Co-infection of Piscichlamydia Trichopodus (Order Chlamydiales) and sp. (Myxosporea, Myxobolidae) in Snakeskin Gourami (Regan 1910).

The present study describes a simultaneous infection of a novel -like organism (CLO) with a Myxozoa parasite, sp. in snakeskin gourami in Thailand. A new CLO is proposed " Piscichlamydia trichopodus" (CPT) based on 16S rRNA phylogenetic analysis. Systemic intracellular CPT infection was confirmed by histological examination, hybridization, PCR assay, and sequencing of 16S rRNA. This novel pathogen belongs to the order but differs in certain aspects from other species. The histopathological changes associated with CPT infection were different from the typical pathological lesions of epitheliocystis caused by previously known CLO. Unlike other CLO, CPT localized in the connective tissue rather than in the epithelial cells and formed smaller clumps of intracellular bacteria that stained dark blue with hematoxylin. On the other hand, typical myxospores of the genus with tails were observed in the gill sections. Infection with sp. resulted in extensive destruction of the gill filaments, most likely leading to respiratory distress. Due to the frequency of co-infections and the unavailability of culture methods for CLO and sp., it was difficult to determine which pathogens were directly responsible for the associated mortality. However, co-infections may increase the negative impact on the host and the severity of the disease. Given the commercial importance of the snakeskin gourami and its significant aquaculture potential, the findings of this study are important for further studies on disease prevention.