Parvovirus Infection: Physical Illness and Treatment
Wendy Brooks, DVM, DABVP
Date Published: 01/01/2001
Date Reviewed/Revised: 06/24/2023
Treatment for parvovirus infection centers on what is called supportive care. This means that the veterinarian’s job is to keep the patient hydrated, comfortable, and as strong as possible so that the puppy has time and ability to generate an effective immune response. We cannot kill the virus inside the patient's body; only the patient's own immune system can do that.
Be prepared for a five to seven-day hospital stay and substantial expense. Intensive care is needed to treat this infection.
There are certain basic treatment principles that can be viewed as “must haves” in addressing the parvo puppy. Beyond these basics are some added pluses that may or may not contribute to the chance of survival. In order to achieve the usual survival rate of approximately 75-80 percent, the basics must be delivered. Many practices will add additional treatments to their basic regimen in order to improve survival or shorten how long the puppy is sick, depending on expense and the preferences of the doctor. We will cover some of the treatments that may be used.
The Basics
Fluid Therapy
One of the ways parvo can kill is via the metabolic derangements that occur with extreme dehydration. It is crucial to replace the vast fluid losses (from vomiting and diarrhea) with intravenous fluids. Fluids are given as a steady drip rather than simply under the skin so that absorption into the circulation is direct. Potassium is usually 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, especially in a small puppy.
Antibiotics
The second way parvo kills is through bacterial invasion of the circulatory system (sepsis). The intestine is normally full of bacteria, and when the parvovirus ulcerates the intestine, there is little to prevent the bacteria from marching easily into the bloodstream. With the GI tract damaged, antibiotics cannot be given by mouth. They are given either as shots or are added into the IV fluid bag. There are a number of antibiotics that may be selected. The important thing is that they are given directly intravenously so as to avoid issues with attempting to absorb medication from the diseased intestinal tract or from poorly perfused peripheral tissues. Intravenous antibiotics are taken directly to the battlefield of the infection in the intestine, where bacteria are attempting to invade. Since the patient's white blood cell count is typically drastically reduced during the height of the parvo infection, we are relying on antibiotics to keep the bacteria out.
Control of Nausea
Patient comfort is an important part of treatment for any disease but is especially important for parvo treatment as these puppies feel extremely nauseated. Again, the GI tract is too damaged for oral medication so medications are given as injections. There are several popular medications for nausea control.
Maropitant (brand name: Cerenia®)
This powerful anti-nauseal is now fully approved for puppies over the age of 8 weeks. It is given once daily.
Metoclopramide (best given as a continuous drip in the IV fluid setup.)
Ondansetron and Dolasetron
These injectables are especially strong anti-nausea medications. In the past, the expense has made these medications uncommon, but recent generics have made them readily available. Ondansetron is typically given two to three times daily while dolasetron is given only once daily.
Heat Support
You might expect your pet would have a fever with such a serious infection (and sometimes there indeed is a fever), but usually, the opposite is the problem. Little dehydrated puppies tend to get cold, and with the cold comes poor blood circulation. It is important to keep the puppy warm enough to maintain a normal body temperature without too much work on the puppy's part, as he or she will need body resources to overcome the infection and not divert extra to body heat. Fluid warmers for IV fluids are sometimes used, and special heated blankets are common.
Nutritional Support
Originally, patients treated for parvo were kept off food in an effort to minimize nausea since they can’t digest much food anyway. More recently it has been found that intestinal cells survive and recover better if they receive some nutrients. Not much is necessary, just enough to lightly coat the intestinal cells. For this reason, a tiny amount of food is now recommended early in the course of treatment and throughout until recovery. The patient will not have an appetite at first, and the goal is not so much to nourish the puppy as to nourish the cells of the intestinal tract.
The vomiting typical of parvo infection is not only uncomfortable but can ulcerate the esophagus. The disease itself ulcerates the stomach and small intestine. Medications called gastroprotectants help heal ulcers and help minimize their formation. These medications might include injectable antacids (H2 receptor blockers or proton pump inhibitors) as well as sucralfate, which forms webbing over ulcers to facilitate healing.
Monitoring
The following tests are helpful in adjusting parvovirus treatment:
Fecal flotation to rule out worms/internal parasites
The last thing these patients need is a parasite burden contributing to their nausea and diarrhea. Since parvo victims are puppies and puppies are at high risk for parasitism, it is important to test for worms and microbes that can contribute to the GI upset and eliminate any. Alternatively, puppies can be dewormed with a broad spectrum product or products to be sure that internal parasites are not contributing to illness.
White blood cell counts/complete blood counts
One of the first acts of the parvovirus is to shut down the bone marrow production of immunologic cells (the white blood cells). White blood cell counts are often monitored as the infection is followed. The white blood cell count bottoms out at the height of the viral infection and recovers as the patient’s immune system gains the upper hand. Following the white blood cell count is helpful in tracking the course of infection and determining when the patient is truly on the upswing.
Electrolytes and Glucose levels
In at least one study of parvo patients, 60 percent of treated puppies required potassium supplementation during treatment, and 75 percent required glucose supplementation. Monitoring of these parameters is ideally performed regularly during the course of treatment.
Urine Specific Gravity/Lactate Levels
In order to assess the fluid therapy’s effectiveness, some objective evaluation of dehydration is useful. If adequate IV fluids have been provided, then the urine produced will be diluted as measured by specific gravity. Similarly, blood lactate levels can be monitored to ensure proper hydration as lactate will build up when tissues are not properly perfused by the circulation.
Abdominal Palpation
Abnormal motility of the intestines occurs with this infection. Sometimes an area of intestine actually telescopes inside an adjacent area in a process called intussusception. This is a disastrous occurrence as intussusception can only be treated surgically and parvo puppies are in no shape for surgery. Euthanasia is usually elected in this event. Less dramatically, some patients experience enough abdominal discomfort to require additional pain support beyond their anti-nausea medications.
Total blood protein
Protein depletion is common when there is heavy diarrhea. If blood proteins drop too low, certain IV fluids or even plasma transfusions are needed to prevent massive life-threatening edema.
Extra Treatment Which May Help
Tamiflu® (Oseltamivir)
While this particular addition to the parvo treatment plan has not caught on universally, news of Tamiflu's potential efficacy has spread far and wide. Tamiflu is a medication geared to suppress influenza viruses, not parvoviruses, but it turns out to have efficacy against harmful intestinal bacteria that are problematic during parvo infection. Tamiflu is typically given for five days starting as soon as the diagnosis is made. This medication is not only believed to be helpful in treating parvo patients, but it may also prevent the development of the disease when given to exposed puppies. The key is to begin this treatment before the virus has had a chance to maximize its numbers.
Plasma Transfusions
Plasma is the protein-rich fluid that remains when the red blood cells are removed from a sample of blood. These proteins may include antibodies against the parvovirus, albumin to help expand the patient’s blood volume, as well as other healing proteins. Plasma can be obtained from donor dogs in the hospital or can be purchased from animal blood banks.
Septi-Serum
This product represents anti-serum (antibodies extracted from horses) that binds the toxins of any invading GI tract bacteria. The use of this product is controversial though the veterinary teaching hospital at Auburn University uses it commonly. It is usually given only one time as the equine origin of the product has the potential for serious immunological reactions.
