Identification of a Novel RNA Virus Lethal to Tilapia (original) (raw)
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Identification of a Novel RNA Virus Lethal to Tilapia J. Clin. Microbiol.-2014-Eyngor-4137-46 (1)
Tilapines are important for the sustainability of ecological systems and serve as the second most important group of farmed fish worldwide. Significant mortality of wild and cultured tilapia has been observed recently in Israel. The etiological agent of this disease, a novel RNA virus, is described here, and procedures allowing its isolation and detection are revealed. The virus, denominated tilapia lake virus (TiLV), was propagated in primary tilapia brain cells or in an E-11 cell line, and it induced a cytopathic effect at 5 to 10 days postinfection. Electron microscopy revealed enveloped icosahedral particles of 55 to 75 nm. Low-passage TiLV, injected intraperitoneally in tilapia, induced a disease resembling the natural disease, which typically presents with lethargy, ocular alterations, and skin erosions, with >80% mortality. Histological changes included congestion of the internal organs (kidneys and brain) with foci of gliosis and perivascular cuffing of lymphocytes in the brain cortex; ocular inflammation included endophthalmitis and cataractous changes of the lens. The cohabitation of healthy and diseased fish demonstrated that the disease is contagious and that mortalities (80 to 100%) occur within a few days. Fish surviving the initial mortality were immune to further TiLV infections, suggesting the mounting of a protective immune response. Screening cDNA libraries identified a TiLV-specific sequence, allowing the design of a PCR-based diagnostic test. This test enables the specific identification of TiLV in tilapines and should help control the spread of this virus worldwide.
Tilapia Lake Virus (TiLV) disease: Current status of understanding
Aquaculture and Fisheries, 2021
Tilapia Lake Virus (TiLV) disease is an emerging and transboundary disease of tilapia cultures, causing mortality up to 90% globally. TiLV is a negative sense single stranded RNA virus belongs to family Amnoonviridae, genus Tilapinevirus and species Tilapia tilapinevirus. The first TiLV outbreak to fishes was reported from Israel followed by other countries viz.
Egyptian Journal of Aquatic Biology and Fisheries, 2022
Indonesia (1.12 MMT) and Egypt (0.88 MMT). Bangladesh, Vietnam and the Philippines are other leading producers. Also, Tilapia are very important for ecological systems (Eyngor et al., 2014) as they are beneficial in algae and mosquito control, habitat maintenance for shrimp farming and an important wild capture species (Bacharach, et al., 2016). Thus, the spread of TiLV has global impact in both economic losses to farmers and fishers, cause significant mortality up to 90% (Dong et al., 2017) and ecological settings. Tilapia lake virus (TiLV), an emerging disease of tilapia, was first reported in Israel in 2011 (Eyngor et al., 2014). Subsequently, the disease was reported in tilapia ARTICLE INFO
Temporal trends of tilapia lake virus disease in Israel, 2017–2018
Transboundary and Emerging Diseases, 2020
Tilapia lake virus (TiLV) is an emerging viral disease that affects several tilapia species in different countries since 2014. In 2017-2018, 129 samples were collected from 14 tilapia farms in Israel. Ninety samples represented mortality events (ME), and 39 were used as control samples (CS). RT-qPCR was performed on 89 and 39 duplicate brain and liver tissue samples from ME samples and CS, respectively. TiLV was diagnosed in 37 (41.6%) ME while only two of the CS samples (5%) were positive for TiLV (OR = 13.2, 95% CI = 3.0-58.1). Additional RT-PCR was performed on positive samples and amplified products were sequenced. Maximum-likelihood phylogenetic analysis of segment-3, revealed three distinct clades: the first clade (A) includes 25
Tilapia Lake Virus (TiLV): a Globally Emerging Threat to Tilapia Aquaculture
EDIS
Tilapia lake virus is a globally emerging virus responsible for episodes of mass mortality in cultured and/or feral tilapia (Oreochromis spp. and hybrids) in Asia, Africa, Central America, and South America. Since 2014, there have been global reports of TiLV disease resulting in 10% to 90% mortality in tilapia fry, juveniles, and adults causing significant economic losses. Currently, the disease has been confirmed in Colombia, Ecuador, Egypt, India, Indonesia, Israel, Malaysia, Mexico, Philippines, Peru, Tanzania, and Thailand. TiLV has not yet been found in the USA or Canada, but it has most recently been reported in 20 aquaculture production facilities across six Mexican states (Chiapas, Jalisco, Michoacán, Sinaloa, Tabasco and Veracruz). This 7-page fact sheet written by Lowia Al-Hussinee, Kuttichantran Subramaniam, Win Surachetpong, Vsevolod Popov, Kathleen Hartman, Katharine Starzel, Roy Yanong, Craig Watson, Hugh Ferguson, Salvatore Frasca Jr., and Thomas Waltzek and published...
Detection of Tilapia Lake Virus (TiLV) in Clinical Samples by Culturing and Nested RT-PCR
Journal of clinical microbiology, 2016
Tilapia are an important group of farmed fish that serve as a significant protein source, worldwide. In recent years, substantial mortality of wild tilapia has been observed in the Sea of Galilee and in commercial ponds in Israel and Ecuador. We have identified the etiological agent of these mass die-offs as a novel orthomyxo-like virus and named it tilapia lake virus (TiLV). Here we provide conditions for efficient isolation, culturing and quantification of the virus, including the use of susceptible fish cell lines. Moreover, we describe a sensitive nested RT-PCR assay, allowing the rapid detection of TiLV in fish organs. This assay revealed, for the first time, the presence of TiLV in diseased Colombian tilapia, indicating a wider distribution of this emerging pathogen and stressing the risk that TiLV poses for the global tilapia industry. Overall, the described procedures should provide the tilapia aquaculture industry important tools for the detection and containment of this pa...
