Parvovirus Infection In Your Dog
Parvo Virus Enteritis - CPV

To learn about the vaccines that protect me from diseases like parvo, go here.

información simplificada sobre parvo de la AVMA

Ron Hines DVM PhD

Lots of my articles are plagiarized and altered on the web to market products and services. There are never ads running or anything for sale with my real articles. Try to stay with the ones with in the URL box or find all my articles at ACC.htm.

Where Did Parvovirus Come From ?
Are There Unique Things About The Parvovirus That Make It Particularly Dangerous ?
Is There More Than One Strain Of Dog Parvo ?
Do Current Vaccines Protect Against All Strains Of Dog Parvo - Even The Newest Ones ?
Does Parvo Appear To Be More Severe In Certain Breeds ?
Is Parvovirus Today Primarily A Disease of Puppies and Adolescent Dogs ?
Can Pets Other Than Dogs Catch Parvo - What About Me ?
Where Do Dogs Catch Parvo ?
How Long Does The Virus Persist Where A Sick Dog Had Been ?

What If I Have Decided To Get My Dog From An Animal Shelter ?
How Long Might It Take After My Dog Is Exposed To Parvo For It To Appear ill ?
What Is Happening Inside My Dog That Is Making It Feel So Bad ?
If My Dog Catches Parvo, What Signs Will I See ?
If My Vet Suspects That My Dog Has Parvo, What Tests Will The Vet Run ?
Is Parvo Always Fatal ?
What Treatments Will Help My Dog ?
What Are Some Key Things My Vet Will Monitor To Tell How Well My Sick Dog Is Responding To Treatment ?
Does My Puppy or Dog Need Special Care Once it Is Out of Danger And Recovering ?
Is The Vaccine Against Parvo Effective ?
Will My Other Pets Catch It ?
At What Age Should My Puppy Be Vaccinated To Prevent Parvo ?
My Puppy Got His Vaccinations – But He Still Caught Parvo - Why !!
How Often Does My Adult Dog Need A Parvo Shot To Keep It Protected ?
Is There An Alternative To Booster Vaccinations For My Adult Dog ?
Can My Dog Catch Parvo More Than Once ?
Are There Ways I Can Disinfect My Home And Yard After A Case of Parvo ?
If I Decide To Get Another Dog, How Long Should I Wait ?
What About The Parvo Cures I See For Sale On The Internet ?

There was a time, - not that long ago - that parvovirus of dogs did not exist - at least not in the developed Western World. Before 1967, distemper was our most serious viral disease of dogs. But in that year, alert veterinarians at Walter Reed Army Institute in D.C. discovered a new virus in the feces of military dogs that were suffering respiratory problems. (ref) The vets named it minute virus of canines, or canine parvovirus 1 (CPV 1). By 1976 veterinarians realized that they had a new and highly dangerous disease to deal with. (ref)

Since those early panic days, the number of dogs dying from parvo has decreased. That is due almost entirely to the superb protection our anti-parvo vaccines produce (although the virus ran out of susceptible adult dogs with no immunity as well). But the virus is still out there throughout the World, taking advantage of unprotected dogs that either received no vaccine or received it improperly.

Parvovirus causes ulcerative enteritis (intestinal inflammation and bleeding) and immunosuppression in susceptible dogs. The bloody diarrhea, blood loss, secondary infection and shock that result can be life threatening. (We tend to think intestine; but all rapidly dividing cells in the dog’s body are attack – bone marrow cells, lymphatic cells, etc.)

Where Did Parvovirus Come From ?

Although dog parvovirus is a relatively new disease, cats have always had their parvovirus - We call it panleukopenia . Related parvovirus affect many other animals as well ( including mink, cows, pigs and humans). However, most parvovirus are choosy about the animal species they attack.

When a new virus disease appears, one of three things has happened; changes in the distribution of animals has made new susceptible animal populations available, the virus has jumped from one species to another, or the virus has mutated from a mild to a more threatening form. Most veterinarians believe that parvovirus of dogs probably jumped to dogs from another animal. Suspicion fell on the cat (ref) ,although we will never know for sure. Sometimes a leap from one species to another is more of a hop-scotch between species, the virus slowly changing its characteristics as it moves from closely to less closely related hosts (animal species). So some believe that the virus hopped from cats to, perhaps some intermediate wild species (fox, mink?) before reappearing in households with the ability to infect dogs. (ref) (Similar things are though to occur with the human flu. ref)

Are There Unique Things About The Parvovirus That Make It Particularly Dangerous ?

Yes, there are two principle reasons. Parvovirus is particularly difficult to kill and the virus is programmed to attack the very cells designated to protect the dog’s body from infection.

A third troubling ability of the virus is its capacity to “reinvent” itself from time to time through its high rate of natural mutation along with its ability to merge with other strains of parvovirus that it encounters (recombinant forms). You can read about that extraordinary ability here.

