Parvovirus is a HIGHLY CONTAGIOUS virus that attacks the intestines and causes sloughing of the inner layers of the intestine. The most common symptoms of this disease (the “intestinal form”) are vomiting and diarrhoea. Another less common form, the “cardiac form”, occurs in very young pups (less than 8 weeks of age) and attacks the heart muscle, often resulting in sudden death.
Parvovirus is contagious to dogs only—not to cats or people. Any age, breed, or sex of dog could be affected by parvovirus. However, infection with parvovirus does not automatically mean illness. Several factors such as age, environment, stress, parasites, and general health status of each individual dog infected could affect the severity of the disease. The degree of illness could range from very mild to unapparent to very severe, often resulting in death. The disease is usually more severe in young dogs (less than 6 months of age), old dogs, Rottweilers, and Dobermans. The younger and smaller the dog, the greater the chance that it will not recover.
Parvovirus is resistant to extremes of temperature (i.e., it survives freezing and extreme heat) and is unharmed by detergents, alcohol, and common disinfectants. Direct transmission occurs when an infected dog comes in contact with a healthy dog. The virus is found in heavy concentration in the infected dog’s stool. Because dogs will usually sniff where another dog has eliminated, this faecal-oral transmission is the most common method of transmission. The virus particles can be easily spread by hands, shoes, clothing, or other inanimate objects (fomites)—this is an indirect source of transmission.
As many as 30 billion parvovirus particles can be shed from the intestines of an infected dog in every ounce of stool. The highest concentration of virus in the stool is seen when the infected dog is showing signs of illness. A dog can, however, be a source of infection to other dogs without it having observable signs of illness (the disease may be incubating). Transmission can occur for at least 3 weeks after a dog becomes infected with the virus. Chronic “carriers” are not known to exist as in other viral diseases. Parvovirus in the environment can infect susceptible dogs for as long as 6 months once shed in the stool.
Clinical signs include vomiting, fever, loss of appetite, depression, and bloody diarrhoea with a very foul odour. Infected animals rapidly dehydrate and severe cases progress to shock and death. Early, vigorous treatment of illness caused by canine parvovirus infection can save lives.
Cardiac form (less than 8 weeks of age):
Crying, difficulty breathing, gasping for breath
Unwillingness to nurse
Intestinal form (any age dog affected, but more severe in puppies):
Loss of appetite
Fever (usually above 103F)
Vomiting with or without blood
Diarrhoea with or without blood (more serious if blood present)
Low white blood cell count (due to immunosuppression)
Treatment is aimed at maintaining the normal body composition and preventing secondary bacterial infection. Because this is a virus, there is NO CURE. Death from parvovirus results from dehydration, overwhelming secondary bacterial infection, blood loss from intestinal haemorrhage, or heart attack from invasion of the heart muscle by the virus.
Early FLUID THERAPY is the most important factor in treating dogs with parvovirus infection. The body is normally about 80% water. Life is NOT possible when 12-15% of the normal body fluids are lost. Intravenous fluids both rehydrate the body and nourish the sick dog.
Additional treatment includes prevention of secondary bacterial infection and drugs to control vomiting and diarrhoea. No food or water is given while the dog is vomiting. Repeated laboratory tests are often necessary to monitor your pet’s white blood cell count and state of hydration.
HOSPITALIZATION enables vets to provide the best medicine and is the best way to achieve success. There is NO GUARANTEE, even with hospitalization, that your pet will survive. With most dogs, there is at least a 70% survival rate. Very small (young) puppies, Rottweilers, and Dobermans usually only have a 30-50% chance of survival. Length of treatment depends on the severity of disease. Most dogs have to stay hospitalised for at least 2-4 days, but may require treatment for as long as a week. Dogs that recover from parvo are often weak, making them even more susceptible to other diseases, such as distemper. Dogs that recover from parvo continue to spread the virus in the faeces for a month or longer.
Prevention/Control of parvovirus by sanitation measures alone is extremely difficult because the virus is such a resistant, hardy organism and because it is so easily spread. Contact with other dogs, and especially their stool, should be minimized. Clorox diluted one part to 30 parts water (4 oz Clorox in 1 gallon of water) has been effective in disinfecting inanimate objects such as clothing, floors, kennels, etc. However, it is impractical, if not impossible, to disinfect public streets, parks, etc. Isolation of infected dogs is another method of control, moderately effective. Both of these measures will help reduce the amount of contagious virus in the environment, but only a full series of vaccinations, with appropriate booster intervals, will help to control the source of infection, the contagious shedding dog.
Guidelines for young puppies:
1. Do not take the puppy to the front yard, park, for a walk around the block, or to pet stores. These are all places where infected dogs have been or presently are.
2. Only have the puppy around adult dogs that YOU KNOW are current on vaccinations. There should be no contact with stray dogs or dogs that you are not sure of.
3. Do not let the puppy be exposed to any other puppies. These pups could be incubating the disease (and therefore be contagious) without showing signs of illness.
4. Always wash your hands after handling any dog.
Vaccination is the most effective preventive measure for canine parvovirus disease. A properly immunized dog will have circulating antibodies in the blood that will destroy parvovirus following exposure. Dogs remain HIGHLY SUSCEPTIBLE to parvo until 2-4 weeks after the last injection of the immunization series.
The Role of Maternal Antibody in Puppy Immunization
Maternal antibodies are antibodies against viruses which are passed from the mother to the puppies through the “first milk” or colostrum. They provide the puppy with an immediate temporary or “passive” immunity. The mother obtains these antibodies from prior vaccination or by natural exposure to parvovirus. However, maternal antibody is a two-edged sword; it protects the puppy against disease early in life, but it also blocks active immunization (the puppy’s immune response to vaccinations). In the case of parvovirus, maternal antibody can interfere with vaccination for as long as 14 to 16 weeks of age in some pups. A refractory period can exist in some pups where very low, almost undetectable levels of maternal antibody will inhibit the vaccination process but will NOT PREVENT parvovirus infection. Since the level of maternal antibody varies from puppy to puppy, IT IS IMPORTANT TO BEGIN VACCINATION AT AN EARLY AGE AND REPEAT EVERY 3-4 WEEKS UNTIL THE PUPPY IS AT LEAST 16-18 WEEKS OLD.