对虾暴发性流行病病原的人工感染研究

用发生暴发性流行病的中国对虾对健康虾进行人工投喂感染。同时，从病虾中分高毒种，毒种液经滤纸、０．４５μｍ和０．２２μｍ滤膜过滤，各滤液对健康中国对虾进行注射、浸泡、和共居感染。结果显示，对虾暴发性流行病的病原可通过投喂和注射感染健康对虾。浸泡和共居的方法均不能感染健康对虾，说明对虾暴发性流行病的传播途径主要为对虾的摄食。病原体对乙醚和５６℃３０ｍｉｎ处理敏感，不易通过０．２２μｍ滤膜。人工感染试验结果证明，对虾暴发性流行病的病原为皮下及造血组织坏死杆状病毒。     

首例斑节对虾越冬亲虾发生杆状病毒的皮下及造血组织坏死症研究

湛江长洪对虾苗种实验场的斑节对虾转入越冬池后３～１０ｄ内发生暴发性死亡，症状与北方地区杆状病毒的皮下及造血组织坏死症一致。病理学研究表明，所有发病虾样的皮下组织、造血组织、结缔组织、肝胰腺血窦、淋巴器官等细胞核均存在严重的ＨＨＮＢＶ病灶，只有２０％的发病对虾肝胰腺中观察到轻微感染的ＭＢＶ包涵体。ＨＨＮＢＶ单抗的酶联免疫染色，可对ＨＨＮＢＶ的病灶产生特异性着色，对虾组织结构和ＭＢＶ包涵体均不着色。在山东培育三代并养殖１６个月的斑节对虾中也观察到与湛江发病的越冬亲虾相同的情况。以上说明，近年来在广东一带ＨＨＮＢＶ是值得重视的病原，其危害可能重于ＭＢＶ。对于发生过对虾暴发性流行病的群体来说，不宜用来作为亲虾。     

中草药作为免疫增强剂在虾类养殖上的应用

对虾养殖业是我国海水养殖业的支柱产业，自1993年全国养殖对虾因感染对虾白斑病毒（WSSV）而发生大规模暴发性流行病以来，对虾养殖业蒙受了毁灭性的打击。到目前为止，已发现有20多种病毒可以感染虾类，而对付这些病毒至今还没有有效的方法。抗生素的使用一定程度缓解了疾病的发生，但由于它在动物体内残留，     

杆状病毒性的皮下及造血组织坏死─对虾暴发性流行病的病原和病理学

１９９３年对虾暴发性流行病的患病对虾经光镜组织病理学研究和电镜观察，在对虾的皮下组织（包括前肠上皮、后肠上皮、真皮和鳃等）、结缔组织、造血组织、触角腺及血淋巴细胞等的细胞核均发现核肿大和深的嗜酸性着色。在电镜下，病变组织的细胞核内为一种杆状病毒充满，病毒大小为１２０ｎｍ×３６０ｎｍ，有囊膜，在细胞内不形成核型多角体或颗粒体类包涵体，属于杆状病毒属的无包涵体型杆状病毒亚群，即Ｃ型杆状病毒亚群。根据该对虾暴发性流行病的症状、病毒感染的靶组织和病毒的特征，该病毒被认为是一种新的对虾病毒，暂定名为皮下及造血组织坏死杆状病毒。     

凡纳滨对虾感染致急性肝胰腺坏死病副溶血弧菌(VpAHPND)的定量分析

对虾急性肝胰腺坏死病(Acute hepatopancreatic necrosis disease, AHPND)是由致AHPND副溶血弧菌(AHPND-causing Vibrio parahaemolyticus, VpAHPND)携带的pVA1-like质粒所表达的PirAVp和PirBVp毒力蛋白对对虾肝胰腺的急性毒性所致。本研究用2.19×105 CFU/ml VpAHPND分离株20130629002S01对凡纳滨对虾(Litopenaeus vannamei)进行浸泡感染,于感染后2~9 d采集对虾的肝胰腺、鳃、肠道、肌肉组织,采用实时荧光定量PCR方法,检测各组织中的pirAVp拷贝数。结果显示,感染后凡纳滨对虾各组织均能检测到pirAVp,其中,肝胰腺在感染后第4天达到峰值, 为8.71×104 copies/mg,而鳃、肌肉、肠道分别在第3、4、5天达到峰值,分别为9.08×103、2.59×104、5.76×104 copies/mg。早期感染鳃组织中先出现VpAHPND的富集,在高死亡发生期,VpAHPND数量在肝胰腺和肠道出现高峰,在死亡数量逐渐下降的后期,各组织的VpAHPND均快速下降,肠道、肝胰腺和肌肉中的VpAHPND水平趋于接近。对虾肝胰腺组织病理切片显示,同一时间有临床症状的病虾和濒死对虾相比,濒死对虾表现出更严重的AHPND病理特征,且二者的组织病理特征均随着感染时间的延长变得更为严重,但检测到的VpAHPND数量呈下降趋势。研究表明,在VpAHPND感染过程中,组织中的pirAVp基因数量不能代表对虾的发病程度,发病程度及组织病理严重的AHPND样品中VpAHPND的数量不一定处于高水平状态。     

