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Canine parvovirus (parvo) is a highly contagious virus that affects most members of the dog family (dogs, wolves, coyotes, etc).  The virus is fatal if treatment is not received, and can still be fatal despite aggressive treatment.


The main source of the virus is the feces of infected dogs.  Susceptible dogs become infected by coming into contact with the infected feces.  The virus is very sturdy in the environment and is resistant to heat, detergents and alcohol.  The virus is easily spread by surviving on the hair or feet of the infected dogs but is also spread by inanimate objects such as shoes, clothes, toys, food and water dishes.  There is no evidence that canine parvovirus affects humans, cats, birds or reptiles



Puppies under 5-months of age are the most susceptible to the virus and are the most seriously affected.  However, a dog of any age that is unvaccinated or undervaccinated can acquire a parvovirus infection.  Dogs develop clinical signs of illness within 7-10 days of initial infection.  The virus invades and destroys rapidly dividing cells, namely the cells that line the intestinal tract and bone marrow (where white blood cells are made).  Signs of illness are reflective of this.  The most seriously ill dogs will have a low white blood cell count, vomiting, and bloody diarrhea.  Many dogs only have vomiting, or diarrhea, and blood is not always present.  The virus kills dogs in two ways:



  1. Diarrhea and vomiting lead to extreme fluid loss, dehydration and shock 

  2. Loss of intestinal cells allow bacteria, that normally live in the intestinal tract, enter the blood stream and without white blood cells, the bacteria can cause a whole body infection (ie sepsis).


There is a rapid fecal test that your veterinarian can perform that only takes a few minutes for results.  This detects viral particles in the stool.  Sometimes the test will be negative even though there is an active infection, thus sometimes dogs will be treated for the virus if they have signs consistent with the disease.  Vomiting and diarrhea are often the first signs of the disease.  The presence and severity of the low white blood cell counts are variable.


Unfortunately, there are no anti-viral drugs against the parvovirus specifically, thus it is a disease of supportive care.  This means aggressive fluid therapy and monitoring.  Antibiotics are used as a preventative measure to decrease the risk of secondary bacterial infections, but antibiotics DO NOT treat the virus itself.  Hospitalization is required to treat patients with parvovirus infections, even if they do not appear very sick.  It is very common for dogs to become more ill before they get better, even with proper hospitalization and treatment.  This phenomenon is the reason why hospitalization can be prolonged, between 3-5 days (sometimes longer).  The vast majority of dogs do not spontaneously recovery from the disease without treatment.


Prognosis is largely dependent upon severity of illness, thus a dog with just diarrhea has a better chance than a dog with diarrhea and vomiting.  The worse prognosis is for dogs that develop low white blood cell counts or those who become septic.  The survival rate can range from 50-70% with veterinary-monitored at home care but can reach upwards to 90% with in-hospital management.


Properly vaccinating your puppy by a local veterinarian is the best way to help reduce the risk of infection.  A proper vaccination schedule includes at least 3 sets of shots starting at 8-weeks of age.  Also keep your puppy away from potentially contaminated areas until they are fully vaccinated (ie dog parks).


Once your dog has been diagnosed with the virus, consider ALL areas he/she (and you) have been contaminated.  Only a 17% (1/2 cup to bleach in 1 gallon of water) chlorine bleach solution will kill the virus in the environment (DO NOT apply the bleach solution to your pets).  At least 10 minutes of contact time with bleach solution is needed to kill the virus.  Steam cleaning is also able to kill the virus.  All toys, bedding, furniture and the yard should be disinfected.  Disinfection becomes problematic for non-bleachable surfaces such as carpet or lawn.  If good drainage is available, thoroughly watering down the yard may help dilute any virus present (well-shaded areas should be considered contaminated for 7 months and areas with good sunlight exposure should be considered contaminated for 5 months).  You should consider your dog’s feces to be contaminated with the virus for 4 weeks past recovery from the disease and should therefore try to avoid high canine traffic areas (dog parks, dog obedience classes, pet stores, etc).