Koi Carp Research Articles

Involvement of galectin-9 from koi carp (Cyprinus carpio) in the immune response against Aeromonas veronii infection

Galectins are β-galactoside sugar binding proteins which function as important pattern recognition receptors (PRRs) in innate immunity. Here, we identified a galectin-9 gene from koi carp (Cyprinus carpio), named kGal-9. The ORF of kGal-9 is 963 bp in length, which encodes a polypeptide of 320 amino acids without either signal peptide. The predicted molecular weight is 36.25 kDa, and the isoelectric point is 8.3. Multiple sequence alignment showed that the putative kGal-9 contains two carbohydrate recognition domains (CRD), which are conserved in Galectin-9s. The phylogenetic tree showed that kGal-9 clustered to Galectin-9s from other teleosts, and shared the highest identity of 87.5% with Qihe crucian (Carassius auratus). kGal-9 mRNA was abundant in head kidney, gills, and gut, but low in liver and muscle. Further, the expression level of kGal-9 in the head kidney and liver increased significantly after Aeromonas veronii (abbreviated A.v) infection. Unexpectedly, kGal-9 showed a remarkable downregulation in the spleen at various time points post A.v infection. Intramuscular injection of pckGal-9 not merely reduced the bacterial load of spleen tissue, but also improved the survival rate of koi carp post A.v challenge. Besides, administration of pckGal-9 stimulated the expression of several immuno-related genes including proinflammatory cytokines (IL-1β, IL-6), anti-inflammatory cytokine (IL-10), complement components (C4, C9), with fluctuation in spleen and head kidney. Taken together, the obtained results suggest that kGal-9 occupies an important role in innate immunity and defense against bacterial infection in koi carp.

Early immune response of two common carp breeds to koi herpesvirus infection

Economic importance of common carp (Cyprinus carpio L.) increases every year. Viral diseases are major threat for carp aquaculture and cause significant economic losses. Koi herpesvirus (KHV) is one of the most serious carp diseases. Current study is focused on confirmation of possible differences in early immune response to KHV depending on level of resistance. Class I interferon signalling, complement cascade and cell-mediated cytotoxicity are hypothesized as major mechanisms of early innate immune response against KHV. Different breeds of common carp show distinct level of resistance to KHV. Two breeds of common carp with completely different susceptibility to KHV were chosen for current research: amur wild carp (AS) as highly resistant and koi carp (KOI) as very susceptible breed. KHV infection caused no mortalities, but the viral load in selected tissues increased during infection. Levels of expressions of chosen genes was examined using qRT-PCR and overall change in protein expression profiles was analysed by mass spectrometry. Significant differences in immune response between AS and KOI were detected mostly at the level of protein expression. Although cell-mediated cytotoxicity showed minimal influence during KHV infection, many immune response parameters related to class I interferon signalling pathway and complement cascade were increased earlier during KHV infection in AS comparing to KOI.

Genetic sources and diversity of the paddy field carp in the Pearl River basin inferred from two mitochondrial loci

Paddy field carp (PF-carp) is an economically important fish cocultured with rice in traditional agricultural systems. Several distinctive strains of PF-carp have been formed through years of artificial and cross breeding. There is a concern about the status of germplasm resources among PF-carp, since little is known about the genetic sources, diversity, or differentiation. In this study we collected 17 PF-carp populations covering Daotian carp (DTL), Ru Yuan No. 1 (RY), Jinbian carp (JBL), Shaijiang carp (SJL), and Wu carp (WL) along the Pearl River basin to explore their genetic sources and diversity using concatenated sequences of the mitochondrial cytochrome b gene and the D-Loop region. According to the haplotype network analyses, 1, 9, and 57 haplotypes originated from Cyprinus carpio carpio, Cyprinus carpio haematopterus and Cyprinus carpio rubrofuscus, respectively, confirming that genetic introgression has occurred in Pearl River PF-carp populations and Cyprinus carpio carpio was the most common species for genetic origin. The results showed that RY exhibited the lowest level of nucleotide diversity (π = 0.0011) due to high-intensity breeding and was significantly differentiated from the other four strains. PF-carp strains in these remote traditional systems tended to experience artificial selection and a lack of farmer connection that gradually increased genetic differentiation among strains. Notably, three populations of JBL exhibited significant high-level differentiation, since they originated from mountainous areas hindering farmers from fry exchange. In contrast, no significant differentiation was uncovered in the WL populations, since this strain is the most popular cultured strain and has undergone artificial exchange of parents and fry in many cultured regions. This study helps us to understand the status of germplasm resources among PF-carp and to trace their genetic origin before being introduced for local cultivation.

