|Ryan, Una - Murdoch University|
|Xiao, Lihua - Centers For Disease Control And Prevention (CDCP) - United States|
Submitted to: Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2014
Publication Date: 11/1/2014
Citation: Ryan, U., Fayer, R., Xiao, L. 2014. Cryptosporidium species in humans and animals: current understanding and research needs. Parasitology. 141:1667-1685.
Interpretive Summary: The importance of the genus Cryptosporidium in human and animal health has long been underestimated. It is recognized as one of the major causes of moderate to severe diarrhea in developing countries. With limited treatment options available, control relies on knowledge of the biology and transmission of the members of the genus responsible for disease. Molecular tools enable us to understand the zoonotic potential of Cryptosporidium species and subtypes. Currently, 26 species are recognized as valid on the basis of morphological, biological and molecular data. Of the nearly 20 Cryptosporidium species and genotypes that have been reported in humans, C. hominis and C. parvum are responsible for the majority of infections. The transmission of C. parvum in humans is mostly human to human in developing countries, while in developed countries animal to human infections play an important role. Livestock, particularly cattle, are one of the most important reservoirs of such infections. Domesticated and wild animals can each be infected with several Cryptosporidium species or genotypes that mostly have only a narrow host range and therefore have no known major public health significance. Recent advances in next-generation sequencing techniques and whole genome sequencing will significantly improve our understanding of the taxonomy of Cryptosporidium spp. and transmission of cryptosporidiosis, and the investigation of outbreaks and monitoring of emerging and virulent subtypes. Important research gaps remain including a lack of sub typing tools for many Cryptosporidium species of public and veterinary health importance, and poor understanding of the genetic determinants of host specificity of Cryptosporidium species and impact of climate change on the transmission of Cryptosporidium.
Technical Abstract: In the United States, there are approximately 748,000 cases of cryptosporidiosis annually and hospitalizations from cryptosporidiosis cost an estimated $45.8 million (Scallan et al. 2011). In developing countries cryptosporidiosis accounts for 20% of all cases of diarrhea in children (Mosier and Oberst, 2000) and, depending on location, at some point in life the percentage of affected persons in a population was estimated to range from 20-90% (Dilligham et al. 2002). With cryptosporidiosis so widespread and prevalent, and with prophylaxis and therapeutic treatment options so limited, the ability to prevent and control disease appears best served by sanitation. The availability of clean water and toilets, fastidious handling of food, and a clear understanding of the sources of Cryptosporidium provide a basis for prevention of transmission. Prevention encompasses epidemiology that requires knowledge of the biology and taxonomy of the members of the genus responsible for disease. For precise taxonomy, molecular methods are essential for identification of the species, genotype, and subtype of Cryptosporidium. These molecular tools are clearly described in this review and all the known taxa for Cryptosporidium in humans and domesticated and wild animals are described.