Canine parvovirus (CPV) disease is currently the most common infectious disorder of dogs in the United States. 'Parvo' is a highly contagious disease characterized by diarrhea that is often bloody. Prior to 1980, most canine parvovirus that caused disease was Type 2 (CPV-2). After 1980, CPV-2 was replaced by CPV-2a became more common and in 1986, another variation called CPV-2b appeared. In the past few years, a new strain, CPV-2c has been detected. Today, CPV-2b has largely replaced the previous strains as the most common parvovirus causing disease in the dog. There is currently some discussion that there may be other strains that are beginning to emerge and have yet to be formally identified. Current vaccinations have helped to control the spread of this disease but despite being vaccinated, some dogs still contract and die from parvo. There is much that we do not know about the virus or the best way to control the disease, but we are learning new information daily. Misinformation about the disease, its spread, and vaccination is widespread. We hope that with a better understanding of the disease, pet owners will be able to make good health decisions for their dogs that will help prevent and reduce the spread of this disease.

How is parvovirus spread?

Parvovirus is spread through contact with feces containing the virus. The virus is known to survive on inanimate objects - such as clothing, food pans, and cage floors - for 5 months and longer in the right conditions. Insects and rodents may also serve as vectors playing an important role in the transmission of the disease. This means any fecal material or vomit needs to be removed with a detergent before the bleach solution is used. The bleach solution should be used on bedding, dishes, kennel floors and other impervious materials that may be contaminated. The normal incubation period (time from exposure to the virus to the time when signs of disease appear) is from 7-14 days. Active excretion of the virus in the feces can begin the third day after exposure, often before clinical signs appear, and may last for one to two weeks after the onset of the disease.

What are the symptoms of parvovirus infection?

There is a broad range in the severity of symptoms shown by dogs that are infected with parvovirus. Many adult dogs exposed to the virus show very few, if any, symptoms. The majority of cases of disease are seen in dogs less than 6 months of age with the most severe cases seen in puppies younger than 12 weeks of age. There are also significant differences in response to parvovirus infections and vaccines among different breeds of dogs, with Rottweilers, Doberman Pinschers, and Labrador Retrievers being more susceptible than other breeds. The most common form of the disease is the intestinal form known as enteritis. Parvovirus enteritis is characterized by vomiting (often severe), diarrhea, dehydration, dark or bloody feces, and in severe cases, fever and lowered white blood cell counts. Acute parvovirus enteritis can be seen in dogs of any breed, sex, or age. The disease will progress very rapidly and death can occur as early as two days after the onset of the disease. The presence of gram negative bacteria, parasites, or other viruses can worsen the severity of the disease and slow recovery. A less common form of the disease causes myocarditis (inflammation of the heart).

How is parvovirus infection diagnosed?

Not all cases of bloody diarrhea with or without vomiting are caused by parvovirus and many sick puppies are misdiagnosed as having 'parvo.' The only way to know if a dog has parvovirus is through a positive diagnostic test. In addition to the more time consuming and expensive traditional testing of the blood for titers, a simpler test of the feces with an enzyme-linked immunosorbent assay antigen test (ELISA), commonly called the CITE test, is also available through most veterinary clinics. Testing of all suspect cases of parvo is the only way to correctly diagnose and treat this disease. A complete physical exam and additional laboratory tests such as a CBC and chemistry panel help to determine the severity of the disease.

How is parvovirus disease treated?

The treatment of parvovirus is fairly straightforward and directed at supportive therapy. Replacing fluids lost through vomiting and diarrhea is probably the single most important treatment. Intravenous administration of a balanced electrolyte solution is preferred, but in less severe cases, subcutaneous or oral fluids may be used. In severe cases, blood transfusions may be necessary. Antibiotic therapy is usually given to help control secondary bacterial infections. In those dogs who have severe symptoms, antiserum against endotoxins may be given. Corticosteroids may be given if the animal is in shock. In cases of severe vomiting, drugs to slow the vomiting may also be used. After the intestinal symptoms begin to subside, a broad spectrum de-worming agent is often used. Restricting the food during periods of vomiting is also necessary and parenternal nutrition (providing nutrients intravenously) may be necessary. Undertaking the treatment of affected dogs and puppies without professional veterinary care is very difficult. Even with the best available care, the mortality of severely infected animals is high. Without the correct amount of properly balanced intravenous fluids, the chance of recovery in a severely stricken animal is very small. All parvoviruses are extremely stable and are resistant to adverse environmental influences such as low pH and high heat. Exposure to ultraviolet light and sodium hypochlorite (a 1:32 dilution of household bleach - ½ cup bleach to 1 gallon of water) can inactivate parvovirus. The bleach solution can be impaired by organic matter and needs to have adequate exposure time and proper concentrations to work effectively.

