Parvo Virus Infection | Diagnosis, Treatment and Prevention

          Parvo Virus Infection | Diagnosis, Treatment, and Prevention

It is a highly contagious disease of the dog and is notorious for its ability to quickly reduce the animal health and make him lethargic. If the animal is not treated at the early stage of the disease then it can also cause death. It is characterized by enteritis and myocarditis with 100% morbidity rate and 91 % mortality rate in untreated cases, but 10% if treated. It spread with the contact of the body secretions of the infected animal. The virus continues to excrete in the body secretions of the animal for 12-14 days after the recovery. Fomites (Inanimate objects that carrying the disease-causing microorganisms) also play role in the spread of this disease because the virus can remain in the fomites for years. 

Cause / Etiology:

It is caused by the canine parvovirus; a DNA virus. It has mainly two types; CPV-1 and CPV-2.

CVP-1: Canine parvovirus 1 is known as minute virus of canine and is relatively non-pathogenic. But sometimes it causes gastroenteritis, pneumonitis, and myocarditis in puppies with 1-2 weeks of age. 

CPV-2: Canine parvovirus 2 is mainly responsible for classic and notorious enteritis with the signs coming 5-12 days after the infection through the fecal-oral route. This virus has great ability to mutate that sometimes causes the vaccination failure and preferentially invade the rapidly dividing cells of the body like intestinal crypts epithelium. Nowadays CPV2b and CVP2c are most commonly involved, in causing the disease, and these strains can also affect the cat.

Most Susceptible Dog Breeds:

 Doberman, Pinscher, Rottweiler, Pitbull, Labrador Retriever and German Shepherd.

Clinical Signs / Disease Signs:

On the basis of clinical signs, this disease has two form; enteric form and myocardial form.

Initial signs are the depression, anorexia, restlessness, ratching and maybe vomiting without diarrhea. But after the 24-48 hrs due to the viral destruction of intestinal crypts, there is severity in the vomiting, diarrhea and intestinal bleeding. But if diarrhea occurs before 24-48 hrs there will be no intestinal bleeding. The dog will show the signs of polydipsia (increased in thirst and excessive drinking). The color of vomitus will be frothy-yellow and the feces will be brownish semisolid with mucous or blood. 

When excessive intermittent gastric contraction occurs, in this disease then there is a possibility that the bile will be sucked up by the stomach and then vomited out. Vomiting will be so severe that it can cause esophagitis. In this case, you will find the greenish-yellowish color in the vomited material. Mass destruction of intestinal crypts also cause the loss of body proteins and lead to the hypoalbuminemia.

Fever present initially but will become subnormal with the advancement of vomiting and diarrhea. The virus also causes the destruction of the bone marrow progenitors that leads to the neutropenia and make the animal susceptible for the secondary bacterial infection; especially when the damage to the intestinal tract allows the bacterial access to the body. So in severe case septic shock can also occur.

In myocardial form, myocarditis and circulatory failure can occur. Pulmonary edema, cardiogenic shock, and respiratory problems can also be seen. But if the animal survives there will be a possibility for myocardial or circulatory complications. Puppies can take infection in utero (in the womb). Puppies that infect in utero and before 8 weeks of age may develop myocarditis. Death occurs in case of severe dehydration due to enteritis or due to the heart failure in case of myocarditis.  

Diagnosis:

On the basis of history and physical examination findings.

Abdominal radiography with barium based contrast media. The gas or fluid will evident. 

CBC: Neutropenia (but it not confirmed, the parvo because it also happens in salmonellosis).

ELISA is the best diagnosis because the virus comes in the feces with a number of  >10^9 particles per gram of feces. But virus shedding will undetected after the14 days of infection.

Histopathology: Intestinal crypts necrosis.

Treatment:

1. Most dogs will live if they survive the first 5 days of the disease.
2. Use Hyperimmune sera against the parvo. (like Canglob with 0.4ml/kg daily with respect to the disease).
3. Use Antiemetics.
4. NSAIDs are contraindicated in parvovirus enteritis. Opioids such as fentanyl are preferred for analgesic effect but only in a small dose because higher dose can worsen the ileus and cause sedation.
5. If the animal is in shock condition, give him steroids.
6. Give Fluid and electrolyte therapy with supportive therapy( like vitamins, jetipar, neurobion or hepamerz).
7. If the patient is hypoglycemic then do glucose therapy with 5% or 10% glucose, on the basis of the animal condition.
8. Use broadspectrum antibiotics ( like cephalosporins but in shock condition use ampicillin plus amikacin or enrofloxacin. Aminoglycosides should not be given until the rehydration and correction of  the renal perfusion.)
9. If serum albumin protein is less than 2g/dl then administer plasma or a colloidal solution like hetastarch at the dose rate of 10-20 ml/kg.
10. Give liquid diet to the dog(like meat extract or soop).
11. If the patient is continuously regurgitating the food then give him H2 receptor blocker( like cimetidine, ranitidine or famotidine).
12. If you don't find any hyperimmune sera or any other better treatment then a makeshift treatment is also possible; that is related to the blood transfusion. Take blood from a stray dog and inject it to the infected one. But the more correct method is that; take 3-5 ml blood from a stray dog and then obtain serum from this blood then inject approximate 1ml of serum to the infected dog. This is because stray dogs are naturally resistant to the parvovirus and have antibodies against it.

Prevention and Control:

• Separate the infected one from the other healthy animals for 2-4 weeks.
• Vaccination of other dogs or cats. If disease occurs in a group of animals(dogs or cat) that are already vaccinated then after the separation of infected one give a booster dose to the remaining ones but only with inactivated vaccine.
• Take the sanitary measures seriously and clean feces and vomiting material as early as possible and clean the utensils, clothes and the area under the use of the infected dog.
• Clean the premises(like the kennel) and fomites( inanimate objects having virus particles e.g. like eating bowl or toys etc.) under the use of infected dog with 2% formalin or 2% NaOH or 2% sodium hypochlorite.
• Dilute bleach with 1:32 is also a readily available source for disinfection. 
• Always follow the vaccination protocol prescribed by your veterinarian.
• Give 2 doses of vaccine to the pup. 1st at the age of 6-8 weeks and 2nd at the age of 12th weak. Use attenuated vaccine because it has a good response. Before 6 weeks the maternal antibodies are enough for the pup. But in case if the vaccine is necessary before 6 weeks of age; may be due to the presence of disease in a member of a group or in case if the mother was not vaccinated; then use the inactivated vaccine.
• If an adult dog that is not vaccinated before and now on the risk of disease then give him a double dose of vaccine.
• Take care of your pet when you take him out for a walk or go to any hospital for a normal routine checkup. Don't allow your pet to lick the dirty things present around as you know that the virus may present in the environment because the virus can survive in the environment(on the fomites) for a very long period of time.

Zoonotic importance:

According to the CDC (Centers for Disease Control and Prevention), the strain (CPV-B19) of parvovirus virus which cause disease in human, will not cause disease in dogs and cats. And the other strains (CPV2b or CVP2c) that cause disease in the dogs and cats will not cause disease in human.

So, it is not zoonotic.

  

Reference:

Centers for Disease Control and Prevention(CDC)/ Parvovirus B19/Transmission

Small Animal Internal Medicine 4th ed. by Richard W.Nelson and C.G.Couto.

A textbook of Veterinary Preventive Medicine by Chakrabarti.