Neupogen
Neupogen is the brand name of a genetically engineered hormone called granulocyte colony-stimulating factor. This hormone is responsible for stimulating the bone marrow to produce white blood cells and its administration easily overcomes the bone marrow suppression caused by the parvovirus. In other words, Neupogen helps the white cell count recover. A recent study did not find increased survival with the addition of this product to the parvo regimen; however, in sicker puppies, it may make a significant difference. It is expensive and can add substantially to the treatment cost.
Fecal Transplantation
Transplanting fecal material from a healthy dog into the colon of an infected dog has been shown to reduce the number of days that parvo puppies have diarrhea. Reducing diarrhea fluid losses potentially can mean the difference between life and death, so this treatment is becoming more popular. Many hospitals actually keep frozen fecal samples properly mixed in saline for this exact purpose. This treatment is emerging for many intestinal diseases and is likely to become more common in the future.
Monoclonal Antibodies
An intravenous treatment that prevents the attachment of the virus to patient cells has been released in 2023. A single injection of monoclonal antibodies against canine parvovirus is given to the puppy as early in treatment as possible so as to minimize the virus' ability to produce infection. This treatment appears to reduce symptoms experienced as well as hospitalization time.
Home Treatment for Parvo
Proper treatment for parvo involves intensive support and monitoring of numerous parameters that may require special, additional treatment. Survival statistics with hospitalization are high and there is no comparable treatment that can be performed at home. That said, sometimes financial concerns preclude hospitalization and home care may be a puppy's only chance. The owner will need to give injections, manage feedings, and clean up a great deal of vomit and diarrhea. Colorado State University has published an outpatient parvovirus treatment protocol that has demonstrated good success but in this protocol, the patient returned daily for hydration assessments and blood sugar and electrolyte testing, which would contribute to expense and effort. If home treatment turns out to be the only option, ask your veterinarian about the most practical options for your own situation.
Wendy Brooks, DVM, DABVP
Date Published: 01/01/2001
Date Reviewed/Revised: 06/24/2023
Treatment for parvovirus infection centers on what is called supportive care. This means that the veterinarian’s job is to keep the patient hydrated, comfortable, and as strong as possible so that the puppy has time and ability to generate an effective immune response. We cannot kill the virus inside the patient's body; only the patient's own immune system can do that.
Be prepared for a five to seven-day hospital stay and substantial expense. Intensive care is needed to treat this infection.
There are certain basic treatment principles that can be viewed as “must haves” in addressing the parvo puppy. Beyond these basics are some added pluses that may or may not contribute to the chance of survival. In order to achieve the usual survival rate of approximately 75-80 percent, the basics must be delivered. Many practices will add additional treatments to their basic regimen in order to improve survival or shorten how long the puppy is sick, depending on expense and the preferences of the doctor. We will cover some of the treatments that may be used.
The Basics
Fluid Therapy
One of the ways parvo can kill is via the metabolic derangements that occur with extreme dehydration. It is crucial to replace the vast fluid losses (from vomiting and diarrhea) with intravenous fluids. Fluids are given as a steady drip rather than simply under the skin so that absorption into the circulation is direct. Potassium is usually 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, especially in a small puppy.
Antibiotics
The second way parvo kills is through bacterial invasion of the circulatory system (sepsis). The intestine is normally full of bacteria, and when the parvovirus ulcerates the intestine, there is little to prevent the bacteria from marching easily into the bloodstream. With the GI tract damaged, antibiotics cannot be given by mouth. They are given either as shots or are added into the IV fluid bag. There are a number of antibiotics that may be selected. The important thing is that they are given directly intravenously so as to avoid issues with attempting to absorb medication from the diseased intestinal tract or from poorly perfused peripheral tissues. Intravenous antibiotics are taken directly to the battlefield of the infection in the intestine, where bacteria are attempting to invade. Since the patient's white blood cell count is typically drastically reduced during the height of the parvo infection, we are relying on antibiotics to keep the bacteria out.
Control of Nausea
Patient comfort is an important part of treatment for any disease but is especially important for parvo treatment as these puppies feel extremely nauseated. Again, the GI tract is too damaged for oral medication so medications are given as injections. There are several popular medications for nausea control.
Maropitant (brand name: Cerenia®)
This powerful anti-nauseal is now fully approved for puppies over the age of 8 weeks. It is given once daily.
Metoclopramide (best given as a continuous drip in the IV fluid setup.)
Ondansetron and Dolasetron
These injectables are especially strong anti-nausea medications. In the past, the expense has made these medications uncommon, but recent generics have made them readily available. Ondansetron is typically given two to three times daily while dolasetron is given only once daily.
Heat Support
You might expect your pet would have a fever with such a serious infection (and sometimes there indeed is a fever), but usually, the opposite is the problem. Little dehydrated puppies tend to get cold, and with the cold comes poor blood circulation. It is important to keep the puppy warm enough to maintain a normal body temperature without too much work on the puppy's part, as he or she will need body resources to overcome the infection and not divert extra to body heat. Fluid warmers for IV fluids are sometimes used, and special heated blankets are common.
Nutritional Support
Originally, patients treated for parvo were kept off food in an effort to minimize nausea since they can’t digest much food anyway. More recently it has been found that intestinal cells survive and recover better if they receive some nutrients. Not much is necessary, just enough to lightly coat the intestinal cells. For this reason, a tiny amount of food is now recommended early in the course of treatment and throughout until recovery. The patient will not have an appetite at first, and the goal is not so much to nourish the puppy as to nourish the cells of the intestinal tract.
The vomiting typical of parvo infection is not only uncomfortable but can ulcerate the esophagus. The disease itself ulcerates the stomach and small intestine. Medications called gastroprotectants help heal ulcers and help minimize their formation. These medications might include injectable antacids (H2 receptor blockers or proton pump inhibitors) as well as sucralfate, which forms webbing over ulcers to facilitate healing.
Monitoring
The following tests are helpful in adjusting parvovirus treatment:
Fecal flotation to rule out worms/internal parasites
The last thing these patients need is a parasite burden contributing to their nausea and diarrhea. Since parvo victims are puppies and puppies are at high risk for parasitism, it is important to test for worms and microbes that can contribute to the GI upset and eliminate any. Alternatively, puppies can be dewormed with a broad spectrum product or products to be sure that internal parasites are not contributing to illness.
White blood cell counts/complete blood counts
One of the first acts of the parvovirus is to shut down the bone marrow production of immunologic cells (the white blood cells). White blood cell counts are often monitored as the infection is followed. The white blood cell count bottoms out at the height of the viral infection and recovers as the patient’s immune system gains the upper hand. Following the white blood cell count is helpful in tracking the course of infection and determining when the patient is truly on the upswing.
Electrolytes and Glucose levels
In at least one study of parvo patients, 60 percent of treated puppies required potassium supplementation during treatment, and 75 percent required glucose supplementation. Monitoring of these parameters is ideally performed regularly during the course of treatment.
Urine Specific Gravity/Lactate Levels
In order to assess the fluid therapy’s effectiveness, some objective evaluation of dehydration is useful. If adequate IV fluids have been provided, then the urine produced will be diluted as measured by specific gravity. Similarly, blood lactate levels can be monitored to ensure proper hydration as lactate will build up when tissues are not properly perfused by the circulation.
