Parvovirus

Parvovirus in Dogs

Canine Parvovirus (CPV), sometimes simply called “Parvo”, is a viral illness that exists in 2 forms. Intestinal CPV is the more common form. This is characterized by vomiting, diarrhea, weight loss and anorexia (lack of appetite). The second less common form is cardiac CPV. This affects the hearts of puppies in the uterus or up to 8 weeks of age and is often fatal. CPV is highly contagious, although the incidence of infections has been considerably reduced by early vaccination of puppies.

Symptoms and Types

The first sign of CPV is usually lethargy. The next symptoms are generally loss of appetite or diarrhea, followed by vomiting.

Intestinal CPV

The intestinal form of CPV drastically reduces the dog’s ability to absorb nutrients. This means that infected animals quickly become dehydrated and weak from a lack of protein absorption. The major symptoms of CPV are severe bloody diarrhea, fever, vomiting, lethargy, anorexia and eventually, severe weight loss. The mucous membranes of the eyes and mouth often become redder and the animal may have tachycardia (rapid heart rate). Infected dogs may respond with pain or discomfort when the abdomen is touched. Another symptom of CPV can be hypothermia (low body temperature) rather than fever.

Cardiac CPV

The cardiac form attacks the heart muscle and the puppy often dies suddenly or after a brief period of breathing difficulty due to the collection of fluids in the pulmonary system. This disease may or may not be seen in conjunction with the signs and symptoms of the intestinal form. However, the cardiac form is now rarely seen due to vaccination of breeding dogs.

Causes and Risk Factors

There are several risk factors that can increase susceptibility to CPV.

The virus is usually transmitted either indirectly from the feces of an infected dog, or directly by contact with an infected dog. The feces of an infected dog have high concentrations of the virus, so when a healthy dog sniffs or ingests infected feces, it may contract the disease. The virus can also reside in the soil and on small items within the environment (fomites); it will be transmitted if these are ingested. Transmission of the virus to a dog’s environment can also occur from shoes that have contacted infected feces or fomites. This is an important route of transmission as the virus can live in the ground for up to 1 year. It is also resistant to most cleaning products and weather changes. If there is a possibility that infected feces have been contacted, the suspected areas should be washed with household bleach, the only disinfectant known to kill the CPV virus.

CPV infections can also be caused by improper vaccination protocols or vaccination failure. Establishments that house a large number of inadequately vaccinated puppies (e.g. some breeding kennels, dog shelters) are particularly hazardous places with respect to transmission. Dog breeds that have a high susceptibility to the virus include German Shepherds, Rottweilers, Pit Bulls, Doberman Pinschers, English Springer Spaniels, Labrador Retrievers and Alaskan Sled Dogs. A poor immune system from immuno-suppressive diseases or drug therapies can also increase the possibility of infection.

Diagnosis

Diagnosis of CPV requires a range of techniques. This will usually start with a physical examination of the dog. If required, biochemical tests and urine analysis will reveal any elevated liver enzymes, lymphopenia (low lymphocyte levels) or electrolyte imbalances. The blood tests will give a chemical blood profile and a blood cell count. Radiograph imaging will show any obstruction of the intestine while ultrasound imaging can reveal enlarged lymph nodes within the body and any fluid-filled sections of the intestine.

The veterinarian will require a thorough history of the dog’s health, recent activities and when the onset of symptoms occurred. Samples of feces or vomit can be examined and used microscopically for detection of the virus.

Treatment

Because CPV is a viral infection, there is no cure for it. Treatment is aimed at controlling the symptoms and preventing secondary infections. The dog will require intensive therapy for it’s bodily systems to recover. Severe diarrhea and dehydration will be treated by intravenous fluids to re-establish and maintain normal body fluid levels. Nutrition therapy is critical in re-establishing protein and electrolyte levels which will then need to be monitored and regulated.

Several medications may be given to your dog to treat symptoms or prevent further complications. These include antiemetics to reduce vomiting, H2 blockers to reduce nausea, antibiotics to prevent secondary infections and anthelmintics to prevent parasitic infections.

Untreated cases of CPV have a mortality rate of 91%. With aggressive therapy, mortality rates are reduced to 5-20%. When death occurs, this is usually due to severe dehydration, secondary bacterial infections, toxins in the blood from bacteria, or severe bleeding from the intestines. Because puppies have a less developed immune system, their prognosis is usually poorer. Puppies that are infected with CPV commonly suffer from shock and sudden death.

Living and Management

During recovery, it is best to feed your dog a form of diet that is easily digested. After the initial recovery, your dog will be a contagion risk to other dogs for possibly 2 months. Therefore, you should isolate your dog from others. In addition, you should consider telling your neighbors that they may need to have their own pets tested. Wash all objects that your dog uses (e.g., toys, kennel, sleeping box, dishes) with a very dilute bleach solution (1:30 ratio) to disinfect and kill the parvovirus.

Having suffered and recovered from a CPV infection, it is likely your dog will have a weakened immune system making it more susceptible to other illnesses. Talk to your veterinarian about how the dog’s immune system can be made as normal as possible and ways in which you can protect your dog from unhealthy situations. Complete recovery means your dog will have long-term immunity against the virus, however, it is still possible that your dog can again be infected with the virus.

Prevention

To prevent CPV infection, the best course of action is to follow the correct vaccination protocol. Puppies should be vaccinated at 6, 9 and 12 weeks of age, and should not be allowed contact with outside dogs until at least 2 weeks after the last vaccination. Breeds with a high susceptibility to CPV may require a longer initial vaccination period, possibly up to 22 weeks.