Differential effects of acute eustress and distress on gene regulation patterns in the carp ( Cyprinus carpio L.) brain

The activities of certain genes as a consequence of exposure to stressors related to typical handling procedures in aquaculture have not been studied in sufficient detail in fish. A stress trial with koi carp was, therefore, conducted, aiming at identifying relevant gene expression patterns in different brain regions during stress responses. The following stressors were selected: tank manipulation, distress caused by exposure to air and eustress due to feed rewards. Responses to these stressors were evaluated 10, 30 and 60 min after their application. The exact determination of gene expression profiles in the carp brain required the comparison of several suitable reference genes, which is also highly recommended for other studies focusing on the fish brain. Moreover, and as expected, the mRNA expression of a number of early immediate genes indicated activity in different brain regions as a response to changes in rearing and experimental conditions. In addition, the mRNA expression of metabolic genes was investigated, since increased brain activity may also increase the metabolic demands of certain brain areas. Furthermore, genes related to the stress axis were included in the study. The mRNA expression patterns of genes belonging to the stress axis revealed that negative stress caused by exposure to air had broad-ranging effects on the gene regulation patterns in the fish brain, even if the fish were only treated for 1 min. This parallels the effects that have been observed on blood cortisol and glucose. In contrast, a limited number of genes allows discrimination of eustress and distress, which indicates that further research is needed in the future. Finally, the use of different control groups is highly recommended for fish experiments to correct for typical experimental procedures such as lid openings or social isolation.

Mapping Growth-Related Quantitative Trait Locus (QTL) in Commercial Yellow River Carp (Cyprinus carpio haematopterus) during Overwintering

The common carp (Cyprinus carpio) is farmed globally; as a subspecies, the Yellow River carp (C. c. haematopterus) is widely farmed in northern China. Since the Yellow River carp grows slowly in winter, it would benefit breeders to implement a breeding program targeting growth in winter. In May 2017, we established a Yellow River carp family and measured the body length, height, thickness, and weight of individuals before (October 2017) and after winter (February 2018). Based on the genetic linkage map established in our laboratory, the quantitative trait locus (QTL) mapping of these four traits led to the detection of 29 growth-related QTLs, of which 9, 7, 3, and 10 QTLs were associated with body length, height, thickness, and body weight, respectively. One consensus QTL contained seven QTLs associated with four traits. Through the two major-effect QTLs (qBL-p-1 and qBL-p-2), we screened three candidate genes (fnd3b, ghsr, and pld1), which were associated with biological activities, such as fat formation, growth, and membrane transport. These results are helpful in exploring the growth regulation mechanism and providing a reference for genetic breeding with regard to the overwintering growth of Yellow River carp.

The Effect of Differences in the Addition of Astaxanthin and Several Sources of Natural ß-carotene in Increasing Color Intensity of Koi Fish (Cyprinus carpio L.)

This study aimed to examine the effect of differences in the addition of astaxanthin and several natural sources of ß-carotene taken from shrimp head flour and marigold flower flour on the color intensity of koi fish. The research was carried out from January 2022 to March 2022 at the Aquaculture Laboratory, Faculty of Fisheries and Marine Sciences, Padjadjaran University, Indonesia. This study used an experimental method with a completely randomized design (CRD) consisting of four treatments and three replications. The treatments given are control (A), Astaxanthin 0.02% (B), Shrimp Head Flour 10% (C), and Marigold Flower Flour 1.5% (D). Feding of koi fish was carried out for 60 days. Parameters observed included color brightness observed using Toca Color Finder (TCF), survival rate, growth and water quality (temperature, DO, and pH). The results showed that each treatment gave a good effect in increasing the color of koi fish. The addition of astaxanthin 0.02% showed the highest value with an increase in color score of 2.2 on the head and 1.2 on the body. The highest survival rate was in the treatment of adding astaxanthin 0.02% and marigold flower flour 1.5% with a value of 100%. The highest fish growth value was in the addition of shrimp head flour 10% treatment with a weight growth value of 1.938 g and a length growth value of 0.852 cm. The water quality parameter values ​​(temperature: 27-30℃, DO 5.3-7.8 mg/L, and pH: 6.7-7.9) were in normal conditions.

