Whirling disease
| Myxobolus cerebralis | |
|---|---|
 |
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| Triactinomyxon stage of Myxobolus cerebralis - note the three "tails" | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Cnidaria |
| Class: | Myxosporea |
| Order: | Bivalvulida |
| Family: | Myxobolidae |
| Genus: | Myxobolus |
| Species: | M. cerebralis |
| Binomial name | |
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Myxobolus cerebralis Hofer, 1903 |
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| Synonyms | |
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Myxosoma cerebralis |
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Myxosoma cerebralis
Triactinomyxon dubium
Triactinomyxon gyrosalmo
Myxobolus cerebralis is a myxosporean parasite of salmonids (salmon, trout, and their allies) that causes whirling disease in farmed salmon and trout and also in wild fish populations. It was first described in rainbow trout in Germany a century ago, but its range has spread and it has appeared in most of Europe (including Russia), the United States, South Africa, Canada and other countries. In the 1980s, M. cerebralis was found to require a tubificid oligochaete (a kind of segmented worm) to complete its life cycle. The parasite infects its hosts with its cells after piercing them with polar filaments ejected from -like capsules.
Whirling disease afflicts juvenile fish (fingerlings and fry) and causes skeletal deformation and neurological damage. Fish "whirl" forward in an awkward, corkscrew-like pattern instead of swimming normally, find feeding difficult, and are more vulnerable to predators. The mortality rate is high for fingerlings, up to 90% of infected populations, and those that do survive are deformed by the parasites residing in their cartilage and bone. They act as a reservoir for the parasite, which is released into water following the fish's death. M. cerebralis is one of the most economically important myxozoans in fish, as well as one of the most pathogenic. It was the first myxosporean whose pathology and symptoms were described scientifically. The parasite is not transmissible to humans.
The taxonomy and naming of both M. cerebralis, and of myxozoans in general, have complicated histories. It was originally thought to infect fish brains (hence the specific epithet cerebralis) and nervous systems, though it soon was found to primarily infect cartilage and skeletal tissue. Attempts to change the name to Myxobolus chondrophagus, which would more accurately describe the organism, failed because of nomenclature rules. Later, the organisms previously called Triactinomyxon dubium and T. gyrosalmo (class Actinosporea) were found to be, in fact, triactinomyxon stages of M. cerebralis, the life cycle of which was expanded to include the triactinomyxon stage. Similarly, other actinosporeans were folded into the life cycles of various myxosporeans.
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Wikipedia