Is There More Than One Strain Of Dog Parvo ?

Yes, There are many strains of dog parvovirus and new ones are continually forming.

The first dog parvo, isolated (CPV1) in the 1960s did not appear to cause serious disease. Within a few years (1978), however, it had mutated into CPV2, with the ability to kill dogs of all ages. (Remember, we had no vaccines in those days and even adult dogs were susceptible). Canine parvovirus 2 was soon replaced by CPV-2a . In those days, destruction of the hearts of very young puppies born to unprotected mothers was not uncommon (ref 1, ref 2)

It wasn’t long (1984) before the virus mutated again. This strain was designated CPV-2b. Both CPV-2a and CPV-2b are still circulating among dogs. In 2008, a third form, CPV2c was isolated from dogs in Italy and quite soon, it was found in the US, UK, Spain, Vietnam and South America as well. Certain dog CPV 2 forms have even regained their ability to infect cats while others are now a significant cause of death in urban raccoons. (ref)

You can read about its remarkable “shape shifting” in detail in an article here. The wild parvovirus strains have even successfully combined with the weakened virus used in vaccines to prevent it to form newer variants.

Do Current Vaccines Protect Against All Strains Of Dog Parvo - Even The Newest Ones ?

Veterinarians believe that they do.

The American Veterinary Medical Association states: “Although there is no vaccine to specifically prevent CPV-2c infection, studies have shown that all of the currently available vaccines produced by the five major vaccine manufacturers (Fort Dodge Animal Health, Intervet, Merial, Pfizer and Schering-Plough), when administered appropriately, provide excellent immunity to all variants of the canine parvovirus.” You can read a study that generally confirms that here. However, the newer wild strains of parvo may make final vaccination dates for puppies even more important than they used to be (ref)

Does Parvo Appear To Be More Severe In Certain Breeds ?

Veterinarians have often remarked that they see Doberman and Rottweiler puppies ill with parvo more frequently than they should. (ref) Others report seeing the disease more frequently and with more severe consequences in Rotties, Dobies, German Shepherds and Pit Bull terriers.

It is unknown if these breeds are actually more susceptible to the virus or if the common lifestyle of those breeds might bring them into more contact with the virus. We do know that Dobermans and Rottweilers have inter-mixed genetics based on photos of them from the 1890s and that many of them also share a genetic tendency to intestinal and other bleeding. (ref 1, ref 2)

Is Parvovirus Today Primarily A Disease of Puppies and Adolescent Dogs ?


When parvo first appeared, no dogs had immunity to it. So it infected the young and the old in equal frequency. Today, it is puppies between the age of 6 weeks and 6 months that are most at risk. That is because the parvo virus now lurks everywhere. By now, the majority of dogs over the age of six months have either been vaccinated against it, or they have survived a milder case of the natural disease. So it is dogs under the age of six months that are most likely to contract it. Puppies under 6-8 weeks of age are usually protected by their mother’s residual immunity that lingers in their bodies; so they are less likely to catch it as well.

Can Pets Other Than Dogs Catch Parvo - What About Me ?

Humans are not susceptible to canine parvovirus infection. We have our own, unique parvovirus. (ref) It is possible to infect abnormal human tissue cells experimentally with parvovirus, you can read about that here if you wish. (probably a really foolish thing to have been done outside of Biohazard Level 4 facilities)

Cat parvovirus (panleukopenia) was not able to infect dogs. However, at least some stains of dog parvovirus have regained the ability to infect cats. (ref)
Because parvoviruses are constantly combining and rearranging their genetic structure (genome) I would not count on the rules of the past being the rules of the future.

Somewhere in it journey from dogs to cats, parvovirus took a side trip to raccoons. Parvovirus is now second only to distemper in the number of raccoons it kills. But it does not appear that the current common strains of raccoon parvovirus are very infectious for dogs or vice versa – each has adapted in its own way.

Ferrets have their own unique parvovirus – the Aleutian Disease virus - that can affect all weasel-like animals (mustella). But there is a 2011 report of dog parvovirus affecting another type of mustella in China, the masked civet. (ref) That is only a single article. But I would be cautious about exposing my ferrets, pet skunks or zoo animals to dog parvovirus - we already know how easily it has jumped between species in the past.

My advice would be to vaccinate all carnivorous mammals against their unique parvovirus when that is possible – or to a killed vaccine available for the most similar species of animal to it. Killed parvovirus vaccines have become hard to find and one must be cautious in usine live virus vaccine in species it was not designed for. (Wildlife rehabilitators in the United States often use Zoetis’Fel-O-Vax 3 and Merial’s PUREVAX® FELINE 4 to successfully to immunize their raccoons against parvovirus. (ref) )

Where Do Dogs Catch Parvo ?

How Long Does The Virus Persist Where A Sick Dog Had Been ?

