Rhabdoviruses

• Rhabdoviruses

  • Single-stranded RNA viruses
  • Enclosed within bullet-shaped capsid
  • 75x180nm
  • Viral matrix protein forms a layer on the inner side of the envelope
  • Viral glycoprotein is on the outer layer and forms the spikes or projections
• Rhabdovirus genera

  • Lyssavirus genus e.g. Rabies
  • Vesiculovirus genus e.g. Vesicular stomatitis virus
• Rabies is the only medically important member of the Rhabdovirus family
• Rabies

  Has a broad host range - can infect all mammals
• Rabies virus

  Produces acute infection of the CNS which is almost always fatal
• Vampire bats transmit infection without showing disease for months
• Domestic animals particularly susceptible to rabies

  • Dogs
  • Cats
  • Cattle
• Virus widely distributed in infected animals, especially urine, lymph, milk, etc.
• Virus can be propagated in tissue cultures, chorioallantoic cavity of chick and duck eggs
• STREET strain

  Virus freshly isolated in the lab
• Virus may invade the salivary glands & CNS when injected into animals
• Rabies has a long and variable incubation period in dogs (21-60 days)
• Rabies produces intracytoplasmic inclusion-Negri bodies in the infected nerve cells
• Multiple passage in embryonated eggs or brain to brain in rabbits will produce attenuated strain-FIXED strain
• Fixed strain serves as a source of vaccine production
• Rabies virus does not multiply in extraneural tissues
• Rabies virus can survive storage at 4C for weeks but is inactivated by CO2
• Freeze dried powdered form of rabies virus can be stored at 4C for years
• Rabies virus is killed by UV or sunlight or heat at 50C for 1 hour
• Infectivity of rabies virus is destroyed by lipid solvents, trypsin, detergents, and propiolactone
• Pathogenesis of Rabies Virus

  1. Transmitted through saliva by the bite of a rabid animal

  2. Multiplies locally at the bite site

  3. Enters peripheral nerves at neuromuscular junctions

  4. Spreads up the nerves to CNS
• Pathogenesis of Rabies Virus

  1. Multiplies in the CNS

  2. Progressive encephalitis develops

  3. Travels down the peripheral nerves to salivary glands and other organs

  4. Enters the saliva from the salivary glands
• Other organs where rabies virus has been found

  • Pancreas
  • Kidney
  • Heart
  • Retina
  • Cornea
• Highest titre of rabies virus is in the sub-maxillary salivary glands
• Within CNS, encephalitis develops with death of neurons and demyelination
• Negri bodies are found in the Ammon's horn of the brain as cytoplasmic inclusions
• Incubation period of rabies varies from 2 weeks to 16 weeks or more
• Shorter incubation period


  When bites are sustained on the head rather than on the leg
• Clinical spectrum of rabies

  • Short prodromal phase
  • Acute neurological phase
  • Clinical rabies: furious or dumb rabies
• Prodromal Phase of Rabies

  1. Lasts for 2-10 days

  2. Non-specific symptoms of malaise, anorexia, headache, nausea, vomiting, fever

  3. Abnormal sensation around wound site
• Acute Neurologic Phase of Rabies

  1. Patient shows signs of nervous system dysfunction

  2. Nervousness, apprehension, and hallucination

  3. General sympathetic over-activity including increase in salivation, dilation of pupils, perspiration
• Clinical Rabies - Furious Rabies

  80% of all cases<|>Hydrophobia is the symptom most identified with furious rabies
• Hydrophobia


  An aversion to swallowing water because it is so painful
• Hydrophobia is due to the painful spasm of the throat muscles on swallowing water or even saliva
• Convulsive seizures, coma, and death occur 2-7 days after onset of furious rabies
• Major cause of death in furious rabies is respiratory paralysis
• Clinical Rabies - Paralytic Dumb rabies

  Patient lacks hydrophobia<|>No seizures<|>Paresis in all limbs - incomplete loss of muscular power<|>Patient becomes confused and then comatose
• Laboratory Diagnosis methods for Rabies

  • Rabies antigen or nucleic acid detection
  • IF for Negri bodies
  • RT-PCR
  • Virus isolation (saliva, spinal fluid, skin biopsies)
  • Intracerebral inoculation of suckling mice with tissue material
• Laboratory Diagnosis: Ag detection

  1. Immunofluorescence or immunoperoxidase staining using antirabies monoclonal antibodies

  2. Biopsy from skin of the neck at the hairline

  3. Impression preparation of brain or cornea
• Laboratory Diagnosis: NA detection

  1. RT-PCR

  2. Fixed or unfixed brain tissue