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Conservation > Fish & Wildlife Diseases Rabies

For questions/concerns about this disease in humans, please call your doctor or the Montana Department of Public Health and Human Services  (DPHHS).

For questions about this disease/parasite in wildlife, please call the FWP Wildlife Health Lab at (406) 577-7882.

Cause

Rabies is an acute infectious disease of the central nervous system caused by a virus of the family Rhabdoviridae (Stitt, 2011). The virus causes inflammation of the brain (encephalitis) (Miller et al, 2003).

Distribution

Rabies is one of the oldest recorded infectious diseases, having been reported in Asia as early as 2000 BC. It was probably imported into North America from Europe in the eighteenth century in domestic dogs. One of the first North American records was of an epizootic in foxes in Massachusetts in the early nineteenth century. It is currently found in every continent except Australia. Most countries that are free of the disease are islands. Worldwide, several variants of the virus have been identified, each associated with a single wild animal host that acts as a reservoir of infection for a particular geographic area (Michigan, 2010). During 2018, 54 U.S. states and jurisdictions reported 4,951 rabid animals to the CDC, representing an 11.2% increase from the 4,454 rabid animals reported in 2017. Texas (n = 695 [14.0%]), Virginia (382 [7.7%]), Pennsylvania (356 [7.2%]), North Carolina (332 [6.7%]), Colorado (328 [6.6%]), and New York (320 [6.5%]) together accounted for almost half of all rabid animals reported in 2018 (Ma et al., 2020). In the United States, more than 90% of reported cases of rabies in animals occur in wildlife. The wild animals that most commonly carry rabies in the United States are raccoons, skunks, bats, and foxes (CDC).  From July 1. 2019- June 30, 2020, 17 bats and 2 skunks tested positive for rabies in Montana.  Infected bats were detected in Flathead, Glacier, Lewis & Clark, Mineral, Hill, Yellowstone, Gallatin, Park, and Rosebud counties.  Infected skunks were detected in Missoula and Bighorn counties (Montana Department of Livestock website). 

Species affected

All mammals are susceptible to rabies infection. Bats and skunks are the primary wildlife reservoirs of rabies in Montana; however, the virus can infect a variety of carnivores (domestic dogs and cats, foxes, raccoons, skunks, wolves, coyotes) and bats (Adrian, 1981), as well as domestic animals.

Transmission

Rabies virus is transmitted through direct contact (such as through broken skin or mucous membranes in the eyes, nose, or mouth) with saliva or brain/nervous system tissue from an infected animal (CDC).

People usually get rabies from the bite of a rabid animal. It is also possible, but rare, for people to get rabies from non-bite exposures, which can include scratches, abrasions, or open wounds that are exposed to saliva or other potentially infectious material from a rabid animal. Other types of contact, such as petting a rabid animal or contact with the blood, urine or feces of a rabid animal, are not associated with risk for infection and are not considered to be exposures of concern for rabies (CDC).

Other modes of transmission—aside from bites and scratches—are uncommon. Inhalation of aerosolized rabies virus is one potential non-bite route of exposure, but except for laboratory workers, most people won’t encounter an aerosol of rabies virus. Rabies transmission through corneal and solid organ transplants have been recorded, but they are also very rare. There have only been two known solid organ donor with rabies in the United States since 2008. Many organ procurement organizations have added a screening question about rabies exposure to their procedures for evaluating the suitability of each donor (CDC).

Bite and non-bite exposures from an infected person could theoretically transmit rabies, but no such cases have been documented. Casual contact, such as touching a person with rabies or contact with non-infectious fluid or tissue (urine, blood, feces), is not associated with risk for infection. Contact with someone who is receiving rabies vaccination does not constitute rabies exposure, does not pose a risk for infection, and does not require postexposure prophylaxis (CDC).

Rabies virus becomes noninfectious when it dries out and when it is exposed to sunlight. Different environmental conditions affect the rate at which the virus becomes inactive, but in general, if the material containing the virus is dry, the virus can be considered noninfectious (CDC).

The virus is rapidly inactivated through exposure to most detergents, chemicals, ultraviolet radiation, strong acids and bases, and direct sunlight (Miller et al, 2003).

