Rabies is a preventable viral mammalian disease that is usually transmitted through the bite of an infected animal.
The rabies virus infects the central nervous system, causing encephalopathy and death. The first symptoms of rabies in humans are non-specific and consist of fever, headache and general malaise. As the disease progresses, neurological symptoms appear and may include insomnia, anxiety, confusion, paralysis, excitement, hallucination, agitation, hyper-salivation, difficulty swallowing, and hydrophobia (fear of water). Death occurs within days of the onset of neurological symptoms such as hydrophobia.
Rabies transmission usually begins when infected saliva is passed to an animal without infection. Several transmission routes have been documented, the most common being through the bite and saliva of a contaminated animal. Following the primary infection, the virus enters the eclipse phase, which cannot be easily detected in the host. This phase can last for several days or months. Virus entry into the peripheral nerves is important for progressive infection to occur.
After the virus enters the peripheral nerves, it is transported to the central nervous system, usually via motor and sensory nerves. The incubation period is this time from exposure to the onset of clinical symptoms of rabies. The incubation period may vary from a few days to years, but usually lasts from 1 to 3 months. The spread of the virus within the central nervous system is rapid. During the period of brain infection the classic behavioral changes associated with rabies develop.
Signals and symptons
The first symptoms of rabies may be non-specific flu-like signs - malaise, fever or headache - which may last for days. There may be discomfort or paraesthesia (subjective skin sensations such as cold, heat, tingling, pressure) at the site of exposure (bite), progressing in days to symptoms of brain dysfunction, anxiety, confusion and agitation, progressing to delirium, abnormal behavior, hallucinations, hydrophobia and insomnia. Once clinical signs of rabies appear the disease is almost always fatal and treatment is typically supportive. Prevention of rabies is through vaccination.
Fluorescent direct antigen testing is most often used to diagnose rabies in animals. This test requires brain tissue from the animal suspected of having rabies and can only be done after death.
Human rabies diagnosis
Several tests are needed to diagnose rabies before death in humans and no single test is sufficient alone. The tests are done with saliva, spinal fluid, plasma and skin samples.
Bats and the anger
If a person is bitten by a bat - or if infectious material (such as saliva) from the bat enters the eyes, nose, mouth or injury - he or she should wash the affected area thoroughly and seek medical attention immediately. Whenever possible the bat should be captured and taken to the laboratory to test for rabies. People are not angry at contact with bat feces, blood or urine, or by touching their skin even though they should never be handled.