Denver's Rabies Laws -- Take Another Look !

I have been asked by concerned Denver animal owners and veterinarians to comment on the rabies laws currently in effect in the City and County of Denver. First, I want you to know that rabies is no stranger to me. I have not only seen rabid dogs, but have experienced the very personal anxiety of having my father undergo the painful rabies postexposure treatments three times after being bitten by rabid dogs. Despite these frightening experiences, I find no medical (human or companion animal) justification for the currently required annual vaccination of dogs and cats for rabies in Denver. Modern public health policy should be based on current disease risk and modern vaccines available today, not those of yesterday. We do not plan or build highways in Denver today based on traffic patterns or technologies seen or available 50 years ago. Current rabies vaccines have been proven by the USDA to protect dogs and cats against rabies for three years and to require by law to have your pets vaccinated against rabies more frequently is, for many reasons, not justifiable. The purpose of any mandated rabies vaccination program for dogs and cats is to protect enough of the pet animal population to prevent the spread of rabies in the pet population that has close contact with humans.

The principle source of rabies in our environment is wildlife rabies that, in most cases, cannot be eliminated from the environment. The largest threat of rabies to the pet population is called terrestrial wildlife rabies (skunk, fox and raccoons). Bat rabies, although a potential threat, is not considered a major source of infection in dogs and cats. Denver, like the state of Colorado, has not had terrestrial rabies for decades but does have bats that carry the rabies virus. Despite the fact that the rabies virus exists in bats, there is seldom infection either in wild or domestic animals. JAVMA 212:1714-1720, 1998. According to Dr. John Pape of the Colorado Health Department, the last case of dog rabies documented in Denver was in the 1950's -- some 40 years ago, and the last case of human rabies in the state was in 1931. Many other parts of Colorado under the same threat of rabies, such as Larimer County, have not had a case of dog or cat rabies while at the same time using the triennial rabies vaccination program for pet animals. According to Dr. Kevin Reily (state public health officer in charge of rabies control for the state of California), the state of California, where the risk of rabies is much higher having both bat and skunk rabies and ten million dogs and cats at risk, has used the triennial vaccination program in dogs and cats for the last 20 years. No currently vaccinated dogs or cats have developed rabies during the two decades. In addition, no animal that received just two rabies vaccines in its lifetime, regardless of current rabies vaccine status, developed rabies in the the state of California during the last 20 years. This experience is similar to that reported in a two year national rabies study published in 1988. Under the triennial program, both dogs and cats receive two rabies injections by one year of age and then booster injections every three years.

It is clear from both controlled laboratory challenges studies and more than 20 years of field experience with the triennial rabies programs, that the three year rabies vaccines are extremely effective. Although some have argued that changing to triennial from an annual rabies requirement would decrease rabies vaccination compliance, that has not been California's experience where rabies compliance with a triennial program is 50 % vs. Denver's compliance rate of 37 % with the annual vaccination program. The triennial rabies vaccines are recognized by the National Compendium on Rabies Control supported by the Panel on Feline Vaccination consisting of veterinarians from four vaccine manufacturers, seven veterinary medical schools, feline practitioners, and other recognized national experts in the immunology and infectious disease and the Colorado Department of Health. Recently, the American College of Veterinary Internal Medicine (oncology) unanimously endorsed the triennial rabies vaccination recommendation. John Ref, VMD, PhD, Professor and Head of the Department of Environmental Health, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, has also stated that he finds no need for annual rabies vaccination in Denver. It is clear that rabies in the pet animal populations can be controlled with the triennial rabies vaccination program in areas where the immediate threat of rabies is far greater that in Colorado or Denver.

This issue also begs to address the potential harm caused by overvaccinating for rabies (i.e., vaccinating yearly). Rabies vaccination is not always a benign medical procedure and can have fatal consequences. The recognized complications include anaphylaxis, acute death, polyarthritis, fatal immune-mediated anemia and cancer, in addition to commonly observed swelling and soreness at the rabies vaccine injection site. One potentially fatal, well recognized complication that has been linked to rabies vaccination has been sarcoma (cancer) development at the vaccine site. The incidence of this often fatal cancer has been documented by several studies to be between 1 to 3.2 per 10,000 cats receiving a rabies vaccine. Scientific studies have also correlated the number of vaccines given to an increased risk for the development of these vaccine site tumors. Unfortunately, these vaccine-associated tumors are often fatal despite aggressive treatment with surgery, radiation therapy and chemotherapy, which may cost owners thousands of dollars. If all the cats in Denver (estimate 400,000) were to be vaccinated yearly for rabies, the unneeded additional rabies vaccinations would result in an additional 26 to 84 vaccine site cancers each year! It can safely be said that more cats will die of vaccine-associated sarcomas due to overvaccinating with rabies vaccines in one year in Denver than have ever died of rabies in the history of Colorado -- a real tragedy. Is the City of Denver willing to pay for the treatment of sarcoma caused by their mandated overvaccination of rabies? The additional cost of just giving the unneeded annual rabies vaccination to dogs and cats (average cost = $25.00) is approximately $13,200,000 annually! The real danger to rabies control by continuing the annual rabies vaccination requirement in Denver will be the backlash from increasingly well educated pet owners that have been informed of the truth through investigative reporting such as Paula Woodward of 20/20, the Internet or other media in this information age of the 90's. These well informed residents may openly defy the City's animal rabies ordinance and further erode the credibility of government in order to protect their family pet from the harm, perceived or real, of overvaccinating for rabies.

The Denver Area Veterinary Medical Society (DAVMS) reports only 37% compliance with the current annual rabies vaccination requirement. If Denver is truly concerned about protecting pet animals or humans against a potential rabies epidemic, they need to sponsor outreach programs such as low cost rabies vaccination clinics to ensure dogs and cats that never receive any rabies vaccines are protected against rabies, rather than using the law to coerce owners of animals who are already protected against rabies to be overvaccinated. Annual revaccination of already protected animals does nothing to increase human or animal protection against rabies and runs the risk of doing real harm to the patient. Denver should stop using the law to coerce Denver residents to needlessly spend millions of dollars for unneeded annual rabies vaccination in the name of human or animal health. Public health policy should reflect our current knowledge of disease risk and today's vaccine technologies. A triennial rabies program with the expanded outreach program will do more to protect Denver residents of the remote threat of rabies than the currently used annual program that many experts in disease control have deemed unnecessary.

Dennis W. Macy, DVM, MS

Board Certified Internal Medicine / Oncology

Professor, Internal Medicine / Oncology

Chief, Preventive Health Program

College of Veterinary Medicine and Biomedical Sciences

Colorado State University

Head, Treatment Section of AVMA Feline Vaccine-Associated Sarcoma Task Force

President-Elect, American College of Veterinary Internal Medicine (Oncology)

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