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Canine parvovirus type 2 or “parvo” is a highly contagious virus that is particularly prominent in the canine community. Parvo is of particular concern for puppy owners due to the severity of symptoms and the weak immune systems of younger dogs. There are ways to help prevent parvo, and it from spreading, and as a responsible dog owner it is important to be familiar with these prevention methods. Effective prevention begins with understanding the virology and pathophysiology of the virus itself.
What Is Canine Parvovirus Type 2 or Parvo?
Canine parvovirus type 2 (known as parvo) is classified as a group II virus in the family Parvoviridae and the genus Parvovirus. Parvo in dogs is extremely contagious and is spread through a dog’s feces whether through direct or indirect contact with the feces of an infected dog. There are two different types of the canine parvo virus, classified by the system of the body that is mainly affected:
The cardiac manifestation of parvo is characterized by cardiovascular failure or respiratory failure in puppies. The cardiac variant of parvo is much less common than the intestinal form and is found in very young puppies under eight weeks old. These puppies usually have been infected by a mother with parvo while they were still in utero. The virus targets the muscles of the heart and these muscles are not strong enough to withstand the virus. In almost all cases of cardiac parvo virus infection, young puppies die. The death of a puppy infected with this variant of parvo can come on suddenly with little sign of distress or it can be accompanied by a short period of respiratory trouble. Veterinary surgeons have found that the virus results in microscopic necrosis of heart tissue in dogs that do not survive. In dogs that are somehow able to withstand this virus, there is evidence of fibrosis or the growth of fibrous tissue which may cause complication in later life.
Fortunately, there are fewer cases of the cardiac presentation of the parvovirus these days due to the availability of a vaccination that is given routinely to dogs intended for breeding.
Where the cardiac manifestation of the parvovirus is passed from the infected mother to her puppies in utero, the intestinal form of this virus is passed through oral contact with the parvo virus. The virus can be spread through fomites, feces or through infected soil and once an uninfected dog comes in to oral contact with the infection through any of these means, the virus can quickly spread. The first step in infection of a dog is when the canine parvo virus is ingested and it replicates in the lymphoid tissue located in the dog’s throat. After replication the virus then spreads to the bloodstream where it attacks cells within the body that naturally divide quickly. There are a number of cells that seem to be most affected by the virus because of their rapidly dividing nature, these include: bone marrow and lymph nodes. The virus then begins to deplete the lymphocytes found in the lymph nodes and destroys and kills the tissue in the intestines. As the intestines are affected by the virus it becomes possible for leakage to occur in the bloodstream which results in sepsis that can quickly lead to death. If the virus is caught quickly enough, treatment can begin and death can be prevented. There are a number of side effects that can result from intestinal parvo that can be extremely severe, so seeking treatment immediately is imperative.
It is important to understand that a dog that has survived parvo will still have remnants of the virus in their feces for as long as three weeks. It is also crucial to know that a dog that has been affected with the parvovirus at some point during their life will forever be a carrier of the virus and they can shed the virus at various points during their lifespan.
Is Parvo Always Deadly?
As a dog owner, one of the most frequently asked questions is whether parvo is always deadly. Many times when we hear of this disease it’s in relation to young puppies and, unfortunately, in these cases puppies generally cannot survive. When puppies are too young to be vaccinated against the parvo virus and they have not been protected by maternal antibodies as a result of vaccination of a breeding female, they lack the defenses to fight against this aggressive virus. In some cases; however, dogs can recover from parvo. When left untreated, the mortality rate of parvo virus infection is around 91%. When treated with more aggressive therapy, parvo mortality rates can drop to 20% to 5%, but not without lasting effects.
Parvo at a Glance
- Parvo was discovered in the 1970’s. In two years, the virus spread worldwide.
- Dogs that develop parvo will show symptoms 3-10 days after being exposed.
- Symptoms include: vomiting, lethargy, diarrhea (usually bloody), and fever.
- Mortality rate: 91 percent if left untreated, 5-20 percent if aggressively treated.
- 80 percent of adult dogs show no symptoms; puppies are most susceptible.
- Extremely resilient, parvo can live in feces or other organic material for more than a year.
- The only household cleaner that will destroy the virus is bleach.
- Vaccination is the only prevention.
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What Happens When Puppies Are Infected With Parvo Through Maternal Exposure?
