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Nursing Care of Parvo
Megan Brashear, BS, CVT, VTS (ECC)
VCA Northwest Veterinary Specialists, Clackamas OR
Canine Parvovirus (CPV) is a potentially devastating viral disease common in young puppies. With
mortality rates as high as 90% in untreated dogs, it can lead to an expensive multi-day hospital stay.
However, with aggressive treatment, almost all puppies can survive the disease and continue on to live
normal, healthy lives. Once contracting CPV, the surviving dog has a lifelong immunity.
CPV is a hardy virus, known to live outside the body for months in the proper environment. It can live in
the dirt and on concrete, waiting to infect a vulnerable puppy. Dogs contract the virus not only by
ingesting it from the ground, but also from exposure to people who have walked through the virus and
carry it to other locations. The virus spreads through the fecal-oral route and quickly begins replicating
first in the lymph nodes. Infected dogs will begin showing clinical signs as early as 3-5 days post
exposure, as the parvovirus targets the rapidly dividing cells of the gastrointestinal tract and bone marrow.
The most susceptible dogs are those with no vaccine history, especially if their mother has little immunity
and does not pass on good maternal antibodies to her litter. Rottweilers, Doberman Pinschers, and Pit
Bulls are at increased risk for developing a severe infection. Dogs suffering from concurrent intestinal
parasitism are also at a higher risk for developing a more severe illness.
CPV is preventable, as a reliable vaccine exists and is an AAHA core vaccine. Vaccinated dogs still in
their puppy series can still contract the virus, as the vaccine schedule is attempting to increase immunity
while maternal antibodies are waning. Dogs that have not yet completed the vaccine series are still at risk
for illness.
As the virus begins destroying cells in the gastrointestinal tract, the infected dog will quickly become
dehydrated, lethargic, and anorexic. They soon will develop vomiting and diarrhea, often progressing to
hemorrhagic diarrhea. The virus replicating in the crypt epithelium causes collapse of the intestinal villi
preventing the absorption of nutrients, and, more critically, destroys the normal barrier between the
intestines and the bloodstream. Meanwhile, the virus is attacking the bone marrow as well, significantly
decreasing the production of lymphocytes, and in severe cases causing a pancytopenia. The combination
of bacterial translocation and decreased ability of the immune system to mount a response can lead to
sepsis, SIRS, MODS and eventually death. These dogs can be extremely critical cases needing specialized
nursing care to survive.
Puppies are the most susceptible to contracting CPV but any unvaccinated dog is at risk. Clinical signs
noted by owners early in the illness include anorexia, lethargy, vomiting, and diarrhea. These signs are
often dismissed as the result of stress due to a new environment or diet change, but vomiting and diarrhea
in a puppy should be taken seriously and assumed to be CPV until proven otherwise. The clinical signs of
dehydration and shock (elevated heart rate, tacky mucous membranes, poor pulse quality, elevated CRT,
increased skin turgor, decreased blood pressure, dull mentation) are present in these dogs on physical
exam, as well as profound nausea and frequent diarrhea.
Diagnosis is made via ELISA SNAP test, which is run using feces from the dog and results are available
in less than 10 minutes. False positive results can be seen with recent vaccination with a modified live
vaccine (if vaccinated 5-15 days prior to becoming ill) and false negative results can be seen early in the
disease process. Despite ELISA test results, a strong suspicion of CPV should be treated as if the dog has
the disease. In about half of dogs infected with CPV, a CBC will reveal a leukopenia, sometimes a
pancytopenia. This is due to the virus replicating in the bone marrow suppressing white blood cell
precursors. The WBC can be monitored throughout the illness and used to monitor the dog’s response to
treatment. Blood chemistry results are often normal, save for the blood protein and albumin levels. These
may be decreased due to the large quantities lost through vomiting and diarrhea. Blood glucose levels can
also be decreased upon admittance to the hospital, or may drop during hospitalization and should be
monitored often.
Even in the face of a positive SNAP test, dogs suffering from CPV may need abdominal radiographs or
an abdominal ultrasound to rule out an intussusception. This can occur in young dogs suffering from
diarrhea, and they will fail to improve with simple medical treatment. If intussusception is suspected,
surgical treatment is necessary and then continued treatment for CPV. These patients will have a tough
recovery ahead of them as the viral infection, hypoalbuminemia, decrease nutritional intake and
pancytopenia makes surgical healing challenging. Parvovirus positive dogs must also be screened for
additional parasites. Coccidia and roundworm infestations are common, and depending on which area of
the world the dog lives, hookworms and other parasites may be detected. These parasites cannot be
ignored as their presence can lead to longer hospitalization times and a more pronounced illness.