Signs

Affected animals may show unusual behavior, be weak, or be found dead (Stitt, 2011). The disease causes acute, fatal encephalitis that leads to marked changes in behavior. Rabies should be suspected in any wild animal exhibiting any behavior considered abnormal including loss of fear or unusual friendliness, excitation or aggression, depression, lack of coordination, paralysis, convulsions or seizures, abnormal vocalizations, appearance of nocturnal creatures exhibiting abnormal behavior during the day, choking or inability to drink or swallow food, and drooling or frothing at the mouth. Bats may get sick and die before being observed or showing symptoms (Miller et al, 2003). There are no gross lesions associated with rabies, but animals may have broken teeth, bite wounds, or sticks/debris in mouth as a result of their unusual behavior.

Public Health Concerns

Humans can contract rabies from the bite or scratch of an infected animal or from saliva of an infected animal if it contacts the eyes, nose, mouth, or skin wounds. People should seek treatment as soon as possible after contact with an animal suspected or known to have rabies. Any scratch or bite wound should be immediately cleaned and flushed with soap and water. Animals that show unusual behavior should not be approached or touched (Stitt, 2011). The best protection against rabies is pre-exposure vaccination (Adrian, 1981), which should be considered for people at high risk of exposure. Rabies is a potentially life-threatening disease for humans. Signs of infection may not be detectable for weeks or months and if left untreated, rabies is always fatal due to swelling of the brain or pneumonia. Symptoms of rabies in humans are similar to those in wildlife: depression, headache, vertigo, stiff neck, inability to drink,spasms and paralysis (Miller et al, 2003). Once clinical symptoms develop, there is no known cure for rabies (Michigan, 2010). Do not go near any animal suspected of having rabies. Report any animal suspected of having rabies to the local wildlife agency (MT FWP) for guidance. If an animal that is found dead must be handled for disposal or for submission to a laboratory, always wear disposable gloves, avoid contamination of clothing and skin with body fluids, and wash hands and forearms well with warm soapy water afterwards.

Intact and unfrozen brain tissue is needed to test an animal for rabies.  If a suspect animal is killed and testing is necessary, avoid destroying the brain, and keep the animal/head cool but not frozen.

Is it safe to eat the meat?

Do not consume meat from an animal with rabies or suspected to have rabies. Do not feed meat from an animal with rabies or suspected to have rabies to dogs (Miller et al, 2003). If you harvest an animal and are unsure whether it is safe to eat, contact your local FWP staff for guidance soon after the animal is harvested.

Citations

Adrian, W.J., editor. 1981. Manual of Common Wildlife Diseases in Colorado. Denver: Colorado Division of Wildlife.

Centers for Disease Control and Prevention. CDC. Website. https://www.cdc.gov/rabies/animals/index.html. Accessed 1/21/22.

Ma, X., Monroe, B. P., Cleaton, J. M., Orciari, L. A., Gigante, C. M., Kirby, J. D., Chipman, R. B., Fehlner-Gardiner, C., Gutiérrez Cedillo, V., Petersen, B. W., Olson, V., & Wallace, R. M. (2020). Public Veterinary Medicine: Public Health: Rabies surveillance in the United States during 2018, Journal of the American Veterinary Medical Association256(2), 195-208. Retrieved Jan 21, 2022, from https://avmajournals.avma.org/view/journals/javma/256/2/javma.256.2.195.xml

Michigan Wildlife Disease Manual. 2010. Michigan Department of Natural Resources. Website

Miller, M.J.R., R.D. Dawson, and H. Schwantje. 2003. Manual of Common Diseases and Parasites of Wildlife in Northern British Columbia. University of Northern British Columbia.

Montana Department of Livestock. Website. https://liv.mt.gov/Animal-Health/Reportable-Animal-Diseases/Rabies#:~:text=Montana%20Regulations,-Domestic%20animals%20with&text=Potential%20actions%20include%20booster%20of,in%20dogs%2C%20cats%20and%20ferrets.

 

Stitt, Tyler. 2011. Diseases You Can Get From Wildlife - A Field-guide for Hunters, Trappers, Anglers and Biologists. British Columbia Ministry of the Environment.

Western Wildlife Disease Workshop Notebook. 2009. Southeastern Cooperative Wildlife Disease Study. College of Veterinary Medicine, University of Georgia.