Abdominal Palpation
Abnormal motility of the intestines occurs with this infection. Sometimes an area of intestine actually telescopes inside an adjacent area in a process called intussusception. This is a disastrous occurrence as intussusception can only be treated surgically and parvo puppies are in no shape for surgery. Euthanasia is usually elected in this event. Less dramatically, some patients experience enough abdominal discomfort to require additional pain support beyond their anti-nausea medications.
Total blood protein
Protein depletion is common when there is heavy diarrhea. If blood proteins drop too low, certain IV fluids or even plasma transfusions are needed to prevent massive life-threatening edema.
Extra Treatment Which May Help
Tamiflu® (Oseltamivir)
While this particular addition to the parvo treatment plan has not caught on universally, news of Tamiflu's potential efficacy has spread far and wide. Tamiflu is a medication geared to suppress influenza viruses, not parvoviruses, but it turns out to have efficacy against harmful intestinal bacteria that are problematic during parvo infection. Tamiflu is typically given for five days starting as soon as the diagnosis is made. This medication is not only believed to be helpful in treating parvo patients, but it may also prevent the development of the disease when given to exposed puppies. The key is to begin this treatment before the virus has had a chance to maximize its numbers.
Plasma Transfusions
Plasma is the protein-rich fluid that remains when the red blood cells are removed from a sample of blood. These proteins may include antibodies against the parvovirus, albumin to help expand the patient’s blood volume, as well as other healing proteins. Plasma can be obtained from donor dogs in the hospital or can be purchased from animal blood banks.
Septi-Serum
This product represents anti-serum (antibodies extracted from horses) that binds the toxins of any invading GI tract bacteria. The use of this product is controversial though the veterinary teaching hospital at Auburn University uses it commonly. It is usually given only one time as the equine origin of the product has the potential for serious immunological reactions.
Neupogen
Neupogen is the brand name of a genetically engineered hormone called granulocyte colony-stimulating factor. This hormone is responsible for stimulating the bone marrow to produce white blood cells and its administration easily overcomes the bone marrow suppression caused by the parvovirus. In other words, Neupogen helps the white cell count recover. A recent study did not find increased survival with the addition of this product to the parvo regimen; however, in sicker puppies, it may make a significant difference. It is expensive and can add substantially to the treatment cost.
Fecal Transplantation
Transplanting fecal material from a healthy dog into the colon of an infected dog has been shown to reduce the number of days that parvo puppies have diarrhea. Reducing diarrhea fluid losses potentially can mean the difference between life and death, so this treatment is becoming more popular. Many hospitals actually keep frozen fecal samples properly mixed in saline for this exact purpose. This treatment is emerging for many intestinal diseases and is likely to become more common in the future.
Monoclonal Antibodies
An intravenous treatment that prevents the attachment of the virus to patient cells has been released in 2023. A single injection of monoclonal antibodies against canine parvovirus is given to the puppy as early in treatment as possible so as to minimize the virus' ability to produce infection. This treatment appears to reduce symptoms experienced as well as hospitalization time.
Home Treatment for Parvo
Proper treatment for parvo involves intensive support and monitoring of numerous parameters that may require special, additional treatment. Survival statistics with hospitalization are high and there is no comparable treatment that can be performed at home. That said, sometimes financial concerns preclude hospitalization and home care may be a puppy's only chance. The owner will need to give injections, manage feedings, and clean up a great deal of vomit and diarrhea. Colorado State University has published an outpatient parvovirus treatment protocol that has demonstrated good success but in this protocol, the patient returned daily for hydration assessments and blood sugar and electrolyte testing, which would contribute to expense and effort. If home treatment turns out to be the only option, ask your veterinarian about the most practical options for your own situation.
Parvovirus: How it Happens
Wendy Brooks, DVM, DABVP
Date Published: 01/01/2001
Date Reviewed/Revised: 10/05/2023
Whether or not infection happens depends on the interaction of three factors: host vitality (including immune experience/vaccination status); virulence of the virus (including virus strain and how many viral particles the host is exposed to); and environmental factors (other stresses and/or concurrent conditions). Obviously, these three aspects interplay somewhat (a stressful environment will reduce host vitality, a dry environment will reduce the number of viral particles, etc.)
Where Does the Parvovirus Come From?
Remember that this virus has been around since the 1970s, is hard to disinfect, and is shed in extremely large numbers by infected dogs. This means that there is a virus everywhere: on every carpet, on every floor, in every yard and park. The virus is shed in the stool for the first two weeks or less after the initial infection, 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 the virus around a large area depending on where they leave their droppings. Basically, because the virus is hardy, it travels wherever dirt travels, and not a lot of virus is needed to create an infection in a susceptible dog.
Why Only Puppies?
The most important factors in whether parvovirus infection occurs seem to be the experience the dog’s immune system has had with the virus plus the number of viral particles the host is exposed to. In the 1970s and early 1980s, when the virus was new, all dogs, young and old, were susceptible, but now that the virus is 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, depending on the dog's age at vaccination and the nature of the exposure; infection in dogs over age one year is rare. It is important to realize, however, that this observation should not be taken to mean that adult dogs should not continue their vaccinations.
Even though infection is unusual in adult dogs, adult dogs should still continue getting vaccinations as this is a life-threatening disease for which treatment is expensive, and no chances should be taken. Widespread vaccination is part of the reason why infection in adult dogs is rare.
Natural Protection?
The younger the dog, the less immunologic experience and the more susceptibility to infection there is.
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 a specific type of milk called colostrum for the first day or two after giving birth. It contains all the antibodies that the mother dog has circulating in her own body, and in this way, she gives her own immune experience to her offspring. These antibodies are protective until they wear off sometime in the first four months of the puppy's life.
How much colostrum an individual puppy gets depends on its birth order and how strong it nurses; not all puppies get the same amount of antibodies. Every nine days, the antibody levels possessed by the puppies drop 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. The age at which maternal antibodies disappear is different for each individual puppy and is not predictable.
We recommend that puppies be restricted from public outdoor areas until their vaccination series is completed at age 16 weeks.
There is a period of a week or so during which the puppy has no antibody protection left over 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 three- to seven-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 in the throat fit the bill, and the virus sets up here first and replicates to large numbers. After a couple of days, so much virus has been produced that significant amounts of it have been released into the bloodstream. Over the next three to four days, the virus seeks new organs containing the rapidly dividing cells it needs: the bone marrow and the delicate intestinal cells.
Within the bone marrow, the virus is responsible for the destruction of young cells of the immune system. By killing these cells, it knocks out the body's best defense and ensures itself a reign of terror in the GI tract, where its most devastating effects occur. Parvoviral infections are characterized by a drop in white blood cell count due to bone marrow infection. Seeing this on a blood test may help clinch the diagnosis of parvoviral infection. Also, a veterinarian may choose to monitor white blood cell count to track the progress of the infection with the recovery of the white cell count correlating with the defeat of the infection. The white cell count, which in a normal dog is measured in the tens of thousands, may drop to nearly zero in the brunt of the disease.
The GI tract is where the heaviest damage occurs. The normal intestine possesses little finger-like protrusions called villi. Having these tiny fingers greatly increases the surface area available for the absorption of fluid and nutrients. To make the surface area available for absorption greater still, the villi possess microvilli, which are microscopic protrusions. The cells of the villi are relatively short-lived and are readily replaced by new cells. The source of the new cells is the rapidly dividing area at the foot of the villi called the crypts of Lieberkuhn. Parvovirus strikes right at the crypt.
