Rabies

• • Viral (ssRNA rhabdovirus) encephalitis of mammals transmitted through the saliva of an infected animal

  • Humans are usually inoculated by the bite of a rabid bat, raccoon, skunk, fox, or other wild animal

  • Modes of transmission include mucous membranes (eyes, nose, mouth), aerosolization, and corneal transplantation

  • After local (primary) infection, the virus enters peripheral nerves and is transported to the CNS, making it difficult to detect (eclipse phase)

  • Subsequent incubation period varies in humans from several days to typically 1-3 months

Epidemiology

• • 30% of victims have no memory or evidence of a bite

  • Only 4 of 8513 reported cases were in humans (1997)

  • Death rate: 1-4 deaths per year

Symptoms and Signs

• • Clinical symptoms begin with pain and numbness around the site of the wound

  • Nonspecific flu-like symptoms of fever, irritability, malaise, and progressive cerebral dysfunction

  • Delirium, hallucinations, insomnia, paralysis, and convulsions occur terminally

Laboratory Findings

• • Direct fluorescent antibody (dFA) test on brain tissue is used most frequently to diagnose rabies in animals

  • No single test can rule out rabies absolutely

  • Serum and cerebrospinal fluid (CSF) are tested for antibodies

  • Skin biopsy is examined by dFA

  • Saliva can be tested by nested reverse transcription polymerase chain reaction (RT-PCR)

• • Rabies virus has distinctive bullet shape and nonsegmented, negative-stranded RNA genome

  • After local (primary) infection, the virus enters peripheral nerves and is transported to the CNS, making it difficult to detect (eclipse phase)

  • Subsequent incubation period varies in humans from several days to typically 1-3 months

• • Information useful in determining the risk of potential rabies infection includes:

  • -Geographic location of the incident

    -Type of animal involved

    -How the exposure occurred

    -Vaccination status of the animal

    -Whether the animal can be safely captured and tested for rabies

  • Test serum and CSF for antibodies

  • Skin biopsy

  • Saliva tested with RT-PCR

  • Suspected cases of rabies: Contact public health department

  • Any animal suspected of being rabid should be killed and its brain studied with a rabies-specific fluorescent antibody

• • Since the established disease is almost invariably fatal, early preventive measures are essential

  • Wound should be washed thoroughly with soap and water

  • Before exposure, rabies vaccine prophylaxis

  • After exposure, vaccine plus immune globin

Surgery

Medications

• • Human rabies immune globulin

  • Human diploid cell vaccine

Complications

• • Established disease is almost invariably fatal

Prognosis

• • Most human deaths occur in people who fail to seek medical assistance

Prevention

• • Wound should be washed thoroughly with soap and water

  • Rabies prophylaxis has proved nearly 100% successful