Written By Dr. Travis McDermott
Last Updated July 12, 2021

The first year in a dog’s life is one of the most crucial stages in its development, which is one of the many reasons that unvaccinated dogs are a cause for concern. This is the stage where a dog is most vulnerable to deadly diseases brought about by highly contagious and highly fatal viral infections. Among the viral infections that affect dogs, none can bring fear and abject horror to pet parents than canine parvovirus.

If the infection is severe enough and prompt and aggressive treatment is not administered at once, you can say goodbye to your pooch in as short as 48 hours, some extending to 72 hours. The key to averting disaster is in the early recognition of the infection’s symptoms and understanding how infected dogs should be treated.

What is Canine Parvovirus?

When vets talk about parvo, they are most likely referring to Canine Parvovirus Type 2 or CPV 2. Animal experts believe that CPV2 came from Feline Panleukopenia Virus (FPLV); a type of feline parvovirus that typically infects cats.

CPV2 is believed to be a mutation of FPLV since both viruses share the same viral structure and characteristics. Because of its mutagenic properties, microbiologists say that the current strain of Canine Parvovirus Type 2 is completely different from the original 1978 strain.

There are two forms of canine parvovirus infections: intestinal and cardiac. An infected dog will show several clinical signs, whether they are young puppies or an adult dog.

dog laying down

Intestinal Parvo

Infection occurs through the oral route where dogs ingest items or objects that may be contaminated with the CPV 2 by other, infected dogs. Upon ingestion, the virus migrates to the lymphoid tissue in the throat of the now infected dog, eventually spreading through the bloodstream. The virus attacks all of the cells in the body that rapidly divide, but will mostly target the cells found in the crypts of the intestines, the lymph nodes, and bone marrow cells.

How the Virus Affects a Dog’s Body

When the virus reaches the small intestine, the epithelial cells are destroyed, releasing anaerobic bacteria into the bloodstream through the gastrointestinal tract. Intestinal bacteria roaming the blood is extremely dangerous. All of this leads to sepsis until such time that systemic inflammatory response syndrome results.

The presence of Clostridium, Salmonella, and Campylobacter species in the blood cells leads to increased clotting tendencies, resulting in acute respiratory distress. If not treated promptly, the dog dies of massive sepsis and septic shock from septic toxins being released into the body.

However, even without the presence of sepsis, the dog will be experiencing massive fluid loss resulting in dehydration and fluid and electrolyte imbalance because of the inflammatory changes that occur in the intestines. Death can still ensue because of hypovolemic shock if not severe electrolyte abnormalities and acid-base imbalances. These severe cases are why knowing the clinical signs of the virus is so vital.

In less severe cases, the virus can actually stay in the dog’s intestines for up to 3 weeks. On the third or fourth day following infection, the dog will begin shedding the virus through its stool. This continues for up to three weeks but does mean that the CPV infection is present in the dog’s stool and can infect another unvaccinated dog.

Cardiac Parvo

The cardiac form of parvo is mostly confined to puppies in the first few weeks of their life. Experts believe that the severe disease is transmitted by an infected pregnant dog to its litter. The virus primarily targets the muscles of the heart. The cause of death of the puppy is mostly related to pulmonary edema leading to respiratory arrest.

What Dogs are More Susceptible to Parvo Infection?

The following types of dogs are regarded as the most susceptible to the development of Canine Parvovirus infections:

  • Puppies that are between the ages of 6 weeks of age and 6 months (adolescent dogs)
  • An unvaccinated puppy or dog
  • Puppies or dogs with incomplete vaccinations
  • Dogs that have concurrent canine coronavirus infections
  • Dogs that have concurrent bacterial and parasitic infections
  • Canines living in highly stressful environments
  • Canines that are black and tan; such as German Shepherds, Doberman Pinschers, American Staffordshire Terriers, Rottweilers, Pit Bull Terriers, and English Springer Spaniels

For the majority of these dogs, the reason for increased susceptibility is closely related to an issue with the dog’s immune system. It could either be still immature or is in a compromised state. As for the different breeds of dogs that are susceptible to parvo infection, scientists still don’t have a clue as to why black- and tan-colored breeds are more vulnerable to such an infection than other breeds.

What Causes Parvovirus Infection in Unvaccinated Dogs?

There are two ways by which parvovirus can be transmitted to dogs. These can include direct contact and indirect contact.

