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

Transmission The virus is typically transmitted by being deposited under the skin, usually through a bite wound. 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. 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. Transmission across mucous membranes is also possible, but less likely than a bite wound.

Aberrant Routes of Transmission A small number of human rabies cases have been reported following corneal transplants. 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. 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.)

Survivability of the Rabies Virus The rabies virus is extremely short lived under most environmental conditions. 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 Thorough and immediate washing of bite wounds with plenty of soap and water is the best preventative treatment for rabies

Course of a Rabies Infection Once introduced, the rabies virus travels retrograde up the nerves to the spinal cord - eventually reaching the brain. 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. 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. The incubation period is usually 6 to 8 weeks in humans but it may be longer.

Viral Spreading in Animals In cats and dogs, the clinical symptoms usually begin before the virus is found in the saliva. 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. 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.

Terrestrial Reservoirs of Rabies Different terrestrial (non-bat) mammalian species are the rabies reservoirs in different parts of the country. 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. This was observed before monoclonal antibody testing revealed that distinctly different strains of the virus were involved.

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

Dumb Rabies?

Furious Rabies?