Causes of Parvoviral Infection in Domestic Dogs
Canine parvovirus is shed in the feces of dogs for several weeks after they become infected. Clinical disease is caused by oral contact with infected fecal matter, which can be present on a dog’s fur, feet, crate, bed, owners’ shoes, carpet and any number of other objects. This is called infection by the “fecal-oral” route. When a dog licks or ingests anything that is contaminated by parvovirus, it typically will become infected. Young dogs, immunocompromised dogs, highly stressed dogs and dogs with other illnesses are more susceptible to parvoviral infection. The incubation period for clinical parvoviral disease is between 5 and 10 days. However, infected dogs typically start shedding the virus in their feces well before they show any symptoms of sickness.
CPV infection occurs worldwide. It is most common in warm, wet seasons and environments, and in the spring when most puppies are born. The canine parvovirus is very resistant to common household detergents and disinfectants and can survive at room temperature, indoors or outdoors, for several months.
Newborn puppies normally are protected from parvoviral infection by maternal antibodies, which they acquire in utero and through their mothers’ milk after they are born. These maternal antibodies naturally decline over time, and puppies become increasingly susceptible to a number of infectious organisms, including canine parvovirus. Infection by CPV is usually preventable by vaccinating young puppies before they reach 8 weeks, and revaccinating every 3 or 4 weeks thereafter until the puppies are 16 weeks old. However, despite appropriate vaccination, there still is a susceptible period, when maternal antibodies are waning and the immune system has not yet fully responded to vaccines, during which puppies are at an increased risk of developing illness from infectious organisms.
Thorough disinfection of areas inhabited or frequented by infected dogs can reduce the risk of infection for other animals. The canine parvovirus is extremely hardy and can survive for months in the environment, despite the presence of household cleaners. The most effective disinfectant for CPV is household bleach, in a 1 to 30 part dilution with water. All surfaces that an infected dog has contacted should be cleansed thoroughly. Dogs known or suspected to be infected with the canine parvovirus should be isolated from all other animals, to limit environmental contamination and to prevent spread of the disease.
Historically, most authorities recommend that healthy puppies be kept away from other dogs, and especially from areas frequented by dogs of unknown vaccination status, until their puppy vaccination series is completed at approximately 16 weeks of age. However, more recent recommendations suggest that the benefits of early socialization with other dogs after the first puppy vaccination may outweigh the risks of becoming infected with parvovirus. Owners should discuss the potential risks and benefits of isolation versus socialization with their veterinarian, their dog’s breeder and/or their trainer.
Canine parvovirus is extremely hardy and can survive up to 7 months or more in the environment – and even longer during winter with frozen ground. Owners of dogs that have suffered from this illness need to thoroughly disinfect all indoor surfaces that the affected dog came into contact with, and should remember that outside areas may still contain infectious CPV organisms for a number of months. The incidence of parvoviral infection has decreased markedly with the increase of routine puppy vaccination series. However, outbreaks are still common in animal shelters, high-volume breeding facilities (“puppy mills”), boarding kennels and other places where large numbers of young, immunocompromised and/or unvaccinated dogs congregate.