Disease & Pathogens
With the rapid changes in the speed of transport of live organisms from all parts of the world, new and unseen pathogens (bacteria, viruses, fungi and parasites) and disease (together, epizootics) will be a major threat to Michigan's natural resources. Wildlife may be particularly susceptible to disease and infection when it is stressed by other factors, such as habitat loss and contamination (Kiesecker et al. 2004). Substantial resources will be required to monitor the status of, understand the ecology of, and develop control or containment strategies for epizootics when they threaten wildlife and natural communities. See the Ecological Overview for background and trends associated with pathogens and disease.
Disease and Pathogens in Aquatic Systems
Up to five years ago, little was known about the distribution and occurrence of pathogens in aquatic wildlife in Michigan waters. This lack of information greatly impaired the ability of resource managers to understand and respond to epizootics. Initial pathogen surveys, started in the mid 1990s, gave an initital glimpse into the range of pathogens occurring in Michigan. In 2004, these surveys were first integrated with other intensive waterbody surveys. However, these surveys do not fully sample all elements of aquatic communities, and additional resources are needed for a complete inventory. When coupled with GIS databases containing both past and present pathogens, these surveys will be a powerful tool to help understand this component of aquatic ecosystems.
Disease outbreaks, also known as epizootic events, in wild fish populations as well as in hatchery production are of great concern in the Great Lakes region. These events have caused large-scale mortality in fish populations. Currently, BKD in salmon and whitefish, whirling disease in trout, heterosporis in yellow perch, piscirickettsia in muskellunge, and LMBV are diseases of concern for wild fish populations. In addition, Furunculosis is re-emerging as a disease in Pacific salmon at this time. Similar epizootic events for other aquatic organisms probably occur throughout the aquatic ecosystem, but little is known about diseases other than those of fish. Even for fish, current knowledge about diseases, beyond those of trout and salmon, is limited.
Disease and Pathogens in Terrestrial Systems
Although large-scale disease events directly affecting Michigan's terrestrial wildlife have been rare (bovine tuberculosis, West Nile Virus), proactive efforts and monitoring to identify new pathogen and disease threats that may affect wildlife or the plants on which they depend is required. Past conservation efforts to address terrestrial wildlife diseases have concentrated on game species; knowledge of pathogens and disease in nongame terrestrial wildlife is more limited. Known direct threats posed to terrestrial wildlife by disease and pathogens include West Nile Virus, Duck Virus Enteritis (duck plague), Leucocytozoonosis, and cerebrospinal nematodiasis caused by Brainworm (Parelaphostrongylus tenuis). Additionally, amphibians are experiencing an ongoing pandemic of a newly discovered fungal disease, chytridiomycosis, which is adding to the overall amphibian crisis worldwide (Kiesecker et al. 2004).
Additionally, disease and pathogens that affect plants will have a negative effect on wildlife species that have obligate relationships with the plants or that depend on the structure the plants provide within landscape features and ecosystems. Beech bark disease threatens Michigan's 7.2 million acres of Maple-Beech-Birch type forests. Ironically, the spread of beech bark disease has been slower in areas with more highly fragmented forest systems. Additionally, incidence of oak wilt continues to increase in Michigan (DNR 2004c).
Conservation Needs to Address Disease and Pathogen Threats:
Land, Water & Species Management
- Implement newly developed diagnostic tools that rapidly determine the pathogen status of aquatic organisms in a non-lethal manner
- Implement newly developed methods to measure fish and other aquatic organism health and quality to increase effectiveness of pathogen surveys for wild and hatchery organisms
Law & Policy
- Require that all fish stocked in Michigan waters are certified free of disease as specified in the Model Fish Health Program developed by the Great Lakes Fish Health Committee
- Implement all possible and practical biosecurity measures at all private and State hatcheries, other wildlife facilities, and nurseries, in conjunction with the Michigan Department of Agriculture
- Develop and implement pathogen and disease survey systems for private aquaculture, the bait industry, the shipping industry, recreational boaters, nurseries and other private/captive wildlife industries
- Develop and implement importation inspection and certification requirements for the aquaculture industry, bait industry, nursery industry, biological control industry (e.g., predatory wasps and lady bugs) and other captive wildlife industries, in conjunction with the Michigan Department of Agriculture
- Develop and implement strategies at all hatcheries, private and State, to achieve A-1 or A-2 status in conjunction with the Michigan Department of Agriculture
Research, Surveys & Monitoring
Conduct research on containment strategies for pathogens which pose significant threats to Michigan's wildlife species or the plants on which they depend
- Develop new spatial databases for pathogen survey data that include all new and historical pathogen information
- Develop treatments for diseases which threaten forest health (e.g., oak wilt, ash decline, beech bark disease)
- Develop and implement a pathogen and disease monitoring system for all types of wildlife and plants
- Develop and test new diagnostic tools that rapidly and non-lethally determine the pathogen status of aquatic organisms
- Develop and test new methods to measure fish and other aquatic organism health and quality to increase effectiveness of pathogen surveys for wild and hatchery organisms
- Conduct research to investigate and produce decision support models for understanding, controlling, and eliminating or containing epizootic events