Rabies Virus Animation : Pathogenesis, Clinical manifestations, Diagnosis & Treatment | USMLE Step 1

Summary

This video provides an in-depth overview of rabies, a deadly viral infection that affects the central nervous system of humans and animals. It details the rabies virus, its transmission through bites or saliva, and its progression from initial infection to severe neurological damage. The video explains the two primary forms of rabies, furious and paralytic, and highlights the low survival rate. Diagnostic methods and postexposure prophylaxis, including vaccination and immunoglobulin treatment, are also discussed, emphasizing the importance of early intervention. Additionally, the video covers risk categories for rabies exposure and the preventive measures for high-risk groups.

Takeaways

• 😀 Rabies is a virus belonging to the rabdoviridae family, characterized as bullet-shaped and enveloped with a single-stranded RNA structure.
• 😀 The rabies virus measures 180 nm in length and 75 nm in width, with a speed of 3 mm per hour for its spread.
• 😀 Rabies is transmitted primarily through animal bites, most commonly from dogs, but can also be contracted from saliva or aerosol exposure from infected animals.
• 😀 The incubation period of rabies ranges from 20 to 90 days, and the virus spreads to the central nervous system (CNS) via neurons.
• 😀 Rabies enters the body through a bite, binds to acetylcholine receptors in muscle cells, but prefers neurons for replication, traveling through axons to the spinal cord and brain.
• 😀 Rabies manifests in two forms: furious (80% of cases) and paralytic (20% of cases), with symptoms like hyperexcitability, autonomic dysfunction, and hydrophobia in furious rabies.
• 😀 The disease progresses rapidly, often leading to coma and death, with extremely low survival rates.
• 😀 Laboratory diagnosis of rabies includes antigen detection via immunofluorescence, RNA detection using PCR, and postmortem detection of Negri bodies.
• 😀 Postexposure prophylaxis (PEP) includes wound care and the administration of rabies vaccines and immunoglobulin, typically given on days 0, 3, 7, 14, and 28.
• 😀 Vaccines available for rabies include purified chick embryo cell vaccine, purified Vero cell vaccine, and human diploid cell vaccine.
• 😀 Rabies risk is categorized into three classes: Class 1 (no risk, no treatment needed), Class 2 (minor risk, start postexposure prophylaxis), and Class 3 (major risk, immediate postexposure prophylaxis and immunoglobulin required).

Q & A

What family does the rabies virus belong to?

The rabies virus belongs to the family Rabdoviridae.

What is the shape and size of the rabies virus?

The rabies virus is bullet-shaped and measures approximately 180 nanometers in length and 75 nanometers in width.

How does the rabies virus replicate in the body?

The rabies virus enters the body via an animal bite, binds to acetylcholine receptors at the neuromuscular junction, enters neurons, and travels within axons to the central nervous system via retrograde transport.

What is the most common form of rabies in humans?

The most common form of rabies in humans is Furious rabies, which accounts for 80% of cases. It is characterized by hyperexcitability, autonomic dysfunction, and hydrophobia.

What is paralytic rabies and how does it progress?

Paralytic rabies, also known as dumb rabies, accounts for 20% of cases and leads to progressive paralysis. It can result in a coma and eventual death.

What is the survival rate for rabies infection?

The survival rate for rabies infection is extremely low, with the disease often leading to death once clinical symptoms appear.

How is rabies diagnosed in the laboratory?

Rabies can be diagnosed in the laboratory by antigen detection using direct immunofluorescence, RNA detection through reverse transcription polymerase chain reaction, and histopathological detection of Negri bodies in brain biopsies.

What is the typical post-exposure prophylaxis treatment for rabies?

Post-exposure prophylaxis for rabies includes local wound care and the administration of the rabies vaccine and rabies immunoglobulin. The vaccination schedule is on days 0, 3, 7, 14, and 28.

What is the difference between street and fixed rabies virus?

The street virus causes natural or Furious rabies and includes hydrophobia and Negri bodies. The fixed virus causes dumb rabies and is used in vaccine production, lacking hydrophobia and Negri bodies.

How is rabies risk categorized in post-exposure prophylaxis?

Rabies risk is categorized into three classes: Class 1 (no risk) requires no treatment; Class 2 (minor risk) requires post-exposure prophylaxis; and Class 3 (major risk) involves facial bites, constant bleeding, or wild animal bites, requiring both prophylaxis and immunoglobulin.