A risk assessment based approach for the management of whirling disease

This article began as an exercise during the 9th Annual Whirling Disease Symposium, "Whirling Disease: Managing the Risk" held in Seattle, Washington, in 2003. The exercise was designed to address the needs of fishery managers to more accurately assess the various factors associated with the risks of the introduction and the establishment of the myxosporean parasite, Myxobolus cerebralis, and the development of whirling disease in salmonids. Here we introduce concepts used in risk assessment, review aspects of whirling disease relevant to risk assessment, present a working model for a whirling disease risk assessment, and work through examples of how this model might be used to estimate risks and identify actions to reduce these risks. While this approach was designed to address factors controlling the introduction and establishment of M. cerebralis and the development of whirling disease in salmonids, the concepts are highly relevant to the management of other infectious diseases of aquatic animals.