Paws in Peril: The Unseen Threat of Parvovirus Among Dogs

by Aubrey Rose Semaning, Elica Giane Tolorio, and Krystal Szeg Mecca Vitto

Image of canine parvovirus under a microscope (Source: Paradiso, Rhode III, & Singer, 1982)

If you’re a dog owner or planning to be one, the last thing you want is for your dog to get sick. Unfortunately, there are viruses in the environment that threaten the lives of our dogs, one of them being canine parvovirus.

Unlike the virus causing COVID-19, canine parvovirus sticks. It can resist common household detergents and disinfectants and can cling to surfaces for weeks, and even months. Every dog is at risk of getting the virus because it can stay in the environment for long periods.

What kind of virus is parvo?

A virus is a microorganism that must infect cells to live and multiply, as defined by the National Human Genome Institute. It can be classified into two types according to its structure: naked and enveloped.

The reason why canine parvovirus (parvo, hereafter) can resist extreme temperatures and disinfectants is that it is a naked virus, according to Dr. John Michael Bernardo, a veterinarian and faculty member of the Department of Veterinary Paraclinical Sciences of the College of Veterinary Medicine (CVM) at the University of the Philippines, Los Baños (UPLB). It has no known origin but is believed to have evolved from feline parvovirus, which causes feline panleukopenia, a highly infectious disease among cats. 

An article by the Virology Research Services of Southeast England reports that compared to naked viruses, enveloped viruses contain an extra layer of fats that covers the two main parts of a virus: the viral genome or the infectious particle, and the capsid, which is made of proteins and acts as the primary protection of the viral genome. The proteins that cling to the infected organism’s cells and cause infection, also called fusion proteins, in enveloped viruses are located along their envelope. However, the envelope is sensitive to chemical and physical factors like heat and disinfectants and can be damaged easily. Once the envelope is damaged, the virus loses fusion proteins and its ability to infect and persist in the organism’s body.

Think of an enveloped virus as a parcel packaged with bubble wrap. Without bubble wrap, your parcel is more fragile, and you cannot expect it to arrive at your doorstep in its best condition. In the same way, an enveloped virus cannot effectively infect an organism without its envelope. 

On the other hand, Dr. Bernardo said that naked viruses are infectious even without an envelope. Even if exposed to harsh conditions, naked viruses still retain their ability to infect because the proteins that cause infection are directly on their outer layer which is naturally resistant to damage.

Naked viruses are like stainless steel in that they don’t need additional layers to protect their fusion proteins just like how stainless steel doesn’t need another coat of protection to resist rust and retain its useful properties. This kind of virus can infect an organism as it is and remain stable on surfaces for a long time.

How parvo spreads

A possible transmission route of parvo is when you happen to step on a field of grass contaminated by parvo and bring your shoes home. Given that parvo is a naked virus that can resist detergents and disinfectants, even after you clean your shoes, the virus can still enter your dog’s body if your dog licks your shoes or their nose that touched your shoes.

Dr. Bernardo explained that parvo mainly spreads when a dog vulnerable to the virus comes into contact with the feces of infected dogs. Parvo from contaminated feces clings to surfaces (e.g., soil, tiles, cement, etc.) even after the surface has been cleaned or disinfected. Thus, once a dog licks or sniffs the contaminated surface—or even the feces itself as most of them do—and the virus enters the dog’s system, it is now ready to destroy its victim’s life.

The symptoms of parvo take 3-7 days to manifest in a dog, but the virus can spread to other dogs even before they show signs of infection until 2-4 weeks after their recovery. 

Dr. Bernardo shared that the virus is so common that veterinary clinics in the Philippines alone record at least one parvo case a day. They also observe a rise in parvo cases during the rainy season. He said that a likely cause is that the water carries the virus from contaminated surfaces to new grounds, increasing the coverage area of the infection.

Signs and symptoms

Image of a canine parvo patient with bloody diarrhea. (Source: Mowbray Veterinary Clinic, 2019)

Andrei only had his dog, Bea the Boggie, a female shih tzu, for almost only a month after it was given to him by their neighbor. However, in October of that year, he noticed that Bea was getting a little sluggish for a shih tzu who was always active and running around before.

We left for Makati that time, and we made sure that she had enough food and water. When we went home during the night, we noticed that Bea had not touched any of her food,” Andrei said.

A couple of days later, Bea started to vomit and have bloody diarrhea. Andrei managed to bring her to a veterinarian, put in an IV, and take medicines prescribed to her—Bea was diagnosed with parvo. Nevertheless, it was a little too late because Bea was only two months old, and it was a bit more difficult for her to fight the virus. It only took a couple of days before Bea passed away, leaving Andrei completely devastated.

