Infection dynamics of Neoheterobothrium hirame (Monogenea) on juvenile olive flounder, Paralichthys olivaceus (Temminck & Schlegel), in coastal waters of Japan

A recent epidemic of the invasive monogenean Neoheterobothrium hirame is suspected to have caused the significant decline of the commercial catch of olive flounder, Paralichthys olivaceus, in Japan. To clarify the causal link between parasite invasion and host depletion, we monitored the infections of N. hirame on juvenile flounder for 2 years at two widely separate bays, Obama Bay, experiencing a devastating reduction in flounder catches, and Miyako Bay with a stable catch. Prevalence, mean intensity and abundance of developmental stages of N. hirame were compared between the bays and between fish year classes. Fishes captured at Obama Bay harboured three times more worms than those at Miyako Bay and had a significantly higher overall prevalence of infection. In addition, there was a negative correlation between parasite intensity and host condition factor at Obama Bay, suggesting a causal link between the N. hirame epidemic and the reduction of local flounder populations.     

Dietary levamisole modulates the immune response and disease resistance of Asian catfish Clarias batrachus (Linnaeus)

In order to determine the immunomodulatory effect of dietary levamisole in Asian catfish (Clarias batrachus), fish were fed four different diets for 10 days: a formulated diet as control and the same diet supplemented with 50, 150 or 450 mg levamisole kg^?1 feed. The serum bacterial agglutination titre against Aeromonas hydrophila as a measure of specific immunity, serum haemagglutination titre, natural haemolytic complement activity (ACH₅₀), myeloperoxidase and lysozyme activities, total protein level and oxidative radical production by neutrophils as a measure of non‐specific immunity as well as disease resistance against A. hydrophila challenge to separate vaccinated and non‐vaccinated groups were evaluated at 0, 1, 2 and 3 weeks after last administration of levamisole. Levamisole supplement at the lowest level (50 mg kg^?1) significantly enhanced oxidative radical production and serum myeloperoxidase (MPO) content immediately after 10 days of feeding, which reached peak values after 3 and 2 weeks of feeding respectively. Haemolytic complement and haemagglutination titre were significantly enhanced after 3 and 1 weeks respectively. Haemolytic complement activity and MPO activities were significantly raised to 150 mg kg^?1 after 3 and 2 weeks, respectively. At the highest level of levamisole feeding (450 mg kg^?1) significant decreases in superoxide production and complement activity were measured immediately after levamisole feeding, which returned to the normal level after 1 week post‐ feeding. Fish were challenged with a virulent strain of A. hydrophila at 0, 1, 2 and 3 weeks after levamisole feeding, and the cumulative per cent survival was recorded over 10 days. Feeding levamisole at 50, 150 or 450 mg kg^?1 increased per cent survival in vaccinated fish immediately after levamisole feeding, and survival was significantly higher at 450 mg kg^?1. There was no difference in mortality patterns in non‐vaccinated fish. The results support the use of levamisole at 50 mg kg^?1 feed for 10 days as an immunostimulant in Asian catfish farming.     

梭子蟹假丝酵母菌病初步研究

2002-2003年,舟山市暂养梭子蟹连续发生被称为“乳化病”的暴发性疾病,并导致大量死亡。发病主要集中在每年10月至翌年2月低水温期的海捕暂养梭子蟹,病蟹蟹体消瘦,肌肉萎缩,横切步足,在断口处有乳白色的液体流出,打开蟹盖,盖内可见大量乳白色液体。从乳白色液体内能镜检出大量酵母菌样微生物,菌体大小为(2.3~7.8)μm×(1.3~6.5)μm,多数呈卵圆形,细胞大多单个或成对排列,多边芽殖。同时,显微组织病理观察可见病蟹肌肉、心脏、肝胰脏以及鳃等部位也可发现相同菌体。该菌可生长在TCBS上形成白色菌落,在孟加拉红上形成红色菌落,经菌体形态、培养特性及生理生化反应,鉴定为假丝酵母菌属酵母菌(Candidaoleophila)。人工感染试验发现,其对健康梭子蟹具有致病性,出现与自然病蟹相同的症状,并在人工感染病蟹中分离出相同菌株,表明假丝酵母菌属酵母菌是该病的病原。     

High yield and rapid growth of Neoparamoeba pemaquidensis in co-culture with a rainbow trout gill-derived cell line RTgill-W1

Neoparamoeba pemaquidensis is an ubiquitous amphizoic marine protozoan and has been implicated as the causative agent for several diseases in marine organisms, most notably amoebic gill disease (AGD) in Atlantic salmon. Despite several reports on the pathology of AGD, relatively little is known about the protozoan and its relationship to host cells. In this study, an in vitro approach using monolayers of a rainbow trout gill cell line (RTgill-W1, ATCC CRL-2523) was used to rapidly grow large numbers of N. pemaquidensis (ATCC 50172) and investigate cell-pathogen interactions. Established cell lines derived from other tissues of rainbow trout and other fish species were also evaluated for amoeba growth support. The amoebae showed preference and highest yield when grown with RTgill-W1 over nine other tested fish cell lines. Amoeba yields could reach as high as 5 x 10(5) cells mL(-1) within 3 days of growth on the gill cell monolayers. The amoebae caused visible focal lesions in RTgill-W1 monolayers within 24 h of exposure and rapidly proliferated and spread with cytopathic effects destroying the neighbouring pavement-like cells within 48-72 h after initial exposure in media above 700 mOsm kg(-1). Disruption of the integrity of the gill cell monolayers could be noted within 30 min of exposure to the amoeba suspensions by changes in transepithelial resistance (TER) compared with control cell monolayers maintained in the exposure media. This was significantly different by 2 h (P < 0.05) compared with control cells and remained significantly different (P < 0.01) for the remaining 72 h that the TER was monitored. The RTgill-W1 cell line is thus a convenient model for growing N. pemaquidensis and for studying host-pathogen interactions in AGD.     

