Mixed Metazoan and Bacterial Infection of the Gas Bladder of the Lined Seahorse—A Case Report

• Published in: Journal of aquatic animal health 2013-03, Vol.25 (1), p.42-52
• Main Authors: Anderson, Paul A, Petty, Barbara D
• Format: Article
• Language: English
• Subjects: adults; Air Sacs - microbiology; Air Sacs - parasitology; Animals; Bacteria; bacterial infections; Bacterial Infections - microbiology; Bacterial Infections - pathology; Bacterial Infections - veterinary; case studies; Dictysarca virens; fish; Fish Diseases - microbiology; Fish Diseases - parasitology; Gordonia; high performance liquid chromatography; Hippocampus erectus; histopathology; inflammation; intermediate hosts; kidneys; leukocytes; Metazoa; Mycobacterium; Mycobacterium poriferae; necropsy; ova; parasites; praziquantel; radiography; ribosomal DNA; seawater; sequence analysis; Smegmamorpha; swim bladder; toxicity; Trematode Infections - parasitology; Trematode Infections - pathology; Trematode Infections - veterinary
• ISSN: 1548-8667; 0899-7659; 1548-8667
• DOI: 10.1080/08997659.2012.743932

Five wild-caught Lined Seahorses Hippocampus erectus from an aquarium system presented with altered buoyancy and distended upper trunks. Radiography of one specimen revealed a reduced air volume in the gas bladder. Pneumocystocentesis revealed a brown exudate of numerous leukocytes, parasite ova, and Gram- and acid-fast-positive bacilli under wet mounts and stains. Necropsies revealed enlarged, friable kidneys and distended gas bladders containing copious purulent exudate, necrotic tissue, and adult digeneans Dictysarca virens . Bacterial isolates from exudate cultures grown on Lowenstein–Jensen medium were identified as Gordonia sp. and Mycobacterium poriferae by high-performance liquid chromatography and 16S ribosomal DNA sequencing. Histopathology demonstrated a histiocytic response in kidney and gas bladder exudate, inflammation of the gas bladder wall, and infection of the gas bladder lumen with parasite ova and acid-fast-positive and Gomori's methenamine silver-positive bacilli. Praziquantel is prescribed for digenean infections but dissolves incompletely in seawater and is toxic to this host. Eradication of intermediate host vectors is a management option. Treatment of Gordonia infection has not been addressed in nonhuman animals, and there is no known effective treatment for Mycobacterium spp. infection in fishes. This is the first case report of digenean infection of the gas bladder in a syngnathid, Gordonia sp. infection in a nonhuman animal, and M. poriferae infection in a fish.