– An acute, viral, infectious, communicable disease of the central nervous system characterized by central nervous system (CNS) irritation, paralysis, and death.
Causes and Incidence
The causative agent is a neurotropic rhabdovirus that is often present in the saliva of infected animals and is usually transmitted to humans through the bite of a rabid animal. Dogs are the most common source of infection, but bats, raccoons, skunks, foxes, cats, and cattle are all known to carry rabies. Rabies is fairly rare in the United States, where vaccination has largely eliminated canine rabies. Rabid dogs are prevalent in Latin America, Africa, and Asia, where they are a health risk to humans.
The virus travels from the site of entry via the peripheral nerves to the spinal cord and brain, where it incubates for 10 days to 1 year. It then multiplies and travels from the CNS through the efferent nerves to many body tissues, including the salivary glands, saliva, urine, cerebrospinal fluid, corneal cells, and skin. It causes vessel engorgement, edema, and punctate hemorrhages in the meninges and the brain, and diffuse degenerative changes occur in the neurons of the brain and spinal cord. Negri bodies may be formed in the hippocampus or neurons in the cerebellum, cortex, and spinal cord.
Signs and symptoms manifest in three stages: a prodrome (lasts 1 to 10 days), acute neurologic or furious rabies (lasts 2 to 7 days), and paralytic or dumb rabies.
Itching, hyperesthesia, and pain radiating from the bite wound
Headache, nausea, fever, chills, apathy, malaise, anxiety, irritability, restlessness, depression
Agitation, excessive salivation, marked motor activity followed by laryngeal and pharyngeal spasms and dysphagia and hydrophobia; 1to 5minute periods of thrashing, hallucination, biting, seizures, and disorientation, followed by calm and lucidity; autonomic hyperactivity with supraventricular arrhythmias, deregulated blood pressure, and tachypnea
Progressive paralysis in an ascending fashion, with ensuing coma and death, usually within 12 days of symptom onset
Death is almost certain without prompt treatment. It is usually caused by fluid depletion and cardiovascular or respiratory collapse and may occur during the acute or paralytic stage.
Diagnosis is difficult in humans before the onset of symptoms, and virus isolation and antibody testing, although effective, may not prove positive until after the individual dies. An animal bite in humans should trigger immediate action. If the bite is from an apparently healthy domestic animal, the animal should be held for 10 days for observation in case of rabies symptoms. If the animal is rabid or suspected of being rabid, it should be killed immediately and its brain subjected to a fluorescent antibody test and viral isolation. If the bite is from a wild animal such as a skunk, raccoon, bat, fox, or other carnivore, the animal should be considered rabid unless it is available for testing and tests negative, or the geographic area is free of rabies.
Rabies vaccine (active immunity) and rabies immune globulin (passive immunity) administered prophylactically after a bite from an animal suspected of being or tested as rabid; preexposure vaccination should be considered for individuals at high risk for exposure to rabid animals (e.g., veterinarians, spelunkers, animal handlers, and laboratory workers who handle infected tissues).
Immediate cleansing of the wound with soap and water, flushing of deep puncture wounds as prophylaxis; once symptoms develop, treatment is supportive only to control respiratory, circulatory, and CNS damage; individual should be placed in isolation, and staff should use precautions in handling body secretions.