Isolation and pathogenicity of pathogens from skin ulceration disease and viscera ejection syndrome of the sea cucumber Apostichopus japonicus

Abstract

The diseases of cultured sea cucumber have been the bottle-neck for the sustainable development of sea cucumber ( Apostichopus japonicus) cultivation in China. Two diseases that occurred from 2004 and caused mass mortalities of sea cucumbers are still prevalent in Liaoning and Shandong provinces in China. One is skin ulceration syndrome and the other is viscera rejection syndrome. The epidemiology and pathogenicity of the diseases were investigated. Microscopic observations were made on healthy and diseased individuals of sea cucumbers to record the bacteria, mold and parasites on the surface of body wall, and the relationship of microbes between skin ulceration disease and viscera ejection disease. The two diseases expressed several differences. Six predominant isolates of bacteria (2004A, 2004B, 04101, 04102, 04103 and 04104) were isolated from the sea cucumbers suffering from skin ulceration in indoor ponds for wintering and outdoor ponds for culturing. Two isolates of bacteria (041201 and 041202) were isolated from the sea cucumbers suffering from viscera ejection syndrome in indoor wintering ponds. Induced infection experiments with these isolates of bacteria showed that all eight predominant isolates of bacteria were pathogenic as they showed the same signs as naturally infected and re-isolates from diseased sea cucumber had the same morphological characteristics. Physiological and biochemical tests and the sequence similarity analysis of the 16S rRNA genes of these bacterial isolates indicated that isolate 2004A was similar to Vibrio cyclitrophicus, 2004B similar to V. splendidus, isolates 04101 and 04103 similar to V. harveyi, 04102 similar to V. tasmaniensis, isolate 04104 similar to Photobacterium sp. isolate 041201 similar to Arthrobacter protophormiae, and isolate 041202 similar to Staphylococcus equorum. Antibiotic sensitive test showed that the eight isolates of bacteria were sensitive to Ofloxacin, Levofloxacin hydrochloride, Cefobid, Doxycycline, Novobiocin, but not sensitive to Oxacillin sodium, Aminobenzylpenicillin, Spectinomycin, or Cefradine.