First things first – What is Parvo?
Almost every mammal species has its own parvovirus. The canine parvovirus was discovered in 1967. At first the strain present CPV-1 did not represent much of a threat except to newborn puppies. In 1978 a new variant appeared called CPV-2. At this time the virus was still new and no dog had any kind of immunity against the virus. With no resistance and no natural immunity to the virus, the resulting epidemic was disastrous.
In 1979, the virus mutated again creating the CPV-2a. This strain was even more aggressive that the first two. Vaccine manufacturers were unable to keep up with the demand. The virus is able to rapidly spread and infect dogs because it is shed in large numbers by infected dogs and is especially hardy once in the environment.
At this point in time, the virus is considered to be in every environment. Simply trying to keep a puppy from exposure to the virus is a futile task. Luckily, most dogs have some level of natural immunity to the virus and vaccination against it is common practice now.
How is it spread?
Parvo is spread through the feces of infected dogs. Very little fecal material is needed to transmit the virus. Parvovirus can remain in the environment for six months to a year. It is especially tough and it can survive both extreme heat and subzero temperatures. The virus enters the body through the mouth as the puppy or dog cleans itself or eats food off the ground. There is a three to seven day incubation period. First, the virus hangs out in the lymph nodes in the throat and begins to multiply. Once the virus has reached sufficient numbers, it then begins to attack the bone marrow and begins to kill the young cells of the immune system.
Signs and Symptoms
Symptoms of parvovirus include severe, bloody diarrhea, lethargy, vomiting, weight loss, lack of appetite, and fever. Parvo should be considered as a possible diagnosis for any young dog presenting with vomiting and diarrhea.
The GI tract is where the most damage is done by the virus. The lining of the intestinal tract is covered in finger like projections called villi. The villi are covered in even smaller finger like projections called microvilli. These projections increase the surface area of the intestine allowing for absorption of nutrients. The cells that make the the microvilli are short lived and are replaced by cells deeper in the tissue that rapidly multiply. The parvovirus strikes these cells. The villi then become blunted and the dog is not able to absorb nutrients. The lining between the digestive bacteria and the blood stream is broken down. This is what causes the characteristic bloody diarrhea of parvo. Bacteria can now enter the bloodstream causing widespread infection.
The virus kills in one of two ways. The first is dehydration and fluid loss brought on by diarrhea and vomiting. The second is bacterial infection from the loss of the intestinal barrier.
How is it Diagnosed?
A diagnosis is made by Parvo ELISA test. This is performed in clinic and takes about 15 minutes to run. The biggest drawback to the ELISA test is that recent vaccination with a live virus vaccine can cause a false positive. In this case, doing a complete blood count to look for a drop in white blood cells may also be done.
With proper treatment and hospitalization, the survival rate is 75-80%. Treatment of parvovirus centers around supportive care. Supportive care includes keeping the dog hydrated, comfortable, and as strong as possible. There is no way to kill the virus inside the dog. The only way to cure parvo is to keep the dog strong enough that eventually the immune system is able to make enough antibodies to the virus to fight it on its own. When treating parvo, be prepared for a 5-7 day hospital stay and intensive care. Unfortunately, treatment can be expensive.
The first step in treating parvo is keeping the dog hydrated. IV fluids are needed to replace the fluids lost by the extreme vomiting and diarrhea. Antibiotics are also needed to help prevent septicemia. The loss of the intestinal barrier allows bacteria from the GI tract into the bloodstream. Since the virus destroys the the immune system, the dog has no way to fight on its own. Keeping the patient comfortable is a key part in treating any disease.
Tests are done to monitor the progress of the disease and effectiveness of the treatment throughout the puppy’s time in hospitalization. These tests include white blood cell counts, complete blood count, electrolyte and glucose levels, urine specific gravity, lactate levels, and total blood protein.
There are some additional treatments that can be done to help the puppy (such as plasma transfusions and certain kinds of cold medicine). However, these options are not a substitute for hospitalization and need to be discussed in detail with your veterinarian before starting them.
Once the puppy has recovered from the worst of the infection, they can then be sent home. They will most likely be sent home with antibiotics, anti-nausea, and anti-diarrhea medications. It is important to follow your veterinarian’s instructions for the medications and home care.
Your puppy will probably be very hungry after going so long without solid food. He should be fed in small portions every 1-2 hours. If he is allowed to gorge himself, this can upset his already delicate tummy.
Your puppy should be considered contagious to other puppies for at least a month after infection. It is important to keep him confined from any dogs that have not had the full vaccine series. Your veterinarian will let you know when it’s ok to resume vaccines. It is possible that your puppy has developed a life long immunity from the parvovirus since the infection. You should still continue vaccinating him for parvo along with all other recommend vaccines. There should be no permanent ramifications from the parvovirus. After the 2-3 week recovery period your dog should go on to lead a happy, healthy life.
To prevent parvovirus infection in your puppy, you must follow the recommended vaccine schedule. Starting at six weeks of age your puppy should be vaccinated every 3-4 weeks until he is 16 weeks of age. Until your puppy has completed the vaccine series, he should be kept away from other puppies and kept out of dog parks or other social situations. Once your puppy has had all necessary vaccines he is ready to begin exploring the world with you!