[Is Cryptosporidium a zoonotic agent?]

13 species and several genotypes have been described so far within the genus Cryptosporidium. All of them have very small stages which makes morphological differentiation difficult. The most common species is C. parvum, an enteric pathogen with a broad host spectrum including man and domestic mammals. Molecular biological studies on isolates of C. parvum and other species have shown that the species is likely not to be monophyletic but consists of several species with different host spectra. Based on DNA marker sequences one human and various animal genotypes can be differentiated. Infections of immunocompetent patients with C. parvum are usually associated with the human genotype, while infections of immunodeficient (HIV-positive) patients can also be correlated with various animal genotypes or even primarily animal pathogenic species of Cryptosporidium (e.g., C. felis). According to our current knowledge cryptosporidia are zoonotic agents; however, an animal source of human infections cannot automatically be assumed. Parasites from human patients with low infectivity for cattle and laboratory rodents could be isolated which are not considered as zoonotic.