Aquaculture, 2018
Tilapines are one of the most widely farmed fish species and currently being cultured in more than 100 countries in the World. Over the last few years, large-scale mortalities have been reported in tilapia due to infection with orthomyxo-like virus i.e. Tilapia Lake Virus (TiLV) which is considered as a threat to global tilapia industry. In the present study, we report outbreak of TiLV disease in farmed tilapia in two states, West Bengal and Kerala from India. Diseased fish exhibited lethargy, inappetance and skin erosions with >85% mortality. TiLV infection was confirmed on the basis of PCR amplification and sequencing of segment 3 of TiLV, histopathology, infection of fish cell line and bioassay. NCBI-BLAST result of the partial sequences of segment 3 of the TiLV revealed that North 24 Parganas (MF502419) and South 24 Parganas (MF582636) of West Bengal, India showed 97.2% and Ernakulam, Kerala, India (MF574205) showed 96.4% similarity with Israel (KJ605629.1) respectively. In histopathology, typical syncytial giant cells in liver and congestion of the blood vessels along with haemorrhages in sections of brain tissue were observed. The filtered tissue homogenate prepared from liver and brain of affected tilapia produced cytopathic effects in CFF cell line derived from Pristolepis fasciatus. The disease was successfully reproduced in naive tilapia following injection of culture supernatant from infected cell line and TiLV was successfully reisolated from experimentally infected tilapia. This is the first report of TiLV from India and adds to the reports of TiLV outbreaks in five countries across three continents.
Aquaculture
Tilapia Lake Virus (TiLV) has been associated with disease outbreaks in cultured tilapia worldwide. In this study, we developed and characterized two cell lines from the brain (OnlB) and liver (OnlL) of the Nile tilapia, Oreochromis niloticus for the efficient propagation of TiLV. Both the cells grew well in Leibovitz's-15 (L-15) medium supplemented with 20% fetal bovine serum (FBS) and have been sub-cultured more than 45 times. Chromosome analysis of the cells revealed that both lines had normal diploid number (2n = 44). TiLV was isolated from diseased tilapia and continuously propagated for 20 passages in these cell lines. The maximum TiLV titer was 10 7.3 ± 0.05 and 10 7.0 ± 0.96 TCID 50 /ml, in OnlL and OnlB respectively. The TiLV isolate consistently produced the same CPE in all passages. In vivo challenge experiments using the TiLV infected cell culture supernatant reproduced symptoms of the disease in healthy tilapia, with mortality commencing 10 days postinfection and we were able to isolate TiLV from the challenged fish The above results suggest both cell lines are highly permissive for propagating TiLV and could be important tools for studying the molecular pathogenesis of TiLV infection.
Aquaculture
Early developmental stages of tilapia, including fertilized eggs were tested positive for TiLV in our previous study (Dong et al., 2017a). We, therefore, hypothesized that infected broodstock is able to pass the virus to their reproductive organs and then to the fertilized eggs. In order to prove this hypothesis, Nile tilapia (Oreochromis niloticus) broodstock were experimentally infected with TiLV by intramuscular injection and non-infected broodstock were used as control group. At day 6 post infection, eggs and semen from each breeding pair were aseptically collected for in vitro fertilization. Fertilized eggs at 3, 12 and 64 h post-fertilization were subjected to detection of TiLV by PCR, ISH, and cell culture. In parallel, blood, serum, liver and reproductive organs from each broodstock were subjected to TiLV analysis. The results revealed that all collected tissues (liver, blood, ovary and testis) from infected broodstock tested positive for TiLV by PCR, ISH, and cell culture. ISH revealed strong positive signals in hepatocytes surrounding blood vessels in the liver, connective tissue and membrane surrounding the oocytes in the ovary and the connective tissue close to blood vessels in the testis. These findings suggested that TiLV causes systemic infection in tilapia broodstock with the virus being able to spread into the reproductive organs, most likely through the blood circulatory system. Subsequently, the fertilized eggs produced by infected broodstock tested positive for TiLV by PCR and ISH revealed location of the virus inside the fertilized eggs. The results of this study suggested that TiLV can be transmitted vertically. We thus recommend for hatchery and multiplication center to use TiLV-tested negative broodstock for the production of TiLV-free tilapia seeds.
Non-lethal sampling for Tilapia Lake Virus detection by RT-qPCR and cell culture
Aquaculture
Tilapia Lake Virus (TiLV) is an emerging virus of tilapia fish. Recently, outbreaks of TiLV associated mortality have been reported in many countries including Israel, Ecuador, Colombia, Egypt and Thailand. However, little is known about the route of transmission and how the virus is spread in fish populations. In this study, TiLV was detected in liver and mucus samples from moribund tilapia using reverse transcriptase quantitative polymerase chain reaction and virus isolation in the cell culture. Comparison of virus detection in the liver and mucus of field samples revealed that mucus could be applied for TiLV diagnosis and the virus in mucus was still viable and could cause a cytopathic effect in E-11 cells. The cohabitation of TiLV-infected fish with healthy fish resulted in 55.71% cumulative mortality of cohabitating fish suggesting that direct contact of infected fish is sufficient for disease transmission. Notably, the TiLV genomic RNA was identified in the mucus of cohabitation challenge fish as early as 1 day post infection (dpi) and the virus was isolated from mucus samples collected at 5 dpi. The presence of TiLV persisted up to 12-14 dpi in the mucus, liver and intestines of cohabiting fish. Taken together, the detection of TiLV in the mucus of field samples and cohabitating fish suggested that horizontal transmission is one of the important routes for the spread of TiLV. Importantly, this study revealed that mucus could be used for non-lethal sampling in TiLV detection.