Abstract
Because of the ability of Cryptosporidium species to infect humans and a wide variety of animals, and because of the ubiquitous presence of cryptosporidium oocysis in the environment, humans can acquire Cryptosporidium infections through several transmission routes Hunter and Nichols, 2002; Chapter 4). These include direct person-to-person or animal-to-person transmission and indirect waterborne and foodborne transmission, and the parasites can be of anthroponotic or zoonotic origin. The role of each transmission route in endemic areas, however, is frequently unclear because of the expensive nature of epidemiologic investigations and the inability to differentiate Cryptosporidium species by conventional microscopy.
Molecular tools have been developed to detect and differentiate Cryptosporidium at the species/genotype and subtype levels (Xiao and Ryan, 2004; Caccio, 2005). The use of these tools has made significant contributions to our understanding of the biology and epidemiology of Cryptosporidium species. This includes better knowledge of the species structure and population genetics of Cryptosporidium, the roles of various transmission mutes in cryptosporidiosis epidemiology, and the significance of parasite genetics in pathogenesis and clinical presentations. These recent developments have enabled researchers to make more accurate risk assessment of environmental and drinking water contamination, and have helped health officials to better educate the public on risk factors invoked in the acquisition of cryptosporidiosis in vulnerable populations.