Direct Transmission

As mentioned, dogs that are infected with CPV2 begin shedding the virus through their stools or feces as early as the third day after infection. This viral shedding can go on for another 2 to 3 weeks. If another dog sniffs or licks this contaminated substance, then they will also get infected with this highly contagious virus.

This kind of transmission is called direct transmission since an otherwise healthy dog got in direct contact with the contaminated feces or stool of dogs infected with canine parvovirus (CPV). You could also see a form of direct transmission take place from food and water bowls, considering the saliva of the infected dog could carry the disease.

The main problem is among most puppies. These young pooches love to explore their surroundings and they use their mouth as their principal organ of discovery. Unfortunately, there are no labels or signs in dog poop that say that it is contaminated. In just a day or two, you’ll be seeing some symptoms from your puppy whose young immune cells will struggle with the virus.

Indirect Transmission

The second method in which CPV2 can be transmitted is by indirect contact. Experts believe that the virus is a very resilient, very tough microorganism. It can survive outdoors for many years provided it can develop adequate protection from harsh rays of the sun. Indoors, the virus can stay alive for up to 2 months. It is very resistant to common household disinfectants and cleaners.

This is where the problem lies. When we go out and we step on a dog poop that is contaminated with CPV2, we are essentially bringing the virus right into our homes. If we bring our shoes right inside the house without bothering to clean and disinfect them with bleach (CPV2 is known to be vulnerable to bleach), then we’re increasing the risk of infecting our pooches. Sadly, we are not really aware that the poop we stepped on is actually contaminated with CPV2. Therefore, it is vital to properly disinfect contaminated areas when things like mud are tracked through a house. Who knows what we bring home with us!

Indirect contact can also happen when most dogs have contact with people or objects that are contaminated with the CPV2. Clinical signs develop within days after transmission has occurred.

What are the Clinical Signs of Canine Parvo?

Now that we have an idea of what Canine Parvo is, what it does to our dogs, and how it is transmitted from one dog to another, it is time to look at the most common signs and symptoms of canine parvo infections. Your prompt recognition of these symptoms will help determine whether your pooch will be able to survive its ordeal.

Symptom List for Infected Dogs

One of the earliest signs of CPV2 infection is lethargy. This usually presents on the 3rd day after infection and is typically followed by a loss of appetite, weight loss, severe diarrhea, and vomiting. The last two manifestations are critical since the condition can deteriorate very rapidly, which is when acid-base imbalance, electrolyte abnormalities, and dehydration occur due to fluid loss.

Because of the rupture of the intestinal crypts, bacteria that should otherwise be confined to the intestinal tract find their way into the bloodstream causing massive secondary bacterial infection, further overwhelming the dog’s immune system. This further weakens the pooch and if treatment is not started promptly and aggressively, shock and death can ensue within the next 48 to 72 hours.

How Can a Parvo Infected Dog Be Treated?

Because of the high level of communicability, virulence, and pathogenicity of CPV2, only aggressive treatment can help avert any disastrous consequences of the infection, namely septic and hypovolemic shock and death. The trick is that the earlier the symptoms of CPV2 are recognized the earlier a confirmatory diagnosis can be made. This is the basis for prompt and definitive treatment that includes the following.

Aggressive Fluid Resuscitation

Since one of the major problems in CPV2 infection is dehydration secondary to excessive vomiting and diarrhea, dogs will require aggressive fluid resuscitation through the administration of intravenous solutions. These IV fluids typically come in the form of balanced electrolyte solutions complete with potassium chloride, dextrose, and vitamin B complex. Additionally, depending on the amount of blood lost through the feces in the form of bloody diarrhea, a vet at a veterinary clinic can also order blood volume expanders and colloidal therapy.

Antiemetic Therapy

To address the issue of severe vomiting in dogs with CPV2 infection, vets can administer antiemetic medications such as metoclopramide, prochlorperazine, dolasetron, maropitant, and ondansetron. This is to help control vomiting and reduce further fluid and electrolyte losses.

Broad-Spectrum Antibiotic Therapy

A variety of antibiotics will be considered in the management of secondary bacterial infections brought about by tissue destruction in the intestinal crypts. Some of the more common broad-spectrum antibiotics given to such dogs include cefazolin/enrofloxacin, metronidazole, ampicillin/enrofloxacin, and timentin. The count of serial white blood cells is generally performed daily to help evaluate the dog’s therapeutic response to antibiotics.

