Rabies immune globulin (RIG) and rabies vaccine are extremely effective for prophylaxis after exposure to rabies but are of no known benefit after symptoms appear. Because rabies is one of the deadliest infections, recognition of potential exposure and prophylaxis are crucial. Any healthy-appearing domestic animal responsible for an apparently unprovoked bite should be observed for 10 days for signs of rabies, without immediate treatment of the victim. Prophylaxis should be administered if the animal is rabid or suspected to be rabid, or if the animal develops signs of rabies while under observation. A captured wild animal should be euthanized (by animal control officials) without a period of observation and its brain examined for evidence of rabies. If the biting animal is not captured, particularly if it is a wild animal of a species known to harbor the virus in the region, rabies should be presumed and prophylaxis administered to the victim. Skunks, raccoons, foxes, woodchucks, most other carnivores, and bats are regarded as rabid unless proved negative by testing. Prophylaxis also should be provided following exposure to a bat for persons who might be unaware or unable to relate that a bite or direct contact has occurred, such as a mentally disabled person, a sleeping child, or an unattended infant.
All rabies postexposure management begins with immediate thorough cleansing of the bite using soap and water and, if available, irrigation with a virucidal agent such as povidone-iodine. RIG at a dose of 20 U/kg should be administered, with the full dose of RIG infiltrated subcutaneously into the area around the wound, if possible. Any remaining RIG that cannot be infiltrated into the wound should be administered as an intramuscular injection. Inactivated rabies vaccine should be administered simultaneously as soon as possible, with additional vaccine doses at 3, 7, and 14 days.
The selection of anti-infective therapy depends on a number of factors: the site of infection and clinical syndrome, host immunity, probable causative agents, the pathogen’s susceptibility to antimicrobial agents and the local epidemiology of resistance, the pharmacokinetics of the selected agents, and their pharmacodynamics in specific patient populations.
Empirical or presumptive anti-infective therapy is based on a clinical diagnosis combined with published evidence and experience of the probable causative pathogens. Definitive therapy relies on microbiologic diagnosis by isolation or other direct evidence of a pathogen. Microbiologic diagnosis permits characterization of the pathogen’s anti-infective drug susceptibilities and delivery of the appropriate anti-infective agent to the site of infection in concentrations sufficient to kill or alter the pathogen and facilitate an effective immune response. Antiviral therapy must include consideration of the intracellular nature of viral replication and, to avoid toxicity to host cells, must be targeted to viral-specific proteins, such as the thymidine kinase of herpesviruses or the reverse transcriptase of human immunodeficiency virus.
Empirical antimicrobial therapy is best initiated after obtaining appropriate cultures of fluids or tissues. In high-risk circumstances, such as neonatal sepsis or bacteremia in immunocompromised persons, empirical therapy includes broad-spectrum antimicrobials (see Chapters 96 and 120).
Empirical antimicrobial therapy may be tailored to specific pathogens based on the clinical diagnosis (e.g., streptococcal pharyngitis) or defined risks (e.g., close exposure to tuberculosis). Definitive therapy can additionally minimize drug toxicity, development of resistant microorganisms, and cost.