The first year in a dog’s life is one of the most crucial stages in its development. This is the stage where a dog is most vulnerable to deadly diseases brought about by highly contagious and highly fatal viral infections. Among the viral infections that affect dogs, none can bring fear and abject horror to pet parents than canine parvovirus. If the infection is severe enough and prompt and aggressive treatment is not administered at once, you can say goodbye to your pooch in as short as 48 hours, some extending to 72 hours. The point is that Canine Parvovirus infections are almost always fatal in their very severe form. The key to averting disaster is in the early recognition of the various signs and symptoms of the infection and how dogs should be treated.
What is Canine Parvovirus?
When vets talk about parvo, they are most likely referring to Canine Parvovirus Type 2 or CPV2. Animal experts believe that CPV2 came from Feline Panleukopenia Virus (FPLV) which is also a type of parvovirus that mostly infects cats. Experts believe that CPV2 is a mutation of the FPLV since both viruses share the same viral structure and characteristics except for 2 slightly different viral capsid proteins in the CPV2. Because of its mutagenic properties, microbiologists say that the current strain of Canine Parvovirus Type 2 is totally different from the original strain discovered in 1978. What this simply means is that the virus is continuously evolving, making it extra difficult to treat, and exceptionally tricky to control.
There are two forms of canine parvovirus infections. These are intestinal and cardiac, typically referring to the organs or regions of the dog’s body that is the locus of infection.
Infection occurs through the oral route wherein dogs ingest items or objects that may be contaminated with the CPV2. Upon ingestion, the virus migrates to the lymph tissues in the dog’s throat, eventually spreading through the bloodstream. The virus attacks all cells in the body that rapidly divide, but mostly the cells found in the crypts of the intestines, the lymph nodes, and the cells of the bone marrow.
The tissues in the intestinal crypts die and are destroyed, releasing anaerobic bacteria into the bloodstream. This is what leads to sepsis until such time that systemic inflammatory response syndrome results. The presence of Clostridium, Salmonella, and Campylobacter species in the blood leads to increased clotting tendencies, resulting in acute respiratory distress. If not treated promptly, the dog dies of massive sepsis and septic shock.
However, even without the presence of sepsis, the dog will be experiencing massive fluid losses resulting in dehydration and fluid and electrolyte imbalance because of the inflammatory changes that occur in the intestines. Death can still ensue because of hypovolemic shock if not severe electrolyte abnormalities and acid-base imbalances.
In less severe cases, the virus can actually stay in the dog’s intestines for up to 3 weeks. On the 3rd or 4th day following infection, the dog will begin shedding the virus through its stool. This continues for 2 to 3 weeks. This also means that if another dog gets in contact with this stool that is contaminated with CPV2, then that dog gets infected, too.
The cardiac form of parvo is mostly confined to puppies below the age of 8 weeks. Experts believe that CPV2 is transmitted by an infected pregnant dog to its litter. The virus primarily targets the muscles of the heart. The cause of death of the puppy is mostly related to pulmonary edema leading to respiratory arrest.
What Dogs are More Susceptible to Parvo Infection?
The following types of dogs are regarded as most susceptible to the development of Canine Parvovirus infections.
- Puppies that are between the ages of 6 weeks and 6 months
- Puppies or dogs that have never been vaccinated or have incomplete vaccinations
- Puppies and dogs that have concurrent canine coronavirus infections
- Puppies and dogs that have concurrent bacterial and parasitic infections
- Puppies and dogs living in highly stressful environments
- Puppies and dogs that are colored black and tan such as German Shepherds, Doberman Pinschers, American Staffordshire Terriers, Rottweilers, Pit Bull Terriers, and English Springer Spaniels
For the majority of these dogs, the reason for increased susceptibility is closely related to an issue with the dog’s immune system. It could either be still immature or is at a compromised state. As for the different breeds of dogs that are susceptible to parvo infection, scientists still don’t have a clue as to why black- and tan-colored breeds are more vulnerable to such an infection than other breeds.
What Causes Parvovirus Infection in Dogs?
There are two ways by which parvovirus can be transmitted to dogs. These can include direct contact and indirect contact.
We learned above that dogs that are infected with CPV2 actually begin shedding the virus through their stools or feces as early as the 3rd day after infection. This viral shedding can go on for another 2 or 3 weeks or so. If another dog sniffs or licks this stool or feces contaminated with CPV2, then this dog will also get infected with Canine Parvovirus. This kind of transmission is called direct transmission since an otherwise healthy dog got in direct contact with the contaminated feces or stool.
The main problem is among puppies. These young pooches love to explore their surroundings and they use their mouth as their principal organ of discovery. Unfortunately, there are no labels or signs in dog poop that says it is contaminated with CPV2. The next thing you know, your puppy will already be licking or sniffing the contaminated poop. In just a day or two, you’d be seeing some symptoms from your puppy already.
The second method in which CPV2 can be transmitted is by indirect contact. Experts believe that the virus is a very resilient, very tough microorganism. It can literally survive outdoors for many years especially if it is protected from the harsh rays of the sun. Indoors, the virus can stay alive for up to 2 months. It is very resistant to common household disinfectants and cleaners.
This is where the problem lies. When we go out and we step on a dog poop that is contaminated with CPV2, we are essentially bringing the virus right into our homes. If we bring our shoes right inside the house without bothering to clean it and disinfect it with bleach (CPV2 is known to be vulnerable to bleach), then we’re increasing the risk of infecting our pooches. Sadly, we are not really aware that the poop we stepped on is actually contaminated with CPV2.
