Disease is described as a decrease in performance of normal functions of an individual caused by many factors, which is not limited to infectious agents. Furthermore, wildlife disease is a disease when one of the hosts includes a wildlife species. In many cases, wildlife hosts can act as a reservoir of diseases that spillover into domestic animals, people and other species. Furthermore, there are many relationships that must be considered when discussing wildlife disease, which are represented through the Epidemiological Triad Model. This model describes the relationship between a pathogen, host and the environment. There are many routes to infection of a susceptible host by a pathogen, but when the host becomes infected that host now has the potential to infect other hosts. Whereas, environmental factors affect pathogen persistence and spread through host movement and interactions with other species. An example to apply to the ecological triad is Lyme disease, where changes in environment have changed the distribution of Lyme disease and its vector, the Ixodes tick.
Wildlife Disease Management
The challenges associated with wildlife disease management, some are environmental factors, wildlife is freely moving, and the effects of anthropogenic factors. Anthropogenic factors have driven significant changes in ecosystems and species distribution globally. The changes in ecosystems can be caused by introduction of invasive species, habitat loss and fragmentation, and overall changes in the function of ecosystems. Due to the significant changes in the environment because of humans, there becomes a need for wildlife management, which manages the interactions between domestic animals and humans, and wildlife.
Wildlife species are freely moving within different areas, and come into contact with domestic animals, humans, and even invade new areas. These interactions can allow for disease transmission, and disease spillover into new populations. Disease spillover can become of great concern when considering outbreaks, not only in humans but in other wildlife species raising a concern for species preservation.
Detection
Wildlife disease is detected primarily through surveys, for example taking samples from wildlife populations in an area to determine the prevalence of disease within a population. Prevalence is define as the percentage of a population that is diseased at a particular time. There are limitations to using this to detect disease within wildlife populations, such as all host may not show signs of disease, the sample distribution, and the disease distribution. Diseases in wildlife tend to form patches of disease throughout an entire population, which can affect the prevalence of the disease within a population. Sampling is assumed to be random, but is often opportunistic. Another form of disease detection is through observation of diseased hosts. However if some hosts within a species do not show signs of disease, this can influence the prevalence of disease detection within a wildlife population.
The reservoir of wildlife disease can also be a challenge when considering wildlife disease detection. An example of a challenge identifying the pathogen is the mass mortality event in bald eagles in southeastern United States in 1994. The challenge identifying the causative agent of disease was due to the neurotoxin being isolated from the areas of outbreak, but not when grown in the laboratory until a brominate metabolite was used. The management of wildlife diseases involve many factors, which should are all important to consider when determining the persistence of a pathogen within a population.
Prevention
Culling
Disease outbreaks in wild animals are sometimes controlled by killing infected individuals to prevent transmission to domestic and economically important animals. Animal rights advocates argue against culling, as they consider individual wild animals to be intrinsically valuable and believe that they have a right to live.
Vaccination programs
Wild animal suffering, as a result of disease, has been drawn attention to by some authors, who argue that we should alleviate this form of suffering through vaccination programs. Such programs are also deemed beneficial for reducing the exposure of humans and domestic animals to disease and for species conservation.
The oral rabies vaccine has been used successfully in multiple countries to control the spread of rabies among populations of wild animals and reduce human exposure. Australia, the UK, Spain and New Zealand have all conducted successful vaccination programs to prevent Bovine Tuberculosis, by vaccinating badgers, possums and wild boar.