Experimental demonstration of the pathogenicity of a frog virus, Bohle iridovirus, for a fish species, barramundi Lates calcarifer

Abstract

Experimental infections indicate that Bohle iridovirus, a Ranavirus, is pathogenic for barramundi Lates calcarifer Bloch. Mortalities after bath-exposure or inoculation of barramundi in both freshwater a n d seawater were 100 % Symptoms of inoculated barramundi held in seawater and freshwater and bath-exposed barramundi in freshwater included cessation of feeding, shivering, loss of muscle coordination, spiral and often erratic swimming and decreased ventilation. Just pnor to death, the fish were incapable of any movement. In bath-exposed barramundi held in seawater, no symptoms were observed before death The infection was characterised by focal to diffuse necrosis of the haematopoletlc tissue of the kidney and spleen. In several BIV-infected barramundi, focal necrosis occurred in the llver. In bath-exposed and ~noculated barramundi, BIV was isolated on BF2 cell monolayers from muscle, llver, kidney and spleen tlssues, with recovery rates of 72.5, 58.5, 17.7 and 17.7 'Yo respectively. This is the first time that a virus isolated from a frog has been shown to cause mortalities in a flsh specles.

Distribution and Host Range of Ranaviruses

“…On just one occasion, BIV may have been associated with high mortality in hatchery-reared Nile tilapia fry in Australia (Ariel and Owens 1997 ). Although the authors did not genetically characterize the iridovirus, feeding the moribund tilapia fry to barramundi fi ngerlings reproduced disease similar to what had been reported following challenge studies of barramundi to BIV (Moody and Owens 1994 ).…”

“…Although designated as a distinct species by the ICTV, the sequence of the MCP gene is 97.8 % identical to that of EHNV, which is endemic in a different part of the continent (Marsh et al 2002 ). As with FV3, laboratory challenge studies demonstrated that BIV is also pathogenic to fi sh, in this case to barramundi ( Lates calcarifer ), a popular sport fi sh in Australia (Moody and Owens 1994 ). On just one occasion, BIV may have been associated with high mortality in hatchery-reared Nile tilapia fry in Australia (Ariel and Owens 1997 ).…”

“…The fi rst evidence for interclass transmission of ranaviruses was provided by Moody and Owens ( 1994 ). Barramundi ( Lates calcarifer ) were exposed to BIV, an isolate derived from amphibians, by water bath exposure or injection.…”

Ranavirus Infection of Free-Ranging and Captive Box Turtles and Tortoises in the United States

“…This suggests that both animals may have been infected with the same virus. Interclass infections have been shown previously in a natural setting where sympatric species of amphibians and fish were infected with the same virus species as well as through experimental transmission studies (Moody and Owens, 1994). There are several ways that chelonians and amphibians might be exposed to the same virus.…”

Ranavirus Ecology and Evolution: From Epidemiology to Extinction

“…For example, morbid fi sh and turtles have been reported in association with amphibian die-offs due to ranaviral disease Farnsworth and Seigel 2013 ). Moreover, several laboratory studies have demonstrated that BIV and FV3-like viruses isolated from one vertebrate class could be used to experimentally infect animals in another (Moody and Owens 1994 ;Ariel and Owens 1997 ;Bang Jensen et al 2009, 2011bGobbo et al 2010 ;Bayley et al 2013 ;Brenes et al 2014b ). Recently, Brenes et al ( 2014a ) paired ranavirus-exposed and -unexposed hosts from different vertebrate classes on opposite sides of a fi ne mesh screen, preventing direct contact but allowing water and virions to pass through.…”