Canine Parvovirus Infection

Maree Doolan, DVM, walks through a case of a puppy with parvovirus from admit to discharge and discusses the available treatments for this disease.

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A 17-week-old Coton de Tulear canine presented to DoveLewis with diarrhea, vomiting, lethargy and inappetence.  The diarrhea had started a few days prior upon being adopted from a breeding facility.  He was seen by his primary care veterinarian the following day and was found to have intestinal parasites and Giardia on fecal examination.  The owner was under the impression that this puppy had been dewormed regularly and vaccinated against Parvovirus while at the breeding facility.

Parvo puppy in hospital On presentation, he was noted to be alert and responsive with tacky mucous membranes and uncomfortable on abdominal palpation.  He was passing dark mucoid diarrhea.  The clinician tested for Parvovirus via snap ELISA and a positive result was obtained.  The owner elected outpatient therapy at that time, but returned the next morning with a dull but responsive, dehydrated, uncomfortable puppy that was anorexic and continued to vomit fluid and pass mucoid feces.  His blood pressure (BP) measured 70mmHG via the Doppler and he was estimated to be 8-9% dehydrated.  CBC and serum chemistry revealed a leukopenia (specifically neutropenia), an increased alkaline phosphatase, hyponatremia, hypokalemia and hypochloremia.  PCV/TS measured 41/5.4.

Reference Range
WBC 5.5-16.9 1.23
LYM 0.5-4.9 0.57
MONO 0.30-2.0 0.25
NEU 3.0-12.0 0.33
EOS 0.10-1.49 0.08
BASO 0.0-0.1 0
HCT 37-55 41.1
RBC 5.5-8.5 5.77
HGB 10.3-18.0 13.0
RETIC   10.5
%RET   0.2
PLT 175-500 554
Test Result Reference Range
Chloride 104 mmol/L (L) 105-119
Potassium 2.7 mmol/L (L) 3.5-5.5
Sodium 142 mmol/L (L) 145.157

On admission, Oxymorphone 0.2mg was given IV for abdominal pain.  An IV catheter was placed, and he was administered a 40 ml IV bolus of Normosol-R, followed by another 40 ml bolus when his BP remained at 70 mmHg.  After the second bolus, his BP measured 90mmHg.  Hetastarch was commenced at 3 ml/hr (1.4 ml/kg/hr), and he was transferred to the isolation ward for hospitalization.

His BP dropped to 70 mmHg later that morning, and a 10ml bolus of Hetastarch was administered, resulting in an improved pressure.  He was offered water approximately eight hours after admission but vomited a short time later.  When he was found non-responsive Saturday evening, his BG measured too low to read.  Treatment with 4 ml of 25% glucose improved his mentation and 2.5% Dextrose was added to his IV fluids; no further hypoglycemic episodes occurred during his hospitalization.  A Fentanyl constant rate infusion (CRI) for more even pain control was started overnight and syringe-feeding 1 ml of a veterinary liquid diet Q2H was also commenced for enterocyte support.

Despite aggressive supportive care, this puppy remained in a critical but stable condition and required many days of hospitalization before vomiting ceased, and he was able to eat and drink on his own.  This was both a financial and emotional struggle for his new owner who worked hard to get him the care he needed.

This is not an uncommon scenario.  Canine Parvovirus (CPV) is seen mostly in dogs less than six months old and particularly in the six to twenty-week age group; thus, many of the clients who are faced with this disease are new pet owners.  They rarely anticipate spending thousands of dollars and watching their puppy struggle for life in a hospital, days after they bring home their new family member.

CPV incubation usually lasts four to six days, but there are reports of three to fourteen-day incubation periods.  When prognosticating, an 80% survival rate is usually offered when early and aggressive supportive care is instituted.  However, clients need to be counseled regarding the possibility that this can mean days in intensive care with periods of time where it appears we do not seem to be making progress at all, and with an 80-85% survival rate comes a 15-20% mortality rate.  Prognosis worsens when treatment is started later in the disease process.

Outbreaks of CPV are notoriously difficult to control due to the resistance of the virus to regular cleaning methods and the ability for the virus to survive more than six months in the environment.  Infected dogs should be vigilantly barrier-nursed to avoid transmission of the virus to other patients in the hospital.

The mainstays of therapy include IV fluid infusions with crystalloid and colloid solutions, analgesics, antibiotics and antiemetics.  Although it is preferred that the patient’s vomiting is controlled prior to commencing nutritional support, one study suggested that even if a patient is still vomiting, nasoesophageal feeding is well tolerated and results in earlier clinical improvement.  Enteral nutrition is preferred because it helps maintain intestinal mucosal integrity and thus, decrease bacterial translocation.  Careful monitoring should be instituted to avoid aspiration of ingesta/enteric feeds.

Although its true value in the treatment of CPV continues to be speculative, and further investigation is thought to be warranted, there remains interest in the use of oseltamivir. Other controversial treatments include equine anti-endotoxin administration, which has been shown to increase mortality in one clinical trial, yet decrease survival in another.  Serum from recovered dogs has been used to provide antibodies to CPV infected puppies and anecdotal reports of improved survival have been reported.  Neupogen (granulocyte colony stimulating factor) has not been shown to improve CPV survival rates.

Canine Parvovirus remains a significant pathogen, and despite early and aggressive supportive care, mortality rates can be high.  Isolation of immuno-naive puppies and adoption of safe and effective vaccination protocols are paramount in protecting dogs against infections and the spread of CPV.

Selected References:
Humm, K.R., Hughes, D.  Chapter 112:  Canine Parvovirus Infection in:  Small Animal Critical Care Medicine.  2009.
Prittie, J.  Canine parvoviral enteritis: a review of diagnosis, management and prevention.  Journal of Vet Emer Crit Care 2004; 14(3): 167-176.
Savigny, M.R., Macintire, D.K.  Use of oseltamivir in the treatment on canine parvoviral enteritis.  Journal of Vet Emer Crit Care 2010; 20(1): 132-142.

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