A news report from The Olympian newspaper reports a localized outbreak of parvoviral enteritis, or “Parvo” in Southwest Idaho. According to the article, “Veterinary clinics and hospitals in Boise, Nampa and Caldwell are all reporting a spike in canines with symptoms of parvovirus. In some Treasure Valley clinics, the increase is 10 times the normal rate.”
Parvo is caused by a virus shed in the feces of infected dogs. Puppies are especially vulnerable to infection between 8 and 20 weeks of age, when the antibodies they receive from nursing gradually decline and their own immune system has not yet produced enough antibodies to be protective. Some breeds are more sensitive to the virus than others, but any puppy can become infected. And the virus is very robust, able to remain infective in the environment for months.
With a series of vaccinations, the disease can almost always be prevented. As discussed in my primer on veterinary vaccines, a series is necessary because the maternal antibodies block the vaccines, and the puppies own antibodies are produced gradually over time and take a while to reach protective levels. It is true that surviving the disease will lead to protective antibody levels, often for life. However, 20% of puppies with the disease will die, and many others will experience needless suffering.
Local vets in the area of the outbreak are theorizing that dog owners are neglecting to get all of the recommended puppy vaccine series due to the troubled economy. As the article correctly states, “The vaccine for parvovirus is very, very effective, 99.9 percent effective. It’s unfortunate to see so many cases because it does not have to happen,” said Dr. Kayla Williams of the Blayney Veterinary Clinic, which has treated 30 cases in the last four weeks.”
Outbreaks like this are unfortunate, but they provide needed reminders that vaccination is critical to prevent diseases like parvoviral enteritis, which persist at low levels in the population waiting for a lapse in vaccination to re-emerge as an epidemic. Vaccines are another medical tool that are in some ways hurt by their very success. Anti-vaccine propaganda can convince people such diseases are no longer a threat because most people who have properly vaccinated their pets will never see a case. Here is yet another piece of evidence that this is a dangerous myth.