Non-lethal sampling for Tilapia Lake Virus detection by RT-qPCR and cell culture

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%

Section: Introductionmentioning

confidence: 99%

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

Chiamkunakorn

Machimbirike

Senapin

et al. 2019

“…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, ). Since the identification of TiLV in 2014, there are concerns of vertical transmission of TiLV in fish.…”

Section: Introductionmentioning

confidence: 99%

“…Such findings demonstrated the possibility of vertical transmission via the contaminated gonadal materials of important aquatic viruses. Despite intensive investigation of TiLV transmission from diseased fish to normal fish under experimental conditions (Eyngor et al, ; Liamnimitr et al, ), little is known whether the vertical transmission could play a role in TiLV outbreak. The aim of the present study was to investigate the possible role of vertical transmission, from broodstock fish to fry and juvenile, in a natural outbreak of TiLV infection and in the spread of TiLV in tilapia hatcheries.…”

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.

“…The virus has been shown to be susceptible to ether and chloroform treatment (Eyngor et al, ). Under laboratory settings, exposing susceptible fish to moribund fish via cohabitation led to disease progression within 10 days (Eyngor et al, ; Liamnimitr, Thammatorn, U‐thoomporn, Tattiyapong, & Surachetpong, ). This suggests controlling the virus's release from the fish or removing contaminated equipment could reduce the occurrence and severity of the disease.…”

Section: Introductionmentioning

confidence: 99%

Virucidal effects of common disinfectants against tilapia lake virus

Jaemwimol

Sirikanchana

Tattiyapong

et al. 2019

Self Cite

Tilapia lake virus (TiLV) is an emerging virus associated with high fish mortality and economic losses. This study investigates the virucidal effects of the following disinfectants (active ingredients) on TiLV: 2.5 ppm iodine, 10 ppm sodium hypochlorite (NaOCl), 300 ppm hydrogen peroxide (H2O2), 80 ppm formalin and 5,000 ppm (0.5%) Virkon®. Factors that affect the disinfectants’ efficacy, including temperature, contact time and soiling (organic matter) interference, were examined under conditions mimicking natural aquaculture practices. TiLV inactivation of higher than 5 log10 TCID50 ml−1 was achieved after 10 min and at 28°C for all disinfectants except formalin; similar inactivation levels were reached by NaOCl and Virkon® at 10 min and 4°C. Extended exposure to formalin from 10 to 60 min at 28°C rendered more than 5 log10 inactivation. Increasing synthetic organic matter in the water to mimic soiling interference reduced the efficacy of NaOCl, iodine and H2O2 when tested at 10 min and 28°C; however, Virkon® still achieved more than 5 log10 inactivation. This study demonstrates that most common disinfectants effectively reduced viral loads to minimum levels. To limit the spread of TiLV in aquaculture farms and related facilities, the appropriate use of such disinfectants should therefore be promoted and implemented.