Without new cells coming from the crypt, the villus becomes blunted and unable to absorb nutrients. Diarrhea in large quantities results, not to mention nausea. The barrier separating the digestive bacteria from the bloodstream breaks down. Diarrhea becomes bloody and bacteria can enter the body, causing widespread infection (remember that that virus has also simultaneously destroyed the bone marrow's ability to respond immunologically).
The virus kills dogs in one of two ways:
Even parvovirus cannot disrupt the entire immune system. Plus, every day that goes by allows more antibodies to be produced. This antibody can bind and inactivate the virus. 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.
Hospitalization with IV fluids and intensive supportive care greatly increases but doesn't guarantee the chance of survival.
Wendy Brooks, DVM, DABVP
Date Published: 01/01/2001
Date Reviewed/Revised: 10/05/2023
Whether or not infection happens depends on the interaction of three factors: host vitality (including immune experience/vaccination status); virulence of the virus (including virus strain and how many viral particles the host is exposed to); and environmental factors (other stresses and/or concurrent conditions). Obviously, these three aspects interplay somewhat (a stressful environment will reduce host vitality, a dry environment will reduce the number of viral particles, etc.)
Where Does the Parvovirus Come From?
Remember that this virus has been around since the 1970s, is hard to disinfect, and is shed in extremely large numbers by infected dogs. This means that there is a virus everywhere: on every carpet, on every floor, in every yard and park. The virus is shed in the stool for the first two weeks or less after the initial infection, 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 the virus around a large area depending on where they leave their droppings. Basically, because the virus is hardy, it travels wherever dirt travels, and not a lot of virus is needed to create an infection in a susceptible dog.
Why Only Puppies?
The most important factors in whether parvovirus infection occurs seem to be the experience the dog’s immune system has had with the virus plus the number of viral particles the host is exposed to. In the 1970s and early 1980s, when the virus was new, all dogs, young and old, were susceptible, but now that the virus is 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, depending on the dog's age at vaccination and the nature of the exposure; infection in dogs over age one year is rare. It is important to realize, however, that this observation should not be taken to mean that adult dogs should not continue their vaccinations.
Even though infection is unusual in adult dogs, adult dogs should still continue getting vaccinations as this is a life-threatening disease for which treatment is expensive, and no chances should be taken. Widespread vaccination is part of the reason why infection in adult dogs is rare.
Natural Protection?
The younger the dog, the less immunologic experience and the more susceptibility to infection there is.
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 a specific type of milk called colostrum for the first day or two after giving birth. It contains all the antibodies that the mother dog has circulating in her own body, and in this way, she gives her own immune experience to her offspring. These antibodies are protective until they wear off sometime in the first four months of the puppy's life.
How much colostrum an individual puppy gets depends on its birth order and how strong it nurses; not all puppies get the same amount of antibodies. Every nine days, the antibody levels possessed by the puppies drop 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. The age at which maternal antibodies disappear is different for each individual puppy and is not predictable.
We recommend that puppies be restricted from public outdoor areas until their vaccination series is completed at age 16 weeks.
There is a period of a week or so during which the puppy has no antibody protection left over 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 three- to seven-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 in the throat fit the bill, and the virus sets up here first and replicates to large numbers. After a couple of days, so much virus has been produced that significant amounts of it have been released into the bloodstream. Over the next three to four days, the virus seeks new organs containing the rapidly dividing cells it needs: the bone marrow and the delicate intestinal cells.
Within the bone marrow, the virus is responsible for the destruction of young cells of the immune system. By killing these cells, it knocks out the body's best defense and ensures itself a reign of terror in the GI tract, where its most devastating effects occur. Parvoviral infections are characterized by a drop in white blood cell count due to bone marrow infection. Seeing this on a blood test may help clinch the diagnosis of parvoviral infection. Also, a veterinarian may choose to monitor white blood cell count to track the progress of the infection with the recovery of the white cell count correlating with the defeat of the infection. The white cell count, which in a normal dog is measured in the tens of thousands, may drop to nearly zero in the brunt of the disease.
The GI tract is where the heaviest damage occurs. The normal intestine possesses little finger-like protrusions called villi. Having these tiny fingers greatly increases the surface area available for the absorption of fluid and nutrients. To make the surface area available for absorption greater still, the villi possess microvilli, which are microscopic protrusions. The cells of the villi are relatively short-lived and are readily replaced by new cells. The source of the new cells is the rapidly dividing area at the foot of the villi called the crypts of Lieberkuhn. Parvovirus strikes right at the crypt.
Without new cells coming from the crypt, the villus becomes blunted and unable to absorb nutrients. Diarrhea in large quantities results, not to mention nausea. The barrier separating the digestive bacteria from the bloodstream breaks down. Diarrhea becomes bloody and bacteria can enter the body, causing widespread infection (remember that that virus has also simultaneously destroyed the bone marrow's ability to respond immunologically).
The virus kills dogs in one of two 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.
-
Even parvovirus cannot disrupt the entire immune system. Plus, every day that goes by allows more antibodies to be produced. This antibody can bind and inactivate the virus. 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.
Hospitalization with IV fluids and intensive supportive care greatly increases but doesn't guarantee the chance of survival.
Sanitizing and Disinfecting the Environment after Parvovirus in Dogs
Heather Howell, LVT, RVT, MBA
Date Published: 05/20/2021
Canine parvovirus is a highly contagious virus. Young, old, unvaccinated, or immune-compromised dogs are particularly susceptible. Parvo, as it is typically called, or CPV, lives well in the environment, both indoors and outside. It is a non-enveloped virus, which means it lacks a membrane often called the envelope that is stronger than enveloped ones. It can survive indoors for months and outdoors it can live for months to years, especially in dark, moist environments.
Parvo can be easily spread by fomites, which are objects such as a doorknob or pet fur that can be contaminated by a virus. Dog-to-dog contact is not required for susceptible dogs to become infected. Dogs can become infected from contact with the remaining virus where an infected dog has been, or on objects an infected dog has used, or even from shoes and clothing carrying the virus. To make matters worse, non-enveloped viruses are not easily killed by most common household disinfectants and antibacterial soaps do not kill it. If you have had a dog with canine parvovirus in your home or yard, you need accurate information about what you can do to decrease or eliminate the risk of exposing other dogs while understanding that you cannot completely eliminate parvovirus from your home; it's simply not possible.
First, Remove Organic Material
Sanitizing is a two-step process that involves both cleaning and disinfecting. Some surfaces and substrates are easier than others to sanitize. For instance, carpet and grass are difficult to properly sanitize, whereas sealed cement is easier.
Before disinfecting, you need to clean since many disinfectants do not work well on organic material, such as stool or urine. Clean up any organic material from the yard and in the house. Bedding and toys that are not heavily soiled can be washed through a soap/bleach cycle and dried on a hot setting. It is best to discard anything heavily soiled. All areas and items still need to be properly disinfected, but the first step is to mechanically clean them.
Water can also be used to spray down outside areas to help remove any dried poop or vomit. Diluting an area such as a lawn by spraying with water may also help, but only if drainage and temperature allow the yard to thoroughly dry afterward.
Bathe any dogs using regular dog shampoo who were exposed or infected and recovered, as well as other dogs who had contact with the infected dog or area. This will help to decrease the risk of fomite transmission from their fur.