Once a natural setting has been contaminated with the feces of a dog shedding the parvo virus, that area is infectious to un-immunized dogs for at least 6 months.
There are many factors that prevent me from giving you an exact length of time – the presence of grime, soil and porosity of the area, the temperature/time of year, the amount of rain that washes over the area, the amount of sunshine the area receives, etc. You can read about some of the conditions that influence the survival time of this group of virus here.

So any place frequented by dogs, especially young, unvaccinated dogs, is also frequented by parvovirus. The less the ability or willingness to sanitize these areas, the greater the threat. The vaccines sold today to protect dogs are superb in their protection. If you use common sense in isolating your puppy until the vaccine has time to work, and purchase or adopt your puppy from a conscientious source, your pets should never encounter it.

do not think you can just avoid those critically-timed parvovirus vaccinations and get by, by avoid exposing your dog to the parvovirus – Your pet will almost certainly encounter it at some point in its life

You might say “I never let my puppies fraternize with sick dogs so I will be OK”. That is not true. Many dogs in the process of shedding the virus look perfectly healthy. They shed the virus in their stools for up to 6 weeks after getting over the initial infection and in some dogs, initial infection is hardly noticeable.

There are innumerable other ways a virus can get from one dog to another, on contaminated shared objects, borne on the feet of houseflies, tracked in on your shoes, etc. But those are not how most dogs become infected. Most catch it by sniffing or ingesting stool-contaminated material passed by another dog not far from where that dog lived or passed by.

What If I Have Decided To Get My Dog From An Animal Shelter ?

Young dogs that end up at animal shelters tend to be brought there from situations where sanitation, worming and vaccination is poor. In a Florida animal shelter, only about a third of the dogs that passed through it were immune to parvo. Those tended to be the dogs over one year of age. If you intend to adopt from a municipal shelter, consider an older dog. If you want a puppy, see if the animal control warden will alert you to a litter of puppies before they pass through their facility. Dogs that have spent four or more weeks in a typical shelter or pound usually have already caught and recovered from parvo - there or before they came there.

When parvo does occur in animal shelter dogs, it tends to be more severe because those dogs are often parasitized, nutritionally deprived and under extreme stress and crowding. See if the staff will work with you by vaccinating young dogs with a quality vaccine and then keeping the young dog at the facility for 12-14 days after you have made a commitment to adopt it. One to two weeks after vaccination a puppy 14 weeks or older is very unlikely to ever develop parvo.

You can read more about parvo in animal shelter situations here.

How Long Might It Take After My Dog Is Exposed To Parvo For It To Appear ill ?

It takes 3-7 days after a dog is exposed to parvovirus for it to appear ill. After the virus enters the dog’s mouth, it sets up housekeeping in the lymphoid tissue of the dog’s throat.
From then on the virus spreads to all rapidly dividing cells in the dog’s body. The cells lining the dog’s intestines and those in its bone marrow fit that bill.

During those initial 1-7 days, dogs may look fine; but they can infect other dogs with parvovirus.

What Is Happening Inside My Dog That Is Making It Feel So Bad ?

Parvovirus destroys rapidly proliferating (cells increasing in number) tissues – the ones where cell turnover is high. This is especially true in the crypts (valleys) present in the dog’s small intestinal lining. Ulceration of those areas results in a severe tummy ache, and diarrhea that can be anything from a bit of mucus to outright bloody. Diarrhea and vomiting quickly dehydrate the dog and lead to acid-base disturbances.

At the same time, the virus attacks the pet’s bone marrow. This results in a drop in the number of defensive white blood cells in its circulation (neutrophils, lymphocytes). Many of these dogs run fevers and in all but the mildest cases, the dogs stop eating and become very depressed. Bacteria are now free to enter the pet’s blood stream through its ulcerated intestines and its damaged immune system cannot respond.

You can read more about that process at work in parvovirus infection here and here .

If My Dog Catches Parvo, What Signs Will I See ?

Parvo is a roller coaster ride downward with but one dip and a bottom that one cannot predict. The depth of that bottom depends on your dog’s age and general health, the number and strain of parvovirus involved, any partial immunity it acquired from its dame and, of course, the veterinary care that it receives.

Parvo comes on abruptly. The first sign of clinical parvovirus disease is always a mopy (lethargic) dog. In serious cases, that quickly progresses to outright depression. These dogs have no interest in eating. They may approach their food and water dishes half-heartedly to sniff now and then, but the progressing inflammation of their intestines has taken away their appetite.

The absorptive portion of your pet’s intestines (small intestine) are lined with small finger-like projections called villi and interspersed valleys called crypts that aid in the absorption of food nutrients. It is here that parvovirus does its worst damage. Because cells in these villi reproduce rapidly, they are a prime target for the virus. The villi in dogs with parvo disease have a distinctive “clubbed” or blunted appearance due to their inability to regenerate themselves. They begin to “leak” loose their integrity as a barrier to bacterial infection, food absorption and body fluid retention.

