Willard Granath Jr.
Office: HEALTH SCIENCES 306
Phone: (406) 243-2975
My current research program is a multi-faceted, epidemiological study of salmonid whirling disease. This disease, caused by the myxozoan parasite, Myxobolus cerebralis, is causing a serious health threat to salmonid fish in many regions of the U.S. The parasite has an obligatory aquatic annelid host, Tubifex tubifex, which has greatly complicated efforts to develop control strategies. In 1998 I initiated a long-term, integrated study to examine the epidemiology of whirling disease throughout the Rock Creek drainage, which is one of Montana's premier blue-ribbon trout fisheries. This study is a cooperative effort that includes colleagues from the U.S. Fish and Wildlife Service, the Montana Department of Fish, Wildlife and Parks, and Montana State University. Currently, this research team is performing studies to address the following specific goals: 1) determine the percentage of T. tubifex releasing M. cerebralis throughout the length of the Rock Creek drainage, 2) determine the intensity of infection of M. cerebralis in trout using sentinel cage techniques stationed throughout the length of Rock Creek, 3) elucidate the diversity and abundance of oligochaetes in Rock Creek, 4) examine the genetic heterogeneity of T. tubifex in Rock Creek, and 5) assess various water quality parameters of Rock Creek. To our knowledge, this is the only attempt to establish the severity of whirling disease throughout an entire drainage and correlate it to oligochaete biology and water quality parameters. Another focus of my lab centers specifically on T. tubifex. This annelid is a common freshwater oligochaete species and is the only known invertebrate host of M. cerebralis.
There is a paucity of data on M. cerebralis-T. tubifex interactions, especially on purported differences in susceptibility of this worm species from different geographic regions to the parasite and/or differences in the number of triactinomyxons (TAMs; infectious stage for trout) released. The overall objective of this research is to develop strains of T. tubifex from various geographic regions via the worms' ability to reproduce by parthenogenesis. The various strains are being characterized genetically, and then tested for their susceptibility to M. cerebralis. For all susceptible tubifex strains, the number of TAMs they release are being quantified. Development of these genetically-characterized stocks will establish an extremely useful laboratory model that can be used to explore numerous questions regarding T. tubifex biology and tubifex-M. cerebralis interactions. For example, other researchers have shown that different environmental factors select for different genotypes of T. tubifex, and that different environmental conditions can have a profound effect on worm biology. The genetically-characterized worms we are developing (with different susceptibilities to the parasite) can be mixed and allowed to cross-breed under a variety of controlled environmental conditions. The progeny will be examined to determine if a particular genotype was selected for by a particular environmental factor. By examining a variety of worm genotypes and environmental factors, this research will provide useful information on the role of worm habitat on tubifex genotypes and if this affects the capacity of worms in certain environments to transmit M. cerebralis.
In addition to my teaching and research program, I am also Director of the University’s Electron Microscopy Facility. Information about the facility can be found at: http://www.emtrix.org/
B.S. Delaware Valley College of Science and Agriculture, 1975
M.S. Illinois State University, 1977
Ph.D. Wake Forest University, 1982
Gilbert, M.A. and W.O. Granath, Jr. 2001. Persistent infection of Myxobolus cerebralis, the causative agent of salmonid whirling disease, in Tubifex tubifex.ï¿½ Journal of Parasitology 87: 101-107.
Granath, Jr., W.O., V.A. Connors and A.E. Raines. 2001. Effects of exogenous interleukin-1b on Schistosoma mansoni (Trematoda) primary sporocysts incubated with plasma and hemocytes from schistosome-susceptible and resistant Biomphalaria glabrata (Gastropoda).ï¿½ Invertebrate Biology 120: 365-371.
Granath, Jr., W.O. and M.A. Gilbert. 2002. The role of Tubifex tubifex (Annelida: Oligochaeta: Tubificidae) in the transmission of Myxobolus cerebralis (Myxozoa: Myxosporea: Myxobolidae),ï¿½ In: J.L. Bartholomew and J. C. Wison (eds.), Whirling Disease: Reviews and Current Topics, American Fisheries Society Symposium Series 29, Bethesda, Maryland, p. 79-86.
Gilbert, M. A. and W. O. Granath, Jr.ï¿½ 2003.ï¿½ Salmonid whirling disease: Life cycle, biology and disease.ï¿½ Journal of Parasitology, in press.