Between December 2024 - January 2025, two female longsnout seahorses (H. reidi), were observed showing abnormal behavior, reduced apetite, and isolation. Upon closer examination, one individual presented a white area in the end of the tail (Fig. 1A). In the other seahorse, no external lesions were observed on the body or tail, but a curly tail behavior was noticed (fig. 2).
In the first case , the fish had previously presented the same disease , was treated, and fully recovered . However , the second occurrence showed rapid progression . Within 5 days, the lesion reached almost one-third of the tail (Fig. 1B). The same treatment protocol (ATB + NSAID IM) was applied , but after 10 days the lesion extended to almost half of the tail (Fig. 1C), leading to the decision of euthanasia.
Histopathology of the skin revealed an ulcerative lesion with infiltrative inflammation (A), associated with Gram-positive cocci bacteria . In the intestine, moderate multifocal infiltrative inflammation was observed . The gills presented severe congestion in the central vein and secondary lamellae . Most of the inflammatory cells were consistent with chronic exposure and stress.
In the second case, the animal showed nonspecific clinical signs , becoming progressively lethargic with reduced appetite for 15 days. Hand feeding was attempted without success . The seahorse eventually died , and necropsy with histopathology was performed.
Histopathology revealed congestion in the gills associated with inflammatory infiltration . In the caudal kidney and intestine, inflammatory infiltration associated with Gram-positive cocci bacteria was also observed . Most of the inflammatory cells were consistent with acute exposure . In both cases, vacuolization of hepatocytes was observed in the liver.