Because CPV is a virus, there is no treatment aimed directly at curing the dog of the virus. The virus will
eventually run its course, and treatment is aimed at supportive care until the body fights off the virus. First
and foremost, fluid therapy is a must. Once a diagnosis is made, these dogs are often extremely
dehydrated and in shock and need IV fluids to restore perfusion. In severely affected dogs, multiple
boluses (10-20ml/kg) may be needed until the heart rate decreases and the blood pressure increases. If
proteins are low, adding a colloid (like Hetastarch or Vetstarch) can help improve the blood pressure and
help with any peripheral edema. Colloid use is controversial in veterinary medicine; in human medicine
synthetic colloids have been linked to acute renal failure in critical patients. A new retrospective study of
colloid use in veterinary medicine shows some concerning results and more studies will be forthcoming.
As more information is discovered, synthetic colloid use may fall out of favor. Due to high volumes of
vomiting and diarrhea, fluid therapy may need to be evaluated multiple times per day to ensure the dog is
receiving the proper amount. Body weight measurements 2-3 times daily are a good way to gauge how
well the dog is maintaining their fluid balance.
Often additives to crystalloid fluids are necessary. Potassium levels can be decreased in dogs suffering
from Parvovirus due to their vomiting, diarrhea, and inability to eat. KCl can be added to combat this, but
should not be infused higher than 0.5mEq/kg/hr. As fluid rates change the KCl may need adjusting. Many
puppies also suffer from hypoglycemia. This can be due to their small size, inability to take in nutrition,
depletion of glycogen stores, or even sepsis. Blood glucose levels should be monitored at least daily to
ensure hypoglycemia does not go untreated, and dextrose added to fluids as needed. Nausea may be
managed with metoclopramide added to fluids at a rate of 1-2ml/kg/day.
Other anti-nausea medications often utilized in Parvovirus infections include maropitant, ondansetron, or
dolasetron. Controlling nausea is important in these patients because nutrition is a vital part of treatment.
Even trickle-feeding the gut will result in decreased death of enterocytes, and will improve patient
morbidity and mortality. Enteral nutrition is preferred over intravenous nutrition for the value to the
enterocytes. Dogs that are vomiting may vomit up a feeding tube, therefore if nausea is controlled a
nasogastric feeding tube can be placed and the patient fed as soon as possible. Patients are fed a fraction
of their RER ((30xwt in kg) +70) and the amount increased as they tolerate larger amounts. Nasogastric
tubes allow the benefit of removing residual volume from the stomach to decrease nausea and the risk of
aspiration.
Nutrition should be aggressively pursued in these patients as gut bacterial translocation can lead to sepsis
and increase mortality.
Antibiotics are an important part of CPV treatment. While they will do nothing to combat the virus itself,
broad spectrum antibiotic coverage is necessary to reduce secondary infection and to protect against
sepsis. The most commonly used antibiotic therapy is ampicillin (or ampicillin-sulbactam) and
enrofloxacin (while there is a risk for cartilage damage, the benefits outweigh the risks for these puppies).
Many patients may also benefit from metronidazole as well. Aminoglycosides have been successful in the
treatment of CPV but carry a significant risk of renal damage and should be used with extreme caution,
especially in dehydrated dogs.
Pain is not something to be ignored in these cases. May dogs suffering from CPV will slough large
amounts of their intestinal lining and are quite painful. Some are too depressed to outwardly show their
pain, but should be treated as painful and monitored closely for their response. Opioids are the drug of
choice for the level of pain these patients are suffering, but can cause ileus which will interfere with
enteral nutrition. Buprenorphine has less of an effect on GI function and when combined with a lidocaine
CRI (30mcg/kg/min) can offer great analgesia in the hospital.
Plasma transfusions may become necessary in dogs that have severely decreased plasma protein levels, or
can be used instead of a synthetic colloid for volume and blood pressure challenges. Fresh frozen and
frozen plasma contains albumin, and in the typical Parvovirus puppy, their small size allows for a
relatively small amount of plasma to make a difference in albumin levels. There is anecdotal evidence
that taking a blood donation from a dog that has survived CPV is beneficial in that the donor’s antibodies
against the virus will be passed on to the suffering puppy and decrease their hospitalization time.
Colorado State University teaching hospital performed a clinical study on this hypothesis and proved,
with their small study population, that this hyperimmune plasma does not offer any additional benefits
over plasma from a donor simply vaccinated against CPV.