As that inflammation and intestinal damage progresses, these dogs develop diarrhea with a particularly offensive and distinctive odor. Depending on the severity of the case, diarrhea might only be mucoid or it might contain considerable blood. Vomiting soon begins as well. Their abdomens are usually tight and tucked in.

These dogs usually have an initial fever spike. But it can pass rapidly enough for the pet’s body temperature to be normal or subnormal by the time its temperature is measured.

Any dog that vomits, develops diarrhea and has no inclination to drink or eat, quickly becomes dehydrated and looses weight. That is true in parvo as well. So the skin of these dogs looses its normal elasticity and the pet’s eyes are often sunken. This leads to a medial canthal exudate at the inner corner of your dog's eyes.

There are dogs, particularly small puppies, which do not survive this initial phase. Their body reserves are just to limited to battle the virus. Some actually die before diarrhea begins. Other things being equal, severity and outcome of parvovirus infection has a lot to do with the age of the dog involved. Healthy adult dogs that become infected can show few if any symptoms at all.

The changes that occur in the sick pet’s immunological system are less apparent to you, but very important. Because parvo attacks the rapidly dividing immunological cells of your pet’s bone marrow and thymus gland, white blood cells (particularly lymphocytes) are not produced nor do they circulate in sufficient numbers in the pet’s blood. (= leukopenia, lymphopenia).

When dogs die from parvovirus infection, they do so due to the shock these two phenomenon, intestinal destruction and immunological destruction produce. When dogs recover from parvovirus infection, it is because their immune system was able to recover and respond with protective antibodies. Good veterinary supportive care is what can tip the balance one way or the other. In my experience, dogs that survive the first eight days of symptoms usually recover. Fatal parvo is a steep steady slope downward. I have also noticed that dogs that look no worse two or three days in a row are almost certain to survive when good nursing care is provided.

When puppies are born to mothers with little or no parvovirus immunity, their heart muscle can also be a target of the virus. Early in the parvo epidemic, cases of heart muscle destruction (myocarditis) and sudden death due to parvovirus infection of infant (neonate) puppies was more common than it is now. A rare, skin form or parvo has also been reported. (ref)

Some dogs with parvo become anemic. But anemia is not a constant symptom of parvo infection.

Four factors govern the severity of the disease: age at exposure, the size of the virus dose, the presence of maternal antibody, and the breed of dog involved.

Severe diarrhea was common in adolescent dogs long before the parvovirus epidemic existed. There are many virus, bacteria and parasites (e.g. hookworms), as well as dietary indiscretions, that cause it (ref). Coronavirus of dogs can cause similar initial signs. (ref) Not all puppies and dogs that have parvo-like symptoms have parvo. That is why your veterinarian might suggest things like x-rays to rule out those other potential causes.

If My Vet Suspects That My Dog Has Parvo, What Tests Will The Vet Run ?

With experience, veterinarians learn to recognize a likely case of parvo. At one time, that was done through a physical examination, history (= signalment, e.g. age, breed, vaccination status, home environment, etc.). An exceedingly low white blood cell count helped confirm the diagnosis.

Today, we look for the virus itself. The most common way to do that is the in-office ELISA (Enzyme-Linked Immunosorbent Assay by Idexx, Agen or Synbiotics ) test that looks for parvovirus in the dog’s stool. These tests are quite reliable. All currently circulating virus strains are detected (ref) They are easy for veterinarians to perform in-office with test results in 15 minutes. (this is the brochure for one of them) When they fail to catch a case, it is usually very early or late in infection when virus numbers are low. Recent vaccination against parvo apparently only rarely gives a weak, false-positive test. (ref) ,Although there is some disagreement about that. (ref)

Is Parvo Always Fatal ?


It’s the sad outcomes that people tend to remember; the outbreak at the animal shelter, the pup lost down the street, the family that forgot to give their puppy immunizations. But probably 80% of the dogs that come in contact with the parvo virus recover.

What Treatments Will Help My Dog ?

Your veterinarian does not have a medication that has been definitively proven to attacks parvovirus. What veterinarians can offer your pet is critical supportive care while waiting for the dog’s own immune system to “kick in”.

It is critical that dogs battling parvovirus not become dehydrated. So intravenous fluids are a first-line treatment for most hospitalized parvo patients. In selecting those fluids, your veterinarian will take into consideration your pets acid/base balance, electrolyte disturbances, blood sugar level and degree of anemia. Lactated ringers solution (LRS) is usually the base fluid of choice.

Dogs often arrive with subnormal body temperatures. Your vet will correct that.

These pets vomit most anything given orally, so required medications will be given by injection. They will probably include antibiotics to combat secondary infection, analgesics to counter abdominal pain, and medications that control vomiting and diarrhea.
Your pet will probably receive an intravenous catheter to facility drug administration. But some patients are in such sad state that through-the-bone (intraosseous) administration is the only option.

