joint – rheumatoid arthritis Hematologic diseases Immune-mediated
Immune-mediated diseases include include hemolytic anemia (AIHA, IMHA) and/or thrombocytopenia (low platelet count, IMTP). They are being reported with increasing frequency in animals and humans. In dogs and occasionally cats, this disorder can be associated with bone marrow failure. Affected animals have one or more of the following signs: lethargy, anorexia, pale mucous membranes, weakness, exercise intolerance, tachycardia (rapid heart rate), tachypnea (rapid breathing), icterus (jaundice), hemoglobinuria (hemoglobin pigment in urine) and fever. Prognosis is guarded to poor with reported mortality rates between 28% and 70%.
Laboratory abnormalities may include red cell auto-agglutination, positive Coombs’ test, spherocytosis (rounded red blood cells), thrombocytopenia and neutrophilia (low neutrophil count). Anemia may be regenerative or non-regenerative depending on the duration of illness and immunological targeting of red cell precursors in the bone marrow. Some dogs may also have other autoimmune diseases.
While many cases may be classified as idiopathic (cause unknown), a stress event such as vaccination, drug, chemical or toxin exposure, surgery, hormonal change, infection or injury within the previous 30 to 45 days may be identified as a potential trigger. Many breeds are reported to have an increased risk for IMHA, although the American cocker spaniel is believed to be at highest risk. Mixed and hybrid breeds can also be affected, and females are more commonly affected than males.
Also called hypoadrenocortism, Addison’s disease results when the adrenal glands are underactive and do not produce enough adrenal cortical hormones. The primary form of Addison’s disease is a self-directed immune reaction within the adrenal glands (i.e. an autoimmune or immune-mediated disease), in which the affected individual’s lymphocytes progressively destroy the glands. Addison’s disease can cause many serious health issues, and is often misdiagnosed as another disorder. The symptoms are non-specific and mimic other general conditions. They include muscle weakness and general lethargy (listlessness), in which affected dogs will be unable to jump up on the couch or bed, will have trouble climbing stairs, lie down a lot or show a lack of enthusiasm for activities involving physical exertion. There may also be vomiting and diarrhea, hyperpigmentation (small patches or spots of darker skin around the armpits, mucous membranes or inside the cheek), joint pain, poor appetite and shivering or muscle tremors.
When combined with autoimmune thyroid disease, the condition is called Schmidt’s syndrome. Once diagnosed, the treatment options for Addison’s disease are very effective, but require the dog to take medication for the rest of his life. There are at least a dozen predisposed breeds, and inheritance has been defined in several, such as the Portuguese water dog, standard poodle and Nova Scotia duck tolling retriever. Again females are more commonly affected than males.
Novel approaches for management and treatment
Standard conventional treatments for immunologic disorders can be augmented or replaced with holistic alternatives. Rather than suppress the immune system with corticosteroids, alternative means of down-regulating the cytokines (cellular enzymes) that trigger cell-mediated immunity can be used.
• Some clinicians use biologically active glandulars such as multiple glandular supplements or thymic extract protein.
• Other treatments that balance and modulate the immune system and offer immune support include plant sterols and sterolins (from fruits and vegetables), bioactive botanicals (plants and herbs), and medicinal mushrooms.
• Treatments should also be aimed at assisting the liver’s detoxifying pathways – e.g. with milk thistle and SAMe – and increasing the amount of protective amino acids by supplementing with glutathiones, cysteine and taurine.
• Antioxidants including vitamins A, C, D and E, selenium, bioflavinoids from vegetables (e.g. red bell peppers, broccoli, Brussels sprouts, spinach), fruits (e.g. blueberries, cranberries, pomegranate) and herbs (e.g. oregano, garlic, turmeric) can be used as bio-support to strengthen the patient’s metabolism and immune system.
You can also help prevent the development of autoimmune diseases in your dog by giving him good nutrition and reducing his exposure to toxins. Though these conditions are becoming more common, awareness, proper healthcare and regular checkups will do a lot to protect your pooch.