Accumulation of organotin compounds and marine birnavirus detection in Korean ascidians

ABSTRACT:   Recently, a serious disease spread extensively in aquaculture sites of the ascidian Halocynthia roretzi in Korea. To understand circumstances of ascidians in Korean aquaculture sites, residue levels of organotin compounds were analyzed, and detection of a marine birnavirus (MABV) in tissues of H. roretzi was attempted. Korean H. roretzi showed high concentrations of butyltins (mono, di, and tributyltins), especially in the gill, hepatopancreas, and digestive tract. However, there was no significant difference in the residues of butyltins in the hepatopancreas between diseased and non-diseased ascidians. The positive rate of MABV detection was high in the hepatopancreas, but also no significant difference was observed between diseased and non-diseased individuals. These observations suggest that an accumulation of tributyltin and a latency of MABV in H. roretzi tissues does not directly relate to the occurrence of the disease.     

皱纹盘鲍（Haliotis discus）脓疱病的研究

１９９３年夏季，大连水产养殖公司槽式养殖的鲍（Ｈａｌｉｏｔｉｓ）发生脓疱病，死亡率高达５０－６０％，经分离纯化得９３０１和９３０２二个菌株，镜检结果表明，两个菌株均匀极生单鞭毛的革兰氏阴性短杆形细菌。在人工感染试验中，健康鲍足肌分别注射两个菌株的菌液，感染率均高达１００％，病症与自然发病的安全相同，因此，证明９３０１和９３０２菌株即为脓疱病的病原菌，药敏试验表明，两个菌株对氯霉素，复方新诺明高度敏     

Reduction of transport stress of ayu by obligated schooling

We investigated stress responses of ayu Plecoglossus altivelis under the hypothesis that overcrowding during transport can be a stressor and the stress predisposes fish to disease by decline in immunocompetence. The extent of stress response was determined under different fish densities. As inferred from the serum concentration of cortisol 1 day after the treatment, the density at more than 23 kg/m³, which was within the range of normal transporting procedures, acutely evoked intense stress responses. To examine a possible way to reduce the stress response of fish under crowding conditions, we compared two fish groups established in water tanks with circulating (whirling) and turbulent currents at the same density. The cortisol levels 1 day after the treatment were 2.5-fold higher in turbulent current than in whirling current. Fish in whirling current formed a school, while those in turbulent current aggregated with each other. Schooling of fish induced by water flow may reduce their stress responses during transport. A transport system with a directional water flow should keep fish in good condition without reducing the number of fish contained.     

鲤鱼单极虫病组织病理研究

本文报道了1989年以来,造成王快水库等网箱养鲤大批死亡的单极虫病,病鱼出现烂鳃、肛门红肿、腹部膨大,腹腔内有大量粘液等症状;显微观察的结果为:各组织器官发生病变,肠上皮细胞严重坏死,平滑肌纤维发生玻璃样变及解体,鳃丝充血,鳃小片融合,肝细胞核溶解、坏死。     

刺参体内的新病原--一种球状病毒

2004年12月中下旬~2005年4月对辽宁沿海地区刺参越冬苗发病严重地区,进行了跟踪调查分析。调查结果显示,2004年刺参越冬苗发病比往年早,来势凶猛,持续时间长,流行面广,具较明显的流行病特征,病症异于往年,发病厂家达50%以上,部分地区超过80%,严重地区80%~90%;从患病参体内分离出2株优势细菌和一种新的球状病毒,经负染和超薄切片在电镜下观察,证实有大量球状病毒存于参体内。     

牙鲆淋巴囊肿病毒一抗原蛋白的确认及定位

以牙鲆淋巴囊肿病毒（LCDV）为抗原免疫Balb/c小鼠，而后将小鼠脾细胞与P3U1骨髓瘤细胞融合，以囊肿组织冰冻切片的免疫荧光染色筛选杂交瘤细胞，阳性结果显示特异性块状荧光信号集中在囊肿细胞的细胞质边缘部分，且多个荧光信号相连呈现链圈状，有限稀释 法克隆阳性杂交瘤细胞，三次克隆后获得4株稳定产生抗LCDV抗体的单克隆杂交瘤细胞株（1A8、1D7、2B6、2D11）。应用Western-blotting法分析单抗识别蛋白的分子量，结果显示，单抗1D7 和2B6均能特异性结合一条分子量116 kD病毒多肽；应用免疫电镜技术定位单抗识别的抗原决定簇，结果发现胶体金颗粒集中吸附在病毒粒子衣壳周围，且背景清洁，无散在的金颗粒或其他污染物。实验结果说明分子量约为116 kD的蛋白多肽为LCDV病毒衣壳蛋白，且具有线性抗原决定簇。