Myxosoma cerebralis

Food Web - This species is a parasite that feeds on the tissues of its hosts.

Life History - TAMs (triactinomyxon, the spore-like stage of the parasite) develop in T. tubifex via asexual and sexual reproduction, requiring a total of 3 months in the region between the epithelial cells of the oligochaete’s intestine to reach maturity. They are then released into the water column and must infect their salmonid hosts within around 1–15 days. Both mechanical and chemical mucus-derived signals trigger their discharge. Upon discharge at the epidermis of the fish, the sporoplasm, containing a group of infective germ cells, is injected into the host. The germ cells then move into the nervous system, reproducing and eventually moving to the cartilage. Development in the fish host is asexual and occurs in inter- and intra-cellular spaces, requiring around 3 months for myxospore formation. Myxospores can be passed to another fish at this point if the first host is ingested by a predator. If this is the case, they will pass out in the second host’s feces to settle in the sediments. Otherwise, the spores remain in the first fish host’s tissue upon mortality and eventually end up in the sediments as the carcass decays. Myxospores can survive temperatures of -20°C.  Evidence suggests that the myxospores free in the environment remain viable for less than a year (Nehring et al 2015). They are then taken up from the sediments by feeding T. tubifex and the life cycle begins again (El-Matbouli et al. 1999; Gilbert and Granath 2003; Kallert et al. 2005; Elwell et al. 2006; Kaeser et al. 2006; Krueger et al. 2006). The severity of infection in salmonids may be correlated with water temperature and water conductivity. Temperatures from 5–17°C are best for TAM production while temperatures of >20°C are inhibitive. Depending on the strain of T. tubifex hosting TAMs, ideal temperature for development can vary.

Summary of species impacts derived from literature review. Click on an icon to find out more...

Environmental	Socioeconomic

Myxobolus cerebralis has a low socioeconomic impact in the Great Lakes.

Economically valuable non-native Rainbow Trout (Oncorhynchus mykiss) is particularly susceptible to this pathogen, and Chinook Salmon (Oncorhynchus tshawytscha) can also be susceptible to a lesser degree. Most reports in the Great Lakes region have been from hatchery stocks.

Myxobolus cerebralis has low potential benefits to the Great Lakes.

Regulations (pertaining to the Great Lakes)
The Great Lakes Fish Disease Control Policy and Model Program have prohibited stocking the Great Lakes and their tributaries with fish from whirling disease infected farms. Fish imported into the North Central Region states must be certified free of whirling disease in order to obtain import permits (Faisal and Garling 2004).

 All eight Great Lakes states (New York, Pennsylvania, Ohio, Michigan, Indiana, Illinois, Wisconsin, and Minnesota) have instated similar baitfish regulations to control the spread of whirling disease and other fish pathogens. Those of New York include that bait harvested from inland waters for personal use is only permitted to be used within the same body of water from which it was taken and cannot be transported overland (with the exception of smelt, suckers, alewives, and blueback herring). Once transported, baitfish cannot be replaced to its original body of water (NYSDEC 2012). Live or frozen bait harvested from inland New York waters for commercial purposes is only permitted to be sold or possessed on the same body of water from which it was taken and cannot be transported over land unless under a permit and or accompanied by a fish health certification report. Bait that is preserved and packaged by any method other than freezing, such as salting, can be sold and used wherever the use of bait fish is legal as long as the package is labeled with the name of the packager-processor, the name of the fish species, the quantity of fish packaged, and the means of preservation (NYSDEC 2012). Certified bait may be sold for retail and transported overland as long as the consumer maintains a copy of a sales receipt that contains the name of the selling vendor, date sold, species of fish sold, and quantity of fish sold. Bait that has not been certified may still be sold but the consumer must maintain a sales receipt containing the body of water where the bait fish was collected and a warning that the bait cannot be transported by motor vehicle. Bait sold for resale require a fish health certification along with a receipt that contains the name of the selling vendor, date sold, species of fish sold, and quantity of fish sold, which must be kept for 30 days or until all bait is sold (NYSDEC 2012).

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.

Control
The following  biological, physical and chemical controls only pertain to fish in captive or hatchery operations. There are no known control methods of whirling disease in wild populations (except for management of spread - see Other below).

A qPCR marker has been developed for the detection of M. cerebralis (Weber et al. 2012, Barry 2020).  Multiple markers are available for the host Tubifex tubifex which show promise in distinguishing genetic strains which may relate to compatibility with the parasite (Weber et al. 2012, Barry 2020).

