Trichomonads are obligate anaerobes generally found in the digestive and genitourinary tract of domestic animals. In this study, four trichomonad isolates were obtained from carabao, dog, and pig hosts using rectal swab. Genomic DNA was extracted using Chelex method and the 18S rRNA gene was successfully amplified through novel sets of primers and undergone DNA sequencing. Aligned isolate sequences together with retrieved 18S rRNA gene sequences of known trichomonads were utilized to generate phylogenetic trees using maximum likelihood and neighbor-joining analyses. Two isolates from carabao were identified as Simplicimonas similis while each isolate from dog and pig was identified as Pentatrichomonas hominis and Trichomitus batrachorum, respectively. This is the first report of S. similis in carabao and the identification of T. batrachorum in pig using 18S rRNA gene sequence analysis. The generated phylogenetic tree yielded three distinct groups mostly with relatively moderate to high bootstrap support and in agreement with the most recent classification. Pathogenic potential of the trichomonads in these hosts still needs further investigation. 1. Introduction Protozoa are prevalent microorganisms found in almost all habitats worldwide. In the recent years, the classification of protozoa has been continuously undergoing successive improvements. The initial classification of protozoa was based on morphological and cytological observations using light and electron microscopy. However, with the recent advancements in molecular biology, DNA sequences, discrete features of gene organization, and biochemical properties have been used to provide phylogenetic classification of protozoa. One of the well-known protozoan phyla is Parabasalia. The Parabasalia is composed of flagellated anaerobic protists defined by the presence of hydrogenosomes, flagellar apparatus, parabasal body, and parabasal filament. Species under parabasalids were grouped primarily according to the morphology and ultrastructural characteristics of their cytoskeletons. Recently, this highly encompassing phylum is divided into six classes based on both morphological and molecular phylogenetic analyses: Trichomonadea, Tritrichomonadea, Hypotrichomonadea, Cristamonadea, Spirotrichonymphea, and Trichonymphea [1]. Species of medical and veterinary importance are generally found in the classes Trichomonadea, Tritrichomonadea, and Hypotrichomonadea [2]. Trichomonads are obligate protozoan symbionts found in the digestive and genitourinary tract of animals. These organisms are believed to be part of
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