MRI of the live fish brain at 3 Tesla: Feasibility, technique and interspecies anatomic variations.

Advances in aquatic animal medicine and continued growth of the fish hobbyist and aquaculture communities have led to a developing interest in antemortem diagnostic imaging of aquatic species. The aims of this prospective, pilot study were to determine whether advanced neuroimaging can be safely achieved in live fish using clinically available equipment, to optimize imaging parameters, and to develop a comparative MRI atlas of a few fish species of economic or research value. Two each of channel catfish (Ictalurus punctatus), koi (Cyprinus rubrofuscus), and grass carp (Ctenopharyngodon idella) of at least 30 cm in length were individually anesthetized for 3 Tesla (3T) magnetic resonance imaging (MRI) of the brain. All fish achieved an adequate anesthetic level for prolonged immobilization during imaging. Diagnostic quality images were obtained for all subjects; however, the spatial resolution was maximized with larger fish. Imaging protocols were optimized for standard neuroimaging sequences. Additionally, inversion times for fluid-attenuation inversion recovery (FLAIR) sequences were adapted to the naturally high protein content of fish pericerebral fluid. Following imaging, the fish successfully recovered from anesthesia, were humanely euthanized, and were immediately processed to assess brain histopathology. Necropsy confirmed the sex and health status of each fish. A limited comparative MRI atlas was created of the brains of these species for clinical reference. Findings from the current study supported the use of 3T MRI as an adjunct diagnostic test for fish with suspected neurologic disease and provided a limited anatomic atlas of the teleost brain for use as a reference.

The Effect of Transfer Factor Formula on Increasing Lymphocytes and Survival Rate of Koi Fish (Cyprinus carpio) Infected by Aeromonas hydrophila

This study aimed to determine the effect of transfer factor on the number of fish blood lymphocytes and survival rate in koi fish infected with Aeromonas hydrophila. This Study implemented with method observation experimental with total lymphocytes and Survival rate on every treatment. Treatment shared into 4 groups namely P0 (not given Transfer factor and infected Aeromonas hydrophila), P1 (given 100 mg of transfer factor and then infected with Aeromonas hydrophila), P2 (given 200 mg of transfer factor and then infected with Aeromonas hydrophila), P3 (given 300 mg of transfer factor and then infected with Aeromonas hydrophila). Data obtained analyzed with analysis of variables (ANOVA) with using device soft SPSS 25 For Windows. Results obtained on study is Giving Transfer factors could Increase Amount Lymphocytes on Koi Fish (Cyprinus carpio). Giving Transfer factors could Increase graduation life or Survival Rate (SR) Koi Fish.Best dose on giving Transfer factor in increase total lymphocytes and increase Survival Rate (SR) on Koi fish is 200 mg.

PENCIPTAAN TOMBAK DHAPUR IKAN KOI

Koi fish (Cyprinus carpio) is a type of ornamental fish that easily adapts to its new environment, this fish is classified as carp (carp). Koi have senses in the form of a pair of eyes (sight), nose (smell), and antennae (taste). And has a swim bladder that helps in swimming such as floating, swooping, or looking up. The creation method used in the process of creating this koi fish spear uses the theory of S.P. Gustami, namely: the first stage of exploration which includes exploration activities to explore sources of ideas through observation, literature study, interviews, and documentation by collecting data in the form of references to writings, pictures, journals, final project reports, photographs of works, photos of objects related to theme. The two design stages include ideas in the form of alternative sketches, selected designs, and working drawings. The three stages of embodiment include the final process starting from the forging, grinding, turning, nyangkling, tinatah, ngamal and warangi processes. Koi fish are a source of inspiration for writers because of the attractive, beautiful, symbolic aspects, meanings and benefits that can be visualized into spear work. Spear is a traditional weapon that is found in all civilizations of the world, during the stone age. Derived from a pointed stone that is given a long stalk, the tool is used for hunting, fishing, and fighting. Over time, spears were used for traditional ceremonies, and were used as heirlooms for generations.