Immunity and vaccination

If a puppy recovers from parvovirus infection, he is immune to reinfection for probably at least twenty months and possibly for life. In addition, after recovery the virus is not shed in the feces. There are many commercially prepared attenuated (modified) live CPV-2 vaccines available. Although some people have expressed concern about the possibility of modified live vaccines reverting to a virulent strain after being given and then causing disease, studies have repeatedly shown that this does not occur. Commercially prepared vaccines are safe and do not cause disease. The primary cause of failure of canine parvovirus vaccines is an interfering level of maternal antibody against the canine parvovirus. Maternal antibodies are the antibodies present in the mother's milk during the first 24 hours after the puppy's birth. The age at which puppies can effectively be immunized is proportional to the titer of the mother and the effectiveness of transfer of maternal antibody within those first 24 hours. High levels of maternal antibodies present in the puppies' bloodstream will block the effectiveness of a vaccine. When the maternal antibodies drop to a low enough level in the puppy, immunization by a commercial vaccine will work. The complicating factor is that there is a period of time from several days to several weeks in which the maternal antibodies are too low to provide protection against the disease, but too high to allow the vaccine to work. This period is called the window of susceptibility. This is the time when despite being vaccinated, a puppy can still contract parvovirus. The length and timing of the window of susceptibility is different in every puppy in every litter. In one study of a cross section of different puppies the age at which they were able to respond to a vaccine and develop protection covered a wide period of time. At six weeks of age, 25% of the puppies could be immunized. At 9 weeks of age, 40% of the puppies were able to respond to the vaccine. The number increased to 60% by 16 weeks, and by 18 weeks of age, 95% of the puppies could be immunized. When we examine all of the information about maternal derived antibodies, windows of susceptibility, breed susceptibilities, the possibility of unidentified strains, and the effectiveness of different vaccines, we begin to see why there are so many different vaccination protocols and why some vaccinated animals still develop the disease. Vaccination protocols have been developed that will help protect the widest range of dogs. In using these protocols, we understand we will be vaccinating some dogs that are not capable of responding and we will be revaccinating some dogs that have already responded and developed a high titer. But without doing an individual test on each puppy, it is impossible to determine where the puppy is in its immune status. We also realize due to the window of susceptibility, some litters will contract parvovirus despite being vaccinated. By using quality vaccines and an aggressive vaccination protocol, we can make this window of susceptibility as small as possible. The generally recommended protocol is to vaccinate puppies against parvovirus beginning at 6-8 weeks of age, and revaccinating every 3 weeks until the puppy is 16-20 weeks of age. A booster is given at one year of age and every 1-3 years thereafter.

Canine distemper is a highly contagious and serious disease caused by a virus that attacks the respiratory, gastrointestinal, and, often, the nervous systems of puppies and dogs. The virus also infects wild canids (e.g. foxes, wolves, coyotes), raccoons, skunks, and ferrets.

Q:  How is Canine Distemper virus spread?

A:  Puppies and dogs usually become infected through airborne exposure to the virus contained in respiratory secretions of an infected dog or wild animal. Outbreaks of distemper tend to be sporadic. Because canine distemper also affects wildlife populations, contact between wild and domestic canids may facilitate spread of the virus.

Q:  What dogs are at risk?

A:   All dogs are at risk but puppies younger than four months old and dogs that have not been vaccinated against canine distemper are at increased risk of acquiring the disease.

Q:  What are some signs of Canine Distemper?

A:   The first sign of distemper is eye discharge that may appear watery to pus-like. Subsequently, dogs develop fever, nasal discharge, coughing, lethargy, reduced appetite, vomiting, and diarrhea. In later stages, the virus may attack the nervous system, bringing about seizures, twitching, or partial or complete paralysis. Occasionally, the virus may cause footpads to harden. Distemper is often fatal. Even if a dog does not die from the disease, canine distemper virus can cause irreparable damage to a dog's nervous system. Distemper is so serious and the signs so varied that any sick dog should be taken to a veterinarian for an examination and diagnosis.

