NS06 - Rabies

Biomedical Sciences III

What family does the Rabies virus belong to?

Rhabdoviridae

What type of genome does the Rabies virus have?

Single-stranded RNA (−)

What is the shape of the Rabies virus?

Bullet-shaped

How many proteins does the Rabies virus encode?

Five proteins

What are Negri bodies?

Inclusion bodies made of nucleocapsids found in the brain post-mortem in Rabies infection

What is the primary mode of transmission for Rabies?

Bite or scratch from an infected animal.

What are other modes of Rabies transmission?

Scratches, abrasions, mucosal exposure, organ transplants, aerosolized virus in caves.

Why do bats account for most Rabies transmission in the U.S.?

Bat bites or scratches often go unnoticed, and bats are common carriers.

What animals are the most common sources of Rabies in the U.S.?

Bats (31%), raccoons (29%), skunks (25%)

What animals account for most Rabies cases worldwide?

Dogs

What happens in animals infected with Rabies?

Brain infection, behavioral changes, aggression, biting, virus spreads to saliva.

What is the pathogenesis in humans?

Virus replicates at bite site, enters peripheral nerves, travels retrograde to brain, causes encephalitis, spreads to salivary glands, eyes, skin, heart.

What blocks the spread of Rabies virus to the CNS?

Antibody response, but only after clinical disease begins (it is too late at that point)

What role does cell-mediated immunity play in Rabies?

Minimal role in protection (once it begins the disease has spread too much for the antibodies to help)

What is the incubation period for Rabies?

30 days to >1 year, depending on inoculum size, site of infection (distance from brain), severity, age, and immune status.

What are the prodrome symptoms of Rabies?

Paresthesias (numbness/pins and needles), fever, malaise, anorexia, nausea, vomiting.

What are the neurologic symptoms of Rabies?

Hallucinations, disorientation, seizures, agitation, hydrophobia, flaccid paralysis.

What causes hydrophobia in Rabies patients?

Spasms of throat and respiratory muscles triggered by swallowing or sight of fluids.

What is the outcome once Rabies symptoms appear?

Almost always fatal within days.

Who should receive pre-exposure prophylaxis?

Veterinarians, lab workers, spelunkers.

How are wild mammals immunized?

Vaccinia virus expressing Rabies protein in bait dropped into forests.

What should be done after contact with a bat?

Seek medical attention, even if no bite is evident.

What are the steps in Rabies PEP?

Wound cleaning, HRIG injection, Rabies vaccine.

How is HRIG administered?

Injected into and around the wound, separate from vaccine site.

What is the Rabies vaccine schedule for PEP?

Days 0, 3, 7, 14, and Day 28 for immunocompromised.

(Usually 4 shots)

How effective is Rabies PEP?

Nearly 100% effective if given before symptoms appear.

What is the cost of Rabies PEP?

Approximately $3,000–$4,000