Rabies

1. Rabies Lecture 6 Dr. Paul Bartlett, MPH., DVM., Ph.D.

2. 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.

3. 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.)

4. 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

5. 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.

6. 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 < 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.

8. 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.

9. Have virus: CNS fluid, saliva, nervous tissue Don’t have virus: milk, urine, feces, muscle

10. Dumb Rabies?

11. Furious Rabies?