The human anti-viral drug oseltamivir was once thought to be a valuable additional treatment for dogs
suffering from CPV. In a single clinical study from 2005 to 2006 of 35 dogs in a university teaching
hospital, oseltamivir was given to half of the CPV patients to monitor both for clinical response and for
any adverse effects of the drug. While the patients who received the anti-viral drug did not experience
significantly shorter hospitalization times or decreased symptoms, they did lose less weight during the
course of hospitalization and their WBC did not decrease as much as those dogs in the control group. No
adverse effects of the drug were found during this trial. While not a rousing endorsement for the use of
the drug, further studies on the use of this class of drugs in CPV cases may be in our future.
Nursing care for dogs suffering from CPV is intense. These often very young, tiny, fragile patients are
some of the more critical patients to treat and they need close monitoring. Add those needs to the
requirement to keep these patients isolated from other animals and you have an intensive patient housed
away from your full attention. Technicians must closely monitor perfusion parameters in these dogs and
report these findings to the veterinarian. Hypovolemia is common, as is hypotension and tachycardia.
Monitoring CRT, heart rate, and frequent blood pressure readings are necessary to remain on top of fluid
losses. Looking for small changes in mentation can signify both improvement and decline in these
patients and the opinion of the veterinary technician is valuable. Knowledge of the various drugs and how
to administer them, math skills for CRI and fluid additives, and blood draw skills are necessary to nurse
these patients through the disease. The most critical dogs may require feeding tube placement and/or
central line placement which will be performed by the technician. The comfort level of these patients is
possibly one of the most important duties of the technician, as keeping them clean and comfortable is part
of their medical needs. Owner care is also intense with these cases, and should not all fall to the
veterinarian. Giving nursing updates to clients and explaining the disease process is helpful to owners
suffering through this disease with their new puppy or dog.
Adhering to isolation protocol with these cases is absolutely necessary to contain the virus and for the
safety of other patients in the hospital. The isolation ward must be separate from the main treatment area.
Only designated employees should enter the isolation area to have contact with CPV patients. Gloves, an
isolation gown and shoe covers must be worn while in the isolation ward, and any contamination with
vomit or diarrhea means scrubs must be changed and gown and gloves disposed of before maintaining
contact with any other patients. No equipment, treatment sheets, bedding or supplies should shuttle back
and forth between the isolation are and main treatment. If it enters the isolation ward, it stays in the
isolation ward. Drug doses should be drawn up outside the isolation area and brought in to the patient at
the appropriate time. Each CPV patient should have their own thermometer, blood pressure cuff, and
dishes, and anything disposable must be disposed of when the patient returns home. Soiled laundry must
be kept in the isolation ward and transported directly to a washing machine (double bagging the laundry
and using care not to transport it through the main treatment areas) and washed twice using bleach. The
drying cycle is just as important as the wash cycle and bedding must be dried completely. If owners visit
their dog, they must also don gloves, a gown and shoe covers to prevent tracking the virus to their home
and neighborhood.
CPV is notoriously difficult to kill, but bleach will kill the virus. Any surfaces that a CPV positive dog
comes in contact with must first be cleaned of any organic debris then disinfected with a cleaner known to
destroy Parvoviruses. Contact time is important and must be followed. Staff members, even with proper
isolation protocol, who are treating CPV positive dogs should not be responsible for treating other at-risk
patients (such as puppies, immunocompromised patients, or unvaccinated dogs) if at all possible. All
employees should maintain proper hand washing procedures. The front desk staff should be trained to
recognize the clinical signs of CPV and immediately isolate possible cases and perform proper cleaning
and disinfection of the lobby and hallways.
With quick diagnosis, proper treatment and intensive nursing care, CPV positive dogs can be nursed
through the disease and return to their families. Outpatient therapy consisting of subcutaneous fluids,
antibiotics and anti-nausea drugs may be implemented in mild cases, but often is not enough support for
the infected dog. 24 hour facilities have a higher incidence of success in treating these cases, as round the
clock care is often necessary.
References:
Hackett, Tim, DVM, MS, DACVECC. "Parvoviral Enteritis: It's More Complicated These Days." 17th
IVECCS. San Antonio, TX.
Mazzaferro, Elisa M., MS, DVM, PhD, DACVECC. "The Parvo Puppy: What Is the Best Approach and
What's New?" 19th IVECCS. San Diego, CA.
Prittie, Jennifer. "Canine Parvoviral Enteritis: A Review of Diagnosis, Management, and Prevention."
Journal of Veterinary Emergency and Critical Care 14.3 (2004): 167-76.
Savigny, Michelle R., and Douglass K. Macintire. "Use of Oseltamivir in the Treatment of Canine
Parvoviral Enteritis." Journal of Veterinary Emergency and Critical Care 20.1 (2010): 132-42.