A gill being fed on by a trophozoite alongside some healthy gills.
Two Myxosoma trophozoites feeding on the gills of a fish.
Myxobolus cerebralis is a member of the Myxozoa group of aquatic parasitic animals of the phylum Cnidaria. Over 1200 Myxozoa species have been described, and all are aquatic parasites. Myxobolus cerebralis is responsible for causing what is known as Whirling Disease in trout, a neurological disorder that causes the trout to swim in a whirling motion. It usually infects juvenille fish, and the whirling motion of their swimming makes it difficult for the trout to feed, and increases their vulnerability to predators. The parasite feeds on the cartilage of nerve cells, thereby causing severe neurological and skeletal disorders which lead to the whirling movement of the fish.
Life Cycle[]
Myxobolus cerebralis makes use of two hosts in its life cycle. These are a salmonid fish, and a tubificid oligochaete, specifically Tubifex tubifex. The worm ingests myxospores, which attach to the lining of the gut and multiply by merogony, an asexual cell fission process. After two to three months in the worm the parasite cells undergo sporogenesis and develop into sporocysts, which are released into the surrounding water. The salmonid fish is infected either through penetration of the skin by these sporocycts or ingestion of the infected worm. The parasite then reproduces by asexual endogeny, taking resources from the cartilage surrounding nervous tissue in the salmon. These will eventually form into myxospores through sporogony, and are released into the environment after the death of the fish. The myxospores are highly resistant to cold, heat, and acidity, and will eventually be ingested by T. tubifex.
Recent Research[]
Risk Of Myxobolus Cerebralis Infection To Rainbow Trout In The Madison River, Montana, USA
Researchers at Montana State University studied the relationships between the environment, T. tubifex, and rainbow trout whi disease in the Madison River. They determined the density of the worm host and the prevalence of infection in the worms. Side channels of the river offered different conditions and densitieswere measured there as well. They showed that rainbow trout whirling disease risk was positively correlated to the density of infected worms, which was higher in the side channels. This study is important for understanding areas of high whirling disease risk and the dynamics of the disease. rling
- Rebecca C. Krueger, B. L. Kerans, E. Richard Vincent, and Charlotte Rasmussen 2006. Risk Of Myxobolus Cerebralis Infection To Rainbow Trout In The Madison River, Montana, USA. Ecological Applications 16:770–783. http://dx.doi.org/10.1890/1051-0761(2006)016[0770:ROMCIT]2.0.CO;2