Abstract
Cryptosporidiosis is one of the major causes of diarrhea in immune-compromised individuals
and children besides causing sporadic water-borne, food-borne, and zoonotic outbreaks.
In 2016, Cryptosporidium species infection was the fifth leading cause of diarrhea and acute infection causing
more than 4.2 million disability-adjusted life years lost besides a decrease in childhood
growth. Human cryptosporidiosis is primarily caused by two species/genotype: Cryptosporidium hominis (anthroponotic) and Cryptosporidium parvum (zoonotic) besides other six rare species/genotypes. Transmission intensity, genetic
diversity, and occurrence of genetic recombination have shaped the genus Cryptosporidium population structures into palmitic, clonal, and epidemic. Genetic recombination
is more in C. parvum compared with C. hominis. Furthermore, parasite–host co-evolution, host adaptation, and geographic segregation
have led to the formation of “subtype- families.” Host-adapted subtype-families have
distinct geographical distribution and host preferences. Genetic exchanges between
subtypes played an important role throughout the evolution of the genus leading to
“adaptation introgression” that led to emergence of virulent and hyper-transmissible
subtypes. The population structure of C. hominis in India appears to be more complex where both transmission intensity and genetic
diversity are much higher. Further, study based on “molecular strain surveillance”
has resulted newer insights into the epidemiology and transmission of cryptosporidiosis
in India. The identification at the species and genotype levels is essential for the
assessment of infection sources in humans and the public health potential of the parasite
at large. The results of the study over three decades on cryptosporidiosis in India,
in the absence of a national surveillance data, were analyzed highlighting current
situation on epidemiology, genetic diversity, and distribution particularly among
vulnerable population. Despite creditable efforts, there are still many areas need
to be explored; therefore, the intent of this article is to facilitate future research
approaches for mitigating the burden associated with this disease.
Keywords
Cryptosporidium species - subtyping - epidemiology - molecular prospecting - India
