43,928 research outputs found

    Mathematical models for wildlife disease management

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    Endemic diseases in wildlife present both intra- and inter-species management problems with risk to conservation of endangered species and spillover of virulent disease to other wildlife, farmed and domestic populations. Mathematical models have been developed to aid understanding of the transmission and persistence of such endemic disease. We review such models with an emphasis on models of tuberculosis. The understanding gained from previous model studies is used to formulate a new mathematical model for the wild boar reservoir of tuberculosis in central Spain where the disease persists at high prevalence and impacts other wild and domestic species. This model is used to investigate the efficacy of hunting and vaccination as management techniques to control tuberculosis in wild boar. Insight from the specific wild boar TB model generates a general result for compensatory population growth following culling of a population harbouring endemic disease. We show that compensatory growth due to a reduction in disease-induced mortality following culling could be a new mechanism for producing the ‘Hydra’ effect. We extend the wild boar TB model to reflect the situation in Asturias where wolf predation may influence the disease dynamics leading to lower prevalence of tuberculosis in wild boar. In conclusion we review how our findings can provide insight for disease management and control, and consider how the model could be extended to investigate emerging diseases for which wild boar may also be a reservoir

    Chronic Wasting Disease in Deer and Elk: a Critique of Current Models and Their Application

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    Chronic wasting disease (CWD), a fatal transmissible spongiform encephalopathy of deer (Odocoileus spp.) and elk (Cervus elaphus), presents a challenge to wildlife managers because little is known about its transmission, yet it could severely threaten wildlife populations if action is not taken rapidly. Published mathematical models predict that CWD could devastate populations of free-living deer and elk, prompting wildlife managers to attempt large-scale eradication of deer in hopes of containing CWD outbreaks. Our objective is to critically examine the theoretical and empirical support for current models of CWD epizootiology, in light of herd health-management actions. We identify a critical, untested premise (i.e., strictly frequency-dependent transmission) that underlies the dire model predictions. We re-evaluate published comparisons of model output with field data and find little support for published model structures. Given the uncertainty surrounding the future effects of chronic wasting disease on deer and elk populations, and the potential costs of unnecessarily culling large numbers of charismatic and valuable animals, we propose that consideration of alternative models and management actions in a decision–theoretic framework is necessary for wildlife management actions to retain their scientific basis

    Modeling Migratory Nongame Birds: A Plea for Data

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    The Bird Damage Management Conference held February 10–13, 2020 in Salt Lake City, Utah, USA provided a forum for professionals from across the United States to discuss and share management approaches, research strategies, policy, and messaging regarding the management of blackbirds (Icteridae), starlings (Sturnus vulgaris), corvids (Corvidae), and vultures (Cathartidae). Mathematical models were presented at the conference and subsequently discussed in a special issue of Human–Wildlife Interactions. Rapidly changing landscape variables point to the need for detailed systematic population monitoring programs with specific objectives. Nationwide periodic monitoring would provide data about changes not only in bird populations due to changing landscapes but also could be used to assess management activities

    Wildlife disease elimination and 1 density dependence

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    Disease control by managers is a crucial response to emerging wildlife epidemics, yet the means of control may be limited by the method of disease transmission. In particular, it is widely held that population reduction, while effective for controlling diseases that are subject to density-dependent transmission, is ineffective for controlling diseases that are subject to frequency-dependent transmission. We investigate control for horizontally transmitted diseases with frequency-dependent transmission where the control is via nonselective (for infected animals) culling or harvesting and the population can compensate through density-dependent recruitment or survival. Using a mathematical model, we show that culling or harvesting can eradicate the disease, even when transmission dynamics are frequency-dependent. E 24 radication can be achieved under frequency-dependent transmission when density-dependent population regulation induces compensatory growth of new, healthy individuals, which has the net effect of reducing disease prevalence by dilution. We also show that if harvest is used simultaneously with vaccination and there is high enough transmission coefficient, application of both controls may be less efficient than when vaccination alone is used. We illustrate the effects of these control approaches on disease prevalence using assumed parameters for chronic wasting disease in deer where the disease is transmitted directly among deer and through the environment

    Linking anthropogenic resources to wildlife-pathogen dynamics: a review and meta-analysis

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    Urbanisation and agriculture cause declines for many wildlife, but some species benefit from novelresources, especially food, provided in human-dominated habitats. Resulting shifts in wildlife ecol-ogy can alter infectious disease dynamics and create opportunities for cross-species transmission,yet predicting host–pathogen responses to resource provisioning is challenging. Factors enhancingtransmission, such as increased aggregation, could be offset by better host immunity due toimproved nutrition. Here, we conduct a review and meta-analysis to show that food provisioningresults in highly heterogeneous infection outcomes that depend on pathogen type and anthropo-genic food source. We also find empirical support for behavioural and immune mechanismsthrough which human-provided resources alter host exposure and tolerance to pathogens. Areview of recent theoretical models of resource provisioning and infection dynamics shows thatchanges in host contact rates and immunity produce strong non-linear responses in pathogen inva-sion and prevalence. By integrating results of our meta-analysis back into a theoretical frame-work, we find provisioning amplifies pathogen invasion under increased host aggregation andtolerance, but reduces transmission if provisioned food decreases dietary exposure to parasites.These results carry implications for wildlife disease management and highlight areas for futurework, such as how resource shifts might affect virulence evolution

    Parasite spill-back from domestic hosts may induce an Allee effect in wildlife hosts

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    The exchange of native pathogens between wild and domesticated animals can lead to novel disease dynamics. A simple model reveals that the spill-back of native parasites\ud from domestic to wild hosts may cause a demographic Allee effect. Because parasite spill-over and spill-back decouples the abundance of parasite infectious stages from the abundance of the wild host population, parasitism and mortality of the wild host population increases non-linearly as host abundance decreases. Analogous to the effects of satiation of generalist predators, parasite spill-back can produce an unstable equilibrium in the abundance of the host population above which the host population persists and below which it is at risk of extirpation. These effects are likely to be most pronounced in systems where the parasite has a high efficiency of transmission from domestic to wild host populations due to prolonged sympatry, disease vectors, or proximity of domesticated populations to wildlife migratory corridors
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