Telemonitoring of Water Quality for Koi Fish Hatchery Using Mechanical Turbine Method Based on Microcontroller

One way to meet the needs of fish seeds in the general public is to cultivate fish species. UPT BBI (Balai Benih Ikan) Tlogowaru, is one of the fish seed cultivation sites located on Tajinan Tlogowaru, Kedungkandang sub-district, Malang City. Fish seeds include koi fish seeds. In the pool using water from the river. To maintain the water of the koi fish hatchery, the condition of color turbidity is monitored as the level of turbidity of the water visible from above the waters of the koi fish hatchery, and a water flow sensor is processed by esp32. The water flows through the gravity pipe which will turn the turbine. With the rotation, the generator will produce power which is used to activate the telemonitoring device. The water then enters the filtration and will be channeled to the koi fish hatchery. The results of this study have an average pH value of 6.8 - 7.2 and a TDS of 257-282 ppm after water filtration with the turbine speed value being influenced by water flow and turbine rotation speed and the average power consumption generated for system performance of 8.265 w/h using a MiFi network with QoS parameters measured are delay and packet loss in the low category. And the use of the website makes it easier for users to monitor fish seed ponds

Optimizing Stocking Density for Rearing Ornamental Koi Carp in Pond Cage Aquaculture System

Optimizing Stocking Density for Rearing Ornamental Koi Carp in Pond Cage Aquaculture System

The comparative studies on growth rate and disease resistance between improved grass carp and common grass carp

Grass carp (Ctenopharyngodonidella, GC) is one of the most economically important freshwater fishes in China. In this study, we use the ultraviolet-treated haploid sperm of koi carp (Cyprinuscarpiohaematopterus, KOC, 2n=100) to activate the eggs of GC with the treatment of 0–4 °C cold shock, and obtain all-female gynogenetic grass carp (GGC). Subsequently, we mated the mature female GGC with the common male GC, and produce the improved grass carp (DR-GC) with the disease-resistance. The experimental results show that the DR-GC has 22.18% higher survival rate than GC and 16.31% faster growth rate than GC. The input–output ratio of DR-GC to GC is 1.00:1.30, demonstrating significant cost-saving, efficiency-increasing, and higher-breeding benefits in DR-GC. The results regarding the morphological characteristics, DNA content, and chromosomes in DR-GC and their parents show that the DR-GC have a greenish-gray body with golden yellow scales on the back of the body, have the 58.01 as the DNA content, and have 48 as the number of chromosome in each somatic cell. DR-GC also has a high fertilization rate (95.30%) and a hatching rate (92.10%). The above results indicate that DR-GC is improved grass carp with some advantages in phenotypes and genotypes, which are significant for fish aquaculture.

Penambahan Tepung Wortel (Daucus carota L.) Terhadap Pertumbuhan dan Peningkatan Warna Ikan Koi (Cyprinus rubrofuscus)

Ornamental fish is a live fish commodity that has many different types. Judging from the color, ornamental fish can be said to be attractive if the colors are contrasting. Efforts to get a bright color that is evenly distributed in fish can be done by providing a source of carotenoids in fish. The most effective and dominant type of carotenoids for fish coloring is carrot flour carotenoids because natural sources of beta carotene can improve the quality and color brightness of ornamental fish such as koi fish. The research design used a completely randomized design (CRD) with four treatments (Carrot Flour 0%, 15%, 30% and 45%) and three replications. The feed was tested on Koi fish measuring + 2-5 cm and weighing + 1.5 grams which were kept in an aquarium measuring 25x25x30 cm3. Parameters observed were daily growth rate, absolute weight growth rate, absolute length growth rate, survival rate, feed conversion ratio, proximate test, feed efficiency and color increase in Koi fish. The results showed that the addition of 15% carrot flour affected the color brightness of Koi fish (Cyprinus rubrofuscus).

Comparative study on nutritional quality and volatile flavor compounds of muscle in Cyprinus carpio haematopterus under wild, traditional pond and in-pond raceway system culture

