VET CHECK: PARVOVIRAL ENTERITIS

Parvo is actually a mutated form of the feline panleukopenia virus, the cause of feline distemper. This viral infection has been around since the early 1970s. Over the last thirty years there have been improvements in vaccines, vaccination protocols, and treatment of infected patients. Unfortunately the nature of this disease is such that it will be difficult (or impossible) to ever let our guard down against it. The virus can persist and remain infectious in the environment for many months; heat, cold, dry and wet will not affect it. Infected dogs may shed the bacteria before showing any symptoms of the disease, and they will continue to shed the virus in their feces for two weeks after if they recover from the infection. Any dog with inadequate immunity that comes in contact with the virus is likely to become infected. The disease attacks a dog’s body on two levels: it rapidly kills off the cells that make up the absorptive lining of the small intestine, while it simultaneously weakens the immune system. This two-pronged assault will usually result in death in untreated puppies; adults with a strong immune system are better able to cope with the resulting secondary infections but they may still become gravely ill and can possibly die. The effects on the gastrointestinal tract result in severe nausea, vomiting and diarrhea which are often, but not always, bloody. This combination quickly produces severe, life-threatening dehydration. At the same time, the weak immune system leaves the body susceptible to all sorts of secondary infections; untreated patients can die as the bacteria from the gastrointestinal tract gain a foothold in the lungs (often from aspiration pneumonia; a weak patient that is vomiting repeatedly can inhale the vomit). The bacteria can also gain direct access to the bloodstream and cause blood infections or septicemia. The bacteria get into the bloodstream directly through the weakened intestine, or through infected lung tissue. Septicemia then leads to multiple organ failure and death.Symptoms of parvovirus may include one or all of the following: lethargy, loss of appetite or no appetite, vomiting (sometimes bloody), diarrhea (sometimes bloody), and fever (body temperature greater than 102.4F). The diagnosis is confirmed by your veterinarian by physical exam findings, fecal analysis, and most often the use of an in-hospital parvovirus test that tests for the virus (NOT for antibodies) in a fecal sample. False positives can occur with some tests in recently vaccinated dogs, but the typical parvo patient has an obvious strong positive response coupled with symptoms. Most veterinarians will perform a complete blood count to assess the status of the immune system; many parvo patients have dangerously low white cell counts and/or anemia (low red cell count). Serum chemistry profiles can indicate electrolyte imbalance, and also identify life threatening low protein levels. Proteins such as albumin are critical for maintaining normal blood pressure, calcium metabolism as well as other metabolites. Low levels are often found in parvo patients as a result of poor protein absorption from infected intestine as well as increased loss of existing proteins in the blood stream.Treatment for parvovirus enteritis (enteritis means intestinal inflammation) is aimed at providing supportive care for nausea, vomiting, diarrhea, dehydration, and prevention of secondary infections. The viral infection must run its course; there is no specific treatment that can cure the virus. Ideally, this means admitting the patient to the hospital in an isolation unit to prevent infection of other patients. Intravenous fluids, electrolytes, anti-nausea drugs, and antibiotics are the backbone of medical care for parvo. Additionally, some patients may receive transfusions of plasma or whole blood from donors with immunity to parvovirus if their bloodwork indicates that it is necessary. Immune system stimulants such as Neupogen are sometimes used to stimulate white cell production in some patients. Recently veterinarians have begun using a drug called Tamiflu, which at least in my experience seems to dramatically help these patients when it is started early in the course of illness. Tamiflu is a neuroaminidase inhibitor; it is used in humans to treat influenza. The influenza virus uses an enzyme called neuraminidase to allow it to “bud” from infected cells and pass on to infect new cells. A neuraminidase inhibitor can “lock” the virus into the cell and prevent it from spreading. It is worth noting that Tamiflu does not have the same mechanism of action on canine parvovirus; it is currently believed that it helps parvo patients by inhibiting bacterial neuraminidase, so it is actually controlling the secondary bacterial infection in the dog’s gut, NOT the actual parvovirus. Availability of Tamiflu became a problem last year while there were fears of human influenza epidemic; some countries began stockpiling the drug for fears of an inadequate supply in the event of a human avian influenza epidemic. More recently, there are concerns about safety of the use of this drug in children. It remains to be seen if it will affect availability in veterinary patients. At the time of this writing it may be used in canine patients, but it may not be legally used in birds.Length of treatment varies greatly. I have had patients who were discharged two days after admission and I have had patients hospitalized for three weeks after undergoing several complications. Generally speaking, animals who are diagnosed and treated early will fare better than those who are not brought in immediately. Patients who are already severely dehydrated and immunosuppressed are more prone to complications like pneumonia or intestinal intussception (this occurs when the inflamed, hypermotile bowel telescopes upon itself, causing a complete obstruction that must treated surgically). If you think your pup or dog might have parvovirus, get her examined by your veterinarian sooner rather than later. Treatment is successful most of the time when the disease is treated early. Unfortunately, some pups and dogs will still die from this disease in spite of the best efforts of their owners and veterinarians.Patients who recover will retain immunity to this disease for life. Remember that they will shed the virus in stool (or vomit) for at least two weeks after discharge, so try to keep the dog close to home to prevent further spread of the virus in the environment. There rare reports of this disease causing permanent damage to the heart muscle, but most patients who survive parvovirus infection will have no persisting health issues. Obviously prevention is the best way to confront this disease. In a parvovirus-free sled dog kennel, vaccination of pups usually starts at six weeks of age; in my practice we boost for parvovirus (as well as Distemper, Adenovirus type 2 and a Parainfluenaza) at nine, twelve and sixteen weeks, then annually for adults. We use the Intervet Progard brand of vaccine (I can also add that I am not in the employ of that particular company in any way, and that in the past I have used vaccines from other manufacturers that have NOT been up to standard either in efficacy or safety). Keep the traffic of dogs with unknown vaccine status out of your kennel, especially while you have pups under sixteen weeks old. If you have parvovirus in your kennel, treating any area exposed to infected dogs with dilute bleach will help kill the virus, but you must assume that it has not been completely eliminated. Consider starting vaccination of young pups for parvovirus at five weeks old and vaccinating every two to two and a half weeks; your veterinarian can help tailor a specific protocol for these situations. The use and misuse of vaccines has been hashed and rehashed in so many forums that I’m going to refrain from going into more detail in this article other than to say that it is important that the vaccines you use on your dogs should be chosen carefully from a manufacturer that you and your veterinarian trust and that the vaccine MUST be properly handled; frozen, overheated and expired vaccines given at poorly timed intervals have no place in a well run sled dog kennel.Dawn Brown D.M.V. graduated from the New York State College of Veterinary Medicine at Cornell University and practices small animal medicine and surgery at Carthage, New York. She has been racing since 1982, currently 6 and 8-dog limited class speed racing in the lower 48, Canada and Alaska.

Share:

More Posts