Dissecting the localization ofTilapia tilapinevirusin the brain of the experimentally infected Nile tilapia (Oreochromis niloticus)

Abstract

Tilapia tilapinevirus or tilapia lake virus (TiLV) is an emerging virus that inflicts significant mortality on farmed tilapia globally. Previous studies reported detection of the virus in multiple organs of the infected fish; however, little is known about the in-depth localization of the virus in the central nervous system. Herein, we determined the distribution of TiLV in the entire brain of experimentally infected Nile tilapia. In situ hybridization (ISH) using TiLV-specific probes revealed that the virus was broadly distributed throughout the brain. The strongest positive signals were dominantly detected in the forebrain (responsible for learning, appetitive behavior, and attention) and the hindbrain (involved in controlling locomotion and basal physiology). The permissive cell zones for viral infection were observed mostly to be along the blood vessels and the ventricles. This indicates that the virus may productively enter into the brain through the circulatory system and widen broad regions, possibly through the cerebrospinal fluid along the ventricles, and subsequently induce the brain dysfunction. Understanding the pattern of viral localization in the brain may help elucidate the neurological disorders of the diseased fish. This study revealed the distribution of TiLV in the whole infected brain, providing new insights into fish-virus interactions and neuropathogenesis.

An Age-Structured Model for Tilapia Lake Virus Transmission in Freshwater with Vertical and Horizontal Transmission

“…considering the different attributes of the infection depending on the time since the infection: transmission rate, mortality rate, birth rate, shedding rate as well as duration of infectious period. Indeed, the infectivity of TiLV-positive fish is high for a relatively short time after becoming infectious, decreases and completely vanish thereafter [10,14,27,37], this suggests that in the spread of the TilV, the effective transmission depends greatly on the infection age (day post challenge [14,27,37], day post infection [10]). This means that the rate of movement out of the infectious class (trought recovery or dead) is better captured as a function of time since infection, rather than a constant value.…”

“…This means that the rate of movement out of the infectious class (trought recovery or dead) is better captured as a function of time since infection, rather than a constant value. Moreover it has been showed recently that tilapia develop a immune response to TiLV see for instance [10,27,37]. This allows us to better choose a model in which the population is divided into members who may become infected and members who can not become infected, either because they are already infected or because they are immune, that is the underlying idea of infection age models [6].…”

“…infectious) period and θ is set to 10 4 copies.day −3 .fish −1 , estimated from [39,43]. According to [10,14,33,36], the clinical signs appeared within 3 -7 days post infection, but since under natural conditions, infected fish without clinical signs might transmit the virus to susceptible fish [31], hence τ 1 = 2 days. Moreover from [37], the level of viral load peaks at day 3 post infection and then gradually declines until its absence at day 15 post infection, Hence τ 2 = 13 days.…”

“…the mean duration of mass mortality) and δ 0 is set to 1.63 × 10 −2 day −3 , so that as in [14], the maximal value of δ equals 0.2. Following [10,14], the onset of mortality occurs from 1 − 5 days post infection and lasted until 9 − 11 days post infection, hence a 1 = 2 days, a 2 = 7 days.…”

Immunization of Nile Tilapia (Oreochromis niloticus) Broodstock with Tilapia Lake Virus (TiLV) Inactivated Vaccines Elicits Protective Antibody and Passive Maternal Antibody Transfer

“…It is a single-stranded RNA virus with ten genomic segments and ranging from 55 to 100 nm in diameter [5][6][7][8]. The mortality rate in natural TiLV outbreaks ranges from 20% to 90% [5,6,9,10], while cumulative mortalities from experimental infection range from 66% to 100% [11,12]. The virus can infect fertilized eggs, yolk-sac fish, fry, fingerlings and adult fish [13,14].…”