What's Happening Inside a Dog Infected With Parvo?

May 24, 2018





Parvovirus is a virus that attacks the cells that line the digestive tract.  This results in vomiting and diarrhea.  The diarrhea is usually bloody as the lining of the intestines is compromised.  Furthermore, this allows bacteria that normally lives within the digestive tract to enter the blood stream.  When this happens, the patient may get a blood infection or sepsis.  If a puppy or dog infected with parvovirus passes away, it is usually due to either severe dehydration and shock or from the blood infection.  While there is no specific cure for the virus itself, as veterinarians we aim to treat the dehydration, shock, and blood infection.  Therefore, our recommended treatment is IV fluids, IV antibiotics, and anti-nausea medications.  We recommend keeping patients diagnosed with parvovirus in hospital until they are eating, keeping food down, and the diarrhea has stopped or improved substantially.  With this treatment, we have an approximately 80% success rate. 


What is parvovirus?

Parvovirus is a disease caused by small viruses that are very hardy and very contagious. Parvoviruses are smaller than most other viruses and can last longer in the environment due to the lack of a fat envelope that is common in other viruses. The fat envelope is easily disturbed which is why other viruses do not live long outside of a host. The parvovirus simply has a protein coating which allows it to survive in the environment.


Where does the virus come from?

The virus is shed in the stool of an infected dog up to two weeks after the initial infection. When the dog defecates each ounce of stool contains extremely large amounts of parvovirus. From there the parvovirus can live just about anywhere in the environment, the carpet, the floor, the yard, etc. until another non-immune dog picks it up.

Why don’t all puppies become infected?

When puppies are born, they are completely unable to make antibodies against any infectious invader. Their mother secretes a specific type of milk called colostrum for the first day or two after giving birth. It contains all the antibodies that the mother dog has circulating in her own body and in this way, she gives her own immune experience to her offspring. These antibodies are protective until they wear off, sometime in the first 4 months of the puppy’s life. Since we do not know the exact time the mother’s antibodies wear off and how much colostrum the puppy received, the puppy must get a series of vaccines every 3 weeks until 16 weeks of age. One of these vaccines contains parvovirus, allowing the puppies own immune system to fight off any parvovirus it may encounter. We recommend that puppies be restricted from public outdoor areas until their vaccination series is completed at age 16 weeks.

If my dog is not vaccinated and encounters parvovirus what should I expect?

The virus enters the body through the mouth as the puppy cleans itself or eats food off the ground or floor. Once the puppy encounters parvovirus they may not show symptoms for about three to seven days after infection, this is known as the virus’ incubation period. The GI tract is where the heaviest damage occurs. Parvovirus effects the source of the new cells that make up the intestinal wall. Without new cells the intestine is unable to absorb nutrients. As the virus continues to cause damage in the intestines the barrier separating the contents of the intestine from the blood stream breaks down and bacteria from the intestines enter the body causing widespread infection.

Symptoms include:

• Diarrhea

• Vomiting

• Lethargy

• Lack of appetite

Is there a cure for parvovirus?

While there is not a cure for the actual virus there are treatments to help combat the internal damage and boost the immune system to help fight off the parvovirus. In order to do this, your veterinarian has to combat the main issues caused by the virus:

• Diarrhea and vomiting lead to extreme fluid loss and dehydration until shock and death result. • Loss of the intestinal barrier allows bacterial invasion of potentially the entire body. Septic toxins from these bacteria result in death. 


Treatments include but are not limited to:

• IV Fluid Therapy: This is where fluids are given intravenously at a steady rate to combat dehydration.

• Antibiotics: Broad spectrum antibiotics are given intravenously to combat widespread infection from the breakdown of the intestinal wall.

• Anti-Nausea Medications: These are also given intravenously to help stop the dog from vomiting. Average hospital stay is 5-7 days and is necessary due to the intestinal tract not being able to handle oral medications. Survival rate for parvovirus is 80% even with intensive treatment.

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