December 2012, Issue 49
Canine Parvo Virus: Treatment and the “New” Approach to Outpatient Care
By: Lindsey Piotrowski, DVM
Emergency Veterinary Intern
Practice Points:
- Parvovirus should be the primary differential diagnosis in any puppy or adolescent dog that presents for vomiting, diarrhea or both.
- Diagnosis is often based on typical clinical signs in conjunction with a positive fecal ELISA (“SNAP”) test.
- Mainstays of treatment include: hospitalization, fluid and colloid therapy, antibiotics, anti-emetics, gastro-protectants and proper nutrition, BUT…
- A new study performed at CSU this past year indicates that outpatient therapy with subcutaneous fluids, anti-emetics (Cerenia) and a long-acting cephalosporin (Convenia) may be a viable treatment alternative to inpatient care in cases where owners cannot afford hospitalization.
- Mortality without treatment may be as high as 91%. With aggressive in-hospital supportive care of severely affected puppies, survival rates may approach 85-90%.
Canine Parvovirus (CPV) is a commonly appreciated disease seen in veterinary medicine. Parvoviruses are very hardy in the environment and easily overwinter in the ground during freezing temperatures. They are readily carried on shoes and clothing which accounts for its spread around the world in a very short period of time.
Parvovirus is transmitted via the fecal-oral route (contact with feces, soil and fomites) and is most commonly seen in juvenile canines. Once the virus enters the bloodstream via the oropharyngeal lymphoid tissue, it localizes in areas where there are rapidly dividing cells: bone marrow, lymphoid tissue and intestinal crypt cells. Shedding of the virus occurs in feces, saliva and the vomitus and can continue for 2-3 weeks post infection. Because of this, infected dogs must be isolated from others.
The most common symptoms include hemorrhagic diarrhea (from GI mucosal sloughing), vomiting, and leukopenia. With mucosal sloughing, there is a risk of bacterial translocation and resultant endotoxemia and sepsis. Other possible clinical signs include: anorexia, lethargy, dehydration, fever, hypothermia, nasal discharge, tachycardia, etc.
Diagnosis is most often based upon clinical signs in conjunction with a positive fecal ELISA (SNAP) test. However, just like most tests, this test is not perfect. False positives and negatives can occur. Diagnosis can also be made presumptively based on history and lab results (presence of leukopenia, neutropenia, panhypoproteinemia, azotemia, etc.). Less common methods of diagnosis includes virus isolation, electron microscopy and real time PCR.
Treatment of CPV is often supportive and is aimed at maintaining hydration, controlling nausea and vomiting, treating secondary infections and administering proper nutrition in the hospital. In-hospital treatment has always been thought of as being superior to outpatient therapy in treating patients with CPV given the large amount of possible complications and the large fluid requirements of these patients. IV fluid therapy is the mainstay of treatment of dogs with CPV and is the best means of rehydrating these patients. If hypovolemia, shock or circulatory collapse is apparent, initial fluid therapy can also be given intraosseous. Potassium chloride is frequently added to the fluids for these patients since they are often hypokalemic due to loss of this critical electrolyte as the result of vomiting and diarrhea. 14-80 mEq/L of KCl can be added to the fluids based on the patient’s serum potassium level as long as the amount administered does not exceed 0.5 mEq/kg/hr. Serum potassium should be monitored frequently to be able to appropriately supplement this electrolyte.
As noted above, puppies with CPV can easily become hypoproteinemic due to protein loss through the damaged GI tract. In cases in which a patient develops edema, cavitary effusions, the albumin drops below 1.5 g/dl or the total protein drops below 3.5 g/dl, colloid therapy will be warranted. Hetastarch works well at a rate of 20 ml/kg/day IV as a CRI or plasma may be administered at 10-20 ml/kg IV over 2-4 hours. Hypoglycemia, another common problem in young patients with CPV, should also be monitored very closely and is easily treated with a 2.5 to 5% dextrose CRI as long as the patient is rehydrated prior to dextrose supplementation. If the patient’s blood glucose remains well within the normal range, do not supplement dextrose as this molecule can cause an osmotic diuresis and will contribute to fluid loss.
Antibiotics are another extremely important part of therapy for dogs with CPV. Antibiotics help to treat secondary infections caused by bacterial translocation in the gut. A combination of drugs is usually warranted to achieve broad-spectrum coverage. A combination of an aminoglycoside (gentacin or amikacin) and a beta lactam (cefazolin or ampicillin) provides excellent coverage from bacteria that may originate from the gut (anaerobes and gram negatives). Use the aminoglycosides with caution however, and only begin therapy with these antibiotics after rehydration has been accomplished due to the risk of acute renal failure. Enrofloxacin is an appropriate second choice if an aminoglycoside is not available, however, keep in mind that it can cause cartilage abnormalities in young animals and is not approved for IV use.
Anti-emetics and GI protectants are also a large part of therapy for CPV in an effort to keep patients comfortable. Metoclopramide and ondansetron (Zofran) and/or Cerenia are good choices along with GI protectants such as famotidine, sucralfate and pantoprazole.
As mentioned above, outpatient therapy was previously thought to be largely unsuccessful in treating CPV due to the large fluid requirements of these patients (necessitating IV fluid therapy in the hospital) and due to the possible complications associated with the disease. However, a recent study performed at CSU may have changed this standard. In the study, inpatient and outpatient management protocols for the treatment of CPV were compared. The inpatient protocol consisted of traditional IV fluids, maropitant, antibiotics and syringe feeding. The intensive outpatient treatment protocol consisted of daily subcutaneous injections of maropitant (Cerenia; an anti-emetic), a single subcutaneous injection of a long-acting cephalosporin (Convenia), syringe feeding and subcutaneous fluid therapy administered three times per day after an initial 2 hours of IV fluid therapy in the hospital. It was found that the puppies with CPV who received the outpatient protocol had a survival rate that was almost identical to those who received the inpatient therapy.
The study ultimately showed that we may be able to treat CPV on an outpatient basis when owners are unable to hospitalize their pet. Inpatient treatment will always be considered ideal and the best practice, but financially, some owners just cannot afford the cost. Traditional inpatient therapy can cost upwards of $1500-$3000 and the above outlined outpatient therapy averages only about $200-$300. This could be the difference between life and death in those situations where the owners are considering euthanasia because of the financial inability to pay for inpatient care. Keep an eye out for this study to be presented at CSU’s CVMBS Research day early next year.
Also keep in mind that CPV can be prevented and that education of your clients about the benefits of vaccination is the best prevention of all!