Canine parvovirus type 2 (CPV2 colloquially parvo) is classified as a group II virus in the family Parvoviridae and the genus Parvovirus. It is a highly contageous virus that mostly causes infection in dogs. The virus particularly targets young, unvaccinated puppies between the ages of six to twenty weeks though infection can occur in any dog of any age.
There are two different types of the canine parvo virus; these are classified by the system of the body that is mainly affected. The more common is intestinal form, characterized by diarrhea, vomiting, weight loss and lack of appetite. The less common form is cardiac form which attacks heart muscles of young puppies and often causes death. The parvo virus has a tendency to attack rapidly dividing cells such as those lining the intestinal tract.
The virus is shed in large amounts in the stools of acutely infected dogs for up to several weeks following infection. The disease is transmitted by oral contact with infected feces. Parvo can be carried on the dog’s hair and feet, as well as on contaminated crates, shoes, and other objects. When the dog licks the fecal material off hair, feet, or anything that came in contact with infected feces, he acquires the disease.
The two forms of the virus cause different symptoms in the infected dogs, depending on which system is being affected. Major symptoms associated with intestinal form are severe, bloody diarrhea, lethargy, anorexia, fever, vomiting, and severe weight loss. The intestinal form of CPV affects the body's ability to absorb nutrients, and an affected animal will quickly become dehydrated and weak from lack of protein and fluid absorption.
The cardiac presentation of parvo is characterized by cardiovascular failure or respiratory failure in puppies. The virus targets the muscles of the heart and in such young puppies(eight weeks or younger), these muscles are not strong enough to withstand the virus. In almost all cases of cardiac parvo virus infection young puppies die. The death of a puppy infected with this variant of parvo can come on suddenly with little sign of distress or it can be accompanied by a short period of respiratory trouble.