Parvovirus in our Community

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What Is Parvo Virus?

Parvovirus is a highly contagious virus which affects various animals and can be fatal. Parvovirus has several different strains. Each virus is pretty specific about what animals it can infect (i.e. the pig parvovirus will not infect people, the canine parvovirus will not infect cats, etc.) The canine parvovirus will affect most members of the dog family (wolves, coyotes, foxes etc.).

Parvoviruses are not enveloped in fat the way many other viruses are. This makes parvoviruses especially hardy in the environment and difficult to disinfect away.
At this time, the virus is considered to be ubiquitous, meaning that it is present in EVERY ENVIRONMENT unless regular disinfection is applied.
Attempting to shield a puppy from exposure is completely futile.
Parvoviral infection must be considered as a possible diagnosis in any young dog with vomiting and/or diarrhea. With proper hospitalization, survival rates approach 85% - 95%.

The Virus in the Environment/Disinfection

Canine parvovirus is especially hardy in the environment. It is readily carried on shoes or clothing to new areas.

• Infected dogs shed virus (in their stool) in gigantic amounts during the 2 weeks following exposure. Because such enormous amounts of virus are shed, there is a HUGE potential for environmental contamination when an infected dog has been there.
• It is important to realize that because the canine parvovirus is so hardy in the environment, it is considered ubiquitous (present everywhere).

A parvoviral infection can be picked up ANYWHERE although it is easier to pick up an infection in an area where an infected dog has been simply because of the larger amounts of virus in a contaminated area.
A typical/average infectious dose for an unvaccinated dog is 1000 viral particles. For some dogs far less is needed. For other dogs, far more is needed. An infected dog sheds 35 million viral particles (35,000 TIMES the typical infectious dose) per OUNCE of stool.
Indoor decontamination:

• Indoors, the virus loses its infectivity within one month; therefore, it should be safe to introduce a new puppy indoors one month after the active infection has ended.

Outdoor decontamination:

• Freezing is completely protective to the virus. If the outdoors is contaminated and is frozen, one must wait for it to thaw out before safely introducing a new puppy.
• Shaded areas should be considered contaminated for 7 months.
• Areas with good sunlight exposure should be considered contaminated for 5 months.

Of course, the above presupposes that no decontamination steps (other than waiting) have been taken. In most households, owners want to know how to disinfect their homes to create a safer environment for the other dogs there or to create a safe environment for a new or replacement puppy.

• parvovirus remains virtually impossible to completely remove from an environment. The goal of decontamination is to reduce the number of viral particles to an acceptable level.
• The best and most effective disinfectant against viruses (including parvoviruses) is BLEACH. One part bleach is mixed with 30 parts water and is applied to bowls, floors, surfaces, toys, bedding, and anything contaminated that is colorfast or for which color changes are not important.
  
  Bleach completely kills parvovirus.

Disinfection becomes problematic for non-bleachable surfaces such as carpet or lawn. Outdoors, if good drainage is available, thorough watering down of the area may dilute any virus present.

How Parvo Infection Happens

Parvovirus has been around for more than 30 years, is very hard to disinfect away, and is shed in large numbers by infected dogs. The virus can be found in every carpet, on every floor, in every yard and park. Virus is shed for the first 2 weeks after infection in the stool of an infected dog but only a tiny portion of infected stool (which could be months old depending on the environmental temperature and humidity) is needed to infect a non-immune dog. Some dogs become what is called subclinically infected, which means they do not appear particularly sick. These animals tend not to be confined since no one knows they are infected thus they can spread virus around a large area depending on where they leave their droppings.

Thirty years ago when the virus was new, all dogs young and old were susceptible but now, because the virus is present everywhere, all dogs, even the unvaccinated ones, have at least some immunological experience with this virus. Any exposure no matter how small is likely to generate some antibodies. Also, vaccination is a widespread process nowadays and it is likely that a dog has had at least one vaccine at some point. Will these antibodies be enough for protection? In general, the answer seems to be yes as infection in dogs over age one is somewhat unusual.

Even though infection is somewhat unusual in adult dogs, adult dogs should still continue their vaccinations as this is a life threatening disease for which treatment is expensive and no chances should be taken.

When puppies are born, they are completely unable to make antibodies against any infectious invader. They would be totally unprotected except that nature has created a system to protect them. Their mother secretes special milk for the first day or two after giving birth. This milk is called colostrum. She gives her own immune experience to her off-spring. These antibodies protect the puppies until they wear off sometime in the first 4 months of life.

Not all puppies get the same amount of antibodies. Every nine days the antibody levels possessed by the puppies drops by half. When the antibody level drops to a certain level, they no longer have enough antibodies to protect them and if they are exposed to a large enough number of viral particles, they will get infected.

We recommend that puppies be restricted from public outdoor areas until their vaccination series is completed at age 16 weeks or older depending on breed of dog and individual circumstances.
There is a good week or so period during which the puppy has no antibody protection leftover from its mother but still is not yet competent to respond to vaccination. This window is where even the most well cared for puppies get infected.

