Susceptibility of important warm water fish species to tilapia lake virus (TiLV) infection

Detection of tilapia lake virus (TiLV) in tilapines is mainly from visceral organs of killed fish. However, lethal sampling might not be viable to broodstock and economically important ornamental cichlids. To contribute towards screening of the virus in asymptomatic infected fish, a subclinically infected population of Nile tilapia adults obtained from a local farm was preliminarily tested to compare different non‐lethal sampling methods, for example liver biopsy, gill biopsy, fin clip, mucus, faeces and blood for detection of TiLV. Only liver and blood samples gave positive results by PCR. Since blood sampling is relatively simpler, it was further used for five naturally co‐cultured juvenile fish species from above‐mentioned farm including 40 red tilapia broodstock and 20 Nile tilapia adults from two other different farms. The results showed that from the tested fish, 4 of 5 Nile tilapia, 2 of 5 hybrid red tilapia and 3 of 5 giant gourami blood samples tested positive, while 38 of 40 blood samples of red tilapia tested positive for TiLV in second‐step PCR. Sequencing representative PCR amplicons of positive samples confirmed sequence identity to TiLV. In conclusion, both blood and liver biopsy are practical non‐destructive sampling platforms for TiLV screening in cichlids with blood being more convenient, especially for tilapia broodstock.

Section: Discussionmentioning

confidence: 99%

Blood and liver biopsy for the non‐destructive screening of tilapia lake virus

Chiamkunakorn

Machimbirike

Senapin

et al. 2019

“…Based on the sequence analyses, TiLV has repeatable sequence at the 3′ and 5′ end of each genomic segment in which the segment 1 of TiLV contains 37% segment coverage and approximately 17% amino acid identity closely related to PB1 of influenza C virus (Bacharach et al, ). To date, tilapiine cichlids and some freshwater fish are susceptible to TiLV infection particularly at the larval and juvenile stages, occasionally causing high mortality (above 80%) in naïve fish (Behera et al, ; Jaemwimol et al, ; Surachetpong et al, ; Tattiyapong, Dachavichitlead, & Surachetpong, ). Previously, the mode of virus transmission via the cohabitation of infected fish and susceptible fish has been demonstrated under laboratory conditions (Eyngor et al, ; Liamnimitr, Thammatorn, U‐thoomporn, Tattiyapong, & Surachetpong, ).…”

Section: Introductionmentioning

confidence: 99%

Evidence of potential vertical transmission of tilapia lake virus

Yamkasem

Tattiyapong

Kamlangdee

et al. 2019

Self Cite

Tilapia lake virus disease (TiLVD) is an emerging viral disease in tilapia with worldwide distribution. Although the horizontal transmission of TiLV has been demonstrated through the cohabitation of infected fish with susceptible fish, no direct experiment showed the potential of vertical transmission from broodstock to progeny. In this study, natural outbreaks of TiLV in broodstock and fry in two tilapia hatcheries were confirmed. The TiLV genomic RNA was detected in liver and reproductive organs of infected broodstock, while infective virus was isolated in susceptible cell line. In situ hybridization assay confirmed the presence of TiLV in the ovary and testis of naturally infected fish and experimentally challenged fish. Moreover, early detection of TiLV in 2‐day‐old fry and the presence of TiLV genomic RNA and viable virus in the testis and ovary suggested the possible transfer of this virus from infected broodstock to progenies. As infective virus was present in gonads and fry in natural outbreak and experimental fish, the importance of biosecurity and prevention of the virus to establish in the hatchery should be emphasized. Hence, the development of TiLV‐free broodstock and the maintenance of high biosecurity standards in the hatcheries are essential for any attempt of virus eradication.

“…Tilapia lake virus (TiLV) is an emergent orthomyxo ‐like virus with negative sense RNA genome affecting tilapines and a few other cultured species of fish including giant gourami ( Osphronemus goramy ) (Jaemwimol et al, ; Tattiyapong, Dachavichitlead, & Surachetpong, ). Since first suspected cases emerged in tilapia in 2009 (Eyngor et al, ), outbreaks of the disease have been confirmed in at least 10 countries on four different continents (Asia, Africa, North America and South America) with evidence of continuous expansion (Eyngor et al, ; Jansen, Dong, & Mohan, ; OIE, ).…”

Section: Introductionmentioning

confidence: 99%

“…The use and development of suitable infection models in fish is important when evaluating disease pathogenesis and the efficacy of therapeutic protocols or prophylactic methods including vaccines, probiotics and prebiotics (Soto et al, ). The fulfilment of Koch’s postulates and disease reproduction in laboratory trials with TiLV has been achieved using two different routes of exposure, cohabitation and intracoelomic/intraperitoneal (IC) injection (Behera et al, ; Eyngor et al, ; Jaemwimol et al, ; Tattiyapong et al, ); however, little is known on the pathogenesis of the disease. A thorough understanding of pathogens associated with its commercial production is of great significance to fish health professionals and commercial producers, particularly since no effective vaccine or treatment options are currently available against TiLV infection in cultured fish and only few diagnostic methods have been reported and properly validated.…”

Section: Introductionmentioning

confidence: 99%

Intragastric and intracoelomic injection challenge models of tilapia lake virus infection in Nile tilapia (Oreochromis niloticus L.) fingerlings

Pierezan

Yun

Surachetpong

et al. 2019

Self Cite

To gain a better understanding of the pathogenesis of tilapia lake virus (TiLV) infections in Nile tilapia (Oreochromis niloticus), fingerlings were challenged with a single dose of 1 × 104 TCID50/fish of TiLV utilizing intracoelomic/intraperitoneal (ICch) or intragastric (IGch) routes. Acute mortalities were present in both groups, reaching 70 and 40% in ICch and IGch after 10 days, respectively. Challenged fish presented erratic swimming, lethargy, anorexia, exophthalmia and cutaneous petechiae and ecchymoses. Histological changes in challenged groups included syncytial formation, intracytoplasmic inclusion bodies and multifocal hepatocellular degeneration and necrosis. In addition, multifocal areas of mild proliferation of glial cells and lymphocytic perivascular cuffing were observed in the brain of exposed challenged groups. TiLV RNA was detected in gills and faeces of challenged fish using quantitative reverse transcriptase–PCR, as well as in the tank water holding challenged fish. Moreover, TiLV RNA was detected in scrolls obtained from formalin‐fixed paraffin‐embedded tissue blocks from challenged fish. Results from this study suggest that IG methods represent an additional method to study the pathogenesis of the disease in this species, as it results in infection and diseases as in naturally occurring cases and does not bypass important mucosal immune responses as injectable routes do.