Kryptosporidiové infekce ryb

Cryptosporidium spp. is able to infect a wide range of hosts including wild and domestic animals, and humans. Although it is well known that fish could be host several Cryptosporidium species and genotypes, little information is available concerning the prevalence of Cryptosporidium in fresh water fish in Europe. Additionally, the infectivity of C. parvum for fish, the species with wide host range, remains poorly studied. In this study we collected 283 specimens of wild fresh water fish from eight localities, 41 specimens of ornamental fish collected from eight pet shops in the Czech Republic. The occurrence and genetic diversity of Cryptosporidium spp. in studied fish was examined by microscopy and polymerase chain reaction (PCR)/sequencing targeting the small subunit rRNA. The infectivity of C. parvum for pike (Esox lucius) and crucian (Carrasius auratus) were experimentally verified. Microscopy and molecular analysis did not revealed presence of oocysts and specific Cryptosporidium DNA in wild fresh water fish. While microscopy analyses of faecal samples of ornamental fish were negative for presence of Cryptosporidium spp. oocysts, molecular analyses shown presence Cryptosporidium avium, Cryptosporidium baileyi, Cryptosporidium muris, Cryptosporidium parvum, Cryptosporidium tyzzeri and Cryptosporidium varanii. Histology did not show the presence of any developmental stages in any pikes and crucians inoculate with C. parvum or inhabit an environment with C. parvum oocysts. The presence of C. parvum DNA was detected only in intestinal contains of pikes and crucians who inhabit an environment with C. parvum oocysts. Presence of C. avium, C. baileyi, C. muris, C. parvum, C. tyzzeri and C. varanii in ornamental fish is probably resulting of the contamination of the water in the tank by caretaker and detected species almost certainly originated from the pet rodents and birds bred in the same shop. The result of the experimental study supports the hypothesis that cryptosporidia of mammals, birds and reptiles are not infectious for fish and their presence in the fish is result of the environmental contamination.