TAM (Triactinomyxon) Filtration Studies

Principal Investigator: Dana Winkelman

Research Associate: Brad Neuschwanger

Ongoing Project

Funding Agency: Colorado Division of Wildlife

Introduction: This project began with the development and testing of a field technique to determine the seasonality, periodicity, and relative abundance of the fish-infective triactinomyxon actinospore of Myxobolus cerebralis in free-flowing streams, natural lakes, and reservoirs in Colorado where the parasite was thought to be enzootic.

Objectives: To quantify the production of the triactinomyxon actinospore of the Myxobolus cerebralis throughout the year in aquatic habitats across Colorado. To gather long-term data on seasonal periodicity and year to year variation in the production of the triactinomyxon actinospore of Myxobolus cerebralis.

Progress: The basic protocol of the field sampling technique was established by 1998. Since then, only minor changes have been made to the sampling and examination protocols. The technique has been used to gather information on TAM abundance and seasonal variability in TAM abundance at over 200 distinct sites in 25 drainages. Currently, about 35 sites are being monitored in 14 different drainages. During the past year, we initiated the building of a microbead packed bed sampler similar to one used in Montana. The apparatus has been assembled and bench-testing will begin in spring 2004. The new sampler is anticipated to yield better estimates of TAM density without as much variation as the current method. Both methods will be used in the future, since the new sampler is trailer-mounted and cannot be taken to many of the sites currently being monitored. The new sampler will be primarily used in areas where a lower threshold of detection is desired, e.g. where manipulations have occurred to reduce TAM densities.

Results/Products: The original technique was the subject of a peer-reviewed paper authored by Thompson and Nehring and published in the Journal of Aquatic Animal Health in 2001. The technique has been used in other studies that resulted in peer-reviewed publications, in which TAM density estimation was a component of the studies. These include Thompson et al. (2002) Response of rainbow trout Oncorhynchus mykiss to exposure to Myxobolus cerebralis above and below a point source of infectivity in the upper Colorado River. Diseases of Aquatic Organisms 49:179-178; and Nehring et al. (2003) Efficacy of passive sand filtration in reducing exposure of salmonids to the actinospore of Myxobolus cerebralis. Diseases of Aquatic Organisms 57:77-83. The data and information collected from this long-term monitoring effort have been used to help develop risk assessment guidelines and provide science-based insights to better manage and control the spread of the Myxobolus cerebralis parasite.