Sugumar G, Nakai T, Hirata Y, Matsubara D, Muroga K
Fisheries College and Research Institute, Tamil Nadu Veterinary and Animal Sciences University, Tuticorin, India.
Dis Aquat Organ. 1998 Jun 19;33(2):111-8. doi: 10.3354/dao033111.
Recurrent outbreaks of a disease leading to mass mortalities in an oyster (Crassostrea gigas) hatchery located in western Japan were investigated. The disease occurred regularly in 2- to 8-d-old larvae and has been experimentally controlled in the hatchery by treating the larval rearing water with streptomycin, without ascertaining the etiological agent. The signs of the disease and the course of infection resembled bacillary necrosis reported in oysters and other bivalve molluscs in the USA and Europe. Quantitative and qualitative examinations of the bacterial flora of hatchery samples including source water, broodstock, larval feed and larvae revealed a very high total bacterial load and presumptive vibrios in diseased larvae. Further, the bacterial profile revealed that Vibrio spp. constituted approximately 60 to 95% of the bacteria isolated from infected larvae and most isolates were identified as V. splendidus biovar II and V. harveyi, suggesting their possible role in the disease. However, experimental challenges proved the pathogenicity of V. splendidus II. Several isolates of V. splendidus II from infected larvae were highly pathogenic, producing 100% mortality at levels of 10(5) cfu ml-1 in 24 h, while isolates from other sources demonstrated a low degree of virulence. Detection of V. splendidus II from broodstock, especially in the gonad of a few breeders, suggests the probability that broodstock could be the source and route of transmission of this pathogen.
对日本西部一家牡蛎（太平洋牡蛎）孵化场中反复爆发导致大量死亡的疾病进行了调查。该病在2至8日龄的幼虫中定期发生，并且在孵化场中通过用链霉素处理幼虫养殖用水进行了实验性控制，但未确定病原体。该病的症状和感染过程类似于在美国和欧洲牡蛎及其他双壳贝类中报道的细菌性坏死。对孵化场样本（包括源水、亲体、幼虫饲料和幼虫）的细菌菌群进行的定量和定性检查显示，患病幼虫中的细菌总载量非常高，且存在推测的弧菌。此外，细菌谱显示弧菌属约占从感染幼虫中分离出细菌的60%至95%，大多数分离株被鉴定为灿烂弧菌生物变种II和哈维弧菌，表明它们可能与该病有关。然而，实验挑战证明了灿烂弧菌II的致病性。从感染幼虫中分离出的几株灿烂弧菌II具有高度致病性，在24小时内10⁵ cfu/ml的浓度下死亡率达100%，而从其他来源分离出的菌株毒力较低。从亲体中检测到灿烂弧菌II，特别是在少数亲体的性腺中，表明亲体可能是这种病原体的来源和传播途径。