Immunologic Support

Some veterinary clinics have packs of blood plasma obtained from a donor dog that was able to survive CPV2 infection. These are stored in air-tight, temperature-controlled containers for maximum effectiveness. Some clinics have frozen serum instead. What they do is administer these products as blood transfusion, transferring the CPV2 antibodies from the donor plasma to the sick dog, conferring passive immunity. However, the practice has not yet gained widespread acceptance because of the dearth of clinical evidence supporting its merits.

Symptomatic Treatment

If the dog has a fever and/or abdominal pain, appropriate canine analgesics are administered. Fluid replacements are also provided for each episode of diarrhea and/or vomiting in the form of intravenous fluids. This is in addition to fluid resuscitation therapy.

dog in bed

If the dog can avoid vomiting for a certain period of time, intravenous fluid therapy is gradually reduced. If the dog hasn’t vomited in the last 24 hours, it may be fed with a soft, bland diet so that it can absorb nutrients from food again. Pups that can’t tolerate enteral feeding will benefit from easily digestible foods.

If the symptoms were detected early and aggressive treatments were initiated at once, a dog usually recovers within 5 days, although it is not unusual for dogs to take up to 3 weeks before fully recovering.

If the symptoms are very mild, recovery is expected within 3 days. Sadly, even with extensive hospitalization, there really is no guaranteeing the dog will come out of the CPV2 ordeal alive. For those that do, many vets will consider them to be miracle pooches because of the survival rate.

Supportive care from the dog’s owner(s) is crucial to ensure the pup recovers. With care, fast and aggressive treatment, and the right pain medication and other, related medications, the poor prognosis of this virus can be turned around.

How Can Parvo be Prevented?

Based on our knowledge of how CPV2 is transmitted, we can think of a variety of ways in which we can prevent Parvo infection in our dogs.

Vaccination

Proper vaccination of all puppies by age 7 to 8 weeks is administered every 3 to 4 weeks until the puppy reaches the age of 16 weeks at the very least. The number of vaccinations should be at least 3. A booster dose is given 1 year after the last vaccine dose and then every 3 years thereafter. The canine parvovirus vaccine is an effective way to prevent all the nastiness of this virus.

Protective Prevention

For puppies that are older than 16 weeks, they should be vaccinated twice about 3 to 4 weeks apart, although a third dose is usually considered highly protective.

All fully vaccinated adult dogs should also receive revaccination against Parvo every 3 years.

Clean and Disinfect

Disinfect all household articles and surfaces of the home using a 1:10 ratio of household bleach to water. This is the only household chemical that is proven to kill Canine Parvovirus.

Quarantine and Treat

If you suspect your dog to be infected with CPV2, it is important to keep it in quarantine for at least 2 weeks to help prevent the transmission of the virus to other dogs and mammals in the neighborhood.

Canine Parvovirus infection is a deadly disease in dogs, especially puppies. Knowing what it is and how to recognize its symptoms should help you decide when to take your pooch to the vet. Remember, the earlier you recognize the symptoms, the earlier your vet can initiate treatment. In severe cases, you must go to your veterinarian immediately.

Sources:

  1. Elena Kilian, Long-term Effects Of Canine Parvovirus Infection In Dogs, PLOS
  2. Canine Parvovirus, American Veterinary Medical Association

Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.

Dr. Travis McDermott is a small animal veterinarian that has been practicing for nearly 15 years in Las Vegas, NV. Dr. McDermott was born and raised in the great State of Texas and grew up on an emu farm raising chickens and pigs for 4H and FFA. He attended Texas A&M University for both undergraduate and DVM studies.After graduation in 2006, Dr. Travis McDermott started practicing at Tropicana Animal Hospital in Las Vegas, NV. In 2012, he took over as hospital director of Durango Animal Hospital – one of the largest veterinary hospitals in Las Vegas. Dr. McDermott treats dogs and cats as well pretty much any exotic animal that walks in the door. His interests include surgery, dental procedures, and ultrasound, but his main passion is endoscopy. Since becoming a veterinarian, Dr. McDermott has served as a board member and president/chair of both the Nevada Veterinary Medical Association and the American Veterinary Medical Association Political Action Committee and currently serves on the board of the Viticus Group (formerly Western Veterinary Conference).

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