The Prevalence of Intestinal Parasites and Molecular Characterization of Cryptosporidium Species in Ethiopia
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Date
2010-06
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Addis Ababa University
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
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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.
Key words: Cryptosporidium, Epidemiology, Genotyping, Sequencing, zoonotic, anthroponotic,
Ethiopia
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Keywords
Cryptosporidium, Epidemiology, Genotyping, Sequencing, zoonotic, anthroponotic ; Ethiopia