Molecular Characterization and Genetic Diversity of Cryptosporidium spp. in Human Infections: A Review

The Cryptosporidium spp. are protozoan parasites of significance in the world and the major cause of the diarrheal disease (cryptosporidiosis) in humans, which presents a significant risk to young children, immunocompromised people, and livestock. The introduction of molecular methods has completely transformed the view on the taxonomy, genetic diversity, and the mode of transmission of the parasite that was not initially evident due to the morphological homogeneity of the oocysts. This review summarizes the existing information and knowledge regarding the molecular characterization of species of Cryptosporidium that infect human beings based on genetic diversity. We touch upon the development of diagnostic and typing methods, starting with the classical microscopy and all the way to the current state of multilocus sequence typing (MLST) and whole-genome sequencing (WGS). The review addresses the two most common human-pathogenic species, C. hominis and C. parvum, includes the description of the population structure, genetic recombination role and the public health importance of different subtype families. We look at the specific epidemiological trends where anthroponotic is more likely in low- and middle-income nations than is zoonotic in the high-income nations. In addition, the clinical consequences of this genetic diversity, especially in the vulnerable groups like the HIV/AIDS patients are discussed. This review brings together the results of the most important molecular epidemiological research and points out how advancing knowledge about the genetic landscape of Cryptosporidium can be very essential in crafting an effective disease management approach, outbreak surveillance and population health interventions.