Q:  How is Canine Distemper diagnosed and treated?

A:   Veterinarians diagnose canine distemper on the basis of clinical appearance and laboratory tests. No specific drug is available that will kill the virus in infected dogs. Treatment consists primarily of efforts to prevent secondary infections; control vomiting, diarrhea, or neurologic symptoms; and combat dehydration through administration of fluids. Ill dogs should be kept warm, receive good nursing care, and be separated from other dogs.

Q:  How is Canine Distemper prevented?

A:   Vaccination and avoiding contact with infected animals are key elements of canine distemper prevention. Vaccination is important. Young puppies are very susceptible to infection, particularly because the natural immunity provided in their mothers' milk may wear off before the puppies' own immune systems are mature enough to fight off infection. If a puppy is exposed to canine distemper virus during this gap in protection, it may become ill. An additional concern is that immunity provided by a mother's milk may interfere with an effective response to vaccination. This means even vaccinated puppies may occasionally succumb to distemper. To narrow gaps in protection and optimally defend against canine distemper during the first few months of life, a series of vaccinations is administered. Until a puppy has received its complete series of vaccinations, pet owners should use caution when taking their pet to places where young puppies congregate (e.g. pet shops, parks, puppy classes, obedience classes, doggy daycare, and grooming establishments). Reputable establishments and training programs reduce exposure risk by requiring vaccinations, health examinations, good hygiene, and isolation of ill puppies and dogs. To protect their adult dogs, pet owners should be sure that their dog's distemper vaccination is up-to-date. Ask your veterinarian about a recommended vaccination program for your canine companion. Contact with known infected dogs should always be avoided. Similarly, contact with raccoons, foxes, skunks, and other potentially infected wildlife should be discouraged.

If you want to completely avoid coming into contact with a rabid animal you should move to Australia, the British Isles, or Antarctica where there is no rabies virus. When traveling around the world, you will encounter certain animals that are much more likely to be carriers of the disease. After leaving the safety of the British Isles and heading eastward into Europe, the fox is the primary carrier. If you dip south into Africa, you will encounter it in jackals in the north, dogs and cats in the central countries, and mongooses in the southern part of the continent. Heading into the Himalayans, you can see it in wolves and in Russia it is seen in dogs. The arctic fox is the main carrier in all parts of the Arctic. If you venture into Indonesia and Malaysia, the dog and cat are again common carriers. When you come back to South America, the dog and cat are again common sources of exposure as well as vampire bats. In Mexico, insectivorous bats cause the most problems. In the United States, the mountain states have the lowest incidence of humans contacting animals with rabies. When you hit the Plains, the Midwest, and Texas the striped skunk is the big carrier. As you work your way to the east, raccoons become important carriers. Fox and bats also cause some human exposures, but very rarely, especially the bat who gets blamed more than it should. If the squirrel or rabbit in the back yard bites you, do not panic, there has never been a reported case of someone contracting rabies from one of these species.

Who is at risk?

People that work closely with wildlife, veterinarians, and travelers are at the highest risk of exposure. Fortunately, there is a vaccine that is available to protect high-risk people. Animals that come into contact with wildlife and are not vaccinated, are at a higher risk of exposure. While the risk of coming into contact with the virus is very low, it nevertheless does exist. When I started my first job in rural Wisconsin, a veterinarian I worked with told me that in over twenty-five years of practice he had never seen a case of rabies. Two years later, I was exposed to two dogs and a cow in one three-week period that all had, and died from, rabies. Because of the movement of carriers, there is always the risk of exposure. In my three cases, there was known contact with raccoons by both dogs and a skunk by the cow.

Transmission of the disease

The transmission of the disease almost always occurs as a result of an infected animal biting a non-infected animal. There have been a few reported cases of infection resulting from aerosolization occurring in caves where large quantities of infected bats reside. Rabies virus does not live very long outside the host and remains viable in the carcass of an infected animal for less than 24 hours. The rabies virus is shed at high levels in saliva. However, being bitten by a rabid animal does not necessarily mean that the animal will become infected. It has been speculated, that only around 15% of exposed people will contract the disease. Humans, dogs, and cats are only mildly susceptible to the disease unlike skunks, raccoons, foxes, and bats that are much more susceptible to the virus.

