Rabies Prevention in Washington State: A Guide for Practitioners
Introduction | Clinical features | Epidemiology | Laboratory testing | Prevention | References

HOW TO EVALUATE ENCOUNTERS BETWEEN HUMANS
AND A POTENTIALLY RABID ANIMAL

When a person or domestic animal has encountered a potentially rabid animal, an evaluation is necessary to determine: 1) whether a true exposure occurred; and 2) whether the potentially rabid animal should be quarantined or tested for rabies.

1) Has a true exposure occurred? Encounters with a rabid animal can lead to rabies transmission when virus from the animal's saliva, brain tissue, or spinal fluid enters open cuts or wounds in skin or mucous membranes. Therefore, not every encounter with a rabid animal is a true exposure requiring intervention. Treatment is often provided unnecessarily to people who have encountered but had no true exposure to a potentially rabid animal.

Any penetration of the skin by an animal's teeth is considered a "bite exposure". Local wound care should be performed immediately on anyone bitten by an animal. A health care provider should be consulted to determine whether or not other measures are necessary. Animal bites are a notifiable condition in Washington and providers should report them to the local health department.

"Non-bite exposures" include any scratches, abrasions, or contamination of mucous membranes by an infected animal's saliva, brain tissue, or spinal fluid. Other types of contacts (such as with the blood, urine, feces, or fur of an animal) would not by themselves be considered exposures capable of transmitting rabies even if the animal were known to be rabid. The virus is not hardy; once dry, saliva containing rabies virus is considered non-infectious2.

Determining whether an exposure to a rabid bat occurred is often difficult. Bats are small and have small teeth (Figure 4), so their bites may be difficult to recognize. Providers should consider that an exposure may have taken place when there is reasonable probability that such contact unknowingly occurred (e.g., a sleeping person awakes to find a bat in the room or an adult witnesses a bat in the room with a previously unattended child, mentally disabled or intoxicated person, or incompletely vaccinated pet3). The presence of a bat inside a building is not by itself sufficient to result in rabies transmission. Questions about whether an encounter with a bat could constitute an exposure should be referred to the local health department.

fangs thumbnail Figure 4: The silver-haired bat. Click on the thumbnail to get the full picture.

If a true exposure occurred, the next question is:

2) Should the potentially rabid animal be quarantined or be tested? Whether to a) quarantine or to b) test an animal depends on whether a true exposure occurred and if so, the type of animal involved. These guidelines are derived from the Immunizations Practices Advisory Committee (ACIP) and the recommendations of National Association of State Public Health Veterinarians.

Dogs, cats, and ferrets: A dog (excluding dog-wolf hybrids), cat, or (as of 1997) ferret that has bitten, scratched, or otherwise exposed a human should be confined and observed for 10 days under local health department supervision, regardless of whether or not the animal is currently vaccinated. In most places in Washington, such an animal can be confined at home by its owner. Rabies vaccination should not be administered to the animal during this period. If the confined animal develops any illness during the 10 days, a veterinarian should evaluate it immediately. If signs of rabies are present, the local health department should be contacted, and the animal euthanized and tested for rabies. A dog, cat, or ferret that develops no signs of rabies during this observation period did not have transmissible rabies at the time the exposure occurred. Any dog, cat, or ferret that is sick at the time it exposed a human should be evaluated by a veterinarian immediately. Note that the 10 day observation applies only to dogs, cats or ferrets that have potentially exposed a human. Quarantine periods for animals that have themselves been potentially exposed to rabies are discussed elsewhere.

All other animals: All other animals that expose humans should be reported to the local health department immediately. No observation periods have been established for such animals (including wolf hybrids). If the animal is available, laboratory testing may be indicated depending upon the circumstances of the exposure (such as whether it was provoked or not) and the species involved. The risks associated with different animals varies from place to place. (See Epidemiology.) The local health department, with the assistance of the Communicable Disease Epidemiology Section, will determine whether testing is appropriate.

Bats: A bat that bites or otherwise exposes a human should be safely captured, euthanized, and submitted to the Washington Public Health Laboratories (PHL) for rabies testing. Neither the species, time of year, geographic location within the state, nor the behavior of the bat is a reliable predictor of whether or not that animal is rabid.

Capturing a bat: Bats are not aggressive but may bite if grabbed. They should not be handled with bare hands. Wear leather or other heavy gloves whenever contact with the animal is possible. Only one person should be in the room when attempting to capture a bat. Wait for the bat to land, then cover the animal with an empty coffee can (or similar container). Slide a piece of cardboard between the container and the surface on which the bat is resting, trapping it inside. Secure the covering to the can (by heavy tape, for example) so that the bat cannot escape.

What to do next:

Tested animals: If a person has had a true exposure to an animal that tests positive for rabies, postexposure treatment should be started immediately. In some situations, providers may choose to begin postexposure treatment before the tests results are available. The treatment can be discontinued if the tests confirm the animal is not rabid. Other than local wound care, no treatment is necessary for a person exposed to an animal that was fully tested but not rabid.

Animals that could not be tested: If a true exposure occurred but the animal could not be tested, the patient and provider must make a decision about postexposure treatment based on the circumstances and species involved. The local health department will assist providers with this decision.

The online Washington State Department of Health Rabies page has more information, including a step-by-step guide to decisions about prophylaxis.


Introduction | Clinical features | Epidemiology | Laboratory testing | Prevention | References

This monograph was produced for the World Wide Web by the Northwest Center for Public Health Practice in cooperation with the Washington State Department of Health. See references for further acknowledgements.