If you look over the treatment medications for a typical case of parvo, these are the medications you are likely to see:

LRS – lactated ringers solution
Given to restore your pet's fluid balance (counteract dehydration)

Potassium chloride – if your vet determines the pet’s blood potassium level is low (hypokalemia)

Sodium Bicarbonate – if your vet determines that your pets blood has become too acidic (metabolic acidosis)

Dextrose – if your pet’s blood glucose has dropped too low. (hypoglycemia)

Hetastarch or dextran = artificial colloids to counteract the loss of natural blood colloids lost through a leaking intestine and starvation.

Whole Blood or blood plasma transfusion - Anemic dogs benefit from the red blood cells in whole blood transfusions. But many veterinarians store frozen blood plasma. Plasma contains natural colloid(ial) proteins the pet may need. When the blood plasma taken from a dog that is immune to parvo, it , just like whole blood, contains antibodies against the parvo virus. For a long time veterinarians (me included) thought that blood serum from dogs hyper immunized to parvo might help ill dogs recover. But a 2012 study did not find that to be the case. You can read that study here.

Worming medications for hookworms – hookworms cause their own form of enteritis and many parvovirus-infected dogs carry them. Not worming one’s puppies adequately goes hand in hand with not getting them their vaccinations on time. So it is quite common to see the two disease problems together. The gentlest drug to remove hookworms is pyrantel, pyrantel. Not all parvo dogs can be prevented from vomiting the medicine so I give it multiple times.

Dogs with severe parvo generally experience nausea and vomiting. To ease their discomfort, veterinarians usually give them an anti emetic . The common ones in use are maropitant/Cerenia, metoclopramide, prochlorperazine, ondansetron and chlorpromazine.

Medications that lessen gastric acidity such as cimetidine, ranitidine and famotidine as well as soothing coating agents like sucralfate (ref) also help in relieving nausea and vomission (vomiting).

Circulating toxins produced by invading intestinal bacteria are thought to be a major factor in the depression experienced by parvo-infected dogs. To counter those bacteria, dogs with this disease are placed on antibiotics. Some in common use today are cefazolin, cefoxitin/Mefoxitin, ampicillin/clavulanate with amikacin, and Baytril/enrofloxacin. (Baytril is not approved for use in growing dogs).

The most common drug used to counteract the abdominal pain of parvovirus is flunixin meglumine (= Banamine). It must be given to parvo dogs cautiously because it in itself can cause stomach and intestinal ulceration.

A possible exception to me telling you that no medication directly targets the parvovirus may be the human anti-influenza medicine, oseltamivir or Tamiflu given in the early days after infection before the virus is widespread in the dog’s body. Oseltamivir inhibits a certain enzyme (neuraminidase) that is required for human flu virus to spread within the body. Parvovirus does not rely on that enzyme. Although a single study found that Tamiflu, while not improving recovery speed or hospitalization time, did appear to decrease weight loss and hasten white blood cell recovery. You can read that article here.
The drug, in itself, can cause nausea vomiting stomach pain and diarrhea, and was ineffective other than in the first few days of infection.)

Another human medication used to increase resistance to bacterial infections is the recombinant granulocyte colony stimulating factor (Filgrastim, rhG-CSF ) trade name Neupogen. This bio-engineered amino acid protein increases the production of neutrophils in human bone marrow. It has been used in dogs ill with parvo with little success. However a 2009 study found that recombinant canine granulocyte-colony stimulating factor (rcG-CSF) appeared to offer more promise. You can read that study here.

A product called Septi-serum is marketed with great hype and fan-fair for treating parvovirus infection in dogs. No scientific data is provided to back up their phenomenal claims that it ‘decreases parvo mortality by 80%” ! The Company has a stable packed with products of questionable value. Their latest wonderproduct is an extract of the Korean spicy fermented cabbage dish, Kimichi, marketed to cure bird flu.

You can read a more inclusive article than this one on the treatment of parvo in dogs here.

What Are Some Key Things My Vet Will Monitor To Tell How Well My Sick Dog Is Responding To Treatment ?

The key things your vet will be monitoring are your pets blood parameters, searching for indications that things are returning to normal or leveling out. Generally, if things do not deteriorate over a three-day period, the dog is on the road to recovery.

Parvo dogs tend to be anemic. Measuring the pet’s red blood cell volume (= RBC, PCV, hematocrit,Hct) is a simple test that the vet can run every day.

The pet’s hydration is very important. We measure that visually and through blood tests that look for over-concentration of certain salt components (Na:K). That same blood sample will be checked for the number of defensive cells (neutrophils & lymphocytes) present to see if the pet’s bone marrow is recovering.

The pet’s blood sugar, albumen and immunoglobulin levels will be monitored pets to be sure they have climbing to adequate levels.

More sophisticated tests are available. Studies have found that a blood marker, C-reactive protein , tends to be highest in dogs with the most danger of dying from the disease. You can read a report about that here.

