EIV 2020 voice over 2

Equine Influenza Virus Overview

  • Presenter: Gisela Soboll Hussey

  • Email: husseygi@msu.edu

Objectives of the Presentation

  • Understanding equine influenza's lineage and viral components

  • Overview of the unique influenza virus genome and its significance

  • Identify critical immune responses for protection

  • Recognize clinical signs of infection

  • Pathogenesis of equine influenza

  • Diagnosis: necessary samples and tests

  • Control measures and treatment strategies

Virus Classification

Genera/Lineage/Sublineage

  • Genera:

    • Thogotovirus

    • Isavirus

    • Influenza A

    • Influenza B

    • Influenza C

  • Specific Strains:

    • H3N8 (equine-2)

    • H7N7 (equine-1)

  • Genetic Evolution:

    • H3N8 has two distinct lineages:

      • European

      • American (further divided into South American, Kentucky, Florida sublineages)

Viral Structure

  • Characteristics:

    • Enveloped RNA virus

    • Easy inactivation with detergents and alcohols

  • Major Envelope Proteins:

    • Hemagglutinin (HA): Types H1-H18

    • Neuraminidase (NA): Types N1-N11

  • Genome:

    • Segmented, allows for genetic reassortment

Immunity to Equine Influenza

  • Dependent on antibody responses

  • Key Immune Components:

    • Mucosal IgA

    • Serum IgG

    • Cytotoxic T cell responses

  • Effects:

    • Immunity does not prevent infection, but aids in viral clearance and recovery

    • Provides heterotypic immunity

Clinical Signs of Influenza Infection

  • Initial Symptoms (48 hours post-infection):

    • Fever

    • Nasal discharge (serous)

    • Cough

    • Anorexia (potential weight loss)

    • Lethargy

  • Resolution Timeline:

    • Uncomplicated cases typically resolve within 7-14 days

Pathogenesis of Infection

  1. Inhalation of Infectious Virus

  2. Infection and Replication:

  • Occurs in respiratory epithelium, leading to cell damage

  1. Spread of Virus:

  • Rapid dissemination throughout the respiratory tract

Effects on Airway Tissue

  • Healthy airway tissue features cilia that clear debris

  • Influenza infection leads to damaged airway epithelium and loss of ciliary function

  • Potential complications include bacterial bronchopneumonia

Complications and Virus Transmission

  • Common complications:

    • Bacterial pneumonia

    • Myocarditis

  • Transmission pathways:

    • Direct contact

    • Fomites

    • Large droplets and aerosols

Diagnosis

  • Samples for Testing:

    • Respiratory tissues

    • Nasal swabs

  • Testing Methods:

    • PCR (Polymerase Chain Reaction)

    • Virus isolation

    • Antigen detection

    • Serum serology

Timing for Sample Collection

  • Considerations:

    • Monitor nasal virus shedding and antibody response over 12 days post-infection

  • Testing should include antigen detection, virus isolation, and serology

Control Measures for Equine Influenza

Vaccination

  • Key Component of Control:

    • Essential for prevention

  • Types of Vaccines Available:

    • Inactivated

    • Modified Live Virus (MLV)

    • Recombinant vaccines

  • Considerations for Vaccine Efficacy:

    • Quantity and quality

    • Viral strain and adjuvants

    • Type of protection: homologous virus specificity

  • Administration:

    • Intranasal, cold-adapted single doses available

    • Protection duration up to 12 months

Challenges in Vaccination

  • Factors Affecting Response:

    • Virus evolution and antigenic drift

    • Inappropriate timing of vaccination

    • Risks of interspecies transmission and antigenic shift

Husbandry Practices

  • Isolation Measures:

    • Isolate infected horses for at least 21 days after last infection

  • Transmission Considerations:

    • Highly contagious, aerial spread can occur up to 50 yards