News Flash from the Animal World

Evidence is building that annual vaccination of dogs and cats -- performed for diseases such as rabies, distemper and parvovirus -- may not be necessary and could even be harmful. Vaccines licensed by the U.S. Department of Agriculture are tested to ensure they protect pets against disease, usually for one year. But the tests don't detect long-term side effects, or measure the duration of a vaccine's effectiveness. Recent and continuing studies at several universities suggest that protection from vaccines may last for years, which would make annual shots for some diseases a waste of money -- at the very least.
Fears of vaccine-induced diseases date back more than 40 years. But a sharp increase during the past decade in cancerous tumors among cats, between the shoulder blades where vaccines typically are injected, has spurred studies. Some have found a higher-than-expected incidence of side effects. "We see health problems in dogs for which we have no explanation. The classic one is autoimmune disease," says Larry Glickman, professor of epidemiology at Purdue University's School of Veterinary Medicine in West Lafayette, Ind., who is studying possible links with vaccinations. "We see an epidemic of hyperthyroidism in cats today, and we suspect that these are happening because we're over-vaccinating our pets."
Dr. Glickman and his colleagues theorize that repeated vaccination causes dogs to produce antibodies against their own tissue. The antibodies are caused by contaminants in the vaccine introduced in the manufacturing process. While the amounts are minuscule, they gradually accumulate with repeated vaccinations over the years. But Dr. Glickman cautions that more research is needed before a clear link can be established between antibody levels and autoimmune disease.
Vaccination recommendations for cats and dogs vary around the country. Most states require rabies vaccinations every three years, while a handful of states -- as well as some individual cities and counties -- have mandated annual shots due to local problems with rabies in wild animals. Some other vaccinations are given only when a pet's lifestyle or environment exposes it to a particular risk, such as Lyme disease.
Pet diseases other than rabies aren't a threat to people, thus vaccinations aren't required by law. But veterinarians and vaccine makers have traditionally recommended annual booster shots against potentially fatal diseases such as distemper and parvovirus in dogs and herpesvirus in cats. In a policy statement last year, the American Veterinary Medical Association acknowledged that the practice of annual vaccinations is based on "historical precedent" and "not on scientific data."
The emerging evidence of health risks is prompting some vets to change their practices. "We're now doing 40% less vaccinations than five years ago," says Kathleen Neuhoff, a veterinarian in Mishawaka, Ind., and president of the American Animal Hospital Association, Lakewood, Colo.
"My own pets are vaccinated once or twice as pups and kittens, then never again except for rabies," Ronald D. Schultz, chairman of the University of Wisconsin's Department of Pathobiological Sciences, wrote in the March 1998 issue of Veterinary Medicine.
Some critics of annual shots accuse some vets of ignoring research about vaccine risks for financial reasons. "Vets are afraid they will go broke" without regular vaccines, which account for about 20% of their practice income, says Bob Rogers, a Spring, Texas, veterinarian and outspoken critic of current practices.
Other vets deny that financial motives are involved. ("No one who is motivated by money would ever become a veterinarian," Dr. Neuhoff says.) "The concern is that if we move too quickly to decrease vaccine frequency across the board, we may be opening the door for some animals to become infected when we could have prevented the problem," says Todd R. Tams, chief medical officer of VCA Antech Inc., in Los Angeles, the nation's largest owner of veterinary hospitals.
No one truly knows how long protection from vaccines lasts. Vaccine makers say that proving their duration would be expensive and would require large numbers of animals to be isolated for years.
One company, Pfizer Inc., decided to test its one-year rabies vaccine on live animals and discovered it lasted for at least three years. It sells the identical formula simply packaged under different labels -- Defensor 1 and Defensor 3 -- to satisfy different state vaccination requirements.

Testing Animals' Immunity Level
Owners anxious about annual vaccinations can ask their veterinarians to check their pet's immunity to certain diseases.
In the past, most such tests were costly and had to be sent to an outside laboratory. If they indicated that a dog or cat wasn't protected, the owner had to bring the pet back for vaccination.

Vets Rethink the Need for Annual Pet Vaccinations
But a new 15-minute blood test, called TiterChek, can help determine if a dog is protected against two of the most common, life-threatening diseases: canine parvovirus and distemper. The test, made available in May, is the first of its kind to be approved by the U.S. Department of Agriculture, which licenses animal vaccines.
The kit is made by Synbiotics Inc., a San Diego veterinary-products company. It includes a total of ten tests that detect antibodies against both diseases and is being sold to vets for $125, or $12.50 per test. Synbiotics says it plans to develop immune status tests for cats, probably for feline leukemia and rabies vaccines. Just as vaccines don't bestow 100% protection against disease, tests like TiterChek aren't 100% accurate.
Still, Michael Dutton, a veterinarian and owner of Weare Animal Hospital in Weare, N.H., says the new TiterChek can help him and his clients determine which pets need a booster.
"There's been a lot of discussion about whether we are over-vaccinating a certain population of pets," he says. "We really don't know how long the vaccines work."
Dr. Dutton says he is charging clients $30 for the new in-office TiterChek test. That's less than half his $64 charge for the lab tests, which take 10 days and require mailing specimens overnight in ice packs. That's still more expensive than a $10 vaccination, so Dr. Dutton thinks demand will be small, at least initially. "Most clients have opted for the vaccine because the chances of having an adverse reaction are very, very small," he says.
Older kinds of lab tests can also determine whether pets need a booster. (For a list of major vaccine titer tests available go to www.antechdiagnostics.com )