Cryptosporidia are intracellular protozoans that parasitize the apical portions of vertebrate occulorespiratory, gastrointestinal, and genitourinary epithelia. These organisms are generally opportunistic and secondary invaders. However, when intestinal infections occur in immunocompromised or malnourished individuals the resulting dehydration may lead to death. Characteristic lesions include loss of villous epithelial cells, atrophy of the villi, and hyperplasia of crypt epithelium.3
In this case report, there was high mortality in a collection of 3-4-week-old Hippocampus capensis. Two animals were submitted for histologic examination. In the examined section of intestine from one animal, small, round, basophilic, 1 to 2 micron diameter protozoa were found closely adhered to the apical surface of the mucosal epithelium. The density of the organisms within the intestinal sections was variable. Individual mucosal epithelial cell necrosis was increased in the areas of protozoal proliferation. Intracellular-extracytoplasmic macrogamete and trophozoite forms were identified by electron microscopy. These forms were contained in parasitophorous vacuoles within the microvillous portion of the enterocytes and had double electron-dense membranes limited to the parasite-enterocyte interface, which is characteristic of Cryptosporidium.2,4 The other seahorse had a similar scattered mucosal epithelial necrosis; however, no microbes were recognized.