Nephropathies appear to be common in seahorses and have been associated with mycobacteriosis, myxozoanosis, and oxalate nephrosis.1,2 Four seahorses from two different captive Hippocampus species (H. erectus and H. procerus) were diagnosed with idiopathic granulomatous nephritis. Two seahorses presented with chronic lethargy and acute dyspnea during their quarantine period. The other two animals were found acutely moribund. The water quality parameters from all tanks were within normal limits prior to and at the time of death. All affected seahorses were euthanatized for humane and diagnostic purposes.
All seahorses had severe granulomatous, necrotizing tubulointerstitial nephritis on histopathology. Microscopic changes were consistent with an infectious disease process involving the kidney. Multiple special staining techniques failed to reveal microorganisms within the renal lesions using conventional light microscopy.
Electron microscopic examination of one H. erectus kidney revealed a protist resembling a protozoan agent within the regions of renal inflammation. The agent was pyriform with a polar flagella and was most consistent with a flagellate. This protozoan agent is possibly responsible for the granulomatous nephritis observed in these animals. Further electron microscopic examination and DNA sequencing are warranted to determine if this protozoan is the etiologic agent for this infectious disease process.
1. Bull, C, ed. Seahorse Husbandry in Public Aquaria. Project Seahorse Manual. 2002.
2. Garner M.M., J.L. Batholemew, S.L. Hallett, R.W. Nordhausen, H. Reed, L. Adams, B. Whitaker. 2004. Renal myxozoanosis in weedy sea dragons (Phyllopteryx taeniolatus). Proc. Am. Assoc. Zoo Vet., Am. Assoc. Wildl. Vet., Wildl. Dis. Assoc. Annu. Meet. Pp. 4–6.