RHABDOVIRIDAE: RABIES VIRUS

• STRUCTURE: ss (-) RNA, helical capsid, enveloped, bullet-shaped.

  • Transcriptase, RNA-dependent RNA Polymerase is present.

• REPLICATION: Cytoplasmic.

  • Primary transcription ------> genome replication ------> more transcription and translation occur post-replication.

  • Nucleocapsids bud through host cell-membrane to form new particles.

• EPIDEMIOLOGY:

  • Racoons are the most common animal carrier today.

  • Bats are most common carrier in U.S. to actually result in infection.

  • Also skunks, wild mammals, and unvaccinated domestic mammals.

• DIAGNOSIS: Look for Negri bodies in the animal tissue.

• MANIFESTATIONS:

  • PATHOGENESIS:

    • Virus replicates in striated muscle at site of bite. Then it travels up nerve endings to spinal cord and brain.

    • Virus hooks to Acetylcholine receptors at neuromuscular junction.

  • Symptoms: Fatal encephalitis. Hypertonic muscle contraction, convulsions, coma, death.

    • Hydrophobia happens as swallowing would precipitate a spasm of throat muscles.

• TREATMENT: No treatment known.

  • PREVENTION: Post-exposure immunization, both passive and active, should be given prophylactically in cases of possible infection.

    • Human Rabies Immune Globulin (HRIG) administered on same day as first vaccine dose, but at a different site.

    • Human Diploid Cell Vaccine (HDCV) is the new active vaccine (inactivated virus), grown in human diploid fibroblast cells. Given in 6 doses.

Category: Microbiology Notes