Unfortunately for puppies, they can become affected with the parvo virus when their unvaccinated mother is exposed to and contracts it herself. The tricky part of this contagion process is that the mother may not always show symptoms of the virus and she may even develop immunity to it after her puppies have already been infected. After puppies exposed to the parvo virus are born, however, they often show symptoms of the disease and rarely survive. Some of the signs seen in young puppies born with the virus include cerebellar hypoplasia, a condition in which the cerebellum is under developed or incomplete. Other neurological abnormalities are also seen in infected puppies and often these dogs will not be strong enough to fight the complications that accompany their condition.
What Are the Symptoms of Parvo?
Parvo generally incubates for five to ten days, meaning that five to ten days after a dog is exposed to the virus they will begin to show symptoms. Symptoms vary from dog to dog for a number of reasons, but a handful of symptoms are most commonly seen with infection. Most commonly dogs that have contracted this virus will become extremely lethargic, will have a fever, will begin vomiting and will also have diarrhea. What tips most people off to there being a problem with their dog is the presence of blood in their diarrhea. It is important that if you ever notice blood in your dog’s stool that you take them to the vet immediately. As a result of these primary symptoms, dogs can also begin to suffer from dehydration and infection. Any dog with diarrhea or vomiting should always be kept properly hydrated, if this is not possible at home or if you suspect a parvo infection, take your dog to the vet and they will begin to administer IV fluids.
In cases of intestinal parvo, the lining of the intestines can become damaged and protein and blood can leak into the bloodstream. This can cause a number of medical concerns such as sepsis, anemia, the escape of endotoxins into the bloodstream and a severe drop in white blood cells. Depending on the overall health of the dog, any one of these conditions can severely debilitate or kill an infected dog.
The first sign to look for in a dog infected with parvo is lethargy. A lethargic dog may be difficult to spot if you have an older dog or a dog that has very little energy as a result of any number of conditions. A lethargic dog will not want to get up for treats or food and they will generally fail to respond to any type of stimulation such as their favorite toy. Failing to notice the lethargy that can be seen in parvo infected dogs is not uncommon but the loss of appetite and diarrhea that follow are much more difficult to miss. After the development of diarrhea, dogs may also begin vomiting.
Is Parvo Different from Heartworms?
As mentioned above, parvo is a virus whereas all worms in dogs, including heartworms, are parasites. Parasites are sometimes easy to spot in dog waste, but often are not easily detected by the human eye. The symptoms for parvo and heartworms in dogs are almost identical and so is the cost of treatment and severity of health concerns. Both can potentially result in death if not treated quickly and correctly but the good news is that both can be treated with preventative medicines such as HeartGard. (Parasites like worms and ticks thrive in warm climates so be especially cautious about remembering the monthly heartworm preventative medicine during summer months. Your dog will thank you.)
How Is Parvo Diagnosed?
If your dog shows any of the signs of parvo virus you should take him or her to the vet immediately. When parvo is suspected, an EIA or hemagglutination test can be performed on feces to look for signs of the canine parvo virus. An electron microscope may also be used to look for signs of the virus. The drawback to using EIA or enzyme immunoassay for testing for signs of the parvo virus is that dogs in later stages of the disease may not shed much of the virus in their feces. In these cases many veterinarians rely upon PCR or polymerase chain reaction to test for the virus. The term PCR refers to a process of amplifying a piece of DNA across various magnitudes. This type of PCR amplification results in thousands (or more) of copies of the DNA sequence being looked at to magnify causes for concern.
Ruling Out Other Causes
If a dog shows symptoms similar to those of parvo, it is important that your veterinarian be able to rule out other potential causes. Looking for signs of parvo in feces is the easiest way to determine infection. Other symptoms that cluster are also indicative of a parvo infection, these include: a low white blood cell count, diarrhea with blood in it and evidence of necrosis in the intestinal lining. These symptoms are more classic to parvo infection than any other illness. While the intestinal form of parvo virus can occasionally be confused with other types of illnesses such as corona virus, there is no mistaking the symptoms of cardiac parvo.
Treatment of Parvo Virus
There are a number of factors that determine how effective treatment can be against parvo virus once a dog has already been infected. There is currently a particularly effective vaccine for dogs that have not yet been exposed to the illness, but dogs that have already been infected with the virus face a much different road of treatment. Time is one of the most significant factors in whether or not a treatment for parvo will be successful: The earlier the virus is detected and treatment begins, the better the outlook for treatment. Age also plays a significant role in how effective a parvo treatment will be. Extremely young, old or immune-compromised dogs will not be able to withstand the more aggressive types of treatments designed to eradicate parvo.
