Ichthyobodosis

Increase aeration and stabilise parameters while minimising capture and handling. Stop transfers and shared equipment and sample before any dip. Fish with severe respiratory distress need a well-oxygenated treatment system and professional oversight.

Ichthyobodosis is a skin and gill parasitosis caused by the small flagellate Ichthyobodo necator, historically called Costia. It is difficult to recognise without microscopy and can become severe in fry or debilitated fish. Grey mucus and flashing describe injury, not the agent.

Fish may develop a steel-grey sheen, excess mucus, clamped fins, flashing, lethargy and anorexia. Gill involvement causes rapid ventilation, gathering near aeration and piping. In young fish, loss of condition and mortality may precede obvious lesions.

Chilodonella, Trichodina and velvet produce similar mucus and distress; chemical irritants and ammonia mimic gill injury. Ichthyobodo is very small and in fresh mounts shows rapid flickering movement close to epithelium. Free material drifting with current is insufficient for identification.

A direct cycle supports spread through contact, water and tools; stocking, transport and unstable water quality increase clinical risk. The parasite attaches to epithelium and can cause intense irritation. Temperature and host species affect progression, so there is no single clinical window.

A direct cycle supports spread through contact, water and tools; stocking, transport and unstable water quality increase clinical risk. The parasite attaches to epithelium and can cause intense irritation. Temperature and host species affect progression, so there is no single clinical window.

Prepare thin skin scrapes and gill biopsies and inspect immediately at high magnification with adjusted illumination and contrast. Sample several newly symptomatic fish because the tiny flagellate is easily missed. Document site, burden and epithelial integrity alongside water readings.

Increase aeration and stabilise parameters while minimising capture and handling. Stop transfers and shared equipment and sample before any dip. Fish with severe respiratory distress need a well-oxygenated treatment system and professional oversight.

After confirmation, select documented options compatible with species, water and biofilter; delivery accuracy is critical in small volumes. The direct cycle requires considering all exposed hosts and environment without automatically treating linked tanks lacking evidence. Repeat wet mounts to verify clearance.

Piping, rapid loss of condition in young fish, mortality or heavy gill burden require urgent review. If parasites are no longer visible but signs persist, investigate residual gill injury, coinfection or environmental disease. Do not empirically increase concentrations.

Use quarantine, dedicated tools and close observation of new groups, especially fry. Maintain appropriate oxygenation and stocking and minimise swings during transport and acclimation. Early microscopy is preferable to repeated prophylaxis.

Piping, rapid loss of condition in young fish, mortality or heavy gill burden require urgent review. If parasites are no longer visible but signs persist, investigate residual gill injury, coinfection or environmental disease. Do not empirically increase concentrations.