Basted on the results of those tests, your dog’s medication dose will be adjusted or new medications added.

The tests I have mentioned are all quite helpful to me. But none are as important as a loving veterinary technician monitoring your sick dog throughout the day, patting its head and offering an encouraging word now and then. The dog’s general attitude (how bright and cheerful it is) and a reduction in diarrhea and vomiting will tell your vet more than any sophisticated test.

Hospitalization in itself causes depression in some dogs. Ever so often, when I have a break, I will smear a bit of really good tasting dog food on my finger and place it near the dog’s nose. I do not let them lick it; but a change in its willingness to do so is a ray of sunshine on the pet’s chances for survival.

Does My Puppy or Dog Need Special Care Once it Is Out of Danger And Recovering ?

I have never personally seen a dog on the road to recovery from parvo, slip back into the disease. Never the less, dogs still experiencing nausea should not receive oral nutrients or food. When those foods are reintroduced, they should be quite bland, and they should be given frequently during the day in very small amounts. These fortunate pets can be ravenously hungry and eat until they do vomit. Food needs to be consumed slowly over an entire day.

Your vet may have sent you home with a bland prescription diet. Most pets will eat them, some dislike them. You have the option of preparing a bland diet yourself. You’ll find some tips here.

Many dogs are sent home with an oral antibiotic. If the dog was released home for one reason or another while still vomiting and experiencing diarrhea, medications to lessen nausea should leave with it. It typically takes a week or so for stools to return to normal color and consistency after recovery from a severe case of parvo.

The recovering pet needs a warm, low stress, location in your home, extra attention, close monitoring and restricted exercise until it is back to its old self.

If the dog becomes soiled, clean it with a damp cloth and dry it well. Move the dog before you clean its area with bleach or other antiseptic products.

Your recovering dog is infectious to other non-vaccinated dogs for a month or so. Do not contaminate parks, yards and communal areas with its infectious stool. Keep the pet at home for that month. The dog has been through an enormous stress. He is more susceptible to catching some second disease until he has fully recovered. If the dog did not have time to finish its initial vaccination series – it still needs them for protection against the other common diseases of dogs.

The Canine Health Golden Rule:   When in doubt thou shalt call thy vet.

Is The Vaccine Against Parvo Effective ?


The vaccines we now have are very effective. The majority of them contain a parvovirus that has been modified (MLV vaccine) to not cause disease symptoms (attenuated). Most contain the CPV-2 strain of parvo, but they protect against all strains you pet is likely to encounter. The amount of virus protein in these vaccines has also been increased (high antigen titer) to make it more likely that it will stimulate your pets immune system into producing protective antibody.

These vaccines are quite safe. Killed parvo vaccines are less effective than MLV vaccines. They also tend to cause more post-vaccination reactions due to the ingredients they contain. But they have their place when used in dogs with weakened immune systems.

When your young dog gets immunized against parvovirus and distemper, that single injection (plus a worming if indicated) is quite enough stress on its body for the next two weeks. Those are the two common life-threatening conditions of younger dogs and we want immunity against them to be as sold as possible.

If you decide to have leptospirosis vaccine administered, have it given as an independent injection - never in a combination vaccine or multiple vaccines given on the same day. Let several weeks pass between its distemper/parvo vaccination and its leptospirosis vaccination. This is because adding leptospirosis elements to combination vaccines can reduce the protection effectiveness of their other components. You can read about how that occurs here.
(It is also apparent from the results of that study that the current recommendation that "one lepto vaccine dose-size fits all sizes of dogs" needs to be rethought out.)

Will My Other Pets Catch It ?

Parvovirus is everywhere. Susceptible dogs are going to catch it eventually whether or not there was a parvo case within the family or not. The vaccine is very effective – but unusual events do occur: a puppy given its vaccines too young, an expired vaccine accidentally used, inactivation of the vaccine by sunlight, a dog immunosupressed or stressed when the vaccine was administered, etc. So I would review the vaccination history of my other dogs and my immediate neighbors dogs and give them a parvo booster vaccination if there is any doubt as to their protection. An alternative is to have their parvo-protective antibody levels measured (as I discussed here).

At What Age Should My Puppy Be Vaccinated To Prevent Parvo ?

There is no one perfect answer to that question. Every puppy is different. What vets generally do is play with the statistics and suggest a schedule that is right for the average pup.

Puppies born to mothers that have been vaccinated against parvovirus or have experienced parvo disease themselves are immune to the disease as long as their mother’s immunity persists (passive immunity) in their bodies. During that same time, they can have problems benefiting from vaccines.

The best vaccines against parvo are the ones that contain modified live virus. That virus must reproduce in your pup’s body for it to produce long lasting immunity (antibodies+memory cells it produced itself = active immunity). If antibodies from the mother are still present in the pup, the virus may not grow within the puppy's body subsequent to receiving the shot. It would then be ineffective, giving no protection. We have gotten around that somewhat with the new, high-antigen vaccines that produce active immunity in pups at a much earlier age than the older vaccines did. The latest studies find that these new vaccines stimulate antibody protection as early as four weeks of age. You can read that study here.

