In the latest Case Record of the Massachusetts General Hospital, a 63-year-old man was admitted to this hospital because of paresthesias, difficulty drinking liquids, and anxiety. Diagnostic procedures were performed.
In 2011 in Massachusetts, 110 animals with rabies were identified. Bats accounted for 20 (18%) of the animals that tested positive. Most of the bats with rabies were identified in the summer and early fall.
• What is the classic presentation of tetanus?
Patients who have tetanus present with muscle rigidity (with early involvement of the masseter and facial muscles) and can have laryngospasm, which can cause difficulty swallowing. Trismus and spasms of deglutition muscles may result in difficulty with swallowing and verbal expression. Patients with tetanus commonly have autonomic instability and a hyperadrenergic state, and the disease can occur after an animal bite.
• What is the principal means of rabies transmission in the United States?
Although a dog bite is responsible for most rabies infections in humans in the developing world, bats are responsible for most infections in humans in the United States. Transmission is usually through a bite, which is often unrecognized. Rabies can also be transmitted by aerosolized exposure, which could occur in a cave with a very large density of bats, and there have also been reports of the transmission of rabies in association with organ or tissue transplantation.
Morning Report Questions
Q: What are the clinical manifestations of rabies?
A: Disease progression occurs in five stages: incubation, prodrome, acute neurologic phase, coma, and death (or, rarely, survival). There are two varieties of rabies: encephalitic (or “furious,” accounting for 80% of cases) and paralytic (or “dumb,” accounting for 20% of cases). The prodrome may last a few days to weeks. Signs and symptoms that commonly occur in the encephalitic phase of rabies include hyperexcitability, agitation, and hydrophobia, which is a fear of swallowing liquids. Hydrophobia is unique to rabies, and conditioning can occur, in which the sight of liquids can trigger laryngeal, pharyngeal, or diaphragmatic spasms. Aerophobia, or fear of air, may also be observed, in which the force of air on the face or airway can trigger spasms. In addition, hallucinations and excessive salivation may occur in this phase of infection. Death typically occurs within 5 days after infection. Autonomic dysfunction is common, with hypertension, cardiac dysrhythmias, priapism, sweating, and fever.
Q: What treatment strategies for rabies exist?
A: Postexposure prophylaxis is highly efficacious, but once rabies encephalitis has begun, there is, unfortunately, no proven treatment, and the mortality rate approaches 100%. Therefore, for most patients with symptomatic rabies, the standard of care is palliation. The Milwaukee protocol is a strategy developed to minimize brain injury while allowing the patient’s immune response to eradicate the virus. Key features of the protocol are sedation and other supportive measures designed to suppress brain activity and minimize injury from catecholamine storm and cerebral vasospasm. In addition, it is important to avoid the administration of glucocorticoids, rabies IgG, and the rabies vaccine in patients. There is no good evidence to support the use of the protocol, although there are no other reasonable alternatives outside of palliative care. This protocol should be considered only for persons early in the course of symptomatic disease who are otherwise in good health. It is critically important that patients and family members understand that this approach is unlikely to be successful and that there is a high risk of neurologic sequelae if the patient survives.