Use an Effective Virucidal Disinfectant
When choosing a disinfectant, make sure it has been proven to kill parvovirus. A label claiming to kill viruses does not mean it kills all viruses, such as the hearty, non-enveloped parvovirus. Additionally, any disinfectant must be mixed to the proper dilution and remain saturated for the proper contact time to be effective against parvovirus. Independent studies or FDA approval backing label claims are the most reliable means of determining a disinfectant's effectiveness.
Types of Disinfectants
Quaternary Ammonium Disinfectant
Despite its popularity for many years and label claims of efficacy against parvovirus, independent studies have shown this disinfectant to be unreliable against parvovirus. The label claims are based on diluting at 18 ounces per gallon, which is four times the typical concentration. Despite repeated reformulation and label claims, this is not seen as a reliable disinfectant against parvovirus and is not endorsed by independent studies or label-approved by the FDA. It must be rinsed off.
5% Sodium Hypochlorite (Bleach)
Bleach can kill parvovirus when it is used properly. It is readily available and relatively inexpensive but has some drawbacks. It can discolor or even ruin surfaces. The fumes can be irritating to the nose, eyes, and skin. Bleach is most effective on non-porous surfaces from which organic material has been thoroughly removed. For areas where you can safely use bleach, dilute household bleach (5% sodium hypochlorite) using 1 part bleach to 32 parts water (that's 1/2 cup per gallon of water). The diluted bleach must have ten minutes of contact time with the surface, which means saturating the area or continually spraying for ten minutes. It must be rinsed off.
Potassium Peroxymonosulfate Disinfectant
This disinfectant has some detergent properties, meaning it is effective for mechanically removing organic matter, such as vomit and feces. It can be irritating to the skin and eyes. The label claims efficacy against parvovirus at 1% dilution, even when mixed with hard water or organic material. It can be used in carpet cleaners to clean carpets and furniture (spot test for staining first) and can also be sprayed on yard surfaces. The area must remain saturated for ten minutes. It can be left to dry and does not need to be rinsed.
Accelerated Hydrogen Peroxide (AHP) Disinfectant
This disinfectant has become widely used in animal shelters, where CPV is not uncommon. Its detergent properties make it effective even when there is some organic matter. It can be used in one step for mechanical cleaning and to kill the virus. As in the other disinfectants discussed, proper dilutions and contact time are crucial to ensuring it kills the virus. It should be diluted using one part AHP to 32 parts water (1/2 cup per gallon of water) with a ten-minute contact time. This can be irritating to breathe but is less corrosive to surfaces and mucous membranes than bleach. It can be used in carpet cleaners and sprayed on grassy surfaces as well. It can be left to dry and does not need to be rinsed.
The Yard
Careful and repeated removal of all visible feces is important. If possible, flush the yard with water and allow it to dry. Then apply a disinfectant that is effective with organic material, such as AHP or potassium peroxymonosulfate. These can be used with a pesticide sprayer or hose-end sprayer at the proper dilution to saturate the outside area. Diluted bleach may also be somewhat effective, but since it does not perform as well with organic matter it is less effective than the others. Bleach is also more dangerous to plant life and other surfaces. If your yard has dirt and grass, rather than just cement, there is no guarantee any disinfectant will be 100% effective. It is best to thoroughly clean, dry, disinfect with the proper contact time and dry at least twice. When possible, maximize exposure to sunlight and allow the area to dry completely.
In most home yard situations where there is grass and dirt, it is not possible to completely disinfect a yard. Out of an abundance of caution, you may want to avoid having unvaccinated dogs come to your yard for 6 to 12 months, even after cleaning and attempting to disinfect.
The House
It helps to understand the difference between porous and non-porous surfaces. Water can go through porous materials. Non-porous materials include stainless steel, glass, metals, rigid plastics, and painted or varnished surfaces. Granite countertops are porous, but quartz is not. Porous materials include unpolished wood, laminate, granite, drywall, carpeting, ceiling tiles, and unsealed cement.
As mentioned, the first step is thoroughly cleaning the house and removing any feces or vomit that can be seen. Once all areas have been mechanically cleaned, you are ready to disinfect. Non-porous surfaces can be disinfected with diluted bleach or AHP or potassium peroxymonosulfate. Make sure you follow the manufacturer's instructions for the proper dilution and contact times for parvovirus.
For carpets and porous surfaces, AHP or potassium peroxymonosulfate disinfectants can be used in carpet cleaners to steam clean carpets and furniture. Understand that these areas are sometimes impossible to disinfect and heavily soiled items should be discarded if possible. Make sure you read the carpet cleaner instructions and spot-test any porous surfaces for possible discoloration. These surfaces will need to remain saturated for ten minutes to ensure the proper contact time. After disinfecting, the areas need to dry thoroughly.
Bedding, Porous Items, or Toys
Bedding and other fabric or porous items should either be thrown away, especially if heavily soiled, or washed thoroughly with detergent, hot water, and bleach and run through a hot dryer cycle if possible. If it is not possible to bleach the items, you could steam clean them with disinfectant as recommended for carpet and furniture. Consider if it is worth the risk to keep porous items such as bedding and toys that can't be bleached, or if it is better to throw them away.
Exposed Bowls and Non-Porous Items
Metal or ceramic bowls and non-porous toys should be washed thoroughly with a detergent, rinsed well, and then disinfected using an effective disinfectant. Throw away any plastic bowls that have any signs of wear, scratches, or teeth marks, which create porous areas. Proper dilution and contact time are important. This can be achieved by soaking the cleaned items in the diluted disinfectant for ten minutes, then allowing the items to dry. After disinfecting, thoroughly rinse the items with water and allow them to dry.
When is my Home Safe?
Unfortunately, there is no guaranteed time frame. There has not been any research that definitively states canine parvovirus can be eliminated from a home or yard environment in a specific number of days. There are many factors that affect whether cleaning and disinfecting efforts will be effective inside the house and outside in the yard. After a parvovirus-positive dog has been in your home or yard, it is safest to only have animals visit who have completed their vaccination series.
Heather Howell, LVT, RVT, MBA
Date Published: 05/20/2021
Canine parvovirus is a highly contagious virus. Young, old, unvaccinated, or immune-compromised dogs are particularly susceptible. Parvo, as it is typically called, or CPV, lives well in the environment, both indoors and outside. It is a non-enveloped virus, which means it lacks a membrane often called the envelope that is stronger than enveloped ones. It can survive indoors for months and outdoors it can live for months to years, especially in dark, moist environments.
Parvo can be easily spread by fomites, which are objects such as a doorknob or pet fur that can be contaminated by a virus. Dog-to-dog contact is not required for susceptible dogs to become infected. Dogs can become infected from contact with the remaining virus where an infected dog has been, or on objects an infected dog has used, or even from shoes and clothing carrying the virus. To make matters worse, non-enveloped viruses are not easily killed by most common household disinfectants and antibacterial soaps do not kill it. If you have had a dog with canine parvovirus in your home or yard, you need accurate information about what you can do to decrease or eliminate the risk of exposing other dogs while understanding that you cannot completely eliminate parvovirus from your home; it's simply not possible.
First, Remove Organic Material
Sanitizing is a two-step process that involves both cleaning and disinfecting. Some surfaces and substrates are easier than others to sanitize. For instance, carpet and grass are difficult to properly sanitize, whereas sealed cement is easier.
