The canine parvovirus (CPV) is an extremely contagious viral infection that usually manifests itself in two distinct ways:
Intestinal CPV, that is characterized by severe diarrhoea (usually bloody), lack of appetite (anorexia), weight loss, fever, lethargy and vomiting. Dogs can contract the illness through oral contact with CPV-infected faeces, fomites, or soil. Once ingested, the virus quickly replicates specifically in the lymphoid tissue present in the throat, before entering the bloodstream, where it attacks the rapidly metastasizing cells in intestinal crypts, bone marrow, and lymph nodes. The CPV causes destruction and necrosis of the intestines, and depletion of lymphocytes in the lymph nodes.
Anaerobic bacteria that commonly inhabit the intestines then undergo translocation, where they cross into the bloodstream with bacteremia (Clostridium, Salmonella and/or Campylobacter) resulting in sepsis. At this point, Systemic inflammatory response syndrome (SIRS) sets in, leading to a range of complications, including but not limited to acute respiratory distress syndrome (ARDS), endotoxemia and hypercoagulability of the blood. Dogs with CPV are likely to contract intussusception, where one part of the intestine prolapses into a different part of the intestine. 3-4 days post-infection, the dog becomes an asymptomatic carrier and the virus tends to shed in the faeces for almost 3 weeks. CPV can be especially fatal, if the 'host' canine is infected with intestinal parasites and/or infested with worms.
Cardiac CPV, that adversely affects the heart muscles of really young puppies (6 weeks to 6 months), often resulting in death. Due to the widespread practice of administering neonatal vaccinations and mandatory CPV tests, Cardiac CPV overall is not very common. Puppies with CPV experience breathing difficulties caused by pulmonary edema and heart muscle necrosis. In extreme cases, the disease can cause lesions and attack the brain, kidneys, lungs, adrenal cortex, and liver. Dogs surviving CPV are usually left with fibrosis that is characterized by the accumulation of excess fibrous tissue.
While puppies tend to be easily susceptible to CPV, more than 80% of grown-up dogs show absolutely no symptoms, making early detection of the disease a difficult process. In case of severe CPV, dogs are likely to die within 48 to 72 hours if immediate treatment by fluids is not administered. In the more common form of CPV, mortality remains 10%. Breeds with tan and/or black colour like Rottweilers, Pitbull terriers and Doberman Pinschers are more susceptible to CPV. Additionally, other influential factors include a stressful environment and simultaneous infections with canine coronavirus, bacteria, and parasites. Dogs with CPV usually pass away from the dehydration or another secondary infection, instead of the virus itself.
Treatment:The survival rate of CPV is heavily dependent on how early the disease was diagnosed, how old your dog is and how aggressive the in-hospital treatment is. Following severe dehydration and potential damage to the bone marrow and intestines, the dog undergoes extensive hospitalization, where they are given crystalloid IV fluids and anti nausea injections (such as dolasetron, maropitant, ondansetron, metoclopramide or prochlorperazine), and a variety of antibiotic injections (such as ampicillin/enrofloxacin, metronidazole, cefazolin/enrofloxacin, enrofloxacin, metronidazole, or timentin).
The fluids are generally a combination of a sterile, well-balanced electrolyte solution containing a suitable volume of B-complex vitamins, potassium chloride and dextrose. Analgesic medications are often used for counteracting intestinal discomfort, however, opioid analgesics are avoided as they can lead to decreased motility and secondary ileus. All the medications are administered intravenously (directly into the vein), subcutaneously (in the subcutis) and intramuscularly (directly into the muscle).
Apart from providing adequate rehydration, fluids are also given intravenously every time the dog has a significant quantity of diarrhea or vomiting. The fluid requirements are decided are evaluating the dog's body weight and the degree of dehydration.
A lot of times blood plasma transfusion is carried out from a CPV-surviving donor dog in order to provide passive immunity to the CPV-infected dog. Some veterinarians might have dogs at their clinic or have frozen serum at hand for this purpose. Additionally, human albumin and freshly frozen plasma transfusions are done in severe cases to combat extreme protein loss and to facilitate tissue healing. Once your dog is able to keep fluids down, they are slowly discontinued and a diet of soft, bland food introduced. Oral antibiotics are expected to continue for several days depending on the dog's ability to tackle secondary infections and the number of white blood cells. A puppy displaying minimal CPV symptoms can bounce back in 2 or 3 days if the IV fluids are administered as soon as symptoms come to light and a CPV test confirms the diagnosis. A CPV test must be performed as soon as possible to initiate early treatment and increase the survival rate.
In more severe cases, puppies might take up to 2 weeks to completely recover. However, some dogs don't make it even after aggressive treatment and extended hospitalization.
Prevention and decontamination:
Since CPV is extremely contagious and virulent, prevention is the only way to make sure your furry friend remains healthy. CPV vaccination should be administered once the puppy is 7–8 weeks old, followed by a booster that's given every 3-4 weeks until 16 weeks. Puppies older than 16 weeks are usually prescribed 3 vaccinations to be given at an interval of 3-4 weeks. Remember to not vaccinate pregnant mothers, as that would lead to abortion and the mother might get extremely ill.
The virus is very resilient and can survive low/high temperatures, and survive in organic material including soil/ faeces for up to 10 years. Bleach is the only household disinfectant that is capable of killing it, so opt for dilute bleach solution (1:10 ratio) to mop your floors.
A CPV-surviving dog remains contagious for almost 3 weeks, and in some cases, up to 6 weeks. Notify your neighbours and family members about your dog being infected, so that they can get their dogs vaccinated or examined for immunity. Since the vaccine is expected to take 2 weeks to reach adequate immunity levels, the contagious animal should be kept in quarantine, until other pets in the vicinity are protected.