Infezione da Vibrio harveyi in cavallucci marini (Hippocampus sp.) con concomitante condizione di struma tiroideo.

Occurrence of an outbreak of chronic mortality among seahorse, Hippocampus erectus and Hippocampus kuda maintained in a public aquarium is reported. The fish were infected by Vibrio harveyi and showed a concomitant condition of thyroid struma. V. harveyi is a waterborne bacterium commonly found in marine environments. Some strains are highly pathogenic to aquatic organisms in reared condition. Diseased seahorses showed melanosis, depigmentate and ulcerative skin lesions and marked swelling of gill chamber. At necroscopy the presence of an exophitic tissue covering the gill arches was noticed. A bacterium identified as Vibrio harveyi was obtained in pure culture from samples of skin lesions, liver and kidney using both conventional bacteriological test and API 20NE system. Histological examination showed a parenchimatous thyroid struma characterized by intense areas of hyperplasia with pseudosolid aspect among follicular colloid areas. By immunohistochemistry high expression of PCNA (Proliferating Cell Nuclear Antigen), Cytokeratin 18 and thyroxin in thyroid tissue was recorded, confirming the high proliferating characteristic of the pathology. In the other organs a septicaemic condition was ascertained. Recently two reports of disease caused by V. harveyi in seahorse were described. In our case the pathology was associated with a concomitant condition of thyroid struma probably due by iodine deficiency. The endocrine dysfunction could have cause a immunodepression condition predisponent for the occurrence of the outbreak.