In ordinary circumstances, there should be no need to vaccinate puppies that young. If the mother dog was immunized, the pups should be immune to parvo for several more weeks due to the transfer of her antibodies to the pups through her first milk (passive antibodies=passive transfer). If, however, the pups did not receive her milk during the first 18-24 hours after birth, they were not protected (by the mother's passive immunity). Antibodies in milk of any kind given after that period will no longer pass through the puppy’s intestinal wall intact. If that may have happened or if the pups must be housed in a highly contaminated environment, an early parvo vaccination at 4 weeks of age might be desirable.

A better alternative is to isolate puppies from unvaccinated pets or parvo-contaminated environments until they are 8 weeks of age. Most veterinarians follow that with booster vaccinations at 12 and 16 weeks of age for as absolute a security of protection as is possible.

Remember, dogs and puppies don't leave the veterinary office after their parvo shot with parvo-protection. It takes 1-2 weeks to fully work !

Never assume a dog is protected against parvo if it did not receive its last parvo vaccination between 14-16 weeks of age (or any time after that).

As I wrote, veterinarians cannot easily predict the perfect dates on which to vaccinate your dog. Both the dogs and the virus are not that predictable. Theoretically, one can be predicted the date that the vaccine will work through multiple determinations of the pup’s blood antibody levels. But for most, that is impractical and unnecessary . That is why you will find so many veterinarians using different vaccination schedules.

My Puppy Got His Vaccinations – But He Still Caught Parvo - Why !!

Here are the most common reasons for that:

1) The shot(s) the puppy received were given at too young an age.
2) The puppy was already incubating or exposed to parvo before the shot was given.
3) The puppy was exposed to parvo after its injection but before the injection became protective.
4) The puppy did not receive its mother’s colostrum; the bitch was in poor health and produced inadequate colostrum or experienced birthing problems.
5) The puppy was severely weakened by hookworm disease
6) The mother had exceptionally high parvovirus antibody levels that persisted in the puppy and block the vaccine's effectiveness. (those pups need another vaccination at 20 weeks)

"Gas-n-go" techniques that give too many vaccines or combination vaccines at one time or combine vaccination with surgery, boarding and other high-stress procedures are not safe medical practices. They are convenient to owners and veterinarians, but they place unnecessary burdens on the pet’s immune system. One I consistently avoid in puppies is the “7-way” vaccination. (Older pets that receive it were probably already immune anyway and really didn't need it)
Image parvo-7way

How Often Does My Adult Dog Need A Parvo Shot To Keep It Protected ?

After its initial puppy series , I give a booster vaccination when the dog is one year old.
I do not routinely administer parvo or distemper shots after that. I have never seen a confirmed case of parvo in a dog that received that care (protocol). I believe that dogs that received that protocol are protected for life. A recent study found that they were protected for at least 9 years - probably more. You can read that most informative study here.

The current most common advise veterinarians give to clients is a booster every three years (that's what it says on the label). But there is no proof they need them that frequently. You can read current AAHA vaccination guidelines for dogs here. Immunity is not something like the gasoline in your car that you run out of, or a dog license with an expiration date.

If you want to be particularly cautious, ask your veterinarian to have the dog’s parvo antibody titer determined to see if it is still at protective levels. (There is more written on that below.)

Over-vaccination of our pets carries its own dangers. Injecting foreign proteins into your pets body stimulates its immune system in ways we do not completely understand. In cats, fibroscarcomas can result and although some associate repeated vaccination as a trigger for autoimmune disease. (ref) ; we really do not know.

Recently, an article was published that found unexpected live retrovirus present in dog vaccines - another reason to give vaccines only when they are truly needed. You can read that article here.

Is There An Alternative To Booster Vaccinations For My Adult Dog ?


You can have your pets immunity levels (antibody titer) measured periodically. Two laboratory tests are used, the Hemagglutination inhibition (HI) test and a virus neutralization test. The results are given in a ratio of how much the pet's blood sample could be diluted and still have protective ability. The more antibody initially present, the higher the final dilution. An HI titer of 1:80 or a Virus neutralization titer of 1:20 against parvovirus or a positive on the Synbiotics TiterCheck office test are all considered protective.

But low blood titer does not necessarily equal susceptibility to parvo. Immunity is more than the level of circulating antibody, it involves specific memory cells within your dog that are primed to rapidly produce more antibody when a particular invader is recognized. We do not have tests that measure the number of immunological memory cells in your pet - at least none that I know of.

Can My Dog Catch Parvo More Than Once ?


A dog that has recovered from a confirmed parvovirus infection is immune for the rest of its life.

Are There Ways I Can Disinfect My Home And Yard After A Case of Parvo ?

