Parvovirus: Symptoms, Treatment, and Prevention
By Maranda Elswick, DVM
Utter the term parvo to any pet parent, and you’ll likely see a flicker of recognition and concern. But what exactly is parvo, and how can pet parents recognize and prevent it?
Canine parvovirus (CPV-2), often abbreviated as “parvo,” is a highly-contagious and potentially deadly virus that attacks the gastrointestinal (GI) tract and immune system of unvaccinated puppies and adult dogs. A feline parvovirus strain is also highly contagious amongst cats, but these viral strains are species-specific and cannot cross-infect between dogs and cats. Neither virus can be transmitted to humans. Fortunately, both canine and feline parvoviruses are preventable with proper vaccination.
Canine parvovirus, common worldwide, is shed in the feces of infected domestic dogs and dog-like wild animals such as coyotes and foxes. It spreads easily and is highly infectious, causing 100% morbidity (or illness) in exposed unvaccinated dogs. The virus can be spread via direct contact between dogs or secondary exposure to a surface or object contaminated with the fecal material of an infected canine. If not promptly diagnosed and treated, it can be fatal.
So what does this mean to pet parents? While all unvaccinated dogs are at risk of parvovirus infection, puppies are most at risk, particularly young pups between 6-20 weeks of age. All dog breeds could be affected, but Pit Bulls, Rottweilers, and Dobermans may be at increased risk of the disease.
That means pet parents who can recognize clinical signs that their dog may have parvo, will be better equipped to seek veterinary care when it matters most. However, prevention is easier than treatment, and all dog owners should follow the vaccination advice of their veterinarians.
What To Look For: Top Parvovirus Symptoms
Parvovirus primarily attacks the gastrointestinal and immune systems of dogs, causing these most common clinical signs of the infection: 1) vomiting, 2) bloody diarrhea, 3) decreased appetite, 4) abdominal pain, 5) lethargy, and 6) fever.
While the clinical signs of parvo may be similar to the GI issues that often accompany dietary indiscretions or a foreign body ingestion -- for example, decreased appetite, vomiting, and mild diarrhea -- the signs of parvo are usually more severe and progress more rapidly. Worsening signs should not be dismissed as something dogs will get over on their own without treatment. Delaying veterinary intervention by even a few hours can lead to a grave outcome.
Pet owners should be especially suspicious of parvovirus symptoms in a puppy or adult dog who has not been fully vaccinated, or who has not been boostered within the past year. Puppies can deteriorate rapidly and parvo is life-threatening, particularly without treatment, so seeking immediate veterinary care is imperative to saving a sick pup’s life. Pet parents who observe the following signs should contact their local veterinarian immediately.
When parvovirus attacks the GI tract, it invades and damages intestinal villi, the tiny finger-like projections of the intestinal lining that normally absorb nutrients. Inflammation of the intestine (enteritis) ensues, leading to nausea and severe vomiting, which then causes dehydration and electrolyte impairment. And because the intestinal villi are damaged, the body cannot utilize dietary nutrients. Furthermore, frequent vomiting can lead to intussusception, a painful and life-threatening condition in which a portion of the intestine telescopes in on itself, leading to an obstruction that requires veterinary intervention.
Parvo enteritis also leads to foul-smelling, bloody diarrhea, the most telltale sign of canine parvovirus. Dogs become even more dehydrated due to ongoing fluid losses in their stool. Look for visible signs of dehydration, such as dry gums and skin that doesn’t bounce back normally after being gently pulled.
Because of inflammation of the intestines and GI upset, dogs and puppies may become inappetent, refusing to eat. Some may act interested in food at first, but then turn away from a meal due to feeling nauseous. Puppies have limited energy reserves and can quickly become hypoglycemic if they stop eating. However, never try to force food or water on a dog with suspected parvovirus. The oral route of administering hydration and nutrients should be avoided because the gut may be too damaged to tolerate them properly, so eating or drinking can worsen vomiting and diarrhea. Veterinary care through the administration of IV fluids and nutrition may be required.
Abdominal discomfort and cramping are common with parvovirus infections. Mild bloating can also sometimes occur. Pets may whine or whimper in pain. Severe pain, which can trigger dogs to try to snap or bite, can be a sign of intussusception, an emergency condition.
Puppies and adult dogs with less serious GI conditions (such as discomfort after eating something that doesn’t agree with them) may have mild vomiting and diarrhea. But they are typically bright and alert, overall feeling good. Dogs with parvovirus, however, deteriorate rapidly, becoming very weak and lethargic. Some become too weak to walk or stand. Their body is fighting off the parvo infection, while becoming dehydrated and depleted of nourishment, leading to exhaustion.
A dog’s normal body temperature is 100.5-102.5°F. Because dogs and puppies with parvovirus are trying to ward off the viral infection, they tend to run a fever. Their immune system is also under attack by parvovirus, which destroys disease-fighting white blood cells, leading to low white blood cell count and making infected dogs more susceptible to other infections. Secondary bacterial infections can result in sepsis, which can be fatal. These bacteria can use up what little blood sugar supplies a puppy has left, thus worsening hypoglycemia. As immunocompromised dogs continue to become sicker, their body temperature can then drop, causing pets to become hypothermic, which carries a very grave prognostic outlook.