Before disinfecting, you need to clean since many disinfectants do not work well on organic material, such as stool or urine. Clean up any organic material from the yard and in the house. Bedding and toys that are not heavily soiled can be washed through a soap/bleach cycle and dried on a hot setting. It is best to discard anything heavily soiled. All areas and items still need to be properly disinfected, but the first step is to mechanically clean them.
Water can also be used to spray down outside areas to help remove any dried poop or vomit. Diluting an area such as a lawn by spraying with water may also help, but only if drainage and temperature allow the yard to thoroughly dry afterward.
Bathe any dogs using regular dog shampoo who were exposed or infected and recovered, as well as other dogs who had contact with the infected dog or area. This will help to decrease the risk of fomite transmission from their fur.
Use an Effective Virucidal Disinfectant
When choosing a disinfectant, make sure it has been proven to kill parvovirus. A label claiming to kill viruses does not mean it kills all viruses, such as the hearty, non-enveloped parvovirus. Additionally, any disinfectant must be mixed to the proper dilution and remain saturated for the proper contact time to be effective against parvovirus. Independent studies or FDA approval backing label claims are the most reliable means of determining a disinfectant's effectiveness.
Types of Disinfectants
Quaternary Ammonium Disinfectant
Despite its popularity for many years and label claims of efficacy against parvovirus, independent studies have shown this disinfectant to be unreliable against parvovirus. The label claims are based on diluting at 18 ounces per gallon, which is four times the typical concentration. Despite repeated reformulation and label claims, this is not seen as a reliable disinfectant against parvovirus and is not endorsed by independent studies or label-approved by the FDA. It must be rinsed off.
5% Sodium Hypochlorite (Bleach)
Bleach can kill parvovirus when it is used properly. It is readily available and relatively inexpensive but has some drawbacks. It can discolor or even ruin surfaces. The fumes can be irritating to the nose, eyes, and skin. Bleach is most effective on non-porous surfaces from which organic material has been thoroughly removed. For areas where you can safely use bleach, dilute household bleach (5% sodium hypochlorite) using 1 part bleach to 32 parts water (that's 1/2 cup per gallon of water). The diluted bleach must have ten minutes of contact time with the surface, which means saturating the area or continually spraying for ten minutes. It must be rinsed off.
Potassium Peroxymonosulfate Disinfectant
This disinfectant has some detergent properties, meaning it is effective for mechanically removing organic matter, such as vomit and feces. It can be irritating to the skin and eyes. The label claims efficacy against parvovirus at 1% dilution, even when mixed with hard water or organic material. It can be used in carpet cleaners to clean carpets and furniture (spot test for staining first) and can also be sprayed on yard surfaces. The area must remain saturated for ten minutes. It can be left to dry and does not need to be rinsed.
Accelerated Hydrogen Peroxide (AHP) Disinfectant
This disinfectant has become widely used in animal shelters, where CPV is not uncommon. Its detergent properties make it effective even when there is some organic matter. It can be used in one step for mechanical cleaning and to kill the virus. As in the other disinfectants discussed, proper dilutions and contact time are crucial to ensuring it kills the virus. It should be diluted using one part AHP to 32 parts water (1/2 cup per gallon of water) with a ten-minute contact time. This can be irritating to breathe but is less corrosive to surfaces and mucous membranes than bleach. It can be used in carpet cleaners and sprayed on grassy surfaces as well. It can be left to dry and does not need to be rinsed.
The Yard
Careful and repeated removal of all visible feces is important. If possible, flush the yard with water and allow it to dry. Then apply a disinfectant that is effective with organic material, such as AHP or potassium peroxymonosulfate. These can be used with a pesticide sprayer or hose-end sprayer at the proper dilution to saturate the outside area. Diluted bleach may also be somewhat effective, but since it does not perform as well with organic matter it is less effective than the others. Bleach is also more dangerous to plant life and other surfaces. If your yard has dirt and grass, rather than just cement, there is no guarantee any disinfectant will be 100% effective. It is best to thoroughly clean, dry, disinfect with the proper contact time and dry at least twice. When possible, maximize exposure to sunlight and allow the area to dry completely.
In most home yard situations where there is grass and dirt, it is not possible to completely disinfect a yard. Out of an abundance of caution, you may want to avoid having unvaccinated dogs come to your yard for 6 to 12 months, even after cleaning and attempting to disinfect.
The House
It helps to understand the difference between porous and non-porous surfaces. Water can go through porous materials. Non-porous materials include stainless steel, glass, metals, rigid plastics, and painted or varnished surfaces. Granite countertops are porous, but quartz is not. Porous materials include unpolished wood, laminate, granite, drywall, carpeting, ceiling tiles, and unsealed cement.
As mentioned, the first step is thoroughly cleaning the house and removing any feces or vomit that can be seen. Once all areas have been mechanically cleaned, you are ready to disinfect. Non-porous surfaces can be disinfected with diluted bleach or AHP or potassium peroxymonosulfate. Make sure you follow the manufacturer's instructions for the proper dilution and contact times for parvovirus.
For carpets and porous surfaces, AHP or potassium peroxymonosulfate disinfectants can be used in carpet cleaners to steam clean carpets and furniture. Understand that these areas are sometimes impossible to disinfect and heavily soiled items should be discarded if possible. Make sure you read the carpet cleaner instructions and spot-test any porous surfaces for possible discoloration. These surfaces will need to remain saturated for ten minutes to ensure the proper contact time. After disinfecting, the areas need to dry thoroughly.
Bedding, Porous Items, or Toys
Bedding and other fabric or porous items should either be thrown away, especially if heavily soiled, or washed thoroughly with detergent, hot water, and bleach and run through a hot dryer cycle if possible. If it is not possible to bleach the items, you could steam clean them with disinfectant as recommended for carpet and furniture. Consider if it is worth the risk to keep porous items such as bedding and toys that can't be bleached, or if it is better to throw them away.
Exposed Bowls and Non-Porous Items
Metal or ceramic bowls and non-porous toys should be washed thoroughly with a detergent, rinsed well, and then disinfected using an effective disinfectant. Throw away any plastic bowls that have any signs of wear, scratches, or teeth marks, which create porous areas. Proper dilution and contact time are important. This can be achieved by soaking the cleaned items in the diluted disinfectant for ten minutes, then allowing the items to dry. After disinfecting, thoroughly rinse the items with water and allow them to dry.
When is my Home Safe?
Unfortunately, there is no guaranteed time frame. There has not been any research that definitively states canine parvovirus can be eliminated from a home or yard environment in a specific number of days. There are many factors that affect whether cleaning and disinfecting efforts will be effective inside the house and outside in the yard. After a parvovirus-positive dog has been in your home or yard, it is safest to only have animals visit who have completed their vaccination series.
Parvovirus: Caring for the Recovered Dog
Wendy Brooks, DVM, DABVP
Date Published: 01/01/2001
Date Reviewed/Revised: 05/10/2023What do you need to know when the parvo puppy goes home?
Medications
Your puppy may be finishing a course of antibiotics and may also be on medication for nausea or diarrhea. It is important that you give your puppy all of the medication for the full amount of time it has been prescribed.
Diet
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, they should not be allowed in public areas until the vaccination series is fully completed. Your puppy can be considered immune to parvovirus but there are many other infectious diseases that your puppy needs to be vaccinated against.
