What is Parvo?

Understanding Canine Parvovirus: A Serious and Contagious Threat

If this article is being read out of concern that a dog may be infected with Parvovirus (commonly known as “Parvo”), it is imperative to contact a veterinarian immediately. Parvo is not a condition to be delayed or second-guessed. It poses a significant health risk to dogs, can cause permanent damage, and in many cases, can be fatal if not treated promptly.

This article provides a comprehensive overview of Parvovirus, a highly contagious viral disease that can only be diagnosed by a licensed veterinarian. There are two main strains of Parvo: one that affects the heart and another that attacks the intestines. The most prevalent strain is CPV-2, which primarily affects the gastrointestinal system. Fortunately, this virus cannot be transmitted to humans.

Parvovirus is remarkably resilient. First identified in the early 1970s, it had spread globally by the end of that decade. It is capable of surviving in a wide range of climates and does not die off simply due to seasonal heat or cold. The virus spreads rapidly, in part due to the microscopic size of its viral particles. According to veterinary professionals, a sugar cube–sized amount of feces can contain up to one billion Parvo particles—and it takes as few as 100 of these to infect a dog.

Parvovirus is transmitted exclusively through dog feces, either directly or indirectly. It cannot be contracted from cats or cat feces. A dog becomes infected by ingesting material contaminated with the virus. Although the virus is shed in feces, it can survive independently in the environment for extended periods. It is commonly spread via indirect contact, such as through contaminated shoes. This is why many shelters, including Humane Societies and ASPCAs, use footbaths containing diluted bleach between wards—to prevent inadvertent spread via footwear.

Years of experience, including a tenure as kennel manager at the Idaho Humane Society, have provided firsthand insight into the challenge of managing Parvo in high-density dog populations. In the facility’s original layout, dogs had access to both indoor and outdoor runs, which allowed wild birds—particularly sparrows—to enter the kennels. These birds would often land in food bowls, potentially spreading the virus from kennel to kennel. While modern shelter designs have mitigated this risk, similar scenarios remain a concern for dog owners.

Prevention is key. The best line of defense against Parvovirus is proper vaccination, beginning at a young age. If a mother contracts Parvo, her puppies face almost certain death if infected. While puppies are most vulnerable, adult dogs can also contract the virus. Although adult dogs may have a higher chance of survival, Parvo remains potentially lethal.

Recognizing the symptoms of Parvo is critical. Dogs infected with the virus will often exhibit severe lethargy and vomiting, followed by fever and dehydration. The most telling sign is bloody diarrhea, which should prompt immediate veterinary consultation. However, before visiting the vet, always call first. Due to the highly contagious nature of Parvo, most clinics have designated quarantine areas and will provide instructions to avoid exposing other animals.

Lastly, monitoring for signs of shock is vital, as it drastically increases the risk of fatality. Swift and appropriate action can make the difference in recovery outcomes.

Parvovirus is serious—but with awareness, prevention, and early treatment, it is manageable.