南美白对虾的病害防(二)

3.黄头病【病因】该病病原是黄头病病毒,呈杆状,有囊膜,病毒粒子(50～95)纳米×(130～380)纳米,属单链RNA病毒。【症状】病虾早期游动迟缓,头胸甲呈黄色或发白,膨大,鳃变成淡黄色到棕色,肝胰腺变成淡黄色。主要感染鳃组织、淋巴器官、血细胞和结缔组织等。该病毒毒力较强,对虾被感染后3～5天内可全军覆灭。患病虾组织多处坏死。胞核缩小或破裂,核周围细胞质内有嗜碱性的球形包涵体。染毒组织的血窦中有一种独特的数目不等的球形细胞。其胞质嗜碱性、球形胞核居中。【流行及危害】该病首先在印度斑节对虾的精养塘中发现,后在东亚地区的其它…     

对虾肝胰腺坏死病的病理与防治

患病对虾最初的症状是在对虾的肝胰腺两侧白色包膜呈弥散状增生,在15天左右的时间内白膜增生不断扩展、增厚,虾的肝胰腺本体先萎缩后肿胀,肝体由正常的青褐色逐渐转暗红色(中期),直至死亡时变为粉黄色。肝胰腺严重糜烂,一触即散,呈水体状。死亡期另一典型特征,在虾的头甲壳内侧可见许     

中国对虾暴发性流行病的血液病理研究

对患暴发性流行病的中国对虾进行了血液生理生化指标检测。与健康虾比较，自然发病与人工感染病虾的血清总蛋白、白蛋白、血糖含量减少，而甘油三酯、尿素氮、肌酐含量及血清碱性磷酸酶（ＡＫＰ）、谷丙转氨酶（ＧＰＴ）、乳酸脱氢酶（ＬＤＨ）活性增加。对人工感染试验病虾跟踪检测显示，对虾在病毒感染后２４ｈ，出现ＡＫＰ升高、血清总蛋白、白蛋白、血糖含量下降，随着感染时间延长，出现变化的血液指标增多，变化幅度也急速增加。结果表明，中国对虾暴发性流行病是杆状病毒急性感染后所引起的一种全身性疾病，患病虾在营养物质代谢、抗病力、消化、呼吸、排泄等方面的生理功能迅即受到严重损害。     

南美白对虾白斑综合症的预防与治疗方法

目前南美白对虾暴发性流行病主要是对虾白斑综合症(WSSV),该病传染性强,危害大,它的病原体是一种无包涵体杆状病毒,在已报道的所有对虾病毒中,该病毒的毒力最强,且其地域分布及宿主范围广泛,严重制约着我国对虾养殖业的发展.     

对虾传染性皮下及造血组织坏死病毒(IHHNV) PCR检测方法的建立

对虾传染性皮下及造血组织坏死病毒(IHHNV)病是国际兽疫局(OIE)划定的甲壳类其他重要疾病之一,它分布较广,危害严重,对世界对虾养殖业发展影响重大.本文根据Genbank登录的IHHNV基因序列(AF218266),设计了1对特异性引物,从纯化的IHHNV DNA和感染IHHNV凡纳滨对虾(Litopenaeus vannamei)组织DNA中成功地扩增出产物大小为703bp的DNA片段,该对引物对IHHNV DNA的检测灵敏度为19.85fg(8.83×103病毒拷贝),与健康对虾组织DNA、对虾白斑综合征病毒(WSSV) DNA及对虾肝胰腺细小病毒(HPV) DNA无交叉反应.本方法可快速、灵敏、特异地检测出对虾感染和携带IHHNV状况,为对虾健康养殖、无特定病原(SPF)种群选育及流行病调查提供了有效的检测手段.     

