Comparison between human and fish species of Cryptosporidium and Cyclospora

Abstract

Background Cryptosporidium and Cyclospora spp. are worldwide emerging parasites in both immunocompetent and immunocompromised individuals. Objective This study was designed to compare Cryptosporidium and Cyclospora spp. detected in fish with the corresponding species isolated from humans, morphologically and genetically. Detection of any similarity could be considered of potential epidemiological importance. Materials and methods Intestinal contents of 35 Tilapia zillii fish and 50 human stool samples were stained and examined to identify Cryptosporidium and Cyclospora oocysts. Thirty male Swiss albino mice were divided into the control group (I) and the experimental group (II), which was further subdivided into four equal subgroups (IIa, IIb, IIc, and IId), that were infected with fish and human Cryptosporidium and Cyclospora spp., respectively. Two weeks later, all mice were killed; parts of their small intestines were subjected to histopathological examination and processed for transmission electron microscopy (TEM). DNA was extracted from frozen oocysts present in human stool samples and fish intestinal samples, and amplification was performed using specific primers for Cryptosporidium parvum and Cyclospora cayetanensis . Results Cryptosporidium and Cyclospora spp. of both fish and humans detected in mice intestinal sections were morphologically similar by both light and electron microscope. However, failure of DNA amplification of oocysts of both parasites in fish intestinal samples, following application of the specific primers, indicates that fish species were not identical to human species. Conclusion It can be deduced that species identified in fish are apparently not infectious to humans.