What Is Canine Parvovirus Infection

1 Canine Parvovirus Infection

Epidemiology

The disease mainly infects dogs, especially 2-4 month old puppies; it rarely occurs under 2 months or over 5 weeks of age, but purebred dogs are more susceptible than mixed-breed and native dogs. Adult dogs are milder. It can also infect wild canids such as wild dogs, coyotes, hyenas, raccoons and foxes.

Sick dogs and recovered carriers are the main source; they shed the virus in secretions and excretions, infecting other susceptible animals via the digestive tract, and possibly transplacentally. People, flies and cockroaches can be mechanical carriers.

It occurs year-round, more in spring and autumn. Weather changes, poor husbandry, and secondary or mixed infections worsen the disease.

Clinical symptoms

Clinically the disease mainly shows two types, enteritis and myocarditis, and mixed cases also occur.

(1) Enteritis form

Incubation 7-14 days; the dog suddenly falls ill with vomiting, depression, anorexia, fever (40-41°C) and diarrhea; the stools are gray or gray-yellow with much mucus and pseudomembrane, soy-sauce-colored or bloody, and foul-smelling. Rapid dehydration follows.

Without secondary infection, the white blood cell count drops. Most dogs recover in 7-10 days, but young puppies often die; mortality generally falls with age.

(2) Myocarditis form

This form mainly affects 3-6 week old puppies. The dog separates from the group, stands dazed, has pale mucosa, a fast weak pulse and labored breathing, with a regurgitant murmur over the heart. Before death the ECG shows a lowered R wave and raised S-T wave. Death is from heart failure.

Pathological changes

(1) Enteritis form

Grossly the small-intestinal mucosa is thickened, the lumen narrowed, with folds or ulcers; the contents are red porridge or mixed with purple-black clots, foul-smelling; the jejunum and ileum show severe hemorrhage.

Mesenteric lymph nodes are enlarged and congested; the gastric mucosa is congested with egg-white mucus; the liver is enlarged and red with light-yellow foci, and the cut surface oozes non-clotting blood; the gallbladder is distended with much yellow-green bile; the spleen is enlarged with purple spots (hemorrhagic infarct) or gray-white necrotic foci; the kidneys are gray-yellow with gray-white spots; the bladder-neck mucosa bleeds.

(2) Myocarditis form

Grossly the heart is dilated, with non-suppurative necrosis foci in the myocardium and endocardium; the lungs are severely edematous and consolidated.

Differential diagnosis

(1) Canine parvovirus infection vs. canine coronavirus

Both show fever, vomiting, diarrhea and congested/necrotic/sloughed small-intestinal mucosa, enlarged bleeding mesenteric lymph nodes.

Difference: coronavirus cases have severe diarrhea, stools white/yellow/green/brown, sometimes projectile, with bleeding and sloughing of the gastric mucosa and enlargement of the spleen and gallbladder. Parvovirus (myocarditis form) shows non-suppurative necrosis of the myocardium or endocardium and a soft heart muscle.

(2) Canine parvovirus infection vs. canine rotavirus

Both show fever, vomiting, diarrhea and congested/necrotic/sloughed small-intestinal mucosa.

Difference: rotavirus cases are mostly 2-4 month puppies; at necropsy the gastric mucosa bleeds and sloughs, and the spleen and gallbladder are enlarged.

(3) Canine parvovirus infection vs. canine distemper

Both show fever, vomiting, diarrhea and congested/bleeding small-intestinal mucosa.

Difference: distemper cases have a biphasic temperature and marked neurological signs; at necropsy the GI mucosa is congested and bleeding, the thymus atrophied, the heart/liver/spleen/kidney/lung congested and bleeding, and the meninges congested with effusion.

(4) Canine parvovirus infection vs. canine campylobacteriosis

Both show fever, vomiting, diarrhea, bloody stool and dehydration, and congested/bleeding small-intestinal mucosa.

Difference: campylobacteriosis cases at necropsy show a congested liver with ascites, and antibiotics give a clear effect.

(5) Canine parvovirus infection vs. canine salmonellosis

Both show fever, vomiting, diarrhea and congested/necrotic/sloughed small-intestinal mucosa, enlarged bleeding mesenteric lymph nodes.

Difference: salmonellosis cases at necropsy show the liver enlarged 2-3x, the spleen 6-8x, studded with petechiae and gray-yellow necrosis on the surface and parenchyma, and antibiotics give a clear effect.

Notes

Based on the epidemiology, clinical signs and characteristic pathology a preliminary diagnosis is made; sudden onset with vomiting then anorexia and severe depression suggests parvovirus. A rapid parvovirus antibody test card can also be used.

Prevention and treatment

(1) Prevention

1. Vaccination. After infection dogs develop strong immunity. Any vaccine works poorly in dogs that already have antibodies; multiple vaccinations are needed to raise immunity.

2. Hyperimmune serum combined with antibiotics has some preventive and therapeutic effect.

(2) Treatment

The treatment principle is antiviral therapy, prevention of secondary infection, symptomatic treatment and supportive care.

1. Antiviral.

Canine parvovirus monoclonal antibody: 0.5-1 mL/kg subcutaneously or intramuscularly once daily for 3 days, double the dose for severe cases.

Ribavirin: 5-7 mg/kg subcutaneously or intramuscularly once daily.

Interferon: 100,000-200,000 IU per dose subcutaneously or intramuscularly every 2 days.

2. Antibacterial/anti-inflammatory.

Ampicillin: 20-30 mg/kg orally 2-3 times daily, or 10-20 mg/kg intramuscularly/intravenously 2-3 times daily.

Cefazolin sodium: 15-30 mg/kg intramuscularly or intravenously 3-4 times daily.

Clavamox (amoxicillin-clavulanate suspension): 0.1 mL/kg intramuscularly once daily.

Enrofloxacin: 2.5-5 mg/kg orally or intravenously twice daily.

3. Antiemetic.

Metoclopramide: 0.2-0.5 mg/kg orally or subcutaneously 3-4 times daily.

Emall (Aimor): 2 mL per dose subcutaneously or intramuscularly twice daily.

Omeprazole: 0.5-1 mg/kg orally, subcutaneously or intravenously once daily, up to 8 weeks.

4. Blood in stool, hemostasis.

Etamsylate (Dianxuanyisuan): 2-4 mL per dose intramuscularly or intravenously.

Vitamin K: 10-30 mg per dose intramuscularly.

5. Treat diarrhea.

Smectite (dioctahedral montmorillonite): 250-500 mg/kg orally.

Videcon (Weidikang): 0.02-0.08 g/kg orally twice daily for 2-4 days.

6. Fluid therapy.

ATP, coenzyme A, vitamin C, 50% glucose-saline, lactated Ringer’s solution, 5% glucose, etc.

Note

Parvovirus strongly resists the external environment; disinfect with bleaching powder, sodium hydroxide, formaldehyde solution or ammonia water.