Incubation

The virus enters the body through the mouth as the puppy cleans itself or eats food off the ground or floor. A minuscule amount of infected stool is all it takes.
There is a 3 to 7 day incubation period before the puppy seems obviously ill.

Upon entering the body, the virus seeks out the nearest rapidly dividing group of cells. The lymph nodes of the throat fit the bill and the virus sets up here first replicating to large numbers.

Over the next 3 to 4 days, the virus seeks new organs containing the rapidly dividing cells it needs: especially in the bone marrow and the delicate intestinal cells.

Related to the bone marrow infection, all parvoviral infections are characterized by a drop in white blood cell count due to the bone marrow infection. Whether survival is possible amounts to a race between the damaged immune system trying to recover and respond versus the fluid loss and bacterial invasion. The veterinarian may choose to monitor white blood cell count or even attempt to artificially raise the white blood cell count in an infected puppy through treatment. The virus doesn’t stop attacking the puppy’s internal system with just the bone marrow infection.
Another place the virus attacks is the intestinal cells. The lining of the intestinal tract is another source of rapidly dividing new cells located in an area at the foot of the villi called the Crypts of Lieberkuhn. It is right at the crypt where the parvovirus strikes as demonstrated below.

Diarrhea in large quantities results not to mention nausea and vomiting. The barrier separating the digestive bacteria from the blood stream breaks down. The diarrhea becomes bloody and bacteria can enter the body causing widespread infection.

The virus kills in one of three ways:

• Diarrhea and vomiting lead to extreme fluid loss and dehydration until shock and death result.
• Loss of the intestinal barrier allows bacterial invasion of potentially the entire body. Septic toxins from these bacteria result in death.
• Damage to the heart from parvovirus leads to cardiac failure.

Parvo: the Physical Illness and its Treatment

Treatment for parvoviral infection centers on support. The goal is to keep the patient alive long enough for an immune response to generate. We do not have effective anti-virus anti-biotics and must rely on the patient’s immune system for cure.
BE PREPARED FOR A 5-7 DAY HOSPITAL STAY AND A SUBSTANTIAL EXPENSE. INTENSIVE CARE IS NEEDED TO TREAT THIS INFECTION.
THE BASICS OF TREATING PARVOVIRUS
FLUID THERAPY:
One of the ways Parvo can kill is via the metabolic derangements that occur with dehydration. It is crucial to replace the vast fluid losses (from vomiting and diarrhea) with intravenous fluids.
Potassium is often added to the fluids in order to maintain electrolyte balance. Dextrose (sugar) is also frequently added as the stress of the disease may lower blood sugar.
ANTIBIOTICS:
The second way Parvo kills is through bacterial invasion of the circulatory system. Patients are given antibiotics either as shots or added into the IV fluid bag. Possible antibiotics include:
*Cefazolin
*Baytril
*Ampicillin
*Gentamycin
*Amikacin
*Trimethoprin-sulfa
*Chloramphenicol

CONTROL OF NAUSEA:
Again, the GI tract is too damaged for oral medication so medications are given as injections. There are three popular medications for nausea control:

• Cerenia: a newer medication with very strong nausea control. Its benefits last more than 24 hours, so patients are treated once daily with this medication.
• Metoclopramide: (best given as a continuous drip in the IV fluid set up) If used as separate injections, relief tends to be short lasting and does not provide around the clock control. If a continuous drip is used, nausea control lasts as long as the drip is running.
• Chlorpromazine: a very strong nausea control medication which lasts 6 to 8 hours per injection and has the added benefit of a drowsiness side effect (so patients can sleep through most of this uncomfortable time).

Injectable antacids (Tagamet, Zantac, or Pepcid) are often used to prevent ulceration of the esophagus of the esophagus should protracted vomited be a problem.
DIAGNOSTIC TESTING:

• Parvovirus ELISA antigen test (“snap” test).
• White blood cell counts/complete blood counts.
• Fecal floatation & giardia testing to rule out worms/internal parasites.
• Urine specific gravity.
• Abdominal palpation.
• Total blood protein.
• Blood chemistries.
• Blood electrolytes.

EXTRA TREATMENT THAT MAY HELP:

• CEFOXITIN (AN ANTIBIOTIC): expensive.
• ONDANSETRON (BRAND NAME ZOFRAN): very expensive.
• OSELTAMIVIR (TAMIFLU): Tamiflu is a medication used in the treatment of the flu in humans.
• SEPTI-SERUM: it is usually given only one time as the equine origin of the product has potential for serious immunological reactions.
• PLASMA TRANSFUSIONS: plasma from a donor dog who has survived parvo is sometimes used.
• ANTI-INFLAMMATORY DRUGS: our hospital favors meloxicam (Brand name Metacam) and flunixin meglumine (brand name banamine) for this use.
• NEUPOGEN: it is very expensive.

