parvo positive puppy

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.

CBC
 
Reference Range
Result
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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Liz Hughston's picture

I'm curious as to why you opted for syringe feeding over an NG tube? Cost concerns?

An IVF cocktail we've found really great for parvo puppies is 2.5% dextrose + KCl PRN + Vitamin B complex + metoclopramide CRI. In general, if they're not eating within the first 24 hours or so, we like to place an NG tube to feed those enterocytes. Most get ampi, +/- enrofloxacin, gentamicin, famotidine and maropitant. We always deworm them, too.

cindy van cott's picture

Great article...I was surprised to read that dextrose was not started immediately upon hospitalization. We treat lots of parvo pups and they are started on LRS/dex/KCL immediately and often concurrently with hetastarch.

Maree Doolan's picture

Hi Cindy, hi Liz.
Cindy, we will start dextrose immediately if they are hypoglycemic on admission but many of them don't need it so we tend to monitor them and start it when/if needed. But it probably would be worth doing in cases like this if the owner couldn't really afford regular BG monitoring.
Liz, yes syringe feeding was done because we were working within the owner's financial constraints. It's always preferable to have an NE tube over force-feeding in these dogs. We tend to put them on Unasyn and Metronidazole although it really depends on the case. GI support is usually with Pepcid, Anzemet or Cerenia. And yes, usually they do have intestinal parasites so deworming is always helpful.

Jennifer Wobensmith's picture

You briefly mentioned pt going home with at home tx, just wondering what antibiotics you use. There seems to be some controversy about the use of convenia vs ampicillin vs unasyn. Thoughts?

Jennifer Wobensmith's picture

I've heard a lot of controversy about convenia vs typical ampicillin/unasyn for at home care. Thoughts?

Christy Michael's picture

Hi Jennifer, you are absolutely correct that the use of antibiotics is controversial and will also probably vary from patient to patient. For a pup that has CPV, there are two primary reasons why we choose to administer antibiotics. The first is that metronidazole in particular (and ideally orally) has some potential anti-inflammatory effects in the lining of those bowels that are so painfully sloughing. The second is the suppression of WBC associated with the virus that leave these pups next to defenseless against any further insult that might come along at the time of their illness. It is the second antibiotic choice that is mightily debated and honestly depends on personal preference. In an dog not showing signs of sepsis, it is fair to choose any broad spectrum antibiotic for this kind of protection. You will probably find just as many people who think that unasyn/ampicillin/clavamox is the source of all bad bugs as you can find who think that cefovecin is the source of all bad bugs. The truth is that with either one, monitor for the effect you seek and if it is not working, change tactics!