Treating Canine Parvovirus


            Since there is no specific therapy to eliminate the virus responsible for causing the clinical signs associoated with parvo, the majority of efforts that go into dealing with the disease are based around symptomatic and supportive care of the patient, and these methods are usually sufficient to allow an animal to recover from the disease.  In addition to early diagnosis and isolation, strong prevention programs and control measures to prevent the spread of the virus from infected to non-infected individuals is the principle means of dealing with the disease.  In addition to this, a new paradigm concerning the use of antiviral medications has developed, which can actually act to minimize the clinical disease process associated with the Parvoviral infection, and aid the patient in clearing the infectious virus faster1.

             Symptomatic and Supportive Care

             Profound dehydration is a common sequelae to the prolific diarrhea that is associated with Parvoviral infection.  Therefore, the first step in the supportive treatment of a parvo patient is the restoration of fluid balance.  Although oral electrolyte solutions are adequate in mildly dehydrated dogs, more severely dehydrated dogs will require intravenous fluid therapy.  In most cases, Lactated Ringer's Solution with 5% dextrose, with an additional 10 to 20 mEq/L of potassium chloride, will provide the necessary electrolytes required by the afflicted animal.  Constant monitoring of electrolyte changes should be performed, and changes in the fluid therapy protocol should be made when appropriate.  In doMerck Veterinary Manualgs where dehydration is further complicated due to vomition, anti-emetic medication, such as metoclopramide can be administered QID, or as a CRI1.

             The provision of food to a dog with parvoviral syndrome is somewhat disputed.  Although it has long been held that food and water should be withheld until the resolution of vomitting, some sources argue that by depriving the patient of food, the enterocytes lining the digestive tract do not receive nourishment.  It is argued that this can further damage to the gut lining and prolong intestinal recovery time.  In order to address this concern, small amounts of bland food (eg, cottage cheese and rice, or Hill's Prescription i/d diet) should be offered at frequent intervals1.  It is important for this bland food diet to be continued for a prolonged period of time during the recovery process1, while the enterocytes of the intestinal tract return to their normal number and function2.

             Another controversial topic in the supportive treatment of Canine Parvovirus is the proactive use of antibiotics.  Obviously, the use of antimicrobial agents will not prevent the virus from multiplying and affecting the host's cells, but antimicrobials are important in the prevention of secondary bacterial infections.  One of the pathological processes often associated with parvoviral infection is a profound leukopenia.  When this is coupled with the denuded intestinal barrier, the host is in no condition to mount the necessary immune response to deal with the transmigration of intestinal bacteria to the bloodstream.  To prevent this, a combination of ampicillin or a first or second generation cephalosporin and an aminoglycoside is recommended in cases of severe Parvovirus to provide broad spectrum antimicrobial coverage.  Although the usage of antibiotics has not significantly demonstrated any positive effects (eg, outcome, reduced period of hospitalization, reduced plasma endotoxin concentration) in mildly or moderately infected individuals, their use significantly improved the prognosis of individuals housed in tertiary care facilities3.

             Prevention and Control Measures

             Parvovirus can be transmitted between animals via fomites.  It is therefore important that any objects encountered by an infected dog be thoroughly decontaminated.  This can be accomplished by using regular household bleach in a 1:30 dilution with water, or with any commercial cleaners that are labelled for use against parvovirus.  In addition to this, afflicted dogs should be isolated from other, non-affected dogs while they are displaying clinical signs.  Pups should also be isolated from adult dogs that have recently partaken in show or field trials, since they are potential vectors for the transmission of the disease1.

             The most important factor in the prevention and control of the disease is regular vaccination against Canine Parvovirus.  The vaccines currently produced protect the dogs from all of the strains of the virus that are currently in circulation.  The modified-live vaccines that are currently on the market engender strong antiviral titres, are safe to use in puppies, and are effective in protecting puppies, even when maternal antibody levels are high enough to interfere with their natural immune response1.  Vaccination should begin at 7 to 8 weeks of age, and should occur thenafter at 12 and 16 weeks of age.  Booster vaccinations should be administered at 1 year of age, and then every 3 years following that4.\

