Microscopical and molecular detection of Trichodina spp. in fish in Mosul, Iraq

Trichodiniasis is a serious fish ectoparasitic infestation worldwide. The ciliate protist distributes it and infests the fish's skin, fins, and gills. Two hundred fish samples of five species (Arabibarbus grypus, Cyprinus carpio, Chondrostoma regium, Luciobarbus xanthopterus and Mesopotamichthys sharpeyi) were collected from local city markets in Mosul from August 2023 to the end of February 2024. For the detection of infestations with Trichodina spp., direct wet mount smears from the skin, gills and fins were done and confirmed the infestation by Polymerase Chain Reaction (PCR) and phylogenetical tree analysis by amplifying the 18S rRNA gene. Depending on morphological characteristics, microscopical examination results revealed that the total infestation rate with Trichodina spp. was 19.5% (39/200). Trichodina sp. appeared pear to round in shape with a distinct adhesive disc with a diameter of 37-60 μm and golden to brown. Molecular and gene sequencing analysis confirmed the infection with Trichodina spp., the reaction product 1700 bp. One positive isolate was recorded in the NCBI under accession number PQ012982. It showed a 100% match with other isolates for the same genus compared with other studies in South Korea registered in the GenBank.