Parvo Virus Infection

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• Cause: Caused by canine parvovirus (CPV)

• Strains:

  • CPV-2a and CPV-2b are the most common.

  • CPV-2c was discovered in 2000.

  • South Africa only has CPV-2a and CPV-2b strains.

• Virus Characteristics:

  • Hardy and can persist in the environment for 5–7 months.

  • Ubiquitous in the environment.

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Pathogenesis

• Clinical Syndromes:

  • Enteritis (most common, especially in pups after weaning).

  • Myocardial failure: Seen in neonatal puppies infected in utero (rare due to vaccination).

• Transmission: Fecal-oral route.

• Target Tissues:

  • Intestinal epithelium, lymphoid tissue, bone marrow.

  • Increased cell turnover (e.g., diet change, weaning, endoparasites) enhances viral replication.

• Effects:

  • Intestinal: Epithelial necrosis, villus atrophy, hemorrhagic diarrhea, vomiting.

  • Lymphoid Tissue: Lymphopenia and sometimes panleukopenia (destruction of lymphoblasts in lymph nodes, myeloblasts in bone marrow).

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Clinical Signs

• Early Signs (non-specific):

  • Anorexia, lethargy, fever.

• Later Signs:

  • Vomiting and diarrhea (mucoid to hemorrhagic).

  • Abdominal pain (acute gastroenteritis or intussusception).

  • Lymphopenia: Severe cases may also show a Systemic Inflammatory Response Syndrome (SIRS).

• Systemic Response:

  • Bacterial translocation from damaged intestines → coliform septicemia.

  • Endotoxemia: Activates coagulation and inflammatory responses → disseminated intravascular coagulation (DIC) and bleeding.

  • Thromboelastography (TEG) shows hypercoagulability in affected puppies.

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Diagnosis

• Definitive Diagnostic Tests:

  • Faecal tests: Electron microscopy, virus isolation, PCR, immunochromatography.

  • Serology and histopathology (necropsy).

  • ELISA antigen test: Available for in-hospital testing (false positives can occur post-vaccination; false negatives may occur with bloody diarrhea).

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Treatment

• General Approach: Symptomatic and supportive treatment (no specific antiviral agent).

  • Hospitalized Treatment: Survival is much higher in treated puppies (up to 90% in tertiary care facilities).

  • Mortality: 9% if untreated, 16-19% in hospital-treated cases.

• Fluid and Electrolyte Therapy

  • Crystalloid Fluids:

    • Initial treatment with lactated Ringer’s solution for fluid resuscitation.

    • Fluid rates adjusted based on clinical response and ongoing losses.

    • Hypokalemia and hypoglycemia are common and must be corrected.

  • Colloid Support:

    • Synthetic colloids (e.g., hetastarch) may be used for low albumin or signs of third-space fluid losses (edema, pleural effusions).

    • Plasma transfusions are not the treatment of choice in cases with low albumin.

    • Natural colloids (e.g., red blood cell transfusions) for severe anemia.

• Passive Immunity

  • Plasma:

    • Limited evidence for clinical benefit of plasma transfusions in CPV cases.

    • Anecdotal positive effects in some cases.

    • Administered at 10–20 ml/kg if needed.

• Medications

  • Antibiotics:

    • Amoxicillin-clavulanic acid for broad-spectrum coverage.

    • Amikacin and enrofloxacin (careful in large breeds) used for severe cases.

    • Metronidazole for protozoal infections.

  • Antiemetics:

    • Ondansetron, maropitant, and metoclopramide to control vomiting.

  • Pain Management:

    • Opioids (e.g., buprenorphine) for abdominal pain.

  • Deworming:

    • Fenbendazole for intestinal helminths.

  • Nutritional Support:

    • Early enteral feeding improves recovery.

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