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Infectious Diseases of Florida's Wildlife1
Don Forrester and Joe Schaefer2Many people are uncomfortable when they hear the term "wildlife disease." Although such diseases are harmful and undesirable, some of us will have to deal with them sooner or later. In this publication we discuss some of the facts, precautions, and regulations related to infectious diseases transferrable to humans by Florida's wildlife.
Definition
For the purposes of this document, we define infectious disease as any impairment of an animal's normal and vital life processes caused when viral, bacterial, fungal, or protozoan (microscopic, one-celled animals) organisms invade (infect) the host animal. (There are other causes of disease such as parasitic worms and insects, physiological stress, nutritional deficiencies, genetic abnormalities, and various chemicals and toxins, but these will not be discussed here.) Those diseases which are transferrable from animals to humans are called zoonotic diseases and are of concern from a public health standpoint.The occurrence of diseases in wildlife is complex: Some infectious disease agents are always present in animals and people. That means at least some individuals, although different ones from time to time, are always infected. Sometimes infections in individuals may not be obvious because the signs or symptoms of the resulting disease are not apparent. Some individuals with inapparent infections may be carriers able to transmit the infectious agent to others. Apparent disease occurs only when the resistance of the infected animal is too low to fight off adverse effects.
Infectious disease agents are harmful to populations in two cases: where there is an abnormal change in the ecological balance between the wild animal population and its environment--or when there is a lowering of resistance of part of that population to the infectious agent.
The introduction of new, potent disease agents into uninfected wild populations can result in serious disease and even die-offs of large numbers of animals that have little or no immunity.
For example, live-trapping a nuisance raccoon with an inapparent infection of rabies, then transporting and releasing that raccoon in another area can be devastating to individuals in the new area, as it will likely enhance the spread of rabies. That is the main reason it is illegal to transport wild-trapped, live raccoons in Florida.
Examples of Infectious Disease Agents
Rabies is probably the most notable and feared viral zoonotic disease. Rabies has been found in a number of Florida mammals including raccoons, bats, skunks, foxes, opossums, otters, bobcats, and panthers.The rabies virus is most commonly transmitted from the saliva of the infected animal into the bite wound of another. Raccoons and bats are probably the most important hosts because they live in close proximity to humans, although the percentage of infected individuals within an area might be quite low.
Brucellosis in wild hogs and salmonellosis in a number of carnivores and other medium-sized mammals are two examples of bacterial zoonotic diseases. These are transmitted by direct contact, either by the handling of infected meat in the case of brucellosis, or contaminated feces in the case of salmonellosis.
Histoplasmosis is caused by a fungus which lives in old buildings, attics and bat caves--especially in guano (feces) enriched soil. Transmission occurs by inhalation of fungal spores and has occurred in spelunkers who have explored Florida's bat caves.
Toxoplasmosis is caused by a microscopic protozoan and is spread to humans by the handling of contaminated cat--such as bobcat--feces and by consumption of infected meat from deer, rabbits, and squirrels.
Transmission of Diseases from Wildlife to Humans
At least 30 different, infectious disease agents can be transmitted from Florida's wild mammals to humans-- while a smaller number of infections can originate from birds, reptiles, amphibians, and fish. Most of these disease agents can be avoided by following common sense practices such as
- minimizing contact with wildlife exhibiting unusual behavior (seen in animals with rabies),
- using gloves and washing hands after handling wild animals (salmonellosis, brucellosis, and toxoplasmosis), and
- cooking wild game well before consumption (toxoplasmosis).
What to do in Case of Exposure to a Diseased Wild Animal
If you are concerned that you may have been exposed to a diseased wild animal, you should consult your personal physician for treatment and advice if he or she is available. If you suspect rabies, you should also contact your local animal control service or county public health office. The telephone number of the latter can be located in the blue pages of your telephone book under the county listing for Public Health Office.If you have the wild animal in captivity or have killed the animal that you believe has done the biting, the Public Health Office will have the animal's brain tested to see if it is infected with rabies virus.
Finally, a veterinarian is also an excellent source of help. Consult one for questions concerning wildlife diseases that affect humans, specific advice about a particular disease source, and even for help in removing the head of a dead wild animal for rabies testing.
Suggested Readings
Davidson, W.R. and V.F. Nettles. 1988. Field manual of wildlife diseases in the southeastern United States. Southeastern Cooperative Wildlife Disease Study, College of Veterinary Medicine, Univ. Georgia, Athens. 309 pp.Forrester, D.J. 1992. Parasites and diseases of wild mammals in Florida. Univ. Press of Florida, Gainesville. 459 pp.
Footnotes
1. This document is Fact Sheet SS WEC-113, one of a series of the Cooperative Urban Wildlife Program, a cooperative effort between the Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, and the Florida Game and Fresh Water Fish Commission's Nongame Wildlife Program. Publication Date: June, 1996.2. Don Forrester, professor of wildlife diseases, and Joe Schaefer, associate professor and extension wildlife specialist, Wildlife Ecology and Conservation Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville FL 32611.
The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.
U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry Arrington, Dean.
Copyright Information
This document is copyrighted by the University of Florida, Institute of Food and Agricultural Sciences (UF/IFAS) for the people of the State of Florida. UF/IFAS retains all rights under all conventions, but permits free reproduction by all agents and offices of the Cooperative Extension Service and the people of the State of Florida. Permission is granted to others to use these materials in part or in full for educational purposes, provided that full credit is given to the UF/IFAS, citing the publication, its source, and date of publication.