Evidence of potential vertical transmission of tilapia lake virus

Abstract

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.

Two‐year surveillance of tilapia lake virus (TiLV) reveals its wide circulation in tilapia farms and hatcheries from multiple districts of Bangladesh

“…Warnings about the risk of the transboundary spread of the virus across borders as a result of vertical transmission were reported in early 2017 following the detection of the virus in fertilized eggs, fry and fingerlings in tilapia hatcheries (Dong, Ataguba, et al, 2017). Further evidence supported this potential vertical route of transmission (Yamkasem, Tattiyapong, Kamlangdee, & Surachetpong, 2019). Our results showed the presence of TiLV in asymptomatic broodstock from several Bangladeshi tilapia hatcheries.…”

“…As further support for this hypothesis, it was found that the virus infected the reproductive organs of these fish and was then passed on to the fertilized eggs (Dong et al., 2020). All these findings point towards strict recommendation to avoid, at all costs, the use of TiLV‐infected broodstock for production of tilapia fry (Dong et al., 2020; Yamkasem et al., 2019). Therefore, we strongly urge that immediate actions should be taken by the relevant authorities and various aquaculture stakeholders to develop systematic testing protocols and a certification system for tilapia hatcheries, as well as the implementation of proper biosecurity to ensure that tilapia fingerlings are produced from reliable sources of TiLV‐negative broodstock.…”

Retracted: Tilapia lake virus disease: Phylogenetic analysis reveals that two distinct clades are circulating in Israel simultaneously

“…In the case of TiLV, horizontal transmission may occur when healthy stocks come into contact with diseased individuals (Eyngor et al, 2014;Jansen et al, 2018). Recently, vertical transmission of TiLV has also been proposed (Yamkasem, Tattiyapong, Kamlangdee, & Surachetpong, 2019).…”

A highly sensitive and specific SYBR Green quantitative polymerase chain reaction (qPCR) method for rapid detection of scale drop disease virus in Asian sea bass, Lates calcarifer

“…Moreover, it is worthwhile to investigate further whether SDDV invades the reproductive organs of Asian sea bass broodfish and could vertically transmit to the offspring as occurred in the case of tilapia lake virus (TiLV), a newly emerging virus of tilapia (Dong et al, 2020; Yamkasem et al, 2019). Understanding the route of disease transmission in combination with highly sensitive detection method is vital for effective disease management and preventing potential widespread.…”