Genetic richness and diversity in Cryptosporidium hominis and C. parvum reveals major knowledge gaps and a need for the application of “next generation” technologies — Research review
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Abstract
Cryptosporidium species (apicomplexan protists) are a major cause of diarrhoeal disease
(= cryptosporidiosis) in humans worldwide. The impact of cryptosporidiosis is also
compounded by the spread of HIV/AIDS and a lack of cost-effective anti-cryptosporidial
chemotherapeutics or vaccines. Mitigation of the impact of cryptosporidiosis in humans
needs to focus on prevention and control strategies, built on a sound understanding
of the epidemiology of Cryptosporidium species. Refined epidemiological studies rely
on the use of molecular tools employing informative genetic markers. Currently, the
60-kDa glycoprotein gene (gp60) is the most suitable and widely used genetic marker
for Cryptosporidium species infecting humans. Here, we undertake an analysis of all
publicly-available gp60 sequence data and associated literature for C. hominis and
C. parvum, and yield useful insights into the richness, diversity and distribution
of genetic variants, and link these variants to human cryptosporidiosis. This global
analysis reveals that, despite high genetic richness in Cryptosporidium isolates from
humans, there is a surprisingly low diversity. It also highlights limited knowledge
about the genetics of cryptosporidiosis in developing nations and in many animals
that might act as infection sources. Clearly, there is a major need for more comprehensive
studies of Cryptosporidium infecting humans and other animals in Africa and Asia.
As molecular technologies improve and become affordable, future studies should utilize
"next generation" sequencing and bioinformatic platforms to conduct comparative 'genome
sequence surveys' to test the validity of current genetic classifications based on
gp60 data. Complemented by in vitro and in vivo investigations, these biotechnological
advances will also assist significantly in the search for new intervention strategies
against human cryptosporidiosis.