Stress-induced transmission of Yersinia ruckeri infection from carriers to recipient steelhead trout Salmo gairdneri Richardson

Abstract. The transmission of Yersinia ruckeri has been investigated in steelhead trout using asymptomatic carriers of the causative bacterium of enteric redmouth disease. It was found that unstressed carrier fish did not transmit the bacterium to recipient fish to cause either an epizootic or produce new carrier fish. However, when the carriers were stressed with heat, the bacterium was transmitted from the carrier to recipient fish producing a lower intestinal carrier state but no deaths. Examination of experimentally infected fish to determine the number of carriers among the survivors indicated that the frequency varied as a function of time following infection. When immunized fish, were challenged with Y. ruckeri they became temporary carriers of the bacterium for up to 3 days; but were not able to transmit the infection to healthy recipient fish.     

The route of entry and progression of infectious haematopoietic necrosis virus in Oncorhynchus mykiss (Walbaum): a sequential immunohistochemical study

Abstract. Steelhead trout, Oncorhynchus mykiss (Walbaum), fry were experimentally infected with infectious haematopoietic necrosis virus (IHNV) Round Butte 1983 (Type 1). Fry were sampled daily, before and during the epizootic. Fish tissues were tested for infectious virus by tissue culture assay and for IHNV nucleocapsid protein by alkaline phosphatase immunohistochemistry (APIH). The progression of virus through the tissues was followed by APIH until the fourteenth day. Viral infection progressed from two major sites: from the gills into the circulatory system; and from the oral region into the gastrointestinal tract and then into the circulatory system. Once in the blood, virus was disseminated to virtually every organ. Progression of IHNV within and between organs is discussed.     

A new viral epizootic of Anguilla japonica Temminck and Schlegel

Abstract. In 1969, a new kind of epizootic occurred among eels in Japan and virological investigation was initiated. A new virus designated eel virus european (EVE) was isolated and biological, cytological, serological tests and infectivity trials were carried out. In its CPE on RTG-2 cells and additionally in its biological properties and particle size, EVE was found to be similar to infectious pancreatic necrosis virus (IPNV). Serologically, EVE was similar to the ď Honnincthun, France, strain of IPNV. However, infectivity trials showed that EVE and IPNV differed; EVE killed Japanese eels Anguilla japonica but not rainbow trout fry Salmo gairdneri , while IPN virus killed rainbow trout fry but not eels. We consider EVE to be the primary agent causing the new epizootic and propose the name viral kidney disease for the resulting clinical condition.     

Transmission of infectious pancreatic necrosis virus in striped bass, Morone saxatilis (Walbaum)

Abstract. Infectious pancreatic necrosis virus (IPNV) did not cause increased mortality in experimentally challenged striped bass, Morone saxatilis (Walbaum). Fry became transiently infected after waterborne challenge but fingerlings were resistant to that route. However, striped bass fingerlings readily became chronic virus carriers following ingestion of IPNV-contaminated food. Vertical transmission was not demonstrated using either IPNV-carrier striped bass adults or IPNV-exposed sex products.     

Pathogenesis of infectious pancreatic necrosis virus infection in brook trout, Salvelinus fontinalis (Mitchill), following intraperitoneal injection

Abstract. The pathogenesis of IPNV infection was examined in young brook trout following intraperitoneal inoculation. Fish were sampled sequentially and the distribution of virus determined by virus isolation, histopathology and immunofluorescence. Following intraperitoneal inoculation, virus entered the peritoneal cavity and by 2 days post-inoculation virus had interacted with the pancreatic exocrine cells. Replication in these cells resulted in the production of IPNV-specific antigen, necrosis of infected cells, and spread of infectious virus to adjacent tissue. Areas of viral replication were at first multifocal but tended to merge as they grew. Eventually, most of the acinar tissue became involved and only small pockets of normal acinar cells remained. Twelve-week old brook trout survived with only a small amount of functional exocrine pancreas and limited virus replication continued in this tissue for weeks. Extensive virus replication appeared to take place only in the pancreas although viral antigen and slight pathological changes were found in the renal interstitium and livers of some fish.     