Hospitalization and Medication
A dog with parvo should always be hospitalized in order to receive treatment. Treatment generally consists of the administration of crystalloid IV fluids and or colloids, administration of anti-nausea medications and injection of antibiotics. The particular types of medications used – both anti-nausea and antibiotics — vary depending upon the dog and the vet issuing the treatment. Some dogs have particular sensitivities to certain medications and some veterinarians have a better track record with using specific treatments. If dogs continue to vomit or void their bowels during treatment, they are also administered additional fluids to rehydrate them. The administration of fluids overall serves to both rehydrate and re-balance levels of electrolytes and other elements in the body that help maintain healthy functions.
Blood Plasma Transfusions
In some cases veterinarians may choose to utilize a somewhat unique procedure called a blood plasma transfusion. This treatment involves taking blood plasma from a dog that has survived canine parvo virus and has developed antibodies to it. This blood is transfused in to the infected dog and is looked upon as providing passive immunity. There are no in-depth studies at the moment to identify whether or not this method is more effective in treating parvo than other more traditional methods.
Returning to Normal Function
After initial treatment for the parvo virus dogs will begin to be weaned off additional fluids, only once they are able to keep fluids down. Sustenance will be administered in the way of bland food; this is generally a prescription-based food that is easy on the gastrointestinal system. Oral antibiotics are generally continued after the initial treatment in dogs that show low white blood cell counts in order to help fight any potential for infection. Any type of infection following treatment for parvo can lead to death due to the weakened system of the infected dog. While some recommend non-conventional or homeopathic remedies for the treatment of parvo virus, it is crucial to understand just how quickly this disease progresses and how quickly it can kill an infected dog. Veterinarian treatment should always be sought in suspected cases of parvo.
Prevention of Parvo
Since parvo is such a devastating virus, one of the most significant things any dog owner can do is prevent infection of their dog. The first step in preventing parvo is vaccination. Puppies will derive immunity from their vaccinated mother and at four months old they receive a series of vaccinations to create their own immunity to the virus. Parvo vaccines are a set of three vaccinations that are spaced within a period of three to four weeks.
Decontamination of Parvo Infected Areas
Decontamination is another important part of ensuring that parvo does not spread. As the owner of a dog that has successfully been treated for parvo, it is important to understand that your dog can still contaminate with their feces and they can spread the virus to otherwise healthy dogs. The parvo virus is such a strong virus that it can survive living in soil for as long as a year so it is crucial to completely decontaminate areas where an infected or successfully treated dog eliminates their waste. Active parvo can be treated with a water/bleach solution with a ratio of 15:1. This bleach solution will kill any active parvo and should be used on any area that has been used as an elimination area for the dog. The general advised period for decontaminating an area and bringing another dog in to that area is six months. While grass and soil can be disinfected with bleach solution, a waiting period of six months is advised before bringing a new puppy home. It is also advised to ensure that a new puppy has all of their vaccinations before bringing them in to a home that has recently been exposed to parvo.
The Importance of Notifying the Neighbors
Another important step that should be taken by anyone who has a dog that has been infected with parvo is informing neighbors. Neighbors with dogs should be told that your dog has contracted parvo. Since parvo can be spread from dog to dog in addition to bring spread through feces and soil, neighbors dogs may have become infected simply by walking their dog on your grass. Share any information that you have learned about parvo with these neighbors and prompt them to have their dogs tested for the virus. Many people are afraid that their neighbors will be upset and as such they avoid notifying them. You should keep in mind however, that if a neighborhood dog has contracted parvo, your notification could be the only thing that gets them treatment before the virus causes too much damage.
Parvo Virus is Preventable
Parvo virus is a relatively new virus, discovered in the 1970’s. It is such a virulent disease that within two years of its discovery it had spread across the world. Parvo is a very destructive and very rapidly moving disease that can kill a dog in a matter of days but with the proper precautions it is possible to wipe out or at least cause a sharp decline in diagnosed cases. All it takes is regular vaccinations of all dogs in addition to treatment and appropriate decontamination of infected areas. Even if a dog is treated and successfully recovers from parvo without appropriate decontamination of the home area it is possible to cause the virus to spread to other dogs in the community. It takes a combination of responsible pet ownership, good veterinary care, and vigilant decontamination of infected areas in order to prevent and hopefully one day eliminate this devastating virus.