Proliferative kidney disease (PKD) of salmonids

Proliferative Kidney Disease (PKD) of salmonids, pathology, occurrence and the causative agent are described according to recent literature. For diagnosis histology and/or impression smears of infected kidneys are recommended. Original coloured photos are added to serve this purpose.     

Further consideration of the haematology of proliferative kidney disease (PKD) in rainbow trout, Salmo gairdneri Richardson

Abstract. A study of selected haematological parameters in rainbow trout, Salmo gairdneri Richardson, exposed to proliferative kidney disease (PKD) under field conditions is described. Changes in the blood picture are related to kidney pathology at different stages of the disease. As extensive renal vascular pathology, haemoglobin crystallization and inflammatory lesions developed, there were progressive decreases in haemoglobin and packed cell volume values, erythrocyte numbers declined to less than 50% of those in control fish, and numbers of misshapen erythrocytes increased. Leucopenia, neutrophilia and thrombocytopenia developed, especially in oedematous fish. With recovery, most values were similar to those of control fish. In recovered, re-challenged fish, erythrocyte counts, packed cell volume and haemoglobin values decreased in infected fish compared with uninfected fish. The results of the study are compared with those of other authors and the type of anaemia in PKD is discussed.     

Immunohistochemical and PCR studies of wild fish for Tetracapsula bryosalmonae (PKX), the causative organism of proliferative kidney disease

Tetracapsula bryosalmonae, previously referred to as PKX, causes proliferative kidney disease (PKD) in salmonids and is an economically important myxozoan pathogen in salmonid culture. A variety of molecular and immunological tools have been developed to detect the parasite. To determine the specificity of four monoclonal antibodies (MAbs) raised against T. bryosalmonae, archive material of fish infected with various myxosporean species was obtained and immunostained. Wild fish were also collected from enzootic waters and examined for T. bryosalmonae infection using immunohistochemistry and the polymerase chain reaction (PCR). Three of the MAb probes appear to be specific for T. bryosalmonae while only two of the five sets of primers tested appeared to specifically amplify T. bryosalmonae DNA. The results of the immunostaining and the PCR demonstrate that T. bryosalmonae occurs in the tubules of grayling Thymallus thymallus L., brown trout, Salmo trutta L. and Atlantic salmon, Salmo salar L. outside of the PKD season (June‐September) in the UK. This confirms the results of previous studies that these species are the preferred fish hosts for the parasite in the UK.     

Proliferative kidney disease (PKD) in rainbow trout Salmo gairdneri: Further observations on the effects of water temperature

The seasonality of proliferative kidney disease (PKD) and the effects of water temperature on the development of the disease in naturally-infected fingerling rainbow trout, Salmo gairdneri, were investigated. Fingerling rainbow trout became infected from May to October, but those infected in October did not develop clinical disease. In naturally-infected fish subsequently held under laboratory conditions, clinical PKD occurred at 12–18°C, but not at 9°C. The disease progressed more rapidly and was more severe as temperatures increased. On re-exposure to infection, rainbow trout previously held at 9°C developed clinical PKD, whereas in those previously held at 12°C it did not develop. Possible implications of these findings for the control of PKD are discussed.     

The effects of malachite green upon proliferative kidney disease

Abstract. When rainbow trout infected with proliferative kidney disease (PKD) held in the laboratory were treated with malachite green and formalin to cure ichthyophthiriasis it was observed that subsequent development of PKD was delayed. Experiments are reported which indicate that this was due to the malachite green treatment. The possible use of malachite green in the treatment of PKD, tissue levels of malachite green achieved during treatments and the toxicity risks from multiple dose therapy with malachite green are discussed.     

Proliferative kidney disease of salmonid fish: a review

Abstract A detailed review of proliferative kidney disease (PKD) in salmonids is presented. The introduction places the disease in a historical context. The various aspects of the disease are described from the existing literature, together with latest findings from current research. Particular emphasis is given to epidemiology, aetiology and pathology.     

Comparison of shell strength in wild and cultured scallops (Pecten maximus)

Shell strength development of the scallop Pecten maximus collected from wild stocks and from suspended cultures was described over the culture period when most of the growth takes place (20–110 mm shell height). Shell strength, shell height and shell thickness were determined in scallops of age groups 2–5 years. Wild and cultured scallops showed a strong divergence in shell strength development in scallops older than age group 3, which was not reflected in the concurrent development of shell height and thickness, indicating that factors other than shell height and shell thickness explain the differences in observed shell strength. In wild scallops, shell height, shell thickness and age accounted for about 65% of the variation in shell strength, while the same variables accounted for about 30% in cultured scallops. Wild scallops had stronger shells than the cultured scallops of the same size (53–68 mm shell height) grown at the same site, suggesting that factors related to suspended culture could explain the weak shells in cultured scallops. The results indicate that conditions related to suspended culture can have a negative impact on shell strength development in P. maximus. As the shell is the primary protection against decapod predation in scallops, a better understanding of what affects the shell strength is of importance for the development of release strategies in bottom culture of P. maximus.     

