Rabies is a viral zoonotic disease typically acquired through the bite of an infected animal. Transmission via aerosolized virus has been documented in bat-infested caves and in laboratory workers. Human-to-human transmission has only been documented in transplant recipients. Infection can be prevented by preexposure or postexposure vaccination.
Rabies has the dubious distinction of having the highest case fatality rate of any infectious disease. It is a severe progressive encephalitis and presents in one of two forms. In 80% of cases, patients will develop the encephalitic (furious) form, with typical symptoms of fever, agitation, laryngeal spasms, severe pain on swallowing, hydrophobia, confusion, and a host of other neurologic signs and symptoms. Patients with the paralytic (dumb) form (20%) present with an ascending paralysis like Guillain-Barré syndrome. Patients with either form often have preceding paresthesias and pain at the exposure site, as well as a nonspecific prodromal phase lasting up to 1 week. Autonomic instability is seen in all patients prior to death. The diagnosis of rabies in developing countries is primarily clinical. Fluorescent antibody testing, biopsy, and PCR are done in areas where available.
Management and Disposition
Management of clinical rabies is traditionally palliative as the outcome has been uniformly fatal. Vaccination after development of clinical rabies is futile. Treatment in developing countries is usually limited to sedation with benzodiazepines and other comfort measures. Survival of several patients using the “Milwaukee protocol” has been reported. This uses an induced coma (midazolam and ketamine) with continuous electroencephalography (EEG) monitoring, antiviral agents (amantadine), and aggressive diagnosis and treatment of cerebral vasospasm. This regimen is considered experimental in the United States and is not practical in most developing countries.
Rabies. A 20-year-old Ugandan patient with furious rabies on the fourth day of clinical illness after a dog bite 2 months earlier. The neck is visibly swollen due to subcutaneous emphysema. The patient developed spontaneous pneumomediastinum due to forceful vomiting during a period of severe laryngeal spasms. (Photo contributor: Seth W. Wright, MD.)
Insect-eating bats cause most US rabies cases, but most patients are unable to recall a bite. Dog bites are the most common cause worldwide.
The shortest incubation periods are associated with extensive bites and bite wounds to the face and scalp.
Rabies vaccine and immunoglobulin are crucial in avoiding rabies following an exposure. They are, however, contraindicated after the onset of clinical rabies as they might lead to an alteration of the natural immune response.
Human-to-human transmission is extremely rare or nonexistent. Nevertheless, postexposure prophylaxis of close contacts is recommended as the virus is present in saliva.
A report from Peru has suggested the possibility of subclinical rabies disease in Amazon residents.
Rabies. Same patient on the sixth day, now unable to swallow ...