Dermocystidium sp. infection in farmed Murray cod, Maccullochella peelii

• Published in: Aquaculture 2020-11, Vol.528, p.735596, Article 735596
• Main Authors: Shamsi, Shokoofeh, Zhu, Xiaocheng, Barton, Diane P., Dang, Mai, Freire, Rafael, Nowak, Barbara F.
• Format: Article
• Language: English
• Subjects: Aquaculture; Aquatic animal health; Biosecurity; Environment health; Introduced invasive species; Seafood safety
• ISSN: 0044-8486; 1873-5622
• DOI: 10.1016/j.aquaculture.2020.735596

Murray cod (Maccullochella peelii (Mitchell, 1838)) is an iconic Australian species, initially farmed mostly for stocking but now also for human consumption. Here, we report an infection with Dermocystidium sp., class Mesomycetozoea, order Dermocystida in the gills of Murray cod, from a hatchery in south-eastern Australia. Based on phylogenetic analyses of the 18S ribosomal DNA the parasite was closely related to D. salmonis, however the size of the spores was smaller than that reported for D. salmonis in other parts of the world. Further studies using additional analyses including ultrastructure of the spores would be useful for elucidating the identification of the microorganism. Histopathology showed inflammatory response and epithelial hyperplasia resulting in lamellar fusion particularly in association with the parasite. The condition was diagnosed as branchitis caused by a co-infection with Dermocystidium and epitheliocystis, with Dermocystidium being the dominant pathogen. •This is the first report of Dermocystidium in Australia (new geographical location).•Murray cod Maccullochella peelii is the first host record for Dermocystidium (new host).•Infection only observed in hatchery fish, under 1 year old.•Phylogenetic analyses suggested identification as most likely to be D. salmonis.