Abstract
Tilapia tilapinevirus, or tilapia lake virus (TiLV), is a highly contagious virus found in tilapia and its hybrid species that has been reported worldwide, including in Asia, the Americas, and Africa. In this study, we experimentally challenged Mozambique tilapia (Oreochromis mossambicus) with a virulent TiLV strain, VETKU-TV01, at both low (1 × 103 TCID50/mL) and high (1 × 105 TCID50/mL) concentration. After the challenge, the Mozambique tilapia showed pale skin with some hemorrhage and erosion, lethargy, abdominal swelling, congestion around the eye, and exophthalmos; there was a cumulative mortality rate at 48.89% and 77.78% in the groups that received the low and high concentration, respectively. Quantitative PCR and in situ hybridization confirmed the presence of TiLV in the internal organs of moribund fish. Notably, severe histopathological changes, including glycogen depletion, syncytial hepatic cells containing multiple nuclei and intracytoplasmic inclusion bodies, and infiltration of melanomacrophage into the spleen, were frequently found in the Mozambique tilapia challenged with high TiLV concentration. Comparatively, the infectivity and pathology of the TiLV infection in Mozambique tilapia and red hybrid tilapia (Oreochromis spp.) were found to be similar. Our results confirmed the susceptibility of Mozambique tilapia, which has recently been determined to be a vulnerable species, to TiLV infection, expanding knowledge that the virus can cause disease in this fish species.
Highlights
Tilapia Lake Virus Disease (TiLVD) is a new disease caused by Tilapia tilapinevirus, or tilapia lake virus (TiLV), which is a linear, negative-sense single-strand RNA virus containing ten segments; it has a total genome size of 10,323 kb [1,2]
This study aimed to investigate the susceptibility of Mozambique tilapia (O. mossambicus) to TiLV infection by comparing TiLV infection in red hybrid and Mozambique tilapia, as well as comparing the infectivity and biology of the infection in Mozambique tilapia after exposure to both low and high concentrations of TiLV
Mortality in fish exposed to high TiLV concentration began at 4 dpc, while the mortality in fish exposed to low TiLV concentration did not start until 7 dpc
Summary
Tilapia Lake Virus Disease (TiLVD) is a new disease caused by Tilapia tilapinevirus, or tilapia lake virus (TiLV), which is a linear, negative-sense single-strand RNA virus containing ten segments; it has a total genome size of 10,323 kb [1,2]. Since 2014, TiLV has been reported on four continents, North America, South America, Asia, and Africa [2,3,4]. From fry to adult and broodstock, are susceptible to TiLV, with mortality ranging from 5% to 100% [2,4,5,6,7,8,9]. Some other species of fish are susceptible to TiLV, including giant gourami (Osphronemus goramy), which showed a high mortality rate during laboratory challenge [17]; the virus was detected in wild river barb (Barbonymus schwanenfeldi) in Malaysia [18]. TiLV primarily affects tilapia and its hybrid species, while most other freshwater fish are resilient to TiLV infection, including snakeskin gourami (Trichogaster pectoralis), iridescent shark (Pangasianodon hypophtthalmus), walking catfish (Clarias macrocephalus), striped snake-head fish (Channa striata), climbing perch (Anabas testudineus), common carp (Cyprinus carpio), silver barb (Barbodes gonionotus), Asian sea bass (Lates calcarifer) [17], and Indian major carp (Labeo rohita) [19]
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