Nodaviridae

Common Name

Nodaviruses

Overview

Nodaviridae is a family of viruses known primarily for infecting fish and insects. They are small, RNA viruses with a simple structure but can cause significant disease in their hosts.

Taxonomy

  • Order: Picornavirales
  • Family: Nodaviridae
  • Genera:
    • Alphanodavirus (infects insects)
    • Betanodavirus (infects fish)

Key Characteristics

  • Genetic Material: Positive-sense single-stranded RNA (ssRNA).
  • Capsid: Non-enveloped, icosahedral structure, around 30 nm in diameter.
  • Genome: Approximately 12.3 kb, comprising two segments (RNA1 and RNA2).

Life Cycle

  1. Attachment and Entry: The virus attaches to host cell receptors and enters the cell through endocytosis.
  2. Replication: In the cytoplasm, RNA-dependent RNA polymerase (encoded by RNA1) replicates the viral genome.
  3. Gene Expression: RNA2 encodes the capsid protein, which assembles into new virions.
  4. Assembly and Release: New virions are assembled and released from the host cell, often causing cell lysis.

Behavior and Ecology

  • Host Range: Primarily fish and insects, with each genera adapted to specific host types.
  • Transmission: Horizontal transmission through contaminated water or tissue (Betanodavirus) and through direct contact or environmental contamination (Alphanodavirus).

Notable Species

  • Nervous necrosis virus (NNV) - Causes viral nervous necrosis in fish.
  • Flock House virus (FHV) - Model organism for studying RNA virus replication in insects.

Conservation

Nodaviridae does not require conservation efforts as they are viruses and often detrimental to their host populations.

Significance to Humans

  • Aquaculture Impact: Betanodaviruses can cause severe economic losses in fish farming due to high mortality rates in affected fish.
  • Research Importance: Nodaviruses, particularly Flock House virus, are used extensively in research to understand virus-host interactions and RNA virus replication.

Fun Facts

  • Particles per Cell: A single infected cell can produce thousands of new virus particles.
  • Model System: Flock House virus is a classic model for studying non-enveloped RNA viruses.
  • Temperature Resilience: Some nodaviruses can remain infectious in aquatic environments for several days even at lower temperatures.
  • Genome Economy: Despite their small genome, nodaviruses effectively hijack host machinery for replication and assembly.