Biochemical composition of wild and cultured seahorses (Hippocampus kuda Bleeker)

The seahorse has been used for thousands of years as an important traditional Chinese medicine (TCM) in China. Many species of wild seahorse have become endangered, but demand for them continues to grow rapidly. Therefore, it is urgent to cultivate seahorses to relieve the strain on natural populations and meet the market demand for this TCM. In this study, medicinal components of wild and cultured yellow seahorses (Hippocampus kuda Bleeker) were analysed and compared. Different parts of the body (cortex and bone), male and female specimens, and seahorses of different ages were analysed. Crude protein, crude fat, trace elements, calcium, amino acid, fatty acid, steroid and cholesterol content were measured. The results showed that moisture content accounted for 70% of wet weight and ash content increased with growth. Crude protein and fat contents were higher in cultured seahorses than in wild specimens, and the content of Zn in cultured seahorses (93.26 ± 10.44%) was significantly higher than that of same‐aged wild seahorses (74.20 ± 3.83%). Amino acid and fatty acid contents of cultured seahorses also were higher than those of wild seahorses. These findings show that cultured seahorses can also be used in TCMs and that 1‐year‐old cultured seahorses have the best properties.     

文蛤养殖群体和野生群体遗传多样性的AFLP 分析

应用AFLP标记技术对辽宁和山东沿海文蛤（Meretrix meretrix）养殖群体和野生群体的遗传多样性进行分析。采用7对AFLP引物组合对5个群体（3个野生群体,2个养殖群体）150个个体进行扩增,共得到364个的位点。5个群体内的多态位点比例为84．3945％～87．6465％,总多态位点比例为99．6300％。群体的Nei’s基因多样性指数（H）为0．2301～0．2634;群体的Shannon多样性指数为0．3617～0．4248,群体间的遗传距离为0．0394～0．1609,群体内个体间的遗传距离为0．2592～0．5360。辽宁大洼野生群体和山东河口野生群体的多态位点比例、Shannon多样性指数和群体内遗传距离均高于辽宁盘山和辽宁庄河养殖群体,辽宁庄河野生群体的遗传多样性处于中等水平。用UPGMA方法构建的群体系统进化树显示,辽宁庄河野生群体单独成为一支,辽宁大洼野生群体与庄河养殖群体聚到一起,辽宁盘山养殖群体与山东野生群体聚到一起,但是用这5个群体的150个个体进行的聚类结果显示,所有个体基本是随机交叉聚类,不能形成明显的类群分支。分子变异分析（AMOVA）表明,文蛤群体94．04%的变异来源于群体内,群体间的变异仅占5．96％。以上结果表明,文蛤群体内遗传多样性非常丰富,群体间相似性较大,且存在较强的基因交流。[中国水产科学,2008,15（2）：215-221]     

A brown trout (Salmo trutta) population faces devastating consequences due to proliferative kidney disease and temperature increase: A case study from Austria

Proliferative kidney disease (PKD) is an emerging parasitic disease that affects wild and farmed salmonid fishes worldwide. Currently, it is widespread in Europe with records in many countries. This study assessed the status of PKD in the river Wulka, a small Austrian river, which was known to host a vital brown trout population despite having high water temperatures. Contrary to the initial hypothesis that the river was free from PKD, we observed an overall PKD prevalence of 92%. Noninfected fish were restricted to the uppermost river section. Twenty-two out of 87 PKD-positive fish of all age classes showed clinical signs, while five individuals exhibited signs of recovering from PKD infection. The severity of clinical signs was significantly dependent on the fish length and age, with smaller or younger individuals being more severely affected. Comparison of data from the earlier fish sampling events with those results from 2017 and 2018, together with the analyses of the pattern of water temperature since 2010, indicates that Wulka's brown trout population might become extinct in the near future.     

牙鲆腹水病的危害及防治

目前牙鲆养殖规模正日益扩大,逐渐成为我国北方地区陆上海水工厂化养殖和海水网箱养殖最主要的养殖品种。但随着养殖规模的不断扩大,各种疾病开始频繁发生,给牙鲆的养殖造成了巨大危害,其中以牙鲆腹水病的危害最为严重。2002年我国北方各牙鲆养殖厂,无论是陆上工厂化养殖还是网箱养殖,从牙鲆苗种(5～6mm)开始一直到秋冬季200～400g／尾的成鱼均深受其害。     

Piscine orthoreovirus: Biology and distribution in farmed and wild fish

Piscine orthoreovirus (PRV) is a common and widely distributed virus of salmonids. Since its discovery in 2010, the virus has been detected in wild and farmed stocks from North America, South America, Europe and East Asia in both fresh and salt water environments. Phylogenetic analysis suggests three distinct genogroups of PRV with generally discrete host tropisms and/or regional patterns. PRV-1 is found mainly in Atlantic (Salmo salar), Chinook (Oncorhynchus tshawytscha) and Coho (Oncorhynchus kisutch) Salmon of Europe and the Americas; PRV-2 has only been detected in Coho Salmon of Japan; and PRV-3 has been reported primarily in Rainbow Trout (Oncorhynchus mykiss) in Europe. All three genotypes can establish high-load systemic infections by targeting red blood cells for principal replication. Each genotype has also demonstrated potential to cause circulatory disease. At the same time, high-load PRV infections occur in non-diseased salmon and trout, indicating a complexity for defining PRV's role in disease aetiology. Here, we summarize the current body of knowledge regarding PRV following 10 years of study.