Neil Duncan, Dixie State University
Whirling Disease (WD) is an ecologically and economically devastating parasitic disease of salmonid fish. WD is responsible for the decimation of wild trout populations in the Rocky Mountain region of the United States, killing up to 90% of the population of some rivers. As a result, there have been large economical losses to fisheries, recreational fishing, and the tourism industry of many western states. WD is caused by a parasite known as Myxobolus Cerebralis. The parasite needs two specific hosts to complete its life cycle; a salmonid fish and a Tubifex worm. When infected fish die, they release spores of M. Cerebralis. The spores are then ingested by the worms. The parasite takes on a new form inside the worm, called a Triactinomyxon (TAM), and becomes capable of infecting susceptible fish. When the TAM enters the cartilage of the fish, it rapidly multiplies into new spores, causing the fish to swim erratically. The fish dies and releases spores, propagating the life cycle of the parasite in perpetuity. The effects of WD are more significant in some areas than others due to environmental conditions. For example, the release rate of TAMs is temperature dependent. In order to understand WD dynamics, we need to better understand the relationship between temperature and the disease. Despite some research on WD, there has not been a temperature incorporated mathematical model developed which predicts the spread of WD in salmonid populations. In this study, our goal is to investigate how temperature variability affects transmission dynamics and spread of the disease. We developed a novel mathematical model incorporating temperature variability to simulate the dynamics of an ecosystem of fish, worms, and parasites. Furthermore, we solved our model using a nonstandard finite difference scheme in MATLAB computational software and explored effective control strategies to mitigate WD. The results of this model could be used as a tool by wildlife agencies, recreational fishers, and fisheries to implement control methods to reduce the spread of WD.