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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/2436

Advisors: Professor Beyene Petros
Keywords: Cryptosporidium
anthroponotic, Ethiopia
Copyright: Jun-2010
Date Added: 4-May-2012
Abstract: Abstract Cryptosporidium spp infections are recognized as important causes of diarrhoea in both immunocompromised and immunocompetent patients. Although a number of studies have been conducted on the prevalence of intestinal parasites in Ethiopia, none of them had indicated the importance of cattle as reservoirs for the prevalent human cryptosporidiosis in Ethiopia. In addition, no study had molecularly characterized Cryptosporidium spp isolates to determine the source (reservior) of human cryptosporidiosis in Ethiopia. This study examined the prevalence and distribution of cryptosporidiosis in 9 different locations in Ethiopia. 1034 human faecal samples from patients with diarrhoea and 350 cattle dung were screened for Cryptosporidium spp oocysts by using modified Ziehl-Neelson staining method. 79 human stool samples (7.6%) and 8 cattle (2.3%) were positive for Cryptosporidium spp. The highest prevalence in humans (10.6%) was detected in the town of Awash 7 (Afar region) and the lowest prevalence (3.8%) in Bishoftu town (Oromia region). Molecular methods were used to determine genotypic and subgenotypic diversity of Cryptosporidium spp. isolates that infect humans in Ethiopia. DNA was extracted from all Cryptosporidium spp positive samples, PCR amplification of the Cryptosporidium spp oocyst wall protein gene (COWP), small sub-unit ribosomal ribonucleaic acid (SSU-rRNA), and 60 kilo-Dalton glycoprotein (GP60) gene fragments were performed. Genotype analysis by PCRRFLP based on COWP and the SSU-rRNA genes, and subgenotyping by DNA sequence analysis of GP60 gene fragments showed the importance of cattle reservoir for the high prevalence of cryptosporidiosis in humans. 52% of the 79 human stool samples and 75% of 8 cattle dung samples were positive in one or other of the three molecular characterization methods. Out of 79 human stool samples, 21(26.6 %) yielded a SSU-rRNA PCR product; 30 (38 %) were positive for xiv COWP and 30 (38 %) were positive for GP60. The majority of isolates (95%) were identified as C. parvum, while only 2.5% were C. hominis and another 2.5% mixed infections of the two species. Sequencing of the GP60 gene fragments of the 13 isolates resulted in three different subgenotypes of C. parvum, belonging to the zoonotic subgenotype family IIa, and one to the subgenotype of C. hominis (Ib). Phylogenetic analysis of the sequences showed C. parvum isolates to belong to three subgenotypes: 8 isolates typed as IIaA15G2R1; 3 isolates typed as IIaA16G2R1; and one isolate typed as IIaA16G1R1. The C. hominis genotype was typed as IbA9G3 subgenotype. The study has identified C. parvum as the major cause of human cryptosporidiosis in Ethiopia and has indicated the major source of cryptosporidiosis to be zoonotic with some (limited) anthroponotic transmission of C. hominis. In addition, it was determined that antiretroviral treatment in HIV/AIDS patients reduces infection with Cryptosporidium and other diarrheogenic protozoan parasites. Based on the findings of the present study, creation of a central national database on the prevalence of human cryptosporidiosis would be a useful step, so that information could be pooled from different regions of Ethiopia to better understand the epidemiology of the disease.
URI: http://hdl.handle.net/123456789/2436
Appears in:Thesis - Biology

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