Canine parvovirus is a deadly disease that can strike fear into the hearts of new puppy owners. Though it's often thought of as a "puppy disease" it can strike dogs of any age.
Risk of Parvovirus to Adult Dogs
Parvovirus affects puppies more often than adult dogs because they lack immunity. According to Veterinarian Dr. Jeff Werber, parvo is mostly an issue for, "Dogs that don't have immunity, either from mother's immunity, which is called passive immunity, or from vaccinations or from the street." Nursing is important for developing immunity because, "especially in the first 36 hours of nursing, puppies are getting the colostrum" in the mother's milk which contains critical antibodies. However, "is it possible" for adult dogs to get parvovirus.
How Adult Dogs Get Parvovirus
Adult dogs who have not been vaccinated and have not developed a natural "street immunity" to the disease, or who have immune systems that are compromised, can get parvovirus if exposed to enough of the virus. Dr. Werber describes the typical incidence of a disease with a dog. "In any disease there's always a battle between immunity, in other words the antibodies and the load of the antigen. If the antigen load is higher than the antibody protection, then the dog gets the disease." He summarizes that, "it all depends on what we call the 'challenge dose,' which is how much virus the dog is exposed to and whether he has enough antibodies to beat it."
Differences Between Adult and Puppy Parvovirus
Both the symptoms and treatment of parvovirus are the same for adult dogs and puppies. Dr. Werber says adult parvo is "probably not," as serious as parvo in puppies but, "You still have to treat it," regardless. Just as with puppies, the treatment of parvo with adult dogs is largely "supportive care and protection against secondary opportunistic invaders."
Dr. Werber describes the typical treatment as, "fluids, plus vitamins or additives in the fluids, and antibiotics to protect against secondary viral infections." He concludes that despite the risk, "The immune system of an adult dog is probably stronger than a little puppy's, therefore as long as you can keep them supported and hydrated and control the vomiting, an adult dog should do a little better than a puppy."
Multiple Cases of Parvovirus
With some diseases, having the virus once and surviving it can give a dog "lifelong immunity." However, this isn't always the case. Dr. Werber explains that a dog could get parvo again if there's a new strain of the virus that the dog to which the dog has not developed an immunity. However, "theoretically having survived a natural infection should afford lifelong immunity, at least to that strain of the virus."
Vaccinated Adult Dogs and Parvovirus
A dog that has been vaccinated against parvo could still potentially get the virus although they may experience a less intense form of the disease. No vaccine can be said to provide 100% complete protection, and this is particularly true if the virus strains change. Some dogs may not properly process the vaccine at the time it was given and therefore their immune response doesn't develop as it should to provide protection. This can happen due to the dog's health at the time or due to receiving a higher than normal amount of antibodies when nursing from their mother. If the amount is too high, it can actually cancel out the effects of the vaccine.
Giving Older Dogs the Parvovirus Vaccine
If you have an older dog that has never been vaccinated, it's still possible to vaccinate them for parvovirus as long as they are healthy. Dr. Werber states that, "The vaccine issue is not a function of age as much as body condition and health." A dog that is younger but very ill would be a bad candidate for vaccination because you would be giving them the antigen of a disease just when they're body's immune system is already compromised. Dr. Werber describes this as "defeating the purpose of the vaccination." On the other hand an older dog, even a senior dog, that is healthy could be safely vaccinated and benefit from the protection afforded by the vaccine.
Older Dogs and Vaccine Titers
Dr. Werber advises clients with older dogs to consider vaccine titers "in lieu of arbitrary vaccinating on some basis often determined by the manufacturer of the vaccine." A titer test can measure the level of antibodies in a dog's system and indicate whether a vaccine is necessary or if antibody protection is low. A dog with poor immunity could then be vaccinated while one with a healthy level of antibodies could forego additional vaccines. Dr. Werber says, "it's my theory if you have a dog that is an adult dog and you're not sure about the vaccine status, run a titer. You'll get your answer" and can make a decision about vaccinating in consultation with your veterinarian.
Older Dogs and Canine Parvovirus
While parvovirus isn't as common in older dogs, they are by no means free of risk of catching the disease. Adult dogs who get parvo may be better able to survive the disease but without treatment a fatality is not impossible. It's important to make sure your dog is properly vaccinated to avoid parvo altogether. If you're unsure whether your dog needs the vaccination, speak to your veterinarian and discuss your options, including titer testing.