Lecture 14 - Rabies viruses: Transmission, pathogenisis and prevention

What type of virus is Rabies Virus (RABV)?

A zoonotic virus from the Lyssavirus genus; it causes fatal encephalitis in mammals.

What is the primary mode of rabies virus transmission to humans?

Through saliva from bites or scratches by infected animals.

What is the fatality rate of rabies after symptom onset?

Approximately 99.9% fatal once symptoms appear.

What animals are common reservoirs for rabies worldwide?

Dogs, bats, raccoons, skunks, foxes, coyotes, and cats.

What is a zoonotic disease?

A disease that can be transmitted between animals and humans.

What is the first step in RABV infection after a bite?

The virus enters muscle tissue near the bite and begins replication at the site of bite

How does rabies virus travel to the brain?

Via peripheral nerves and up the spinal cord.

What is the incubation period for rabies?

Ranges from a few days to several years, depending on bite location and viral load.

Why are children at higher risk for rabies?

They’re more likely to approach animals and less likely to report bites.

What leads to death in rabies cases?

Progressive inflammation of the brain and spinal cord.

When is rabies treatable in humans?

Only before the onset of symptoms.

How quickly do rabid animals usually die after symptoms appear?

Within 1 week.

Who developed the first rabies vaccine and when?

Louis Pasteur in 1885.

What immune cells are suppressed in rabies infections?

T-cells infiltration is limited and T cell inactivation is promoted (systemic immunosuppression). Also inhibition of INF signalling

What was a drawback of early rabies vaccines?

Required 21–25 painful abdominal injections and had safety issues.

What does modern rabies post-exposure prophylaxis include?

Human rabies immune globulin (HRIG) + inactivated rabies vaccine.

Why is post-exposure prophylaxis (PEP) ineffective after symptoms appear?

Because the virus has already reached the CNS and caused irreversible damage.

Do bats usually get sick from rabies?

No, they rarely show symptoms.

Why do bats rarely show symptoms of rabies?

They have adapted immune responses, including constitutive IFN-α expression

Why are bats such effective viral reservoirs?

Long evolutionary history, immune tolerance, social behavior, echolocation, long lifespan.

How might bat echolocation contribute to viral spread?

Vibrations of the larynx can aerosolize virus particles.

What feeding behavior in bats can spread viruses?

Chewing and spitting out food covered in saliva, which other animals may ingest.