Molecular detection and characterization of Histomonas meleagridis in fighting cocks Thailand

Histomoniasis caused by the protozoa Histomonas meleagridis is a disease of gallinaceous birds which is of special importance to the poultry industry. The turkey is highly susceptible and results in high mortality. However, the disease is less severe in chickens but sometimes leads to mortality especially in those reared in the free-range system. During the present study, four dead fighting cocks were presented to the Veterinary Diagnostic Laboratory, Livestock Animal Hospital, Faculty of Veterinary Science, Chulalongkorn University for post-mortem examination. Based on history and pathological changes, it was preliminarily diagnosed as histomoniasis. The affected livers and caeca samples were collected from which the genomic DNA was extracted. Using species-specific primers, the 18S rRNA gene was amplified by PCR and sequenced. The sequences thus obtained were analyzed using the BLAST search algorithm demonstrating that they are specific for H. meleagridis. The sequences were aligned and compared with the other related sequences published in the GenBank database. The four Thailand isolates showed 98-100% nucleotide sequence identity. While it shows 93-100%, 93-99%, and 88-99% nucleotide sequence identity to China, France, and Austria genotypes respectively. Phylogenetic analysis of 18S rRNA gene fragments with pair-wise deletion of all gaps and insertion showed that out of the 4 Thailand isolates 3 were closely related to China and France isolates and formed a distinct cluster. While the other Thailand isolate formed a separate cluster along with Austria isolates. Therefore, the PCR method sequences and phylogenetic tree analysis based on the 18S rRNA gene carried out during the present study revealed that the PCR method is highly sensitive for the detection of H. meleagridis and there is the genetic diversity of H. meleagridis which indicates the presence of different genotypes of this parasite in Thailand. Histomoniasis caused by the protozoa Histomonas meleagridis is a disease of gallinaceous birds which is of special importance to the poultry industry. The turkey is highly susceptible, whichand results in high mortality. However, the disease is less severe in chickens but sometimes leads to mortality, especially in those reared in the free-range system. During the present study, four dead fighting cocks were presented to the Veterinary Diagnostic Laboratory, Livestock Animal Hospital, Faculty of Veterinary Science, Chulalongkorn University for post-mortem examination. Based on history and pathological changes, it was preliminarily diagnosed as histomoniasis. The affected livers and caeca samples were collected from which the genomic DNA was extracted. Using species-specific primers, the 18S rRNA