This study compared the physical characteristics, nutritional components, mineral elements, and volatile matter of the muscle of the Yellow River carp (Cyprinus carpio haematopterus) grown under the traditional pond system (TPS), in-pond raceway system (IPRS), and wild (WYRC) to reveal the differences in its muscle quality under aquaculture and natural growth conditions. The results demonstrated a significantly lower water-loss rate in the Yellow River carp muscle of both the WYRC and IPRS groups than that in the TPS group (P < 0.05), whereas the cooked rate was significantly higher than that in the TPS group (P < 0.05). The firmness, chewiness, and gumminess relationships were in the order of WYRC > IPRS > TPS, and significant differences (P < 0.05) were observed among the groups. The WYRC group had a significantly higher muscle fibre density than the TPS and IPRS groups (P < 0.05). The crude fat content of the WYRC and IPRS groups was significantly higher than that of the TPS group, whereas their crude protein content was significantly lower than that of the TPS group (P < 0.05). The collagen content was ranked WYRC > IPRS > TPS, and there was a significant difference between the groups (P < 0.05). The EPA (C20: 5n-3) content followed the order WYRC > IPRS > TPS, and the groups exhibited significant differences (P < 0.05). The As and Hg contents in the WYRC group were 8 and 5 times higher, respectively, than those in the cultured group. The content of hexanal, heptanal, octanal, butanal, and other substances did not differ significantly between the IPRS and WYRC groups (P > 0.05). These results suggest that different growth conditions significantly influence the physical characteristics, nutritional components, mineral elements, and volatile substances of the Yellow River carp muscle.

Marine yeast Rhodotorula paludigena VA 242 a pigment enhancing feed additive for the Ornamental Fish Koi Carp

Skin colour is an important criterion in determining the aesthetic appeal of ornamental fishes, and thus their market worth. Hence the pigment enhancement in ornamental fishes has been the subject of extensive research by using various synthetic as well as natural pigment sources. Dietary composition is one of the most important elements that influence the development of pigmentation in fish. This study is an attempt to assess the possibility of using carotenogenic marine yeast as pigment enhancer in fish diet for Koi carp, Cyprinus carpio. The 60 days feeding experiment was done by using feed incorporated with mangrove associated marine yeast Rhodotorula paludigena VA242. Greater pigmentation in the scales of fishes fed with experimental feed was observed than that fed with the control diet (normal pellet feed). Furthermore the improved growth rate and general wellbeing in fishes fed with experimental feed provides scope for further studies in this field with respect to the growth and survival of fishes.

Potential benefits of exogenous neurotransmitters in alleviating transport stress in koi carp, Cyprinus carpio

The transport of live fish is an important process in the ornamental fish trade. As such, reducing transport stress plays a vital role in improving fish survival and minimizing economic losses. The objective of this study was to assess the efficacy of exogenous neurotransmitters in alleviating transport stress in koi carp, Cyprinus carpio. First, fish were subjected to simulated transport, and samples were collected at 0, 4, 6, 12, 24, and 48 h for the determination of water quality parameters and serum indices. The results indicated that the pH of the water decreased and ammonium nitrogen (NH4-N) was enhanced with the increase of transport time. The most significant changes in stress-related indices were observed at 4 h after transport, and thus the subsequent transport experiments were scheduled for 4 h. Three types of exogenous neurotransmitters were added to the water, and fish were transported for 4 h to determine the efficacy of the neurotransmitters. Gamma-aminobutyric acid (GABA) increased the pH, and decreased the NH4-N content of the water. The concentrations of serum adrenaline, cortisol, and glucose were decreased by GABA supplementation. Guanidine acetic acid (GAA) increased the pH of the water, and decreased the concentrations of serum adrenaline and cortisol. The addition of 5-hydroxytryptamine (5-HT) lowered the NH4-N level of the water, and decreased the concentrations of serum adrenaline and cortisol in the fish. In conclusion, the addition of exogenous neurotransmitters to transport water may help to alleviate transport stress by improving water quality and depressing the enhancement of stress-related hormones.

PPTTG Pencetak Pelet Untuk Peternak Ikan Koi Dusun I Timur Karang Anyar

Karang Anyar Village with an area of ​​4.63 km2 and a population of 9,366 apart from farming, the residents are also cultivating ornamental fish species of koi fish in ponds/ponds which are formed side by side with rice fields by utilizing good irrigation around the pond, including Mr. Hendrayen as this service partner currently has land for a fish pond of 2.4 hectares with fish pellets as the main feed which currently relies heavily on factory-made fish feed, the price of which is not affordable by most farmers in Karang Anyar Village with the need for pellets. per day for 36 kg, for that the service implementation team carried out activities in the form of demonstrations on the use of pellet molding machines, training on the use of pellet molding machines and their maintenance as well as machine handover which during demonstrations, the machine was able to produce 50 kg of pellets every hour with cylindrical pellets of diameter 3 mm long and 4 mm long

