Rabies

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

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

Introduction

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.

Epidemiology

Researchers estimate that 30,000 to  70,000 deaths are attributable to rabies each year. 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.

Characteristics/Clinical Presentation

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 and occurs 2-10 days after exposure and can last up to 2 weeks. 
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.

Etiology

Rabies is a zoonotic disease and is caused by a virus that can live in the saliva of most mammals.  The most common cause of transmission to another mammal is by way of a bite from the infected one.  It can also be transmitted through the mucous membranes by way of airborne particles.  Both humans and animals can be infected by this disease which will lead to death if not properly treated before symptoms begin to show.  Once the symptoms begin to present themselves, the prognosis is very poor.  Once the virus enters the body, it travels along the nerves to the CNS producing inflammation.  Symptoms usually develop in about ten days but can take seven months or longer after exposure.  The disease can progress very rapidly and only lasts two to twelve days before death occurs.

Systemic 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.

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