Symptoms

 After coming in contact with the virus, the bitten animal may go through one or all of several stages. If the bitten animal is a skunk it may not show any symptoms at all but could become a lifelong carrier. With most animals, however, the virus will spread through the nerves of the bitten animal towards the brain. The virus is relatively slow moving and the average time of incubation from exposure to brain involvement is between 3 to 8 weeks in dogs, 2 to 6 weeks in cats, and 3 to six weeks in people. However, incubation periods as long as 6 months in dogs and 12 months in people have been reported. After the virus reaches the brain it then will move to the salivary glands where it then can be spread through a bite. After the virus reaches the brain the animal will show one, two, or all of the three different phases.

Prodromal phase

The first is the prodromal phase and usually lasts for 2-3 days in dogs. Apprehension, nervousness, anxiety, solitude, and a fever may be noted. Friendly animals may become shy or irritable and may snap, whereas, aggressive animals may become affectionate and docile. Most animals will constantly lick the site of the bite. In cats, the prodromal phase lasts for only 1-2 days and they usually develop more fever spikes and erratic behavior than dogs.

Furious phase

From the prodromal phase, animals may enter the furious stage; cats are particularly prone to developing this phase. The furious stage of the disease in dogs usually lasts for 1 to 7 days. Animals become restless and irritable and are hyperresponsive to auditory and visual stimuli. As they become more restless, they begin to roam and become more irritable and vicious. When caged, dogs may bite and attack their enclosures. Animals progress to become disoriented and then have seizures and eventually die.

Paralytic (dumb) phase

Animals may develop the paralytic phase either after the prodromal or furious stage. The paralytic phase usually develops within 2 to 4 days after the first signs are noted. Nerves affecting the head and throat are the first to be involved and animals may begin to salivate as a result of their inability to swallow. Deep labored breathing and a dropped jaw may result as the diaphragm and face muscles become increasingly paralyzed. Animals may make a choking sound and many owners think that there is something lodged in the dog’s throat. This was the case with both dogs I was exposed to (as mentioned earlier) and the owners were also exposed as they had been looking in the dog’s mouth for a foreign object. The animal will get weaker and eventually go into respiratory failure and die.

As a side note, many of the dogs with rabies that I encountered while in Central America also presented with the dumb form. The one cow that I saw bellowed incessantly and staggered aimlessly. Many animals present with a combination of the above symptoms and phases.

Diagnosis

The current way to diagnose rabies in animals is to submit the brain for microscopic exam. Some new testing techniques utilizing skin and or blood samples are being studied and used in a few research settings and show promise as a way of testing potentially exposed humans and animals. They are not routinely being used at this time.

Treatment

There is no treatment. Once the disease develops in humans, death is certain. There have a couple of reported cases of dogs surviving the infection, but they are very rare.

Vaccination and prevention

Vaccination is the best way to prevent infection and properly vaccinated animals stand very little chance of contracting the disease. While rabies vaccination for dogs is mandatory for all states, it is estimated that up to half of all dogs are not vaccinated. Some communities are also requiring cats to be vaccinated, which is very important because there are currently more cases of cat rabies than dog rabies. Some people estimate that less than ten percent of the cat population is vaccinated thus leading to the high incidence of rabies in cats. The standard vaccination protocol is to vaccinate dogs and cats at three or four months and then again at one year of age. After the 4-month-old initial vaccine a three-year rabies vaccination is recommended. The three-year shot has been tested and shown to be very effective. A few counties, states, or individual veterinarians require yearly or once every two-year vaccination for a variety of reasons that need to be explored more closely. There is also a rabies vaccination available for high-risk people. There are some vaccines available for large animals also. The question of vaccinating exotic animals is a common one. There are no approved products for most exotics, however, canine vaccine is used on some species to offer some protection. Vaccinating exotics or wolf hybrids should be dealt with individually in cooperation with your local veterinarian. Keeping a wild animal that is at high risk of being a carrier such as a skunk or raccoon is never recommended.

Human exposure

If an animal bites a human, the animal will be either quarantined or observed for a period of at least ten days to ensure that it does not have rabies. Whether or not the animal was currently vaccinated the community that you live in will dictate the requirements of the quarantine. People that do become exposed to a rabid animal can be given a five-shot post exposure series of Human Rabies Immune Globulin to protect them against being infected. There is a three-shot series of Human Diploid Cell Vaccine that can be used to vaccinate people at high risk.