Indirect contact can also occur whenever dogs get in contact with persons, items or objects, or even an environment that is contaminated with the CPV2.
What are the Signs and Symptoms of Canine Parvo?
Now that we have an idea of what Canine Parvo is, what it does to our dogs, and how it is transmitted from one dog to another, it is time to look at the most common signs and symptoms of canine parvo infections. Your prompt recognition of these symptoms will help determine whether your pooch will be able to survive its ordeal.
- Weight loss
- Severe bloody diarrhea
- Abdominal pain
One of the earliest signs of CPV2 infection is lethargy. This usually presents on the 3rd day after infection and is typically followed by a loss of appetite, weight loss, diarrhea, and vomiting. The last two manifestations are critical since the condition can deteriorate very rapidly, leading to dehydration, acid-base imbalance, and electrolyte abnormalities. Because of the rupture of the intestinal crypts, bacteria that should otherwise be confined to the intestinal tract find their way into the bloodstream causing massive secondary bacterial infection, further overwhelming the dog’s immune system. This further weakens the pooch and if treatment is not started promptly and aggressively, shock and death can ensue within the next 48 to 72 hours.
How Can Parvo be Treated?
Because of the high level of communicability, virulence, and pathogenicity of CPV2, only aggressive treatment can help avert any disastrous consequences of the infection, namely septic and hypovolemic shock and death. The trick is that the earlier the symptoms of CPV2 are recognized the earlier a confirmatory diagnosis can be made. This is the basis for prompt and definitive treatment that includes the following.
- Aggressive fluid resuscitation
Since one of the major problems in CPV2 infection is dehydration secondary to excessive vomiting and diarrhea, dogs will require aggressive fluid resuscitation through the administration of intravenous solutions. These IV fluids typically come in the form of balanced electrolyte solutions complete with potassium chloride, dextrose, and vitamin B complex. Additionally, depending on the amount of blood lost through the feces in the form of bloody diarrhea, vets can also order blood volume expanders and colloidal therapy.
- Antiemetic therapy
To address the issue of severe vomiting in dogs with CPV2 infection, vets can administer antiemetic medications such as metoclopramide, prochlorperazine, dolasetron, maropitant, and ondansetron. This is to help control vomiting and reduce further fluid and electrolyte losses.
- Broad-spectrum antibiotic therapy
A variety of antibiotics will be considered in the management of secondary bacterial infections brought about by tissue destruction in the intestinal crypts. Some of the more common broad spectrum antibiotics given to such dogs include cefazolin/enrofloxacin, metronidazole, ampicillin/enrofloxacin, and timentin. Serial white blood cell count is generally performed on a daily basis to help evaluate the dog’s therapeutic response to antibiotics.
- Immunologic support
Some veterinary clinics have packs of blood plasma obtained from a donor dog that was able to survive CPV2 infection. These are stored in air-tight, temperature-controlled containers for maximum effectiveness. Some clinics have frozen serum instead. What they do is they administer these products as blood transfusion, transferring the CPV2 antibodies from the donor plasma to the sick dog, conferring passive immunity. However, the practice has not yet gained widespread acceptance because of the dearth of clinical evidence supporting its merits.
- Symptomatic treatment
If the dog has a fever and/or abdominal pain, appropriate canine analgesics are administered. Fluid replacements are also provided for each episode of diarrhea and/or vomiting. This is in addition to the fluid resuscitation therapy.
If the dog can avoid vomiting for a certain period of time, the intravenous fluid therapy is gradually reduced. If the dog hasn’t vomited in the last 24 hours, it may already be fed with soft bland diet. If the symptoms were detected early and aggressive treatments initiated at once, a dog can usually recover within 5 days, although it is not unusual for dogs to take up to 2-3 weeks before fully recovering. If the symptoms are very mild, recovery is expected within 3 days. Sadly, even with extensive hospitalization, there really is no guaranteeing the dog will come out of the CPV2 ordeal alive. For those that do, many vets will consider them to be miracle pooches.
How Can Parvo be Prevented?
Based on our knowledge of how CPV2 is transmitted, we can think of a variety of ways in which we can prevent Parvo infection in our dogs.
- Appropriate vaccination of all puppies by age 7 to 8 weeks administered every 3 to 4 weeks until the puppy reaches the age of 16 weeks at the very least. The number of vaccinations should be at least 3. A booster dose is given 1 year after the last vaccine dose and then every 3 years thereafter.
- For puppies that are older than 16 weeks, they should be vaccinated 2 times about 3 to 4 weeks apart, although a third dose is usually considered as highly protective.
- All adult dogs should receive revaccination against Parvo every 3 years.
- Disinfect all household articles and surfaces of the home using a 1:10 ratio of household bleach to water. This is the only household chemical that is proven to kill Canine Parvovirus.
- If you suspect your dog to be infected with CPV2, it is important to keep it in quarantine for at least 2 weeks to help prevent the transmission of the virus to other dogs and mammals in the neighborhood.
Canine Parvovirus infection is a deadly disease in dogs, especially puppies. Knowing what it is and how to recognize its symptoms should help you decide when to take your pooch to the vet. Remember, the earlier you recognize the symptoms, the earlier your vet can initiate treatment.
- Elena Kilian, Long-term Effects Of Canine Parvovirus Infection In Dogs, PLOS
- Canine Parvovirus, American Veterinary Medical Association