Rabies

Original Editors - Deric Parrish from Bellarmine University's Pathophysiology of Complex Patient Problems project.

Top Contributors - Deric Parrish, Lucinda hampton, Kim Jackson, Admin, Elaine Lonnemann, WikiSysop, Vidya Acharya, 127.0.0.1 and Wendy Walker   

Introduction

Human with rabies.

Rabies is a vaccine-preventable, zoonotic, viral disease. Dogs are the source of the most rabies virus transmissions, through bites or scratches, usually via saliva. When clinical symptoms appear, rabies is virtually 100% fatal.

Rabies elimination is feasible through vaccination of dogs, prevention of dog bites and ensuring universal access to post-exposure immunization.

Epidemiology

Dog bite, usual route of transmission

Researchers estimate that 30,000 to  70,000 deaths are attributable to rabies each year. As noted by many in the past, human rabies deaths is only an estimate as it remains underreported

Rabies exists on all continents, except Antarctica, with over 95% of human deaths occurring in the Asia and Africa regions. Rabies predominantly affects poor and vulnerable populations who live in remote rural locations, with around 80% of human cases occur in rural areas. Globally, rabies deaths are rarely reported and children between the ages of 5–14 years are frequent victims.

Etiology

After being exposed to an infected animal's saliva, rabies's first symptoms usually appear within 2 to 3 months however they may appear anywhere from 5 days to a year after exposure. Once the virus enters the body, it travels along the nerves to the CNS producing inflammation. The time from exposure to a person showing symptoms depends on many aspects, examples being the amount of virus entering the body, the size of the wound, or how close the wound is to the brain.

Characteristics/Clinical Presentation

After being exposed to an infected animal's saliva, rabies's first symptoms usually appear within 2 to 3 months however they may appear anywhere from 5 days to a year after exposure. The time from exposure to a person showing symptoms depends on many aspects, examples being the amount of virus entering the body, the size of the wound, or how close the wound is to the brain.

Clinically, it has two forms:

1. Furious rabies is the most common with symptoms consisting of hydrophobia, hyperactivity, hallucinations and pharyngeal spasms leading to paralysis, coma and death. 
2. Paralytic rabies is less common and presents as paralysis leading to death. 

There are five stages of the disease:

1. Incubation phase which can range from 10 days to 2 years. 
2. Prodrome stage in which flu-like symptoms may be present.
3. Acute neurological symptom stage where more CNS involvement is noted with symptoms such as diplopia, dysarthria, nystagmus, mild to moderate paralysis, confusion, anxiety, paranoia, insomnia, hallucinations or delerium.  Excessive saliva, difficulty swallowing and fear of water and other liquids can also present in this stage of the disease. 
4. Coma
5. Death.

Nervous System Involvement

Rabies causes inflammation of the CNS once it enters the body and can quickly lead to death if not aggressively treated.  Pain, burning or numbness at the site of infection can be among the first symptoms to present.  Complaints of headache and sleeplessness are also reported.  Muscle spasms in the throat can make it difficult to swallow especially at the sight of water for some infected individuals which is known as hydrophobia.  In later stages of the inflammation, unconsciousness, respiratory and cardiovascular failure can occur and lead to death.

Treatment

There is no effective treatment for rabies.

• Because the disease caused by rabies is nearly always lethal, anyone potentially exposed should have the post-exposure vaccination, if required (including people who may be allergic and women who are pregnant or breastfeeding).
• A course of rabies vaccine is needed after potential exposure and if needed, administration of human rabies immunoglobulin. The vaccine stimulates the immune system to produce antibodies that destroy the virus before it has time to cause an illness.
• Wound care: immediately wash the wound thoroughly. If available, after washing, an antiseptic with anti-virus action such as povidone-iodine or alcohol (ethanol).

Elimination

The goal and approaches to eliminate rabies, a disease with clear transmission dynamics, although well-accepted, are not successful to date. Rabies elimination is achievable through vaccination of dogs, prevention of dog bites and securing universal access to post-exposure immunization. This requires a whole-of-system approach with a multisectoral interventions and community engagement.