Molecular characterization and genotyping of Histomonas meleagridis isolated from chicken in Thai Nguyen and Bac Giang provinces using 18S ribosome genetic marker

Abstract

Histomonas meleagridis is a flagellated protozoan pathogen causing “black head” disease (histomoniasis) in chicken with considerable loss for the animal husbandry sector. In this study, we analyzed 18S ribosomal sequences as genetic markers for taxonomic classification and genotyping of 4 Histomonas sp strains (such as: Hm-H1-TN-VN; Hm-H2-BG-VN; Hm-C1-TN-VN and Hm-C2-BG-VN) isolated from liver and cecum samples of the infected chickens collectingin Thai Nguyen and Bac Giang. The result from comparative analysis of 18S ribosomal nucleotide sequences showed that 4 Histomonas sp strains isolating from the histomoniasis chickens in Viet Nam, belonged to H. meleagridis. This identification based on the similarity level of 18S ribosomal sequence of 4 above strains and 13 reference strains of H. meleagridis from Australia, China, France reached 99.3 – 100%, and quite distinct in comparison with the strains of interspecies (Parahistomonas wenrichi, Tritrichomonas nonconforma and Dientamoeba fragilis). Thus, the H. meleagridis strains isolating in Viet Nam were classified, they belonged to the Histomonas genus, Dientamoebidae family, Tritrichomonadida class. Phylogenetic analysis basing on 18S ribosomal sequences affirmed that the Vietnamese H. meleagridis strains placed in the same group with H. meleagridis of genotype I from France. In this study, genotype of the Chinese H. meleagridis strains was also determined as genotype I. This study provided some additional features on genetics and taxonomic classification/genotyping of H. meleagridis in chicken originating in Viet Nam.