Technically, the phrase, “immune-mediated disease” can refer to any imbalanced response of the immune system from fairly innocent allergic reactions to life-threatening auto-immune syndromes. We have dealt with allergic skin disease elsewhere, so here we will concentrate on auto-immune syndromes, feline triaditis (including inflammatory bowel disease), feline gingivostomatitis, and feline asthma.
Auto-Immune Disease of Dogs & Cats
As its name implies, an autoimmune condition occurs when a patient’s own immune system turns on itself and begins to destroy certain types of cells in the body. The particular cell type attacked determines the particular symptoms we see, but the treatment is similar for all the various syndromes. Dogs and cats are both subject to these diseases, but in our practice we see a prevalence among our canine patients.
One of the most common auto-immune conditions we see is called autoimmune hemolytic anemia, or AIHA. This condition occurs when the immune system determines that red blood cells (RBCs) no longer belong in the body and are targeted for destruction and removal. The result is broken-down red blood cells in circulation, which then have to be removed by the spleen and the components recycled to make new red blood cells. The degree of illness depends on the degree of attack: if only a few RBCs are damaged, neither the patient nor the owner notices. But, when the attack causes the number of RBCs to drop to a point of profound anemia, where oxygen-carrying capacity is reduced, the patient will becomes sluggish, may pant to breathe, or even collapse with the slightest exertion. This is a true medical emergency.
A cousin condition to AIHA is called ITP, immune-mediated thrombocytopenia, which is an attack on the platelets of the body. Thrombocytes (also known as platelets) and are very important in the complex cascade of events that leads to normal clotting of blood. If platelet production is too low, or platelet destruction or usage is too high, normal clotting fails and bleeding ensues. Patients with ITP can show signs of weakness similar to AIHA patients, or they may develop visible bruising in their skin and mucous membranes, or they may present with an acute bleed from an orifice such as a nosebleed or bloody diarrhea.
The other big category of autoimmune conditions affecting dogs shows up in the skin and may at first glance be misdiagnosed as atopic dermatitis(allergy) or pyoderma(bacterial infection of the skin). Conditions such as erythema multiforme, pemphigus foliaceous, bullous pemphigus and systemic lupus erythematosis (which can affect nearly every organ of the body in addition to the skin), are among the most common of these that we see. These diseases primarily attack the proteinaceous components of the skin and/or structures immediately under the skin. The lesions frequently appear as deep, draining wounds with thick crusts that may be very itchy. The lesions are often infected and will not heal without specific aggressive treatment.
The exact cause of auto-immune conditions is still a bit mysterious. We do know that genetics plays a big role, where inherited abnormal genes are responsible for creating a dysfunctional immune system capable of mistaking its own tissues for invading or foreign substance. Exceptions to this rule are circumstances where disease intervenes to create abnormal tissue morphology that facilitates the immune system targeting the tissue for attack. Certain cancers can be responsible for this, as can certain infectious diseases, such as tick born bacterial infections. That stated, most cases of autoimmune disease are genetic in origin.
It has become a popular notion that vaccines cause autoimmune disease. This needs clarification. While it is true that vaccines can trigger or exacerbate autoimmune disease in a patient already genetically predisposed to it, they are simply not the cause. As such, attempts to prevent autoimmune disease by not having pets immunized are both misguided and dangerous, leaving pets susceptible to deadly infectious disease when the main determination of whether or not a pet will develop autoimmune disease lies in its genetic code.
Having said that, in a patient with known autoimmune disease, vaccines whose protective properties stem from their ability to stimulate the immune system, could aggravate existing disease. Therefore, in patients with known existing autoimmune disease, it is best to administer vaccines minimally if at all, focusing more on reducing risk through lifestyle adjustment and trying to gauge the necessity for vaccine administration by evaluation of protective antibody titers. While protective antibody titers are far from a fool proof measurement of disease preventability, they still offer some value for patients that have diseases that can be exacerbated by vaccines.
Triaditis refers to a syndrome of concurrent inflammatory diseases of the liver, pancreas, and small intestines in cats. Predominant symptoms of triaditis can be due to liver disease, pancreatitic inflammation, or inflammatory bowel disease. Some cats have only one or two of these organs affected (called IBD, cholangiohepatitis, and/or pancreatitis), but many have all three - hence the name triaditis or “inflammation of three.”
A truism of veterinary medicine is that “cats are not small dogs,” and this is true even in their internal anatomy. In dogs (and humans), there is a bile duct connecting the liver and the intestine, and a separate duct between the pancreas and the intestine. In cats, the duct from the pancreas, and the bile duct from the liver, join together to make a common duct that enters the intestine through a single opening. That means that if there is any inflammatory process or infection in the small intestine (part 1 of the triad) it can easily ascend up one duct and cause problems with direct access to both the liver (part 2 of the triad) and the pancreas (part 3 of the triad).
Symptoms of this irksome condition are, as you might expect, variable depending on which of the three organs are most severely affected. They may display any combination of lethargy, lack of appetite, vomiting, diarrhea, abdominal pain, and weight loss. Occasionally we will find abnormalities in routine blood work on asymptomatic cats that end up leading us to a diagnosis of triaditis or one of its components.