Biological
Managing T. tubifex populations can be implemented as a biocontrol of M. cerebralis. Maintaining water quality, reducing favorable habitat by preventing sediment accumulation in aquaculture (Crosier et al. 2012), and desiccating holding tanks, equipment, and intake pipes may help control T. tubifex (Kaster and Bushnell 1981). Lampricide TFM (3-triflouromethyl-4-nitrophenol), administered at (4.2-14.0 mg/L) doses, is effective at destroying T. tubifex (Liefers 1990). Tubifex tubifex can also be treated in 30°C water for four days, causing triactinomyxon (TAM) spore production to stop, thus preventing the next stage of the parasite's life cycle (El-Matbouli et al. 1999).  Tubifex tubifex ability to support M. cerebralis’ triactinomyxon (TAM) spore production may be due to genetic differences among T. tubifex populations. This variability may be an important factor in determining infection rates among fish (Baxa et al. 2006) and therefore might support certain management practices (Stromberg 2006).

It has been proposed that selective processes are yielding a surviving population of fish that is more resistant to M. cerebralis infection on the Madison River, Montana (Vincent 2006). The implications of this for management are still unclear. However, research is continuing to evaluate the possibility of a developing resistance within salmonid populations(Stromberg 2006).

Physical
Managers have observed that using concrete in aquaculture facilities can reduce the abundance of T. tubifex and thus limit the ability of M. cerebralis to reproduce (Mills et al. 1993, Ricciardi 2001). Most hatcheries now use concrete bottoms to break the life cycle of M. cerebralis (R. Kinnunnen, Pers. Comm. 2025).

The Colorado Division of Wildlife (CDW 2011) administers routine fish health sampling at hatchery sites to help slow the spread of M. cerebralis infections by early detection. At the Roaring Judy Hatchery, a project is underway to install an ultraviolet system that kills M. cerebralis spores (CDW 2011).Treating water with 2537Å UV at doses of 35mWs/cm2 can be 86-100% effective at preventing whirling disease in rainbow trout fry (Hoffman 1974) and administering 1,300 mWs/cm2 of UV under a static collimated beam, can inactivate 100% of the TAM spores present (Hedrick et al. 2000).

There is evidence that electricity (1,000 s exposure to low-level DC voltage for 48 hrs) can destroy T. tubifex in aquaculture (R. Ingraham and T. Claxton, pers. comm. in Wagner 2002). Electrical charges of 1-3 kV pulsed 1-25 times at 99 µsec/pulse are effective at killing large numbers of TAM spores (Wagner 2002). Exposing myxospores to 90°C water for 10 minutes is also effective at destroying the spores (Hoffman and Markiw 1977).
Experiments by Hoffman (1974) have demonstrated that filtration is not an effective method for removing TAM spores from water – due to the small spores size, the filter needed to remove them slows flow to rates unacceptable for most applications.

Chemical
Hatchery intake water treated with chlorine (0.5 ppm) administered at two hour intervals once a week can reduce infection rates in rainbow trout by 63-73% without causing harm to the fish (Markiw 1992). Supply water treated with calcium cyanide (488 g/m2) mixed with chlorine gas (300 ppm) can be very effective at destroying M. cerebralis spores (Hoffman and Dunbar 1961). Water treated with chlorine (130-260 ppm) for 10 minutes may kill 100% of TAM spores present (Wagner 2002), and treating with chlorine (5,000 ppm) for 10 minutes is sufficient enough to destroy both triactinomyxon and myxospore (E. MacConnell, pers. comm. in Wagner 2002). Treating fry with chlorine (10 ppm) for 30 minutes may prevent whirling disease infection (Hoffman and O’Grodnick 1977).

It has been demonstrated that feeding Rainbow Trout with pellets containing (0.1%) Fumagillin is effective at reducing whirling disease infection. Two groups of Rainbow Trout were administered pellets from days 14-64 and 30-160 post infection. Approximately 10-20% of the medicated fish harbored spores, whereas 73-100% of non-medicated fish harbored spores (El-Matbouli and Hoffman 1991).
Earthen pond substrate treated with quicklime (CaO) at concentrations >380 g/m2 for two weeks prior to introducing fish can prevent whirling disease infection by destroying M. cerebralis spores (Hoffman and Hoffman 1972).

Other
Adherence to local laws regarding transportation of live fish between bodies of water, contacting local agencies immediately upon noticing signs of whirling disease, properly disposing of fish and fish parts, and not transporting mud on boots and shoes between bodies of water are useful in controlling the transmission of M. cerebralis spores in the wild.

Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.