Dogs are at risk of enteritis (intestinal disease) caused by two common viruses, canine parvovirus and canine coronavirus. Canine parvovirus enteritis is generally considered to be more severe than coronavirus enteritis. However, parvovirus enteritis may be more serious if coronavirus is also present. Diarrhea and vomiting caused by these viruses can range from mild to severe and are accompanied by depression and loss of appetite. Unvaccinated puppies and young dogs are most commonly affected because they have not been previously exposed or vaccinated and are susceptible to infection. Viral enteritis is easily spread because of the large volume of virus in feces, which contaminates the environment and is readily spread from one animal to another. Severe cases of viral enteritis can be fatal due to dehydration and loss of appetite. Puppies are at greatest risk of death because of their limited body reserves.
What is “parvo”?
Canine parvovirus (CPV) infection is a relatively new disease that appeared
for the first time in dogs in 1978. Because of the severity of the disease and
its rapid spread through the canine population, CPV has aroused a great deal
of public interest. The virus that causes this disease is very similar to feline
panleukopenia (feline distemper) and the two diseases are almost identical.
Therefore, it has been speculated that the canine virus is a mutation of the
feline virus. However, that has never been scientifically proven.
Are there different strains
of canine parvovirus?
Two slightly different strains of canine parvovirus, named CPV-2a (1980) and
CPV-2b (1984), are recognized. They cause the same disease and vaccines give
protection against both. CPV-2b is associated with the most severe disease.
A distinct type of parvovirus (CPV-1) has been found in pups with diarrhea and
also in normal dogs. CPV-1 is not thought to be an important cause of disease.
How does a dog become infected
with parvovirus?
The main source of the virus is from the feces of infected dogs. The virus begins
to be shed just before clinical signs develop and continues for about ten days.
Susceptible dogs become infected by ingesting the virus. Subsequently, the virus
is carried to the intestine where it invades the intestinal wall and causes
inflammation. Unlike most other viruses, CPV is stable in the environment and
is resistant to the effects of heat, detergents, alcohol, and many disinfectants.
A 1:30 bleach solution will destroy the infective virus. CPV has been recovered
from surfaces contaminated with dog feces even after three months at room temperature.
Due to its stability, the virus is easily transmitted via the hair or feet of
infected dogs, contaminated shoes, clothes, and other objects or areas contaminated
by infected feces. Direct contact between dogs is not required to spread the
virus. Dogs that become infected with the virus and show clinical signs will
usually become ill within six to ten days of the initial infection.
What are the clinical signs
of parvo?
The clinical signs and symptoms of CPV disease can vary, but generally they
include severe vomiting and diarrhea. The diarrhea often has a very strong smell,
may contain lots of mucus and may or may not contain blood. Additionally, affected
dogs often exhibit a lack of appetite, marked listlessness and depression, and
fever. It is important to note that many dogs may not show every clinical sign,
but vomiting and diarrhea are the most common and consistent signs; vomiting
usually begins first. Parvo may affect dogs of all ages, but is most common
in dogs less than one year of age. Young puppies less than five months of age
are usually the most severely affected, and the most difficult to treat. Any
unvaccinated puppy that has vomiting or diarrhea should be tested for CPV.
How is it diagnosed?
The clinical signs of CPV infection can mimic many other diseases that cause
vomiting and diarrhea; consequently, the diagnosis of CPV is often a challenge
for the veterinarian. The positive confirmation of CPV infection requires the
demonstration of the virus or virus antigen in the stool, or the detection of
anti-CPV antibodies in the blood serum. Occasionally, a dog will have parvovirus
but test negative for virus in the stool. Fortunately, this is an uncommon occurrence.
A tentative diagnosis is often based on the presence of a reduced white blood
cell count (leukopenia) and clinical signs. If further confirmation is needed,
stool or blood can be submitted to a veterinary laboratory for additional tests.
The absence of a leukopenia does not mean that the dog does not have CPV infection.
Some dogs that become clinically ill may not have a low white blood cell count.
Can parvo be treated successfully?
There is no treatment to kill the virus once it infects the dog. However, the
virus does not directly cause death; rather, it causes loss of the lining of
the intestinal tract, and destroys some blood cell elements. The intestinal
damage results in severe dehydration (water loss), electrolyte (sodium and potassium)
imbalances, and infection in the bloodstream (septicemia). When the bacteria
that normally live in the intestinal tract are able to get into the blood stream,
it becomes more likely that the animal will die. The first step in treatment
is to correct dehydration and electrolyte imbalances. This requires the administration
of intravenous fluids containing electrolytes. Antibiotics and anti-inflammatory
drugs are given to prevent or control septicemia. Antispasmodic drugs are used
to inhibit the diarrhea and vomiting that perpetuate the problems.
What is the survival rate?
Most dogs with CPV infection recover if aggressive treatment is used and if
therapy is begun before severe septicemia and dehydration occur. For reasons
not fully understood, some breeds, notably the Rottweiler, Doberman pinscher
and English springer spaniel, have a much higher fatality rate than other breeds.
Can parvo be prevented?
The best method of protecting your dog against CPV infection is proper vaccination.
Puppies receive a parvo vaccination as part of their multiple-agent vaccine
given at 8, 12, and 16 weeks of age. In some situations, veterinarians will
give the vaccine at two-week intervals with an additional booster at 18 to 22
weeks of age. After the initial series of vaccinations, all dogs should be given
a booster vaccination at one year. Thereafter your veterinarian will discuss
with you an appropriate schedule of revaccination. Dogs in high exposure situations
(i.e., kennels, dog shows, field trials, etc.) may be better protected with
a booster every six to twelve months. Pregnant females might be boostered with
a killed parvo vaccine within two weeks before whelping in order to transfer
protective antibodies to the puppies. Adult dogs considered to be at low risk
for contracting the disease may be vaccinated every two to three years. Your
veterinarian and you should make the final decision about the vaccination schedule
that best fits your pet’s lifestyle.
Is there a way to kill the
virus in the environment?
The stability of the CPV in the environment makes it important to properly disinfect
contaminated areas. This is best accomplished by cleaning food bowls, water
bowls, and other contaminated items with a solution of 1/2 cup of chlorine bleach
in one gallon of water (133 ml in 4 liters of water). It is important that chlorine
bleach be used because most disinfectants, even those claiming to be effective
against viruses, will not kill the canine parvovirus.
Does parvovirus pose a health
risk for me? How about for my cats?
It is important to note that there is no evidence to indicate that CPV is transmissible
to cats or humans.