Canine Vaccines

             Antiviral Therapy
Oseltamivir (Tamiflu) Packaging
             There are currently 2 antiviral compounds that are currently being tested in order to determine their efficacy in treating Canine Parvoviral infections.  The first is the antiviral medication Oseltamivir, originally manufactured to treat influenza infections.  Although formal scientific studies have not been conducted to test the efficacy of this drug on Canine Parvovirus, several anecdotal reports are arising from practicing veterinarians in North America, saying that the antiviral helps to alleviate the signs associated with the infection5.  Although the method of action of the drug on parvovirus has not been elucidated, it is suspected that it prevents bacterial multiplication and action, thereby reducing the severity of clinical signs observed5.  The manufacturers of Oseltamivir do not claim that the drug can be used for the treatment of Canine Parvovirus, however, and control studies need to be carried out before the drug can be considered part of the normal treatment protocol for this condition.


Intercat (Feline Interferon)
             The second compound that is used in the treatment of Canine Parovirus infection is Feline omega-Interferon6.  This compound has been used for several years in Japan and Europe in the control of not only Canine Parvovirus, but a myriad of bacterial, viral, and neoplastic diseases in both dogs and cats7.  Interferon is an antiviral cytokine that is produced in cells that are infected with a foreign agent.  These cytokines diffuse out of the infected cell and into surrounding cells, where they inhibit viral replication and assist in the immune response6.  The producers of this product are currently seeking approval for sale in North America.




             Homeopathic and Naturopathic Treatments

             In rececnt years, there has been a strong movement towards the integration of naturopathic and homeopathic treatments and remedies into veterinary medicine.  Homeopathic and naturopathic remedies are available for almost every disease or condition, including parvoviral enteritis.  Although many owners may think this represents a valid form of treatment for their pet, there is little clinical or scientific proof that supports the claims made by these products.  In many cases, the sole use of these products can permit the decay of the patient to the point where standard medical treatment requires a longer duration in order to be effective.

             In some instances, the homeopathic treatment may even be more harmful than the original condition.  An example of this is Parvo K, a homeopathic remedy for parvoviral enteritis.  The principle ingredients within this mixture are arsenic, belladonna, and toxic plant alkyloids.  Although they are present in low concentrations, they can accumulate within the body and with long-term exposure, can begin to exert deliterious health effects on the patient8.  Common side effects to toxicity by these compounds includes central and peripheral neuropathies, renal and hepatic failure, and immunosuppression9.

Parvo K Homeopathic Parvo Treatment

             References:
            

             1
The Merck Veterinary Manual.  9th Edition.  Eds: Kahn C, Line S.  Published by Merck & Co., Inc.  Whitehouse Station, NJ.  2005.

             2 Dr. Christopher Clark, Personal Communication.  2007.  Saskatoon, Saskatchewan.

             3 Otto C, Jackson C, Rogell E, Prior R, Ammons W.  Recombinant bactericidal/permeability-increasing protein (rBPI21) for treatment of parvovirus enteritis: a randomized, 
                double-blinded, placebo-controlled trial.  Journal of Veterinary Internal Medicine.  2001.  15(4):355-360.

             4 Dr. Susan Taylor.  Personal Communication.  2006.  Saskatoon, Saskatchewan.

             5 Campbell N, Keith C.  Oseltamivir: Is there a new treatment for parvo?  Personal weblog.  Updated: April 20, 2005.
                
http://vettechs.blogspot.com/2005/04/oseltamivir-is-there-new-treatment-for.html

             6 de Mari K, Maynard L, Eun H, Lebreux B.  Treatment of canine parvoviral enteritis with interferon-omega in a placebo-controlled field trial.  The Veterinary Record.  2003. 
                152(4):105-108.

             7 Maehara N, Shimoda K, Kobayashi T, Nakayama S.  The effects of interferon and its applications for treating and preventing virus infections.  Infovets.  1998.  1(6):1-3.

             8 Mind, Body and Paw - Veterinary Homeopathic Remedies.  Online Manual:  http://www.mindbodyandpaw.com/parvo.htm

             9 Casarett & Doull’s Toxicology – The Basic Science of Poisons.  6th Edition.  Ed: Klaassen C.  Published by McGraw-Hill.  2001.