Though parvovirus primarily attacks the gastrointestinal tract and immune system of unvaccinated puppies (typically 6-20 weeks of age) and older dogs, parvo infection can also result in other less common, but equally serious complications like inflammation of the heart muscle.
How To Treat Parvovirus
It’s crucial for pet parents to contact a local veterinary clinic as soon as they observe any of the above signs in a puppy or adult dog. Prompt detection and diagnosis are key to implementing early treatment, which is integral to the dog’s survival. Without treatment, the mortality rate is 91% for infected puppies and 10% for adult dogs. Many patients, particularly younger puppies and small breed dogs, die within 48 hours of the development of clinical signs, secondary to dehydration or sepsis. Many others are euthanized to end suffering when the prognosis is poor or when treatment costs become too expensive for owners to continue.
The good news is that with proper early veterinary therapy, the survival rate increases significantly to 75-80% survival with a full recovery. Routine vaccination is even better as it is virtually 100% effective at preventing disease in the first place.
Any dog exhibiting signs of parvovirus should be strictly isolated from other unvaccinated dogs or young puppies until the virus can be ruled out by a veterinarian to prevent potential spread. Infected dogs begin to shed the virus in their stool 4-5 days after being exposed, and they can remain contagious to other dogs for roughly 10 days following the resolution of their clinical signs. If parvovirus is suspected, your veterinary clinic will follow strict biosecurity and cleaning protocols to prevent its spread to other canine patients in the hospital.
Diagnosis involves a physical exam, parvovirus antigen test, and bloodwork. A stool sample is analyzed for the presence of parvovirus antigen (a viral protein that triggers an immune response in exposed dogs) to confirm the diagnosis within minutes.
Therapy involves supportive care to manage the symptoms of enteritis and panleukopenia rather than directly curing the viral infection. The body’s own immune system must rid the actual virus as it receives support from these therapies. Therapy includes IV fluids, IV dextrose (for nutrition), anti-nausea medications, and IV antibiotics to prevent secondary infections.
Severe cases may require a whole blood or plasma transfusion. Puppies and dogs will be hospitalized in isolation for around 2-5 days during treatment, receiving constant monitoring. Pet insurance, such as 24PetWatch Pet Insurance Programs, can greatly help offset the costs incurred with such intensive care. Attempts at in-home treatment are not often successful.
How To Prevent Parvovirus
The key to a successful parvovirus outcome lies in prevention. Proper vaccination, particularly in puppies, is vital to their health. The parvovirus vaccine is a core vaccine, most commonly administered in a combination vaccine called DHPP, which immunizes canines against distemper, hepatitis, parvovirus, and parainfluenza. This combo vaccine is administered to puppies as a 3- or 4-part series, roughly every 2-3 weeks between the ages of 8-15 weeks of age. (Some vets may vaccinate as young as 6 weeks old or as late as 18 weeks old.) Vaccination is recommended at this age since puppies have been weaned around this time, meaning they are no longer receiving protective antibodies against these viruses from their mother’s milk.
Once this initial series is completed, the vaccine should be boostered annually for the remainder of the dog’s life. Not completing the vaccine series in a puppy or allowing the vaccine booster to lapse in an adult dog can leave them at risk for infection. To ensure efficacy, vaccines should only be administered by a veterinarian, who will ensure that the vaccines are stored, handled, and injected properly. Vaccines acquired from a feed supply store or directly from a breeder should not be used.
Before puppies have completed their full vaccine series, they should be kept indoors only and away from other unvaccinated dogs or those in contact with other dogs. Even if they are fully vaccinated, dogs that are immunocompromised (such as those receiving chemotherapy or other immunosuppressant drugs) should also be kept away from high-risk areas because they are at increased risk of acquiring infections.
Since parvovirus is so prevalent in the environment, unvaccinated pups can easily become infected with outdoor exposure or direct contact with another dog. Avoid puppy playdates, dog parks, and daycare until after the full vaccine series is complete. Pet parents should also wash their hands and clothing thoroughly after handling another dog and before petting a puppy. Shed parvovirus particles can survive up to 1 month indoors and several months or even a year outdoors. Parvo is a hardy virus, thus highly resistant to most cleaners. Bleach is one of the only cleaners effective at killing the virus. After removing fecal material, any surface or material with which an infected dog has been in contact should be thoroughly disinfected with bleach; this includes flooring, bedding, food and water bowls, and toys.
By adhering to the preventative measures of proper vaccination as well as avoiding contact with the environment or other dogs until after immunization is complete, pet owners can essentially drop their pup’s risk of parvovirus infection to zero. A 3-series vaccination is roughly $100 (may vary depending on location) while up to $2000 or more can be incurred via diagnostics and treatment of dogs infected with parvo, and sadly 20-25% of these dogs die or are euthanized despite receiving this costly treatment. Thus, proper preventative care not only saves money and energy in the long run, but it can save the life of your dog.
Purchasing pet insurance, such as 24PetWatch Pet Insurance Programs, when you acquire a new pet is also important, as pet insurance (just like human medical insurance) can help offset the costs of unexpected illness or injury that your pet may endure. No one wants to be caught financially unprepared in the case of a pet emergency like parvovirus.
Dr. Maranda Elswick is a licensed veterinarian in Florida and Virginia with special interests in preventative medicine, hospice care, and client communication. Dr. Elswick is also founder of The Meowing Vet, LLC, a quirky veterinary web presence for pet owners and veterinary professionals.