الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
Abstract
SUMMARY AND CONCLUSION
Cryptosporidium parasite has been recognized
worldwide as the most common cause of protozoal diarrhea
leading to significant morbidity and mortality in
industrialized and developing countries. Although person-toperson
transmission has been considered the major route of
transmission, zoonotic transmission of this protozoan may
also occur. The majority of human cases of cryptosporidiosis
are caused by two species: C. hominis and C. parvum.
However, wide range of Cryptosporidium spp. and subtypes
infect humans. Exposition of Cryptosporidium genotypes by
molecular assays is required to recognize sources of
infections and routes of transmission, facilitating the
improvement of risk assessment and measures for prevention
and control.
Hence, the present study aimed to determine
Cryptosporidium genotypes in human stool samples with
correlation with their respective demographic, environmental
and clinical data among Egyptians from greater Cairo.
A cross sectional study was done during the period
from June 2013 to March 2015. A total of 350 human cases
with variable demographic, environmental and clinical
presentations were subjected to mZN stain, then were
examined by ICT kit. All positive Cryptosporidium cases
diagnosed by mZN stain and/or ICT kit were processed for
DNA extraction. The extracted DNA samples were
genotyped using nPCR-RFLP targeting SSU rRNA and
COWP genes.
Based on the obtained results, screening for
Cryptosporidium infection was done using mZN stain, the
prevalence of Cryptosporidium among the study population
Summary and Conclusion
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was 5.7% (20/350). 33/350 (9.4%) were immune reactive for
Cryptosporidium using ICT kit.
All positive stool samples by microscopy and/or
Crypto-Giardia ICT kit methods (40 samples) were subjected
to DNA extraction. After DNA extraction, nPCR was done
using SSU-rRNA and COWP genes. All samples couldnot be
amplified by SSU rRNA gene.
Regarding nPCR targeting COWP gene, 15 (37.5%) of
positive samples by mZN and 13 (32.5%) of positive samples
by Crypto-Giardia ICT kit were successfully amplified.
However, 5 (12.5%) of positive samples by mZN and 20
(50.0%) of positive samples by ICT were not amplified.
To validate the diagnosis of cryptosporidiosis, we
considered detection of the organism by two of the three
techniques as true positive cases. Among the diagnostic tests
used, nPCR showed the highest sensitivity and specificity
100%, followed by mZN stain with 100% sensitivity as there
were no false negative samples, 83.3% specificity as there
were 5 false positive samples, with positive predictive value
(PPV) 75% and negative predictive value (NPV) 100%.
While, ICT showed 86.6% sensitivity as there were 2 false
negative samples, 20% specificity as there were 20 false
positive samples, with positive predictive value (PPV) 39.4%
and negative predictive value (NPV) 71.4%.
Occurrence of Cryptosporidium was analyzed for
associations with potential risk factors determined for the
patient who is positive for Cryptosporidium. There was a
significant association between Cryptosporidium infection
and gender of the patients, with a higher prevalence among
males when compared to females.
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Also, a significant association of infection was found
among those drinking ground water when compared to those
who drinking tape water. Besides, patients with
immunodefficency experienced a significantly higher
prevalence of Cryptosporidium infection than
immunocompetent patients. Similarly, the prevalence of
infection was higher among those who had fever than those
with no fever, and the difference was statistically significant.
It was found that watery and mucoid stool samples showed
significantly higher prevalence than watery samples.
The prevalence of Cryptosporidium infection is
significantly associated with consumption of ready made
salad and unwashed fresh vegetables, when compared to their
counterparts. As regards, age, residence, animal contact,
governorate and water contact did not correlate with
Cryptosporidium infection. Most of Cryptosporidium cases
were detected during summer mainly in August 10 cases and
a second infection peak in May 3 cases.
For genotypic discrimination, nPCR-RFLP analysis
used to digest the positive amplicons of COWP gene. C.
hominis is the predominating strain with no other strains
detected, which means that the main source of
Cryptosporidium infection in the study individuals was
anthroponotic rather than zoonotic source.
Having anthroponotic Cryptosporidium strain
predominance with no association between Cryptosporidium
prevalence and animal contact in our study population
reveals that population dynamics influence the transmission
pattern of Cryptosporidium in greater Cairo, Egypt. Water
contamination may be the key determinant of distinct
seasonality in Egypt and may be coupled with population
dynamics that increase person to person transmission in hot
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125
months and spring due to outdoor activities, including
recreational water use.
Moreover, higher population densities and
compromised infrastructures, low socio-economic class
populations, depending mainly on chlorinated water, in
which Cryptosporidium can survive. All these favour personto-
person anthroponotic transmission.