Submitted to: Emerging Infectious Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/4/2014
Publication Date: 2/28/2014
Citation: Li, N., Xiao, L., Alderisio, K., Elwin, K., Chalmers, R., Santin, M., Fayer, R., Kvac, M., Ryan, U. 2014. Subtyping Cryptosporidium ubiquitum, an emerging zoonotic pathogen in humans. Emerging Infectious Diseases. 20(2)217-224. Interpretive Summary: The species Cryptosporidium ubiquitum was described and named by ARS scientists. Previously it was simply known as the Cryptosporidium cervine genotype. It is emerging as another major zoonotic species having been found worldwide in humans, mostly in industrialized nations. C. ubiquitum is of public health concern because of its wide geographical distribution and broad host range, infecting the greatest number of animal species among all Cryptosporidium species. It has been commonly detected in domestic and wild ruminants, rodents, and primates. It has also been found in drinking source water, storm water runoff, stream sediment, and wastewater. To accurately identify isolates and conduct epidemiological studies of outbreaks it was necessary to develop a molecular subtyping method. The gp60 gene was used and several subtype families were identified in specimens from ruminants, rodents, humans, and water sources. This tool is now available for medical and veterinary technicians, epidemiologists and others to use for detection and identification of this pathogen.
Technical Abstract: Cryptosporidium ubiquitum is an emerging and important human pathogen with a broad range of mammalian hosts. Linkage between human and animal cases of C. ubiquitum has not been possible because of a lack of subtyping tools. In this study, we utilized the 60 kDa glycoprotein gene of C. ubiquitum to develop a subtyping tool based on sequence analysis to identify six subtype families (XIIa to XIIf) in C. ubiquitum. Host adaptation was apparent. Subtype family XIIa was found in ruminants world-wide, subtype families XIIb to XIId were found in rodents in the United States, and subtype families XIIe and XIIf were found in rodents in the Slovak Republic. Subtype families XIIa to XIId were found in C. ubiquitum from 41 humans. Humans in the United States were mostly infected with XIIb, XIIc, and XIId, whereas those in other areas were mostly infected with XIIa. Subtype families XIIb and XIId were also detected in drinking source water in the United States. Contact with sheep and drinking water contaminated by wildlife could be the major sources of human C. ubiquitum infections. Domestication of sheep and sheep farming might have played a major factor in the spread of C. ubiquitum from the Old World to the New World and Australia.