Multilocus genotyping of Giardia duodenalis isolates from calves in Oromia Special Zone, Central Ethiopia

• The overall prevalence of Giardia duodenalis infection in calves was 9.6% (43/449) in central Ethiopia.
• Genotyping result revealed the presence of assemblage E, 95.3% (41/43) and assemblage A (AI), 4.7% (2/43) of the positive samples.
• Sequence analyses showed the existence of genetic polymorphism (10 distinct genotypes) within assemblage E at the SSU rRNA, tpi, bg and gdh genes, Three of them represented novel isolates.
• The analysis showed that cattle isolates of assemblage A identified in this study was clustered with the sub-assemblage AI of human isolate suggesting the possibility for zoonotic transmission.

Giardia duodenalis is a widespread protozoan parasite that infects human and other mammals. Assessing the zoonotic transmission of the infection requires molecular characterization as there is considerable genetic variation within the species. This study was conducted to identify assemblages of Giardia duodenalis in dairy calves; and to assess the potential role of cattle isolates in zoonotic transmission in central Ethiopia. A total of 449 fecal samples were collected and screened using microscopy and PCR targeting the small-subunit (ssu) rRNA, triose phosphate isomerase (tpi), β-giardin (bg) and glutamate dehydrogenase (gdh) genes. The overall prevalence of Giardia duodenalis in dairy calves was found to be 9.6% (43/449). The prevalence of infection based on sex, age and breed difference was statistically not significant (p > 0.05). Genotyping results revealed the presence of assemblage E and assemblage A (AI). The genotypic frequency reported was 95.3% (41/43) for assemblage E and 4.7% (2/43) for assemblage A. There was one mixed infection with assemblages AI and E. Sequence analyses showed the existence of 10 genotypes within assemblage E. One genotype that showed novel nucleotide substitution was identified at the ssu rRNA locus. The other 9 genotypes, 3 at each locus, were identified at the tpi, the bg and the gdh loci with two of the gdh genotypes were novel. Findings of the current study indicate the occurrence of the livestock-specific assemblage E and the potentially zoonotic assemblage A, with the former being more prevalent. Although the zoonotic assemblage was less prevalent, there is a possibility of zoonotic human infection as AI is reported from both animals and humans.