Spinal curvatures and an encephalotropic myxosporean, Triangula percae sp. nov. (Myxozoa: Ortholineidae), enzootic in redfin perch, Perca fluviatilis L., in Australia

Abstract. A new myxosporean, Triangula percae sp. nov., (Myxozoa: Ortholineidae) from the brain of redfin perch, Perca fluviatilis L., is described. Spinal curvatures are prevalent in many perch populations in Victoria, Australia, Triangula percae infection was detected in all perch displaying spinal curvatures and in 67% of normal perch from Lake Nillahcootie in north east Victoria. Perch populations exhibiting spinal curvatures in several other waterways were also infected with Triangula percae but the infection was absent in one population which was apparently normal. Triangula percae infection is, thus, considered to be the cause of a proportion of the spinal curvatures. Certain fish surviving outbreaks of epizootic haematopoietic necrosis virus (EHNV) also developed spinal curvatures, which may have been due to viral infection of the central nervous system.     

Experimental infection of European crustaceans with white spot syndrome virus (WSSV)

Eight European marine and freshwater crustaceans were experimentally infected with diluted shrimp haemolymph infected with white spot syndrome virus (WSSV). Clinical signs of infection and mortalities of the animals were routinely recorded. Diagnosis was by direct transmission electron microscopy (TEM), DNA hybridization (dot-blot and in situ hybridization) using WSSV probes and by PCR using WSSV specific primers. High mortality rates were noted between 7 to 21 days post-infection for Liocarcinus depurator , Liocarcinus puber , Cancer pagurus , Astacus leptodactylus , Orconectes limosus , Palaemon adspersus and Scyllarus arctus . Mortality reached 100%, 1 week post-infection in P. adspersus . When infection was successful, direct TEM observation of haemolymph revealed characteristic viral particles of WSSV, some observed as complete virions (enveloped), others as nucleocapsids associated with envelope debris. WSSV probes showed strong positive reactions in dot-blots and by in situ hybridization in sections and specific virus DNA fragments were amplified successfully with WSSV primers. White spot syndrome virus was pathogenic for the majority of the crustaceans tested. This underlines the epizootic potential of this virus in European crustaceans.     

Epidemiology of epizootic haematopoietic necrosis virus (EHNV) infection in farmed rainbow trout, Oncorhynchus mykiss (Walbaum): findings based on virus isolation, antigen capture ELISA and serology

Abstract. The epidemiology of epizootic haematopoietic necrosis virus (EHNV) infection was studied in farmed rainbow trout, Oncorhynchus mykiss (Walbaum). Estimates of mortality during five outbreaks on a commercial farm from 1986 to 1992 ranged from 0033 to 0.2% per day and total mortality did not exceed 3–4% in any outbreak. Affected fish were 0+ and less than 125 mm forklength. Clinical signs were non-specific, and laboratory examination was required to confirm the diagnosis. At the height of the outbreak in 1992, EHNV was demonstrated by virus isolation and antigen capture ELISA in 89% of clinically affected fish and 51% of dead fish, while the prevalence of infection in apparently healthy in-contact fish was 4%. Two and 4 months later the virus was not detected in a group of apparently healthy fish that had been affected earlier. Antibodies specific for EHNV were not found in rainbow trout from the infected farm; however, strong humoral responses were detected by ELISA in two immunized fish, indicating that the virus was immunogenic. These data suggested that EHNV was poorly infective but highly virulent in rainbow trout. Clinical EHNV infection was positively correlated with high rearing density and a low rate of water exchange, and therefore, with presumed poor water quality. Water temperature, which ranged from 11 to 17°C during outbreaks, did not appear to determine the incidence of clinical infection. EHNV infection in farmed rainbow trout was preceded by infection in free-living redfin perch, Perca fluviatilis L., in the water catchment, but it was uncertain whether this represented the source of infection for rainbow trout.     

池塘养殖患病泥鳅两种病毒病原的电镜观察初报

利用电子显微镜技术,对湖北荆州池塘养殖患病泥鳅的组织进行超薄切片电镜观察。电镜观察结果显示:在患病泥鳅的脾脏、肾脏、心脏及肠道组织中观察到大量球形和杆状两种形态的病毒颗粒。球形病毒颗粒无囊膜,直径约50~75 nm;杆状病毒颗粒有囊膜,形态多样,大小约为(50~100)nm×(300~500)nm;细胞培养分离病毒结果显示,球状病毒可在鲫鱼脑组织细胞系(Gi CB)中增殖,可导致细胞出现典型的细胞病变效应(CPE,cytopathic effect),但没有观察到Gi CB细胞中杆状病毒的增殖。