Rabies

Key Features

• History of animal bite 10 days to 1 year (usually < 90 days) previously

• Paresthesias or hyperesthesia in bite area

• Progressive limb and facial weakness in some patients (dumb rabies; 30%)

• Irritability followed by fever, confusion, combativeness, muscle spasms (especially pharyngeal with swallowing) in all patients (furious rabies)

• Rabies antigen detected in corneal scrapings or tissue obtained by brain or skin biopsy; Negri bodies seen in brain tissue

Clinical Findings

• Paresthesia at the bite site is usually the first symptom

• Nonspecific anxiety, excitability, or depression follows, then muscle spasms, drooling, hydrophobia, delirium, and lethargy

• Swallowing or even the sensation of air blown on the face may cause pharyngeal spasms

• Seizures, fever, cranial nerve palsies, coma, and death follow within 7–14 days after onset

Diagnosis

• Leukocytosis is common

• CSF is usually normal, but may show elevation of protein and mononuclear cell pleocytosis

• Cerebral imaging and electroencephalography are not diagnostic

• Infection in an animal may be determined by use of the fluorescent antibody test to examine brain tissue for antigen

• Classic Negri cytoplasmic inclusion bodies in brain tissue are not always present

• Seroconversion measured by neutralizing antibody occurs after 7–10 days and clinical recovery has been associated with detection of neutralizing antibody and clearance of infectious rabies virus in the central nervous system

Treatment

• Survival is very rare but has been reported in a very small number of patients receiving meticulous intensive care and the Milwaukee protocol that focuses on the altered central nervous system metabolic state

• Early diagnosis is important for the protection and postexposure prophylaxis of patient contacts