Environmental persistence of amphibian and reptilian ranaviruses

Abstract

Ranaviruses infect fish, amphibians, and reptiles. The present study was conducted to compare the persistence of amphibian and reptilian ranaviruses in a pond habitat. The 4 viruses used in this study included 2 amphibian ranaviruses, Frog virus 3 (FV3, the type species of the genus Ranavirus) and an isolate from a frog, and 2 ranaviruses of reptilian origin (from a tortoise and from a gecko). A sandwich germ-carrier technique was used to study the persistence of these viruses in sterile and unsterile pond water (PW) and soil obtained from the bank of a pond. For each virus, virus-loaded carriers were placed in each of the 3 substrates, incubated at 4 and 20°C, and titrated at regular intervals. Serial data were analyzed using a linear regression model to calculate T-90 values (time required for 90% reduction in the virus titer). Resistance of the viruses to drying was also studied. All 4 viruses were resistant to drying. At 20°C, T-90 values of the viruses were 22 to 31 d in sterile PW and 22 to 34 d in unsterile PW. Inactivation of all 4 viruses in soil at this temperature appeared to be non-linear. T-90 values at 4°C were 102 to 182 d in sterile PW, 58 to 72 d in unsterile PW, and 30 to 48 d in soil. Viral persistence was highest in the sterile PW, followed by the unsterile PW, and was lowest in soil. There were no significant differences in the survival times between the amphibian and reptilian viruses. The results of the present study suggest that ranaviruses can survive for long periods of time in pond habitats at low temperatures. KEY WORDS: Ranaviruses · Pond water · Persistence · Soil Resale or republication not permitted without written consent of the publisherDis Aquat Org 98: [177][178][179][180][181][182][183][184] 2012 transmitted to healthy salamanders after putting them in the water where infected salamanders were previously kept, even after passing the water through 0.45 µm pore size filters. In one transmission study, it has been observed that salamanders acquired infection after water-bath exposure to ATVcontaminated water and also transferred the infection to other healthy individuals (Brunner et al. 2007). The exposure of Rana sylvatica tadpoles to sediments collected from a pond where a ranavirus die-off had occurred resulted in the development of infection in the exposed individuals (Harp & Petranka 2006). Similarly, experimentally inoculated moist sediments also transmitted ATV infection and caused mortality in larval salamanders (Brunner et al. 2007). These studies indicate that in a small pond habitat, contaminated water and soil can be a potential source of virus transmission to susceptible animals.There is scarcity of data on the environmental persistence of iridoviruses infecting reptiles and amphibians. One report shows that the infectivity of ATV-contaminated water was lost after a 2 wk incubation at 25°C (Jancovich et al. 1997). Langdon (1989) observed that a fish ranavirus, closely related to amphibian ranaviruses, can survive for 97 d in water at 15°C. A comparison ...

Rapid Response to Evaluate the Presence of Amphibian Chytrid Fungus (Batrachochytrium dendrobatidis) and Ranavirus in Wild Amphibian Populations in Madagascar

“…Both Ranomafana and Andasibe are frequently visited by tourists and researchers and the movement of potentially contaminated footwear and equipment provides a likely vector for the spread of disease among and between biodiversity hotspots. Ranavirus can remain viable from days to weeks when protected from high temperatures, desiccation, and microbial action [54,55] providing considerable time for spread via fomites, and the same applies to Bd [56]. Even if these pathogens may be endemic to Madagascar, human-assisted introduction to naive isolated amphibian populations or the spread of different strains to new regions may lead to more severe outcomes and increased risk of declines.…”

Amphibian pathogens at northern latitudes: presence of chytrid fungus and ranavirus in northeastern Canada

“…Possible vectors have been investigated for both diseases, including contaminated water and amphibian trade (Brunner et al 2004, Johnson & Speare 2005, Harp & Petranka 2006, Greer et al 2008, Picco & Collins 2008, Nazir et al 2012, and although transmission of the chytrid fungus and the ranavirus can be influenced by anthropogenic disruptions (St-Amour et al 2008), such as habitat destruction and fragmentation (Phillips 1990), their presence in seemingly undisturbed areas led to alternate hypotheses about their transmission routes. For instance, migrating birds or other animals can act as vectors (Johnson & Speare 2005, Garmyn et al 2012, and climate change has been shown to alter host and pathogen distributions (Parra-Olea et al 2005, Pounds et al 2006) as well as susceptibility and virulence (Rojas et al 2005, Altizer et al 2013.…”

Ranavirus Ecology and Evolution: From Epidemiology to Extinction

“…An important caveat is that all of these studies used virus grown in cell culture; ranaviruses shed in mucous, sloughed skin, etc., may be protected from microbes and the environment. Nazir et al ( 2012 ) also tested the persistence of ranaviruses in soil and found T-90s of 30-48 days, which raises concern over the potential for ranaviruses to be translocated in contaminated soil (Harp and Petranka 2006 ). Brunner et al ( 2007 ), however, found that ATV becomes noninfectious in pond substrate that is allowed to dry.…”

“…In one study, LMBV lost 90 % of its infectivity in water in 24 h (its T-90 value), although it remained detectable in water for at least 7 days (Grizzle and Brunner 2003 ). Nazir et al ( 2012 ) found that four FV3-like viruses isolated from frogs, a tortoise, and a gecko had T-90s of between 22 and 34 days in unsterile pond water at 20 °C and up to 72 days at 4 °C, which is long enough to allow for continued transmission from the environment within an epidemic, if not between years. However, their experiment isolated virus particles from the direct action of microbes, which is problematic because bacteria and other microbes might otherwise be able to consume and inactivate pathogens.…”