Enteromyxum leei (Myxozoa), a Lethal Intruder of Tropical Pet Fish: First Case in Humphead Wrasse, Cheilinus undulatus (Rüppell, 1835)

The lethal effect of enteromyxosis is recorded for the first time in the humphead wrasse, Cheilinus undulatus, a tropical pet fish. Enteromyxosis was caused by the myxosporean parasite Enteromyxum leei, and the gut was the only tissue affected in this case. Severe enteritis and degeneration of the intestinal mucosa may have caused a digestive function disorder, thereby resulting in the fish's death. The histopathological findings of this case included destruction of normal tissue architecture of the intestinal mucosa, chronic inflammation, and infiltration of mast cells/eosinophilic granular cells, which resembled findings described in other fish that were diagnosed with enteromyxosis. Induced stress by transportation and entrance to a new environment possibly played an underlying role in the virulence of the parasitic infection and associated tissue pathology.