Detection and phylogenetic analysis of carp edema virus in common carp (Cyprinus Carpio) in Iran; 2020–2021

Carp edema virus (CEV), a member of the family Poxviridae, is the etiologic agent of carp edema virus disease, also known as the koi sleepy disease (KSD). The disease is important across the world because it increases mortality rates in common carp and koi carp. From autumn 2020 to spring 2021, gills and internal organs were collected from suspected common carps cultured in twenty Iranian farms in Khuzestan, Gilan, and Mazandaran provinces. The presence of CEV was confirmed by molecular diagnosis. PCR was performed using specific primers to amplify the p4a gene, and positive samples were subsequently sequenced. Phylogenetic analysis assigned them to CEV genogroup I, and they shared high nucleotide sequence similarity with CEVs from Italy, Hungary, Iraq, Poland, the United States, and the Czech Republic. The results confirmed the presence of CEV in Iranian freshwater aquaculture after five years of observing clinical symptoms strongly reminiscent of CEV disease. The results also warned of the spread of the virus throughout the continent and point to the need to implement restrictions on the fish trade. Further studies are needed to determine the full-genome sequences of circulating viruses in order to provide insights into the epidemiology of fish viruses in Iran and the region.

Identification of Thelohanellus pseudonikolskii n. sp. and Myxobolus koi Kudo, 1920 from goldfish Carassius auratus

During a parasitological survey of goldfish Carassius auratus (Linnaeus, 1758) in China, two myxosporeans were collected in the present study including a Thelohanellus species and a Myxobolus species. To identified the two myxosporeans, a morphological, histological and molecular study was performed. The Thelohanellus species was characterized by round, white plasmodia in fins of goldfish. Compared with all described Thelohanellus species, spore morphology of the Thelohanellus species in the present study was distinct from them. BLAST search showed that SSU rDNA sequence of this Thelohanellus species did not match any sequence in GenBank database. Phylogenetically, the Thelohanellus species obtained in the present study was sister to Thelohanellus nikolskii Achmerov, 1955. So, the present Thelohanellus species was identified as a novel species and named Thelohanellus pseudonikolskii n. sp. The Myxobolus species was characterized by a number of round or irregularly shaped, white plasmodia in gills of goldfish. When compared with all reported Myxobolus species, spore morphology of the present Myxobolus species was most similar to Myxobolus koi Kudo, 1920. Histological analysis showed that plasmodia of this Myxobolus species simultaneously developed in stratified epithelium of filament and in lamellae, which was same to M. koi. Moreover, BLAST search showed that SSU rDNA sequence of the present Myxobolus species was identical to M. koi. Thus, the morphological, histological and molecular analysis demonstrated that the present Myxobolus species was conspecific with M. koi. Due to M. koi consistently described from gills of common carp Cyprinus carpio Linnaeus, 1758 and koi carp C. carpio in the previous researches, M. koi was first found to infect gills of goldfish in the present study. Considering koi carp and goldfish both as ornamental fish frequently cultured together in China, the possible host shift of M. koi from koi carp to goldfish is of interest for further investigation.

First report on the occurrence of cyprinid herpesvirus 3 in koi carp (Cyprinus carpio koi) in India.

This study reports the occurrence of cyprinid herpesvirus 3 (CyHV-3) in koi carp (Cyprinus carpio koi) for the first time in India. The koi carp, with clinical signs of ulcer with haemorrhage on body surface, necrosis of fin and discolouration of gill associated with huge mortality, were observed in aquarium shops, rearing tanks and grow-out ponds located in Chennai, India. The PCR assay carried out on infected fish samples using different primer sets specific to CyHV-3 confirmed its presence in the infected fish. Sequence analysis of partial thymidine kinase gene revealed 100% similarity with the sequence of CyHV-3 available in GenBank. Cell lines of koi carp and catla were found to be susceptible to CyHV-3 and its replication was confirmed by viral-specific cytopathic effect, PCR and bioassay. The CyHV-3 infection was reproduced by intramuscular injection of inoculum prepared from CyHV-3-infected fish to satisfy Koch's postulates. Tissue tropism of CyHV-3 in infected fish by PCR assay revealed the presence of CyHV-3 in all vital organs with prominent band in gill and gut tissue.