Parvovirus is a tough, resistant critter. It is "showered" around in the diarrhea that accompanies the disease in amounts too large to contemplate. In this foul mix, it sticks to surfaces it comes in contact with where the fecal residues shield and protect it.

The virus lives for long periods of time on floors, food containers and other household objects. Rugs and soil (earth. dirt) are particularly difficult to sanitize. It is likely that household vermin such as cockroaches and contaminated clothing and shoes could move the virus from place to place, but in most cases it is direct exposure to areas soiled by dog stool or a dog sick with the disease that are the source of infection. Areas that contain parvovirus, particularly outdoor areas, kennels and runs can look and smell perfectly clean - but still be dangerous.

One part of ordinary household bleach, diluted with 20-32 parts tap water (4 ounces of bleach to a gallon of water) will inactivate (kill) parvovirus. (it can also ruin fabrics and rugs). When you use bleach solution, do so in open or airy areas and wear gloves. Remove all pets and plants from the area until no bleach smell remains. There are many other disinfectants marketed for parvo, but none are better than ordinary bleach and some are not as effective as bleach. Pre-wash with soap and water anything you can. I leave objects contact with the bleach solution for 30 minutes – longer if they are grimy with organic mater. No disinfectant works as well when applied to grimy surfaces and areas or anything that is porous or has a high content of organic material. So one needs to clean all surfaces as scrupulously as you can before applying the bleach solution. If you can't leave them in bleach longer. (make only what you need at the time - bleach solution should be diluted fresh at each use.)

Although parvovirus are somewhat heat resistant, enough heat will kill them. Temperatures of 140F will inactivate the virus in about 10 hours. At 165F, ninety minutes is sufficient. Steam or wet heat is more effective than dry heat. (ref)

Exposure to bright sunshine (UV light) also kills the virus - but slowly.

Winter subfreezing temperatures do not kill it (it will be back knocking on your door in the spring.)

As I mentioned earlier, the virus can hang around in its infective form for about 5 months.

Bleach solution is great for indoor, smooth surfaces or when applied in sufficient quantity to get down into cracks, crevices and porous surfaces. When in doubt, leave it on longer or increase the strength of the solution.

In kennel situations, I gather up all small bleachable items, fill a 55 gallon plastic barrel with solution, and leave these pre-cleaned objects in it overnight. If they are rustable items, I remove them sooner, rinse them, wipe them dry or blow them dry with a hair dryer or leaf blower and spray them with WD40.

The tough problem occurs with items and areas than cannot be bleached or pre-cleaned. Things like carpets, wood flooring, sofas and the like and contaminated back yards. If you have access to a steam jenny, they work well on indestructible items. (Some of these jennys reach 325F at the nozzle – so test a small piece of carpet or sofa material to be sure you do not ruin them. Wear a face mask and goggles. If you utilize a profession steam cleaning service, they need to use a machine that reaches 240-270F at the nozzle tip , not the wimpy rental units.)

Outdoors, cleanup is much more difficult than indoor cleanup. Open up the outdoor area to sunlight and drying by clipping back tree limbs and close mowing. Remove trash and stored junk from your yard. Encourage lawn growth but keep it mowed. Water the areas heavily to try to drive the virus below the top layers of soil but do not keep the areas continuously damp. Spread a fresh layer of sand or topsoil over the area. If you have a lawn, add the layer a half inch at a time so the grass doesn't smother. Wait 5 (warm) months, if you can, before allowing your dogs re-access the area. If you cannot do that, be sure the new pet is solidly immune to parvo (through vaccination or titer-check) before introducing it to its new home.

If I Decide To Get Another Dog, How Long Should I Wait ?

It is considerably easier to make your new dog immune to parvo than it is to clean up a parvo-contaminated environment.

Pick out your puppy early. If the puppy is between 4 and 8 weeks old, have it receive a high antigen parvo vaccination but do not take it home until it is 8-12 weeks old or two weeks have passed. See to it that quality vaccines are administered to it at 8, 12 and 14 weeks as well and that it receives worming medications on those visits. (your local feed store vaccines may or may not work) Do not purchase dogs from pet stores, bulk breeders or third parties. Those dogs tend to have weak immune systems and pre-existing medical problems of all kinds. Do not purchase pets sight unseen – if you cant see both parents thank the sellers for them for their time - then leave. If you adopt from a shelter, follow the advice I gave earlier. Do not let their staff sweet talk you into something I said not to do. Their priorities are not your priorities.

Wait a few months before considering purchase of another dog. The family needs to come to terms with the loss of a pet. (grieving over a lost pet) If you long for immediate companionship, consider fostering some adult (vaccinated) pets for a rescue group. When you do find your dog, see to it that it is immune to parvo before it joins your family. A blood titer for parvo antibody will confirm that.

What About The Parvo Cures I See For Sale On The Internet ?

If I did not mention them, they do not work.

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