It's hard to believe that in an advanced country like the United States, fewer than half of all puppies and kittens are being vaccinated.
Yet that's exactly what was found in a study recently completed by veterinarians at the University of Wisconsin-Madison School of Veterinary Medicine, in cooperation with the Dane County Humane Society.
"This is an issue, because a population must reach a certain threshold of immunity - called 'herd immunity' - in order to protect the whole group," says Ronald Schultz, a vaccinologist at the School of Veterinary Medicine who has devoted his career to studying the effectiveness of vaccines. "If not enough individuals in a population are protected, disease can always find a new foothold."
That fact is especially problematic at no-kill shelters, he says, where bringing in one diseased animal can quickly ignite illness throughout a facility.
"Letting animals die in their own feces and vomit rather than euthanizing them is not a humane way to reduce a population of unwanted animals," Schultz says.
He stresses that we must make an effort to vaccinate a higher percentage of puppies and kittens and at the same time vaccinate the pet animal less often. That is the program that will improve herd immunity in the safest and most effective way.
Based on samples taken from various animal shelters around the nation, he and his colleagues found that only about 50 percent of dogs had been exposed (either naturally or by vaccination) to canine distemper and parvovirus. If they had ever been vaccinated, they would have carried antibodies against distemper and canine parvovirus for a lifetime because all commercial vaccines carry both.
"These results suggest that there would be a high percentage of dogs not vaccinated for rabies virus as well, even though we didn't test for that," Schultz says.
Only 25 percent of cats had been vaccinated against panleukopenia, the feline version of distemper.
Schultz reminds pet owners that unvaccinated animals can spread disease when they defecate in yards, thereby exposing even seemingly isolated pets. Unvaccinated pets are also at risk whenever they visit a high-risk exposure area such as a dog park or puppy socialization class.
The core diseases of distemper and parvovirus (canine and feline) can cause severe respiratory, gastrointestinal and neurological problems, as well as death, in a high percentage of unvaccinated animals.
Without the general immunity offered by broad vaccination, diseases such as parvovirus remain active in the environment, waiting to infect any animal that hasn't been immunized.
Source: University of Wisconsin-Madison
Explore further: Penis transplant offers hope to victims of botched circumcisions