IN OUR EXPERIENCE A PUPPY THAT HAS NOT SHOWN OBVIOUS IMPROVEMENT BY THE 4TH DAY OF TREATMENT HAS A MUCH LOWER SURVIVAL RATE.
Caring for the Recovered Dog

The Parvo puppy goes home - What you need to know
Medications
Your puppy will be finishing up a course of antibiotics and may also be on some medication for nausea or diarrhea. It is important that you give your puppy the medication prescribed for the full amount of time it has been prescribed.
Diet
Your puppy is recovering from some extensive damage to his/her intestinal tract. It is typical for stool to be a little loose at first or for no stool to be produced for a few days as the tract recovers. The stool should gradually firm up over the first 3-5 days at home and your puppy should be active and of normal attitude. If the diarrhea persists, if vomiting occurs, or if your puppy seems depressed, please contact your veterinarian at once for instructions.
Your puppy may be ravenously hungry after going so long with minimal to no food. Do not allow the puppy to gorge as this can result in vomiting or diarrhea. Feed smaller meals separated by at least an hour or two.
It is important for your puppy’s food to be easily digestible so stick to the diet and protocol your veterinarian has recommended. Do not feed table scraps.
Exercise
Your puppy should be considered contagious to other puppies for a good month so it is important to “play it safe” by restricting trips to the park, obedience school or other neighborhood areas. If your puppy is less than 16 weeks of age, he/she should not be allowed in public areas until the vaccination series is fully completed.
Other Pets
Cats and humans are not susceptible to canine parvovirus infection. Adult dogs that have been vaccinated are not susceptible, either. Puppies, however, are at risk. If your sick puppy was indoors only, wait at least one month before any new puppies come to your home.
Bathing
Your puppy may be bathed any time as long as you do not allow him/her to get cold or chilled after the bath. Bathing will reduce the amount of virus left on the puppy’s fur and will help reduce contagion.

Resuming Vaccines
Your puppy cannot be re-infected with this virus for at least 3 years (and probably is protected for life simply by virtue of this infection) but there are other viruses that your puppy should be protected against. Your veterinarian will give you a vaccination schedule to adhere to for the future.
There should be no permanent ramifications due to this infection. The recovered puppy should lead a normal life once the recovery period is completed (1-2 weeks).

Parvo Vaccination Options/Prevention
As mentioned previously, puppies obtain their immunity from their mother’s first milk, the colostrum, on the first day of life. This special milk contains the mother’s antibodies against parvovirus and until these maternal antibodies wane to ineffective levels, they will protect the puppy.
The problem is that they will also inactivate vaccine injected in the puppy.

Vaccine is a solution of inactivated virus, either live and weakened (attenuated or modified) or killed. This virus is injected into the puppy. If there is still adequate maternal antibody present, this vaccine virus will be destroyed just as if it were a real infection. There will be a period of about a week when there is not enough maternal antibody to protect the puppy but too much to allow a vaccine to work. (This period is called the window of vulnerability.) Then after this, vaccine can be effective.
The next problem is the age at which vaccine can be effective is different for each individual puppy.
To get around this, we vaccinate puppies in a series, giving a vaccine every 2 to 4 weeks until age 16 weeks. By age 16 weeks, we can be certain that maternal antibodies have waned and vaccine should be able to take. It should be recognized that some individuals, especially those of well vaccinated mothers or of higher risk breeds, must be vaccinated out to age 20 weeks (unless a high titer vaccine is used).
After a puppy is born, maternal antibody levels drop by half approximately every 9 days.
Puppies that were born first or were more aggressive at nursing on the first day, will get more maternal antibody than their littermates.
Mother dogs vaccinated at approximately the time of breeding will have the highest antibody levels to pass on to their puppies.
REMEMBER, the more maternal antibody a puppy has, the less likely a vaccine is to work.
Should Live or Killed Vaccine be Used?
Killed vaccine is the least effective at penetrating maternal antibody. It is also associated with more undesirable vaccine reactions.
Vaccines should be spaced 2 to 4 weeks apart.
It is commonly held that puppies need a certain number of vaccines for protection to be achieved (usually either 3 or 4 is the ‘magic number’). The number of vaccines given has nothing to do with protection. In order for protection to be achieved, vaccine must be given when it can penetrate maternal antibody.
Each puppy’s individual risk factors for parvovirus are evaluated during their series of puppy examinations and consultations. From these risk factors, each puppy’s individual plan for a vaccination series is determined. If needed, this plan will be changed during the series of puppy visits.
Vaccinating Adult Dogs

Classically, parvovirus vaccine has been administered annually to all dogs. Vaccine against canine parvovirus has been included in the distemper combination vaccine (the DHLPP, 6 in one, etc.).
If you have further questions, please ask our staff, or go to www.veterinarypartner.com and type in parvo in the search box.