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Recommendations for use of passive and active immunization after exposure to an animal suspected of having rabies have been detailed by the US Public Health Service Immunization Practices Advisory Committee (ACIP).
Every exposure to possible rabies infection must be individually evaluated. The following factors should be considered before specific antirabies treatment is initiated:
Species of Biting Animal: Carnivorous wild animals (especially skunks, foxes, coyotes, raccoons and bobcats) and bats are the animals most commonly infected with rabies and have caused most of the indigenous cases of human rabies in the United States since 1960. Unless the animal is tested and shown not to be rabid, post-exposure prophylaxis should be initiated upon bite or non-bite exposure to these animals (see Type of Exposure). If treatment has been initiated and subsequent testing in a competent laboratory shows the exposing animal is not rabid, treatment can be discontinued.
In the United States, the likelihood that a domestic dog or cat is infected with rabies varies from region to region; hence, the need for post-exposure prophylaxis also varies. However, in most of Asia and all of Africa and Latin America, the dog remains the major source of human exposure; exposures to dogs in such countries represent a special threat. Travelers to those countries should be aware that >50% of the rabies cases among humans in the United States result from exposure to dogs outside the United States.
Rodents (eg, squirrels, hamsters, guinea pigs, gerbils, chipmunks, rats and mice) and lagomorphs (including rabbits and hares) are rarely found to be infected with rabies and have not been known to cause human rabies in the United States. However, from 1971 through 1988, woodchucks accounted for 70% of the 179 cases of rabies among rodents reported to CDC. In these cases, the state or local health department should be consulted before a decision is made to initiate post-exposure antirabies prophylaxis.
Circumstances of Biting Incident: An unprovoked attack is more likely to mean that the animal is rabid. (Bites during attempts to feed or handle an apparently healthy animal may generally be regarded as provoked.)
Type of Exposure: Rabies is transmitted only when the virus is introduced into open cuts or wounds in skin or mucous membranes. If there has been no exposure, post-exposure treatment is not necessary. Thus, the likelihood that rabies infection will result from exposure to a rabid animal varies with the nature and extent of the exposure. Two categories of exposure should be considered:
Bite: Any penetration of the skin by teeth. Bites to the face and hands carry the highest risk, but the site of the bite should not influence the decision to begin treatment.
Bat-associated strains of rabies can be transmitted to humans either directly through a bat's bite or indirectly through the bite of an animal previously infected by a bat. Because some bat bites may be less severe, and therefore more difficult to recognize than bites inflicted by larger mammalian carnivores, rabies post-exposure treatment should be considered for any physical contact with bats when bite or mucous membrane contact cannot be excluded.
Non-Bite: Scratches, abrasions, open wounds or mucous membranes contaminated with saliva or any potentially infectious material eg, brain tissue, from a rabid animal constitute non-bite exposures. If the material containing the virus is dry, the virus can be considered non-infectious. Casual contact eg, petting a rabid animal and contact with blood, urine or feces (eg, guano) of a rabid animal, does not constitute an exposure and is not an indication for prophylaxis. Instances of airborne rabies have been reported rarely. Adherence to respiratory precautions will minimize the risk of airborne exposure. The only documented cases of rabies from human-to-human transmission have occurred in patients who received corneas transplanted from persons who died of rabies undiagnosed at the time of death. Stringent guidelines for acceptance of donor corneas have reduced this risk.
Bite and non-bite exposures from humans with rabies theoretically could transmit rabies, although no cases of rabies acquired this way have been documented.
Vaccination Status of Biting Animal: A properly immunized animal has only a minimal chance of developing rabies and transmitting the virus.
Presence of Rabies in Region: If adequate laboratory and field records indicate that there is no rabies infection in a domestic species within a given region, local health officials are justified in considering this in making recommendations on antirabies treatment following a bite by that particular species. Such officials should be consulted for current interpretations.
Rabies Post-Exposure Prophylaxis: The following recommendations are only a guide. In applying them, take into account the animal species involved, the circumstances of the bite or other exposure, the vaccination status of the animal, and presence of rabies in the region. Local or state public health officials should be consulted if questions arise about the need for rabies prophylaxis.
Local Treatment of Wounds: Immediate and thorough washing of all bite wounds and scratches with soap and water is perhaps the most effective measure for preventing rabies. In experimental animals, simple local wound cleansing has been shown to reduce markedly the likelihood of rabies.
Tetanus prophylaxis and measures to control bacterial infection should be given as indicated.
Active Immunization: Active immunization should be initiated as soon as possible after exposure (within 24 hrs). Many dosage schedules have been evaluated for the currently available rabies vaccines and their respective manufacturer's literature should be consulted.
Passive Immunization: A combination of active and passive immunization (vaccine and immune globulin) is considered the acceptable post-exposure prophylaxis except for those persons who have been previously immunized with rabies vaccine and who have documented adequate rabies antibody titer. These individuals should receive vaccine only. For passive immunization, rabies immune globulin (human) is preferred over antirabies serum, equine. It is recommended both for treatment of all bites by animals suspected of having rabies and for non-bite exposure inflicted by animals suspected of being rabid. Rabies immune globulin (human) should be used in conjunction with rabies vaccine and can be administered through the 7th day after the 1st dose of vaccine is given. Beyond the 7th day, rabies immune globulin (human) is not indicated since an antibody response to cell culture vaccine is presumed to have occurred.
(See table.)
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