| dc.description.abstract | Cryptosporidium causes cryptosporidiosis, an infectious diarrheal disease, which
can become chronic and life-threatening in immunocompromised individuals.
Cryptosporidium parvum and C. hominis are the primary causes of human
cryptosporidiosis. Of these species, C. hominis only infects humans while C. parvum
additionally infects ruminants, in particular neonatal calves. Therefore, understanding the
transmission dynamics of C. parvum, particularly the specific contribution of zoonotic and
anthroponotic transmission, is critical to the control of this pathogen. Cryptosporidium
parvum genotypes have been identified which appear to be restricted to a single host,
which suggests that this may be a heterogeneous species, with varying infection and
transmission dynamics. The first objective to this thesis was to determine the population
structure of pathogenic C. parvum in the upper Midwest United States. A total of 216
isolates from cases of human cryptosporidiosis in Minnesota and Wisconsin and 64
isolates from diarrheic calves in Minnesota, Wisconsin, and North Dakota were genotyped
at 8 polymorphic loci. A total of 213 isolates, 167 from humans and 46 from calves, had
complete multilocus types (MLT). There were 93 different Ml Ts and sixty of those Ml Ts
were only represented by one isolate. Population analysis revealed a highly recombining,
panmictic population that does not have any genetic, geographic, or host sub-structuring.
The second objective to this thesis was to determine the variability in the in vitro infectivity of different C. parvum strains, IOWA II and Moredun. A quantitative RT-PCR
approach was used to quantify expression of target genes during infection of HCT-8 cells.
Fluorescence microscopy was used to quantify life cycle stages during infection. Our data
showed that the IOWA II reached its sexual stages earlier and had a greater number of
trophozoites/meronts at 24 h p.i. than Moredun. The host used for propagation of C.
parvum also affected subsequent infectivity of HCT-8 cells. | en_US |
