Effects on the Animal
Clinical Signs of Disease
Treatment and Prevention
Viruses of Dogs
Canine parvovirus-2 (CPV-2) is part of the Parvoviridae virus family. It causes parvoviral enteritis within 5 to 12 days after infection. Rottweilers, Pit Bulls, German Shepherds, Doberman Pinschers and Labrador Retrievers tend to be more susceptible to the disease than are other breeds such as Toy Poodles and Cocker Spaniels, which seem to have a decreased risk of developing the disease. The virus is also capable of infecting other canids, such as wolves and coyotes.
CPV-2 is very stable in the environment and can survive several months in contaminated areas. It is able to withstand high temperatures and wide ranges of acidity and basicity. It is therefore resistant to many disinfectants. The virus is transmitted via direct contact with an infected dog, or via oral contact with infected feces. The virus starts to be shed in the feces within three to four days of infection, with shedding peaking at the onset of clinical signs of disease. Shedding can occur for up to three weeks following infection. In addition, puppies can be infected prior to birth if the bitch is infected. It preferentially invades and obliterates rapidly-dividing cells in the intestinal crypt epithelium and bone marrow.
An artist's rendering of the parainfluenza virus.
on the Animal
When the virus is ingested, it replicates in the lymph tissue of the pharynx. It then spreads to the blood stream and attacks rapidly diving cells in the body. The virus invades and destroys the intestinal crypts within 3 days of infection. This results in intestinal villus collapse, diarrhea and bleeding, as well as vomiting. Subsequent invasion by bacteria that is native to the intestine (For example, E. coli) often follows this insult. Intestinal protein loss may occur as a result of inflammation. Invasion and damage to the bone marrow can result in temporary or prolonged loss of white blood cells, making the animal somewhat immune-deficient and more susceptible to bacterial infection, particularly in the damaged intestine.
Young pups that are infected prior to birth, or before they are eight weeks old can develop myocardidits which is the death and disease of heart muscle cells. This causes either acute heart failure or scarring of the heart muscle, causing insufficient heart function.
Young puppies are at risk of developing severe heart problems if they are infected with parvovirus.
The degree of severity of disease is dependent on the amount of virus the dog is inoculated with, as well as the individual’s host defenses against the virus. Some animals experience only mild or sub-clinical disease, while others suffer much more serious symptoms.
Depression, lethargy, anorexia and vomiting are usually the first signs to be noticed. Diarrhea is typically not seen until 24 to 48 hours after the onset of illness. The diarrhea may or may not contain mucous and blood. Severe vomiting is quite common and often leads to inflammation of the esophagus. Fever and septic shock (systemic inflammation) is often seen in severely affected dogs, but may not be seen in less-severely affected dogs.
Severe vomiting is a common effect of parvovirus infection in dogs- granted, not as tidy as this image suggests.
Estimates of mortality associated with CPV-2 range from 16-48 percent of all cases. However, although some dogs die within hours of the onset of clinical disease, if affected dogs are treated promptly with appropriate therapy, they typically survive if they are able to live through the first four days after onset of illness. Puppies may develop infolding and obstruction of the intestines while they recover from the viral infection. This can cause persistent diarrhea and may slow or prevent recovery.
Dogs that recover from CPV-2 infection develop immunity to the virus that may last their whole lives. Occasionally, recovered dogs can serve as carriers of canine parvovirus and can shed periodically throughout their lives.
Areas that have been contaminated by an infected dog must be thoroughly cleaned with bleach ( dilution) or commercial disinfectant products that are labelled for use against canine parvovirus. Pups should be isolated from any other dogs that may have been exposed to the virus.
Immunization via vaccination is a critical step in preventing and controlling the disease. Vaccines containing live attenuated (modified) virus is recommended over use of inactivated virus, since they appear to be more effective in establishing immunity. These vaccines are capable of stimulating sufficient immunity to young pups, in spite of the presence of maternal antibodies. Pups should receive their first vaccination at 5 to 8 weeks of age, and receive their second vaccination at 16 to 20 weeks of age. Annual revaccination is recommended. (Vaccination Program in Dogs)