(leukopenia) leading to immunosuppression, loss of appetite, mucopurulent nasal discharge, dehydration, and rapid weight loss. The chronic diseases we see frequently in cats correspond to many of these symptoms. Inflammatory bowel disease, an autoimmune inflammation of the intestines, is occurring at epidemic levels today. This disease was virtually nonexistent twenty years ago, yet today it is one of the most frequent diagnoses.
Cats are also extremely susceptible to immune malfunction and immunosuppression. The immunosuppressive state has been associated with two retroviruses (feline leukemia virus and feline immunodeficiency virus), and others are suspected. Rather than these being separate diseases, I believe they are the same, but that more than one virus can fill the niche opened by the immunosuppression (remember that with chronic diseases the illness precedes the infection). This is probably the same in people with HIV (human immunodeficiency virus) related viruses. Parvoviruses, which include the feline panleukopenia virus, are known to be very immunosuppressive. Additionally, I suspect the feline upper respiratory infections are a chronic state of the panleukopenia virus-induced immunosuppression and the tendency to get eye discharges.
A similar scenario now exists in dogs. While immunosuppressive states are not common in dogs, reports of their occurrence are on the rise. I believe the massive vaccination program for canine parvovirus, which began some thirty plus years after we began vaccinating cats with feline parvovirus (panleukopenia virus), is creating this situation in dogs. If this is true, then the imminent future bodes poorly for dogs if the problem in cats is an indication. Furthermore, we have been seeing inflammatory bowel disease in dogs over the past five to ten years. Prior to this it was virtually nonexistent. I am certain that vaccination for parvovirus and coronavirus is a major cause. I commonly see inflammatory bowel disease that arises within a month or two after vaccination for one of these viruses.
There is still another syndrome associated with parvoviruses, one that occurred first in cats, and later in dogs. Cardiomyopathy is a disease of the heart muscle. The muscle may either weaken and stretch (dilated cardiomyopathy), or it may thicken greatly (hypertrophic cardiomyopathy). Either condition will limit the heart's ability to pump blood. Cardiomyopathy is often fatal.
We have been diagnosing cardiomyopathy in cats for over twenty years, approximately the same period of time as for inflammatory bowel disease. Many (but not all) cases of the dilated form of cardiomyopathy have been associated with a deficiency of the amino acid L-taurine. The cause for hypertrophic cardiomyopathy, as well as the cause for the nontaurine-associated cases of dilated cardiomyopathy, is unknown. I believe that the answer may have appeared in dogs.
When canine parvovirus first erupted in the late 1970s, many young puppies died rapidly, sometimes within hours. It turned out that parvovirus was capable of attacking the heart muscle in young puppies, and this form of the infection killed the puppies rapidly.
Cardiomyopathy did not affect dogs before the parvovirus outbreak (or if so it was very rare), but in the years since the outbreak it has appeared. The number of cases has especially risen over the past five to ten years, coincident with the rise of inflammatory bowel disease in dogs. The Merck Veterinary Manual states that, "The cause [of dilated cardiomyopathy in dogs] is still unknown although viral infection and resultant autoimmune reaction against the damaged myocardium are suspect.... Since the canine parvovirus (CPV) pandemic of 1978, male Doberman pinschers appear to be highly vulnerable to both CPV and cardiomyopathy." (Fraser) In the years since this was written (in 1986), we have begun to see cardiomyopathy in many other breeds as well as Doberman pinschers.
I believe the author of this section of The Merck Veterinary Manual was correct, but I believe that parvovirus vaccination is even more li