الفهرس 
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Abstract
The present study was aimed to explore the distribution of genotypes and subtypes of both Cryptosporidium and G. duodenalis in kindergarten age children (≤8 years) and dairy calves (≤6 months) in order to improve our understanding of the transmission of both protozoa in Egypt. For this purpose, the following points were investigated. 1- The distribution of Cryptosporidium species, genotypes and subtypes in children and calves. 2- The distribution of Giardia duodenalis assemblages, sub-assemblages and subtypes in children and calves. 3- The genetic diversity and population structures of Cryptosporidium species and Giardia duodenalis in children and calves. In this study, a total of 585 children and 248 dairy calves’ fecal specimens were collected from different kindergartens and farms in El-Dakahlia, El-Gharbia and Damietta provinces, Egypt. Specimens were kept at 4 ◦C and preserved in 70% ethanol in order to prevent DNA deterioration in the Department of Hygiene and Zoonoses, Faculty of Veterinary Medicine, Mansoura University from May 2015 till April 2016. DNA extraction, molecular characterization and genotyping/subtyping of Cryptosporidium spp. and G. duodenalis were done in the Centers for Disease Control and Prevention, Atlanta, GA, USA from May 2016 till April 2018. The results revealed the following: The overall occurrence of Cryptosporidium spp. and G. duodenalis in children were 1.37% (8 out of 585) and 11.28% (66 out of 585), respectively. While the overall occurrence of Cryptosporidium spp. and G. duodenalis in calves were 9.68% (24 out of 248) and 13.31% (33 out of 248), respectively. The results of RFLP analysis of the SSU rRNA gene products and DNA sequencing analysis of all 8 Cryptosporidium specimens which are successfully amplified by the nested PCR from children were five and three specimens belonged to C. hominis and C. parvum, respectively. In calves, of the 24 successfully amplified Cryptosporidium positive specimens by nested PCR, Three Cryptosporidium species (C. parvum, C. bovis, and C. ryanae) were identified by the RFLP analysis of the SSU rRNA gene products and DNA sequencing analysis. C. parvum was identified in 16 specimens, five specimens were C. bovis and C. ryanae was found in three specimens. Multi-locus genotyping (MLG) of the 66 positive children specimens by using tpi, gdh and bg genetic loci detected the presence of assemblage A and B. Of these, 31/66 (46.97%) were assemblage A and 34/66 (51.51%) were assemblage B. Multi-locus genotyping (MLG) of the 33 positive calves specimens by using tpi, gdh and bg genetic loci detected the presence of assemblage E and A. Of these, 32/33 (96.97%) were assemblage E and 1/33 (3.03%) was assemblage A.