Other Pets
Humans are not susceptible to canine parvovirus infection though some strains can be contagious to cats. (Feline distemper vaccination is protective to cats as feline distemper is a parvovirus.) Adult dogs who are current on their parvo vaccinations are not susceptible to infection. If an adult dog at home is not current, a booster shot is definitely in order. Introducing new puppies poses a problem as the parvovirus persists for a long time in the environment; if possible, only puppies that have completed their vaccination series should be introduced. Any obviously contaminated material should be removed (fecal- or vomit-contaminated objects that cannot be bleached, any remaining areas of feces, etc.) For more details, learn about disinfecting the environment.
Bathing
Your puppy may be bathed at any time as long as you do not allow her to get cold or chilled after the bath. Bathing will reduce the amount of virus left on her fur and will help reduce contagion.
Resuming Vaccines
Follow your veterinarian's recommendations. 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 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). If you have any questions about your puppy's care after discharge, contact your veterinarian.
Wendy Brooks, DVM, DABVP
Date Published: 01/01/2001
Date Reviewed/Revised: 05/10/2023What do you need to know when the parvo puppy goes home?
Medications
Your puppy may be finishing a course of antibiotics and may also be on medication for nausea or diarrhea. It is important that you give your puppy all of the medication for the full amount of time it has been prescribed.
Diet
- Your puppy is recovering from some extensive damage to the 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 to 5 days at home, and your puppy should be active and have a normal attitude. If 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 limited 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.
- Do not feed table scraps. Stick to the diet recommended by your veterinarian. A therapeutic diet may have been sent home, or a home-cooked diet may have been recommended (such as boiled chicken and white rice, or fat-free cottage cheese and pasta). It is important for your puppy's food to be easily digestible, so stick to the protocol your veterinarian has recommended.
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, they should not be allowed in public areas until the vaccination series is fully completed. Your puppy can be considered immune to parvovirus but there are many other infectious diseases that your puppy needs to be vaccinated against.
Other Pets
Humans are not susceptible to canine parvovirus infection though some strains can be contagious to cats. (Feline distemper vaccination is protective to cats as feline distemper is a parvovirus.) Adult dogs who are current on their parvo vaccinations are not susceptible to infection. If an adult dog at home is not current, a booster shot is definitely in order. Introducing new puppies poses a problem as the parvovirus persists for a long time in the environment; if possible, only puppies that have completed their vaccination series should be introduced. Any obviously contaminated material should be removed (fecal- or vomit-contaminated objects that cannot be bleached, any remaining areas of feces, etc.) For more details, learn about disinfecting the environment.
Bathing
Your puppy may be bathed at any time as long as you do not allow her to get cold or chilled after the bath. Bathing will reduce the amount of virus left on her fur and will help reduce contagion.
Resuming Vaccines
Follow your veterinarian's recommendations. 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 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). If you have any questions about your puppy's care after discharge, contact your veterinarian.
Parvovirus: Vaccination and Prevention
Wendy Brooks, DVM, DABVP
Date Published: 01/01/2001
Date Reviewed/Revised: 07/11/2023
It should not be too surprising that the biggest step in preventing parvovirus is vaccination. As discussed in other sections, the virus exists virtually everywhere. It is hardy in the environment and easily carried on the surfaces of inanimate objects. Every dog will be exposed and every puppy will be vulnerable at least for a time. Prevention is about minimizing exposure to the virus until the vaccination series is completed. We will be discussing how to go about achieving immunity for your puppy.
Maternal Antibody: Our Biggest Obstacle in Vaccination
The biggest obstacle in protecting a puppy against this infection ironically stems from its own natural mechanism of protection. As mentioned, 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 all the infections she has experienced or been immunized against, parvovirus included, and until these antibodies wane to ineffective levels, they will protect the puppy.
The problem is that they will also inactivate the vaccine.
Graphic by MarVistaVet
A vaccine is a solution containing a harmless version of the virus, either live and weakened (attenuated or modified live virus vaccine) or killed (inactivated virus vaccine). This virus is injected into the puppy. If there is still adequate maternal antibody present, the 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.) After this period, a vaccine can be effective.
Graphic by MarVistaVet
To get around this, we vaccinate puppies in a series, giving a vaccine every 2 to 4 weeks until age 16 weeks. By giving the vaccine at intervals, we are trying to catch the puppy's immune system after their window of vulnerability has closed. We know that by age 16 weeks, we should be able to get a vaccine to take, but we still begin at a younger age in an effort to provide immunization as soon as possible.
If the mother has been well-vaccinated (booster vaccine given at approximately the time of breeding so as to maximize her colostral antibodies), an extra dose at 20 weeks may be a good idea to be sure all the maternal antibodies have waned adequately.
After a puppy is born, maternal antibody levels drop by half approximately every 10 days. Puppies that were born first or were more aggressive at nursing on the first day will get more maternal antibodies 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, and the longer one must wait for antibodies to wane and for vaccination to be effective.
Should Live or Killed Vaccine Be Used?
The killed vaccine is the least effective at penetrating maternal antibodies. It is also associated with more vaccine reactions since more stabilizing chemicals are used in a killed vaccine. As a general rule, a live parvovirus vaccine is absolutely the way to go.
What is a High Titer Vaccine?
In the mid-1990s, a new innovation in parvo vaccination was developed: the high titer vaccine. The term high titer refers to the amount of virus in the dose of vaccine and means that there is a great deal more virus than in the vaccines that were standard at the time. Nowadays, any vaccine against parvovirus is going to be high titer. When the puppy is vaccinated, the maternal antibody binds to the virus present. When a high titer vaccine is used, there is still a virus left over after all the maternal antibody has been used up. This extra virus can then stimulate the puppy’s own immune system. High titer vaccines commonly produce full protection by age 12 weeks (though most experts recommend carrying vaccination out to age 16 weeks to be certain - an excellent idea for predisposed breeds such as the Rottweiler, Doberman pinscher, and American pit bull terrier).
At this point, virtually all commercially available live vaccines are of the high titer type.
It should be noted that giving vaccines more frequently than every two weeks will cause interference between the two vaccines, and neither can be expected to be as effective as they normally would. This includes giving vaccines for different infections. 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 three or four is the magic number). The number of vaccines given has nothing to do with protection. In order for protection to be achieved, a vaccine must be given when it can penetrate maternal antibodies.
A vaccine FAQ can answer common vaccination questions.
Vaccinating Adult Dogs
Traditionally, the 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.)
There has also been some thought that annual vaccination is not necessary, especially for a disease where adult dogs are considered low risk. Many university teaching hospitals have switched to a 3-year schedule for adult dogs, plus the American Animal Hospital Association recommends that parvo vaccination be given to adult dogs on a 3-year schedule. There is still controversy regarding this practice and many hospitals continue to use the annual guideline as that is usually as far as formal vaccine challenge testing has gone. Do not be surprised if your veterinarian has chosen to follow the university and begins recommending a 3-year vaccination protocol for this virus.
Read the AAHA vaccination guidelines.
What is the Meaning of a Vaccine Titer?
