Molecular characterisation of a disseminated Cryptosporidium infection in a Koi carp (Cyprinus carpio).

Cryptosporidium is a protozoan parasite that infects a wide range of hosts, yet relatively little is known about the epidemiology of cryptosporidiosis in fish. Here we report a disseminated Cryptosporidium infection in a male Koi carp (Cyprinus carpio), with parasite stages identified deep within the epithelium of the intestine, kidneys, spleen, liver and gills causing severe granulomatous inflammatory lesions. Molecular characterization at two loci; 18S ribosomal RNA (rRNA) and actin, revealed this to be a novel Cryptosporidium genotype, most closely related to Cryptosporidium molnari.