Bea never left Andrei’s house, so how did Bea get the virus in the first place? It is important to note that Bea has not been vaccinated nor dewormed before she was given to Andrei. A possible reason might be that Bea got the virus through other dogs outside before she was given to Andrei or that the virus made its way to their house due to an unsuspecting carrier—a possible parvo transmission as described by Dr. Bernardo.

Aside from the common CPV-2 variant, commonly detected in dogs, another strain that is more rarely detected in dogs is the CPV-1 variant. Some symptoms of this strain include pneumonia, myocarditis or inflammation or swelling of the heart muscles, and swelling of the intestines. Possible reasons for the uncommonness of this strain, according to Dr. Bernardo, is that the strain might just be as rare as it is, or it might also be the lack of records of its detection.

Bea the Boggie (Source: Andrei Bacuño, 2022)

Why puppies?

Puppies, naturally curious and playful, are more likely to contract parvo than adult dogs. Since puppies are growing dogs, they have rapidly dividing cells in the walls along their intestines. As the virus enters a dog’s system, it will then find those rapidly dividing cells and infect them, making the cells unable to regenerate. According to Dr. Bernardo, when these cells don’t regenerate, organs fail to develop and eventually fail to function. Due to this, the intestinal walls of the dog can no longer absorb nutrients, leading to diarrhea. Aside from absorbing the supposed nourishment, these rapidly dividing cells act as guards and provide an extra layer of protection for the intestines from microorganisms, such as bacteria and viruses, that can cause diseases. Parvo, leaving the intestines destroyed and vulnerable, allows both good and harmful bacteria to enter the dog’s bloodstream and cause an infection.

Parvo attacks cells that protect dogs from infection. — Parvo destroys intestinal walls

Dr. Bernardo added that adult dogs, on the other hand, are less susceptible to parvo because the rapid division of cells in their already-developed organs has slowed down. They also require less nutrition than growing puppies, thus slowing down the division of cells in their bodies.

Additionally, although all dog breeds are at risk of getting infected by parvo, veterinarians observe that some dog breeds are at higher risk of infection or show more severe symptoms when infected. Dr. Bernardo stated that breeds more susceptible to parvo include Rottweilers, Doberman Pinschers, Labrador Retrievers, and German Shepherds. The reason behind this, however, is not yet known.

Can my dog have another disease while being infected with parvo?

While parvo is risky on its own, it is still possible to have another disease infecting dogs simultaneously with parvo. This instance is called co-infection—individual hosts may be infected with multiple agents such as viruses, bacteria, fungi, protozoa, or parasites at the same time.

When multiple infections exist in a dog’s body at the same time, the immune system might have a harder time identifying which is which and will have fewer fighting powers to defeat the infections simultaneously, especially if we are talking about parvo and helminthic infection or worms as per Dr. Bernardo.

It’s like a party where your two different friend groups come, causing you confusion and panic about which friend group you’ll tend to first—except nothing is to be celebrated with parvovirus and another infection.

Dr. Bernardo stated that every time a suspected parvo patient with diarrhea is brought to the veterinary hospital, it is highly suggested that fecal analysis or analysis of the dog’s poop is done aside from parvo testing. This is not just to confirm whether the dog has worms or not, but also to give the veterinarian an idea of the patient’s chances of survival. Dogs with co-infection have worse symptoms such as lethargy, vomiting, and diarrhea, ultimately causing worse dehydration and infection compared to dogs with only worms or only diagnosed with parvo.

Parvovirus treatment and prevention

However, despite its infectious nature, parvo can be treated and prevented.

Dr. Bernardo expressed that, just like COVID-19, we cannot target parvo, such that there is no specific drug or medicine that kills parvo in infected dogs. Fortunately, there are treatments to support the dog’s body system and strengthen its immune system to combat parvo infection.  

Image of a canine parvo testing kit. (Source: PAWSsion Project FB Page, 2023)

Veterinary clinics can provide symptomatic and supportive treatment.

Symptomatic treatments focus on treating symptoms. These involve licensed veterinarians prescribing and administering medications to address parvo-related symptoms such as bloody diarrhea, vomiting, and fever. These treatments are administered through oral medicines or intravenously through fluid injections.