A vaccine titer is a blood test that measures the antibody level a dog is carrying against a certain virus. There are two methods of measuring parvovirus antibody titer: hemagglutination inhibition and serum neutralization. The result obtained, expressed as a ratio, refers to how diluted the dog’s serum (blood) must be for the antibody to still be detectable. Based on work at Cornell University, the following titer levels are generally considered protective:
There is a great deal of controversy regarding whether or not a certain level of antibody can be considered tantamount to protection. Many veterinarians do not feel it is useful to run titers until this issue is resolved (i.e., there is more to protection than an antibody level; there is an entire immune system involved, and there is no simple way to assess the entire immune system). Other veterinarians find it cost-ineffective to recommend titers prior to vaccination; it costs a great deal more to run the titer than to simply give the vaccination. If the titer is adequate, the worst possible outcome is that the vaccine will be ineffective. Other veterinarians question whether or not it is harmless to annually give vaccinations when there is already adequate immunity. At this time, there is no single answer to this issue, and we recommend trusting your veterinarian’s educated opinions regarding these issues.
Protection After Infection
A puppy that has recovered from a parvovirus infection can be expected to have strong immunity. This has been tested out to 20 months after infection, and immunity is believed to be lifelong; because this is unproven, continued vaccination is commonly recommended.
Prevention by Environmental Control
Because of parvovirus, puppies should not be allowed out in the public world until their vaccine series has been completed. This means not going for walks or to the park and not socializing with other puppies. There is some controversy regarding the socialization of young puppies if they are kept isolated in this way until age 16 weeks; however, from an infectious disease standpoint, this is the safest way to go. If the home has previously housed a parvo-infected dog or puppy, disinfection (especially removing fecal matter) is paramount. By getting an older puppy whose vaccination series is already complete, you can avoid this entire issue.
Wendy Brooks, DVM, DABVP
Date Published: 01/01/2001
Date Reviewed/Revised: 07/11/2023
It should not be too surprising that the biggest step in preventing parvovirus is vaccination. As discussed in other sections, the virus exists virtually everywhere. It is hardy in the environment and easily carried on the surfaces of inanimate objects. Every dog will be exposed and every puppy will be vulnerable at least for a time. Prevention is about minimizing exposure to the virus until the vaccination series is completed. We will be discussing how to go about achieving immunity for your puppy.
Maternal Antibody: Our Biggest Obstacle in Vaccination
The biggest obstacle in protecting a puppy against this infection ironically stems from its own natural mechanism of protection. As mentioned, 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 all the infections she has experienced or been immunized against, parvovirus included, and until these antibodies wane to ineffective levels, they will protect the puppy.
The problem is that they will also inactivate the vaccine.
Graphic by MarVistaVet
A vaccine is a solution containing a harmless version of the virus, either live and weakened (attenuated or modified live virus vaccine) or killed (inactivated virus vaccine). This virus is injected into the puppy. If there is still adequate maternal antibody present, the 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.) After this period, a vaccine can be effective.
Graphic by MarVistaVet
To get around this, we vaccinate puppies in a series, giving a vaccine every 2 to 4 weeks until age 16 weeks. By giving the vaccine at intervals, we are trying to catch the puppy's immune system after their window of vulnerability has closed. We know that by age 16 weeks, we should be able to get a vaccine to take, but we still begin at a younger age in an effort to provide immunization as soon as possible.
If the mother has been well-vaccinated (booster vaccine given at approximately the time of breeding so as to maximize her colostral antibodies), an extra dose at 20 weeks may be a good idea to be sure all the maternal antibodies have waned adequately.
After a puppy is born, maternal antibody levels drop by half approximately every 10 days. Puppies that were born first or were more aggressive at nursing on the first day will get more maternal antibodies 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, and the longer one must wait for antibodies to wane and for vaccination to be effective.
Should Live or Killed Vaccine Be Used?
The killed vaccine is the least effective at penetrating maternal antibodies. It is also associated with more vaccine reactions since more stabilizing chemicals are used in a killed vaccine. As a general rule, a live parvovirus vaccine is absolutely the way to go.
What is a High Titer Vaccine?
In the mid-1990s, a new innovation in parvo vaccination was developed: the high titer vaccine. The term high titer refers to the amount of virus in the dose of vaccine and means that there is a great deal more virus than in the vaccines that were standard at the time. Nowadays, any vaccine against parvovirus is going to be high titer. When the puppy is vaccinated, the maternal antibody binds to the virus present. When a high titer vaccine is used, there is still a virus left over after all the maternal antibody has been used up. This extra virus can then stimulate the puppy’s own immune system. High titer vaccines commonly produce full protection by age 12 weeks (though most experts recommend carrying vaccination out to age 16 weeks to be certain - an excellent idea for predisposed breeds such as the Rottweiler, Doberman pinscher, and American pit bull terrier).
At this point, virtually all commercially available live vaccines are of the high titer type.
It should be noted that giving vaccines more frequently than every two weeks will cause interference between the two vaccines, and neither can be expected to be as effective as they normally would. This includes giving vaccines for different infections. 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 three or four is the magic number). The number of vaccines given has nothing to do with protection. In order for protection to be achieved, a vaccine must be given when it can penetrate maternal antibodies.
A vaccine FAQ can answer common vaccination questions.
Vaccinating Adult Dogs
Traditionally, the 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.)
There has also been some thought that annual vaccination is not necessary, especially for a disease where adult dogs are considered low risk. Many university teaching hospitals have switched to a 3-year schedule for adult dogs, plus the American Animal Hospital Association recommends that parvo vaccination be given to adult dogs on a 3-year schedule. There is still controversy regarding this practice and many hospitals continue to use the annual guideline as that is usually as far as formal vaccine challenge testing has gone. Do not be surprised if your veterinarian has chosen to follow the university and begins recommending a 3-year vaccination protocol for this virus.
Read the AAHA vaccination guidelines.
What is the Meaning of a Vaccine Titer?
A vaccine titer is a blood test that measures the antibody level a dog is carrying against a certain virus. There are two methods of measuring parvovirus antibody titer: hemagglutination inhibition and serum neutralization. The result obtained, expressed as a ratio, refers to how diluted the dog’s serum (blood) must be for the antibody to still be detectable. Based on work at Cornell University, the following titer levels are generally considered protective:
- Hemagglutination inhibition titer of 1:80 or more
- Virus neutralization titer of 1:20 or more
There is a great deal of controversy regarding whether or not a certain level of antibody can be considered tantamount to protection. Many veterinarians do not feel it is useful to run titers until this issue is resolved (i.e., there is more to protection than an antibody level; there is an entire immune system involved, and there is no simple way to assess the entire immune system). Other veterinarians find it cost-ineffective to recommend titers prior to vaccination; it costs a great deal more to run the titer than to simply give the vaccination. If the titer is adequate, the worst possible outcome is that the vaccine will be ineffective. Other veterinarians question whether or not it is harmless to annually give vaccinations when there is already adequate immunity. At this time, there is no single answer to this issue, and we recommend trusting your veterinarian’s educated opinions regarding these issues.
Protection After Infection
A puppy that has recovered from a parvovirus infection can be expected to have strong immunity. This has been tested out to 20 months after infection, and immunity is believed to be lifelong; because this is unproven, continued vaccination is commonly recommended.
Prevention by Environmental Control
Because of parvovirus, puppies should not be allowed out in the public world until their vaccine series has been completed. This means not going for walks or to the park and not socializing with other puppies. There is some controversy regarding the socialization of young puppies if they are kept isolated in this way until age 16 weeks; however, from an infectious disease standpoint, this is the safest way to go. If the home has previously housed a parvo-infected dog or puppy, disinfection (especially removing fecal matter) is paramount. By getting an older puppy whose vaccination series is already complete, you can avoid this entire issue.
Need More Resources?
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