Where M. cerebralis has become well-established, it has caused decline or even elimination of whole cohorts of fish. Impact in Europe
The impact of M. cerebralis in Europe is somewhat lessened because the species is endemic to this region, giving native fish stocks a degree of immunity. Rainbow trout, the most susceptible species to this parasite, are not native to Europe; successfully reproducing feral populations are rare, so few wild rainbow trout are young enough to be susceptible to infection. On the other hand, they are widely reared for restocking sport-fishing waters and for aquaculture, where this parasite has its greatest impact. Hatching and rearing methods designed to prevent infection of rainbow trout fry have proved successful in Europe. These techniques include hatching eggs in spore-free water and rearing fry to the "ossification" stage in tanks or raceways. These methods give particular attention to the quality of water sources to guard against spore introduction during water exchanges. Fry are moved to earthen ponds only once they are considered to be clinically resistant to the parasite, after skeletal ossification occurs. Impact in New Zealand
M. cerebralis was first found in New Zealand in 1971. The parasite has only been found in rivers in the South Island, away from the most important aquaculture sites. Additionally, salmonid species commercially aquacultured in New Zealand have low susceptibility to whirling disease, and the parasite has also not been shown to affect native salmonids. An important indirect effect of the parasites presence is quarantine restriction placed on exports of salmon products to Australia.
In its non-symptomatic form, it is more common among Asians and Native Americans than among other populations, and in some families there is a tendency to inherit the condition unilaterally; that is, on one hand only.While it is often found in people with Down Syndrome, many who have this syndrome do not have this crease, and thus is not a diagnostic indicator of the Down Syndrome. The presence of a single transverse palmar has been associated with a number of abnormal medical conditions — that is, it is found at a higher than 1.5% frequency, but in all of these conditions many do not have this crease. Examples of conditions with such an association are fetal alcohol syndrome, and with the genetic chromosomal abnormalities  Down syndrome (chromosome 21), cri du chat syndrome (chromosome 5), Klinefelter syndrome, Wolf-Hirschhorn Syndrome, Noonan syndrome (chromosome 12), Patau syndrome (chromosome 13), IDIC 15/Dup15q (chromosome 15), Edwards syndrome (chromosome 18), and Aarskog-Scott syndrome (X-linked recessive), or autosomal recessive disorder, such as Leukocyte adhesion deficiency-2 (LAD2). A unilateral single palmar crease was also reported in a case of chromosome 9 mutation causing Nevoid basal cell carcinoma syndrome and Robinow syndrome. It is also sometimes found on the hand of the affected side of patients with Poland syndrome, and craniosynostosis. A 1971 study refutes the hypothesis that the phenomenon is caused by fetal hand movement: the appearance of the crease occurs around the second month of gestation, before the digital movement phase in the womb begins. See also
Dermatoglyphics

References


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