For supportive treatment, licensed veterinarians may prescribe or administer supplements such as vitamins to enhance immunity, and electrolytes to replace losses due to vomiting and diarrhea. This also involves prescribing soft diets. In the case of parvo, Dr. Bernardo recommends feeding soft diets, such as shredded chicken, or easily digestible food to parvo-infected dogs, as they cannot easily digest hard foods due to their damaged bowels.  

While these clinical treatments do not guarantee the elimination of the virus, they are done to save your pets and boost their immunity to help fight the virus. 

Parvo is potentially a lethal and contagious disease among dogs thus requires close monitoring and attention. Hence, immediate action or hospitalization is vital for parvo-infected dogs to further increase their chances of overcoming the disease. 

“Since we’re combating a virus, it’s really best that [pet owners] submit their pets to professionals and not go with home remedies,” said Dr. Flor Marie Immanuelle R. Pilapil-Amante, of the Department of Veterinary Clinical Science at CVM.

Significantly, Dr. Pilapil-Amante added that bringing the parvo-infected dog to a licensed veterinarian can give a survival rate of about 90% to 95%, whereas if left untreated, fatality results in about 91%.  

Parvo vaccinations

Dr. Bernardo advised that pet owners should be proactive in having their pets vaccinated with the help of licensed veterinarians; essentially, vaccination helps build up or strengthen the immunity of puppies or dogs against parvo. 

Before the vaccination process, Dr. Bernardo stated that their recommended protocol is that pet owners should make sure that their pets are dewormed starting at two weeks of age; deworming is done up to three to six times within a two-week interval. 

Puppy deworming guide. (Reference: Bernardo, 2023)

The vaccination process starts as early as when pets are six weeks old, with a two- to four-week interval until they reach four months of age or 16 weeks of age. Dr. Bernardo mentioned that pets would have high protection against parvo if a series of vaccinations are already done when they are at 16 weeks of age.

As for dogs beyond 4 months of age that are yet to be vaccinated, the deworming process should also be done. But, before deworming, fecal analysis is performed to check the dog’s poop; this identifies what kind of worms are present, as the dewormer varies depending on the type of worm. After deworming, the vaccination starts after two more weeks. Dr. Bernardo stated that older dogs should receive two shots of vaccine at an interval of two weeks. 

Parvovirus vaccination guide for dogs. (Reference: Bernardo, 2023)

In the case of co-infection, such as in parvo-infected dogs diagnosed with worms, the puppy or dog should be stable or healthy before deworming. According to Dr. Bernardo, depending on the state of co-infection, the puppy or dog should be clinically administered or treated with intravenous (IV) fluids, supplements, or antibiotics to stabilize their condition before targeting the worms. Significantly, these processes should all be done with the consultation and help of a licensed veterinarian. 

The best preventive measure involves keeping the pet’s environment as clean as possible. 

“The virus is just in the environment,” said Dr. Pilapil-Amante.

Pet owners should be cautious of the places where they bring their pets, whether in pet parks, pet shops, grooming establishments, at home, at a neighbor’s house, or other locations. Always make sure that the pets’ surroundings are clean and that pets don’t eat other dogs’ poop or any other animals’ feces, as this is one of the primary routes of transmission of parvo, which is through the fecal-oral route.

When pets are infected with parvo, make sure that they don’t come into contact with other pets or be in a place where there are many pets. Also, when a pet owner or a person comes into contact with a parvo-infected dog, they should make sure that they don’t come into contact with other pets or that they are physically clean or disinfected. Parvo-infected dogs should immediately be clinically hospitalized and isolated from other dogs to prevent further transmission.  

Going forward with responsible pet ownership

Image of a dog getting parvo vaccination. (Source: PAWSsion Project FB Page, 2021 )

For all dog lovers, the severity of parvo should not be taken lightly. Ignoring this virus only results in either the death of your dog or another person’s.

Dr. Bernardo and Dr. Pilapil-Amante strongly advise against pet owners taking matters into their own hands without the consultation of licensed veterinarians. If you notice your dog refusing meals, not wanting to play, vomiting, or doing anything out of the ordinary, do not hesitate to approach the licensed veterinary clinic nearest you. Doing things on your own may only harm your dog even more.

When it comes to vaccinations, dog owners are to never take the word of breeders that the dog purchased or adopted is already vaccinated. Only licensed veterinarians are mandated by law to oversee and administer dog vaccinations.

Parvo may pose a dangerous threat to the welfare of our dogs, but times are changing, and the field of veterinary medicine is continuously evolving. The time will come when the field develops a specific treatment for parvo or even finds a way to eliminate it before it can reach your fur babies. Meanwhile, every dog owner should practice responsible pet ownership beyond feeding them for the welfare of every dog around us.