From Janet Tobiassen Crosby, DVM,
Your Guide to Veterinary Medicine.
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Parvovirus infection is a serious disease that affects the gasstrointestinal or cardiac systems of dogs. Parvo is a highly contagious and often sudden viral disease; puppies are particularly susceptible. Learn what the common clinical signs are in this FAQ.

A. There are three main manifestations of Parvovirus infection:

• Intestinal - This virus causes extreme damage to the intestinal tract, causing sloughing of the cells that line the tract. This can leave the patient open to secondary bacterial infection. Most of the affected dogs (85%) are less than one year old and between 6-20 weeks old -- before the full set of vaccinations can be given. The death rate from infection is reported to be 16-35% in this age group.*

The intestinal signs may include:

• Lethargy or listless behavior
• Vomiting
• Loss of appetite
• Diarrhea - usually bloody, and very foul-smelling (a characteristic odor, particular to Parvovirus infection)
• Fever
• Cardiac - This form of the disease is much less common than the intestinal form due to widespread vaccination. Severe inflammation and necrosis (cell death), of the heart muscle causes breathing difficulty and death in very young puppies (<8 weeks of age). Older dogs that survive this form have scarring in the heart muscle.
• Asymptomatic - No signs seen. Common in dogs over 1 year of age and vaccinated dogs.

The incubation from exposure to seeing the clinical signs varies from 3 to 10 days. After the incubation period, the onset of clinical signs (vomiting/diarrhea, lethargy) is often sudden, usually 12 hours or less.

As always, if you suspect that your pet is sick or "not himself or herself", please contact your veterinarian as soon as possible. For quick-onset diseases such as Parvo, time is critical; initiating treatment quickly may just be the difference between life and death.

If you know or suspect that your pet has been exposed to Parvo, please call your veterinarian to check your pet's vaccination status and what preemptive measures may be taken to protect your pet.

* Stats from The Merck Veterinary Manual, 8th ed.