Saprolegniasis in wild populations of astyanax eigenmanniorum and A. fasciatus (pisces, characidae) from Argentina

MANCINI M; RODRIGUEZ C; BONANSEA M; ASTORECA A; BAGNIS G; DA ROCHA C.A.R; DALCERO A

Revista Brasilera de Medicina Veterinaria

Editora Pan Americana

Año: 2008 vol. 30 p. 115 - 122

The oomycete Saprolegnia parasitica affected a large variety of fish in different parts of the world. Saprolegniasis outbreak in different reservoirs from central Argentina was carried out. The most affected species of fishes were Astyanax eigenmanniorum and A. fasciatus. The prevalence of the disease in these species was higher than 95%, with a high mortality. The skin’s specimens presented a covering similar to cotton aspect with a white brownish color that agglutinated with air contact. The aetiological agent was identified as Saprolegnia parasitica. The mean water temperature was 16.2 (±0.79) ºC. In histopathological study of the skin, areas of degeneration with absence of epidermis and dermis were observed. The surface of the external musculature was displayed, where we could appreciate filamentous colonies detachments. Near the adjacent muscles fibers, edema and bacterial colonies were observed. The low temperature of the water may facilitate the fungal infection. The presence of ectoparasites in association to secondary bacterial infection was responsible to aggravate the pathology. The clinical signals observed and the behavior of the affected fishes were associated to the severe outbreak saprolegniosis.