Rabies

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Rabies

• Lecture 6
• Dr. Paul Bartlett, MPH., DVM., Ph.D.

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Transmission

• The virus is typically transmitted by being
  deposited under the skin, usually through a bite
  wound.
• Contamination of a pre-existing wound is possible
  but unlikely because the local inflammatory
  reaction which follows a wound, quickly seals the
  comprised skin and prevents entry of the virus.
• Transmission across mucous membranes is also
  possible, but less likely than a bite wound.

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Aberrant Routes of Transmission

• A small number of human rabies cases have been
  reported following corneal transplants.
• This suggests that human rabies cases may be
  underreported.
• Aerosol (airborne) transmission of the virus has
  also been reported. However, this is possible
  only under unusual circumstances.
• Persons have contracted rabies presumably by
  airborne transmission after visiting bat caves
  (Frio Cave, Texas.)

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Survivability of the Rabies Virus

• The rabies virus is extremely short lived under
  most environmental conditions.
• It is easily inactivated by heat and drying.
• Capable of surviving for a few days in cold
  temperatures.
• Thorough and immediate washing of bite wounds
  with plenty of soap and water is the best
  preventative treatment for rabies

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Course of a Rabies Infection

• Once introduced, the rabies virus travels
  retrograde up the nerves to the spinal cord -
  eventually reaching the brain.
• From the brain, the virus spreads to the salivary
  glands.
• The incubation period is usually 6 to 8 weeks in
  humans but it may be longer.

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Viral Spreading in Animals

• In cats and dogs, the clinical symptoms usually
  begin before the virus is found in the saliva.
• Sometimes virus can be found one to three days
  before clinical symptoms in cats and three to
  five days in dogs. Ferrets is something lt 10
  days.
  
• No reliable information regarding the appearance
  of virus in the saliva is available for other
  animal species .
• There is some evidence that certain wildlife
  species, like skunks and bats, may excrete virus
  in their saliva for long periods before becoming
  ill.

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Terrestrial Reservoirs of Rabies

• Different terrestrial (non-bat) mammalian species
  are the rabies reservoirs in different parts of
  the country.
• Strains in the USA include - skunk, raccoon, fox,
  and coyote.
• For a given strain, only transmission within the
  host species is sufficiently successful to
  maintain the disease from year to year.
• This was observed before monoclonal antibody
  testing revealed that distinctly different
  strains of the virus were involved.

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Have virus CNS fluid, saliva, nervous tissue
Dont have virus milk, urine, feces, muscle
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Dumb Rabies?
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Furious Rabies?
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