Animal bites are always unpleasant experiences. Unfortunately, animal bites do occur; to insure the health of the victim, it is essential that the proper precautions be followed.

One possible health problem associated with an animal bite is rabies, an acute encephalitis (infection of the brain). Bites inflicted by domestic animals with no history of a rabies vaccination or by a wild animal require immediate attention. Open wounds, scratches, or mucous membranes exposed to saliva or brain material of an infected animal are also possible modes of transmission.

Disease Rabies is an acute encephalitis (infection of the brain) caused by a virus believed to be infectious for most mammals. Transmission of the virus is usually through a bite. Transmission also can occur by exposure of a scratch, abrasion, open wound, or mucous membrane to the saliva or brain material of a rabid animal. The virus has an affinity for the central nervous system tissue and travels along the peripheral nerves to the brain. Once the virus is established in the brain the disease is seldom reversible and usually fatal. The average incubation period varies from 20-90 days after exposure and depends on the following circumstances:

• severity of bite or laceration,
• location of bite (incubation periods may be shorter after bites on head, neck, and fingertips, than bites on the trunk or lower extremities due to extensive nerve endings in the former areas),
• age of the victim (children have faster onset). Two clinical patterns may be manifest and are referred to as "dumb" or paralytic rabies and furious rabies (prone to bite).

The disease is usually fatal in humans; reversal is not possible once symptoms appear.

Epidemiology
Several wildlife populations serve as reservoirs for the rabies virus. The skunk is a natural reservoir for rabies in Iowa and many of the north central states. Raccoons have been a long-standing reservoir in the southeastern United States, and more recently have spread at epidemic levels along the entire eastern coast. Coyotes/dogs and foxes continue to spread rabies in the southwestern United States. Bats, highly mobile creatures found throughout the contiguous United States, have been increasingly associated with rabies. The rabies variant from bats has been associated with 13 of 16 human cases of rabies since 1980. Only two of the 13 cases involved an actual bite.

Prevention
Mass vaccination of domestic pets and control of strays has markedly reduced urban rabies. Even though the numbers of positive rabies cases are fewer in domestic animals than in wild animals, dogs, cats, and farm animals continue to present a substantial risk to humans. Their close contact with humans introduces the risk when rabies immunizations are not kept current. This is especially true in the rural settings where it is not economically feasible or justified to vaccinate livestock. Owners of valuable animals and breeding stock should consider vaccination especially in areas of high wildlife rabies.

Making pets of wildlife or exotic animals should be discouraged since many could be infected with the rabies virus. High-risk individuals such as veterinarians, animal handlers, laboratory workers, people with occupational or a vocational risk (trappers, taxidermists), and individuals living and working in a country where rabies is a constant threat should consider pre-exposure immunization. Vaccines are specific for each animal. Immunization is limited by techniques and tolerances, hence should be administered by a veterinarian.

Testing
Public health microbiologists at the University Hygienic Laboratory perform rabies testing on brain material of animals suspected of being rabid. The staff members who perform the tests are available seven days per week, 24 hours per day to answer questions about rabies and insure that proper procedures are followed for the submission of animals to the laboratory. All positive results are immediately phoned to the physician or veterinarian so that post exposure treatment can be administered. University Hygienic Laboratory reports all results to the federal Centers for Disease Control and the Iowa Department of Public Health so that rabies trends can be tracked locally and nationally.

Exposure and Treatment
Each exposure to a possible rabies infection must be individually evaluated by a physician and the following circumstances considered:

1. Animal species
   Wild or domestic species (vaccination history)
   Carnivore or rodent
2. Circumstances surrounding the bite
   Unprovoked attack is more likely to indicate that the animal is rabid
   Provoked bites are inflicted on a person attempting to feed or handle a healthy animal
3. Petting a rabid animal or other casual contact does not constitute an exposure and is not an indication for prophylaxis

Additional Information
For information about rabies and for submission of specimens contact:

• Centers for Disease Control and Prevention 877.554.4625
• University Hygienic Laboratory 319.335.4500
• Iowa Department of Public Health 800.362.2736
• State Public Health Veterinarian 515.281.4933
• Ames Veterinary Diagnostic Lab 515.294.1950