If only one of the three organs is affected, it is most commonly the small intestines as that is where we believe the problem originates, either from bacterial infection or from primary inflammation not associated with infection. Possible infection is treated with appropriate antibiotics. Inflammation without concurrent infection can be due to a true hypersensitivity to a certain food, and if we are lucky enough to be able to identify and/or remove that food from the cat’s diet, that in itself will help alleviate symptoms. More often than not, we are not able to find a dietary trigger for the inflammation, and we need to treat these patients with potent cortisone-type medications.
The liver is most commonly the second organ in the triad to be affected, and since it performs so many functions in the body, when it becomes inflamed, there are a whole host of problems that can occur. Luckily, the liver is a very forgiving organ and treatment with anti-inflammatory medication along with some natural liver support products is usually effective in returning the liver to good health.
The third organ in the triad to be affected is the pancreas which has two separate functions - one to produce insulin and the other to produce digestive enzymes. If the pancreas becomes acutely inflamed, the condition can be very painful and require hospitalization in intensive care. Sometimes the inflammation is more insidious and festers asymptomatically for quite some time until either the cat becomes diabetic (because the cells that produce insulin have been destroyed by chronic inflammation) or begins to exhibit some combination of gastrointestinal signs (because the inflamed enzyme-producing cells are either too active or underactive). In rare cases, the inflammation can eventually damage the enzyme producing cells so severely that a cat can develop a condition called pancreatic insufficiency which requires life-long supplementation with pancreatic enzymes at every meal.
Another example of our feline companion’s unique physiology is the existence of this most frustrating of oral diseases seen only in cats. Cats with this chronic, painful inflammatory disease can be severely compromised, medical treatment can cause adverse effects, and surgery is not always 100% effective. Feline gingivostomatitis is a debilitating oral disease marked by severe and chronic inflammation of a cat’s gums (gingiva) and mucosa, the moist tissue that lines the entire mouth (stoma).
The classic clinical signs of gingivostomatitis include extreme oral pain; swollen, ulcerated, and bleeding gums; lack of appetite or—if an affected cat seems eager to eat—the inability to do so; consequent weight loss; excessive salivation; blood in the saliva; bad breath; and pawing at the mouth. If the condition remains untreated experts suggest (and our clinical evaluation confirms) it is possible for it to become so painful that an affected cat will be unable to take in any food and could conceivably starve to death. These patients are truly suffering before treatment is initiated.
The exact cause of this debilitating condition is still being debated among veterinary dental specialists. Some believe that there might be an underlying infectious cause such as the Feline Immunodeficiency Virus (FIV) or the tick borne bacterial infection by the Bartonella organism. Some believe there may be a food hypersensitivity or even an environmental allergen contributing to the problem. What everyone does agree on is that the inflammatory lesions associated with feline gingivostomatitis are the result of a highly reactive immune system. The fact that most of these lesions will resolve when the teeth are removed suggests the involvement of an antigen that is intimately associated with the teeth - i.e. the bacteria that normally live in the plaque found on all cats’ teeth. However, because cases exist where not all inflammation resolves when the teeth are removed, it must be conceded that multiple antigens might be involved.
Treatment of this debilitating oral condition will typically involve either one or both of two options, depending on the extent of the disease: medical management using drugs to suppress the immune system (cortisone-like medications) and control the proliferation of bacteria (antibiotics) in an affected animal’s mouth; or surgical management, which is likely to entail removal of all of a cat’s teeth. Sometimes the teeth in the front of the cats mouth, including the large fang-like teeth, can be spared, but this varies from case to case. Removing the teeth effectively removes the bacteria-laden plaque usually responsible for the inflammatory reaction. Once a cat recovers from a full-mouth extraction, during which time we give exquisite attention to pain control, she will usually go on to thrive and live a happy life. Most cats will need no further medical management and will return to their normal eating habits, including the consumption of dry cat food!
Another example of “cats are not small dogs” is the occurrence of true asthma in the felines. This is another example of the cat’s immune system overreacting to the presence of an allergen, but in these patients there is a release of stimulants that cause inflammation and swelling of the sensitive tissue lining the bronchi and contraction of the surrounding muscle. This results in the narrowing of the airway and causes breathing difficulty (dyspnea), especially when exhaling.
As with all the other immune-mediated conditions in dogs and cats, it is very difficult, often impossible, to identify the triggering allergen. Nonetheless, suspected allergens include tobacco smoke, dusty kitty litter, vapors from household cleaning solutions and aerosol sprays, pollen (from trees, weeds and grass), mold and mildew, dust mites, smoke from fireplaces and candles, and even some foods.
The severity of the condition can be divided into four general categories: (1) mild (the symptoms occur intermittently — but not daily — and they do not interfere with the cat’s lifestyle); (2) moderate (the symptoms do not occur daily, but when they do, they are more severe and debilitating, and they interfere with the cat’s activities); (3) severe (significantly debilitating symptoms occur daily); and (4) life-threatening (bronchial constriction results in potentially lethal dyspnea and consequent oxygen deprivation, which causes normally pink tissues, such as the lips and nose, to turn blue).
Like human asthma, chronic feline asthma is incurable but generally manageable, and treatment depends on the severity of the condition. Most commonly, it involves the use of a corticosteroid drug to reduce bronchial inflammation in combination with a bronchodilator to open up the airways. In most cases, these drugs can be used at home, they are effective both therapeutically and preventively, and they may be administered in a variety of ways — orally in tablet form, through injection, or, ideally, via an inhaler.