Introduction

Classification

Taxonomy

• Family: Parvoviridae.
• Genus: Parvovirus.
• CPV 1: also known as minute virus of canines.
• CPV 2: several variants identified including CPV 2a, 2b and 2c.

Etymology

• Latin: parvus- small.

Active Forms

Clinical Effects

Epidemiology

Habitat

• Canine parvovirus survives in the gastrointestinal tract of dogs.
• Cats may be a potential reservoir, as canine and feline parvoviruses are closely related.
• CPV 2a and CPV 2b can infect cats.
• May survive for years in the environment.

Lifecycle

• Replicates in actively dividing cells of the natural host.
• Single-stranded DNA virus.
• Virions are assembled in the cell nucleus, associated with the formation of intranuclear inclusion bodies.

Transmission

• Feco-oral route.
• Environmental contamination more important than contact with infected dog.
• Via food and water contaminated with feces containing virus. The virus can survive in the environment for long periods.

Pathological effects

• Virus targets lymphoid tissue, resulting in (in the early stages at least) lymphocytolysis and leukopenia.
• Viremia followed by infection of bone marrow → leukopenia.

CPV 1

• Mild diarrhea.

CPV 2

• Initial sites of replication are lymph nodes and spleen.
• Viremia occurs 2-5 days after infection.
• The intestinal mucosa is involved after 6 days, targets intestinal crypt cells → complete denudation of mucosa in severe infections → fecal excretion follows.
• Damage to the small intestine allows secondary bacterial infection, vomiting, diarrhea, and endotoxemia (diarrhea often hemorrhagic).
• As parvovirus can cross the placenta pregnant bitches should not be immunized with modified live parvovirus vaccine; could cause abortion or fetal infection.
• Myocarditis may occur in puppies when infected between 3 and 8 weeks old. Necrosis and infiltration by mononuclear cells occurs in the ventricular myocardium.

Other Host Effects

• Virus is excreted in the feces for up to 8 weeks after recovery. This maintains the virus in the environment.

Control

Control via chemotherapies

• Interferon Interferon.
• Symptomatic:
  • Replace fluid and electrolyte losses.
  • May use antibiotics to prevent 2° sepsis.
  • Anti-emetics to control vomiting.

Vaccination

• Most adult animals are immune due to vaccination or exposure.
• Antibody levels correlate directly with degree of protection.
• Modified live vaccine usually stimulates a good antibody response.
• Live modified vaccine available Therapeutics: immunological preparation Vaccination protocols.
• Interference from maternal immunity is a significant problem. Initial puppy vaccinations are recommended to finish at an age when maternally derived antibody has declined to low levels such that the animal can respond to vaccination: this may be up to 16 weeks especially where prevalence of infection in the population is high.

Other countermeasures

• Prompt cleaning with effective disinfectants, eg bleach.
• Remove organic material, eg feces prior to disinfection.

Diagnosis

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• Decaro N, Martella V, Elia G et al (2007) Tissue distribution of the antigenic variants of canine parvovirus type 2 in dogs. Vet Microbiol 121 (1-2), 39-44 PubMed.
• Martella V, Decaro N & Buonavoglia (2006) Evolution of CPV-2 and impliance for antigenic/genetic characterisation. Virus Genes 33 (1), 11-13 PubMed.
• Martella C, Cavalli A, Pratelli A et al (2004) A canine parvovirus mutant is spreading in Italy. J Clin Microbiol 42 (3), 1333-1336 PubMed.
• Cohn L A, Rewerts J M, McCaw D et al (1999) Plasma granulocyte colony-stimulating factor concentrations in neutropenic, parvoviral enteritis-infected puppies. JVIM 13 (6), 581-586 PubMed.
• Horiuchi M, Yamaguchi Y, Gojobori T et al (1998) Differences in the evolutionary pattern of feline panleukopenia virus and canine parvovirus. Virology 249 (2), 440-452 PubMed.
• Houston D M, Ribble C S & Head L L (1996) Risk factors associated with parvovirus enteritis in dogs: 283 cases. JAVMA 208 (4), 542-546 PubMed.
• Greenwood N M, Chalmers W S, Baxendale W et al (1995) Comparison of isolates of canine parvovirus by restriction enzyme analysis, and vaccine efficacy against field strains. Vet Rec 136 (3), 63-67 PubMed.