Parvo is the shortened term for the Canine parvovirus, a serious viral disease that affects dogs. The disease most commonly affects puppies and young dogs, but animals of all ages can become infected. Usually, the worst effects are on the intestines, causing vomiting and diarrhea that is often bloody, but it also affects the bone marrow and may damage the heart, causing it to fail. The disease is often, though not always, fatal. Parvo is the most common lethal virus known to affect dogs, but it is preventable with a vaccine.
Sources of Infection
The virus is spread through the feces and vomit of infected dogs. It is extremely contagious, but direct contact with other dogs is not necessary, as it is found practically everywhere. Infected animals release very large quantities of the virus, which can live for weeks or months in areas where feces or vomit from infected dogs have been deposited. As these bodily products break down, the virus is scattered around and can be carried by humans on shoes, clothing and skin, and by other animals. It can therefore be found in homes and gardens, and dogs can become infected without coming near another animal.
Effects and Symptoms
Canine parvovirus tends to infect cells that divide frequently, such as those in the walls of the intestine, the bone marrow and the lymph nodes. The first symptoms generally appear after an incubation period of three to seven days. During this time, the virus multiplies in the lymph nodes of the throat without causing any symptoms. After a few days, large numbers enter the bloodstream and infect the immune cells in the bone marrow, reducing the dog’s immune response and leaving the cells of the intestinal wall vulnerable to attack.
Since this infection prevents the regeneration of cells in the intestinal wall, a dog with parvo will be largely unable to absorb nutrients from food, and will suffer from severe diarrhea, resulting in dehydration. Other complications are blood loss through damage to the intestinal wall, and the effects of toxins produced by bacteria, normally confined to the gut, which have entered the bloodstream. The heart may also be affected. The initial symptoms of the disease are lethargy and loss of appetite, followed by fever, diarrhea, and vomiting.
A dog that displays any of these symptoms should be taken to a veterinarian without delay, because if left untreated, the disease can sometimes kill in 24 hours. Fortunately, there is a quick, simple, and fairly accurate test using a sample of feces that can usually detect the presence of the virus. This may be combined with a blood test to check for a low white blood cell count. If both come up positive, parvo is the likely cause.
Like most viral infections, there are no drugs that are effective in eliminating the virus itself, although antibiotics may be given to combat bacteria from the intestines that have entered the bloodstream. Otherwise, the treatment centers on alleviating the worst of the effects until the disease has run its course. To combat dehydration and the inability to absorb food through the intestines, the dog may be given fluids and nutrients by an intravenous drip, although this treatment is not always successful.
There is no practical way of preventing a dog from coming into contact with parvovirus. Parvo is unusually resilient, and it can survive harsh conditions in the open air and also contact with most household cleaners. Strong bleach will kill it, but there is little that can be done about virus particles in gardens, parks, or other outdoor areas.
The most important preventative measure is vaccination. This is part of routine veterinary vaccinations recommended for all puppies and dogs. It is generally administered around six weeks, re-administered three to four additional times before the dog is a year old, and annually after that. With the proper vaccination, the dog will be protected from the virus, but any pet owner who believes that his unprotected dog has contracted this disease or knows it has been exposed to it should consult a veterinarian. People who have a dog without vaccination records or who are unsure of its medical history should take it to a veterinarian for examination.