Therapy and vaccination for a new canine parvovirus (Proceedings) - Veterinary Healthcare


Therapy and vaccination for a new canine parvovirus (Proceedings)


• With diarrhea, severe dehydration, weight loss, abdominal discomfort and pain are consistent features.
• Dogs may present in endotoxic shock or disseminated intravascular coagulation. These are extremely difficult to save and require 24-hour intensive care.


• Young pups under 16 weeks old, particular breeds affected (Rottweilers, Dobermans, English Springer Spaniels), kennels, acute onset of typical signs with lympho/neutropenia (sometimes absolute).
• The progression of leukopenia can help to set a prognosis. When band cells appear in the blood smear, prognosis improves markedly.
• Blood chemistry reflects dehydration and electrolyte disturbances (hypokalemia, hypoglycemia).
• Virus can be detected in stools for 2-4 days after onset of disease by commercial fecal ELISA tests that appear to be highly specific and sensitive. Blood in the stool may give false negatives due to antibody binding virus in stool.
• Again, remember that virus shedding in feces occurs 3-4 days PI, reaching a peak about the time clinical signs first occur, and stops 8-12 days PI.

Management and treatment
• The most important principle of therapy is to address the tremendous fluid loss associated with diarrhea and vomiting, and prevent secondary bacterial infections.
• Replace fluid loss. First, assess dehydration. Dehydration less than 5% is difficult to appreciate clinically. Most dogs with diarrhea and vomiting from CPV infection are 8 to 10% dehydrated as indicated by sunken eyes in orbits, prolonged capillary refill time, dry mucous membranes, signs of shock (increased heart rate, weak pulses), skin tenting. Simple laboratory tests help: A PCV and Total Plasma Protein are useful but will be also affected by blood loss (diarrhea). Urinalysis should show markedly concentrated urine (> 1.030). It is essential to realize that little or no change can occur in laboratory values in severely dehydrated animals. Estimate fluid volume to be replaced (% dehydration X body weight in Kg = liters of fluid to replace). Also add in estimated ongoing losses (diarrhea and vomiting) as well as "normal" (insensible and sensible) losses (about 15ml/kg/day). Use a balanced fluid, such as Lactated ringers, Plasma-Lyte, Normosol, or 0.9% sodium chloride supplemented with dextrose and potassium. Fluids containing dextrose is usually indicated especially in small puppies (Chihuahuas), and may need to be preceded by a bolus in some cases.
• Route of administration. If can, always administer fluids to CPV-infected dogs by the IV route. Avoid the subcutaneous route especially in leukopenia animals as can introduce infections. Avoid oral route at least until 24 hours after vomiting has stopped and preferably after diarrhea has stopped.
• Replace electrolytes - hypokalemia is not always present but whole body depletion of potassium will occur during the illness due to no oral intake, increased loss in feces, and renal loss. Put in IV fluids not to exceed 0.5 mEq/kg/hr. Use Scott's table to calculate how much K to add. However, generally 20 to 30 mEq/L can be added to fluids. Dogs with severe and persistent diarrhea can suffer from hyponatremia and hypochloremia which will be replaced with balanced fluids.
• Correct acid-based abnormalities. Dogs may be acidemic (due to dehydration and bicarbonate loss and diarrhea if not much vomiting) or alkalotic (loss of gastric acid from vomiting), but rapid IV fluids will usually replace deficit. There is no need to use bicarbonate or ammonium chloride to off set acid-base abnormalities.
• Prevent secondary bacterial infection. Use broad spectrum antibiotics against enteric bacteria, especially in leukopenic animals. Enteric Clostridium perfringens frequently proliferates in dogs with CPV. Cephalosporins, enrofloxicins, or combinations such as IV ampicillin and gentamicin (NOTE: probably best combination but do not give gentamicin to dehydrated dogs unless can monitor urine and BUN). In less severe cases, oral metronidazole has been used. Be aware however that CPV-infected dogs with CPV on extended antibiotic therapy have developed oral and intestinal candidiasis.
• Prevent further fluid loss. Antiemetics (not anticholinergic drugs) - metoclopramide and prochlorperazine are most effective in the recovering dog that persists in vomiting. Do not use too early as mask clinical signs. Serotonin receptor antagonists (ondansetron and dolastron) are also very effective. Gut motility modifiers (dephenoxylate or loperamide) are rarely ever needed.


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