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Parvo : An Introduction

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Canine parvo type 2 (CPV-2) first appeared in the U.S. in 1978, wreaking havoc among unvaccinated puppies between the ages of 6 weeks and 6 months (although all unvaccinated dogs can be susceptible to parvo).

Today, there are three types, or variants, to the parvo virus, which has resulted in easier transmission of parvo between host animals than when parvo first appeared on the scene. Regardless of the type involved, parvo is highly contagious, spreading from puppy to puppy through parvo infected feces or vomit. The incubation period for parvo (the period of time from first exposure to the parvo virus to the onset of clinical signs caused by the parvo) is 7 to 14 days.

The sad fact is that parvo is one disease that can be prevented with timely immunizations started at a young age, so the emotional grief and financial hardship that accompanies parvo is totally avoidable. Yet veterinarians still find themselves battling parvo on a daily basis.

How Parvo Attacks

The parvo virus is attracted to areas of the body where cells actively divide and multiply. In puppies, the areas parvo attacks include the lymph nodes, bone marrow, and intestinal lining. Rarely, the heart can also become infected with the parvo virus, leading to sudden death.

The intestinal form of parvo is the most common presentation seen. Symptoms caused by the parvo include loss of appetite, persistent vomiting, and profuse, odoriferous, bloody diarrhea. In severe parvo infections, the lining of the intestines can actually be shed in the stool!

As the parvo progresses, dehydration occurs and bacteria from the gut enter the bloodstream. If these secondary problems to parvo disease are not addressed immediately, organ failure and death usually result.

Diagnosis of Parvo

Diagnosis of parvo is based on clinical signs, vaccination history (or lack thereof), and laboratory tests. A quick in-house parvo test performed on the sick pup's feces can help confirm parvo infection. Also, the blood can be evaluated for a declining white blood cell count, which corresponds with the parvo 's invasion into the bone marrow. In fact, this low white cell count is one of the most consistent signs seen with parvo infection, so much so that veterinarians use it as a prognostic indicator for parvo infected patients. If the count continues to fall even after three days of parvo treatment, the prognosis for recovery is poor. However, if the count rebounds and rises by the third day of parvo treatment, recovery from the parvo infection can usually be expected, provided of course that aggressive supportive parvo therapy is continued.

Parvo Treatment

Because no specific antiviral drugs exist for parvo, treatment involves supportive care and the prevention of secondary complications. Parvo treatment success depends on many factors, including how quickly it is instituted after signs appear, how aggressively treatment is applied, and which strain of parvo is causing the infection.

Intravenous fluids are the mainstay of parvo treatment to correct and prevent dehydration. Potassium, an electrolyte vital to the normal motility of the intestinal tract, must be supplemented as well to replace what was lost due to vomiting and diarrhea caused by parvo. Administration of anti- parvo antibodies can greatly improve prognosis. These can be delivered through transfusions of blood, plasma, or hyper-immune serum obtained from dogs previously vaccinated for parvo. Since pups infected with parvo have a tough time keeping food down, nutrition can be temporarily provided through an intravenous line. Antibiotics and anti-vomiting drugs can be administered through this line as well.

Attentive nursing care for the parvo patient is needed to achieve and maintain an adequate body temperature and to keep outside environmental stress to a minimum.

Parvo Aftermath

Puppies that do survive will have excellent immunity to parvo, usually lasting a lifetime. Yet they can still shed the parvo virus in their stools for weeks after they recover. And not only that, parvo can linger and remain infective within an environment for up to seven months.

Parvo is a tough virus to kill with standard disinfectants other than bleach, the latter of which is often impractical to use due to the damage it can inflict on inanimate objects, even when used at the recommended 1:30 dilution. As a result, new puppies should not be introduced to a parvo contaminated environment for at least 7 months (8 months to be safe), and even then only after they themselves have been properly vaccinated against the parvo virus.

Parvo Prevention

As mentioned earlier, parvo can be prevented through vaccination.  The modified-live parvo vaccine is preferred over the killed parvo vaccine, since the former will help reduce interference to immunity to parvo in puppies that receive parvo antibodies from their mother's milk. These parvo antibodies passed from the mother (assuming she herself was properly vaccinated for parvo before she became pregnant) to her nursing pups will help protect against parvo for a time, but as levels wear off, so does this parvo protection. Parvo antibody levels wear off in puppies at 8 to 16 weeks of age, on the average. As a result, parvo vaccinations should start around eight weeks of age (6 weeks if the mother wasn't vaccinated for parvo), with a parvo booster given monthly until the pup is 16 weeks old.


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