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Andrew Kim 7790-7232 The Effects of FV3 Ranavirus on the American Bullfrog and Aquatic Communities In aquatic habitats such as pond ecosystems and lake communities around the eastern half of North America, there is a problem that has made its presence known in American Bullfrog (Rana catesbeiana) populations. Ranaviruses are this problem, and they have been gaining attention as an emerging threat to bullfrog populations in the U.S. and to amphibians in general around the world. Ranaviruses exhibit a parasitic relationship with bullfrogs in North America in that they increase their own fitness by infecting and lowering the fitness of bullfrogs. Furthermore, ranaviruses directly, negatively affect bullfrogs, but they also present a threat to the communities that bullfrogs live in. It has been found that through different intra- and interspecific reservoirs, the ranavirus is able to infect not only American bullfrogs, but also other members of the communities. Bullfrogs are frequently traded globally, and human export and import of infected bullfrogs have helped spread the amphibian ranavirus globally. It is necessary for traded bullfrogs to be screened. This could be enforced by government agencies such as the U.S. FTC (United States Federal Trade Commission) that regulate trade and would greatly help decrease the spread of ranaviruses globally. The most noted strain of ranavirus that affects bullfrogs is Frog virus 3, FV3 for short. The virus exhibits a parasitic relationship with bullfrogs because it infects the bullfrog and lowers the frog’s fitness while increasing its own. The virus lowers a bullfrog’s fitness by decreasing mobility through the swelling of limbs, anorexia due to forced fasting, and by killing the frog in many cases. FV3 has been labeled an emerging threat and much research has been undergone recently to understand the effects that the virus can have on aquatic communities around the world. The virus is an effective parasite due to its virulence and survivability. Jason Hoverman and his team conducted research as to the prevalence of ranaviral infection in pond communities and found that infection was found in 83% of his 33 sample ponds. (Hoverman et al. 2011) FV3 is capable of surviving outside of a host in an aquatic environment for extended periods of time and remains virulent during this time. (Blaustein et al. 2012) A bullfrog that is swimming in water contaminated by an infected host can be infected by FV3 in a matter of hours. (Miller et al. 2011) Combined with the fact that FV3 ranavirus has been found to persist in multiple seasons makes for very problematic transmission efficiency. In Hoverman’s research, his team found that ranavirus infections were found over multiple seasons in a majority, 63%, of the ponds they sampled. (Hoverman et al. 2011) This means that even in winter or other extreme seasons, the virus is able to persist and remain infectious. FV3 has also been found to infect horizontally, which means that it doesn’t spread from parent to child but from an infected host to any non-infected host without immunity. (Miller et al. 2011) This is can be seen through the cannibalistic behavior of bullfrogs. Adult American bullfrogs will eat mostly anything that will fit in their mouths, including smaller frogs and bullfrog larvae. If they consume any of the flesh of an infected frog, they can contract the virus. (Miller et al. 2011) Although these characteristics make FV3 a very efficient parasite, they are not the main factors that make FV3 the large problem for American bullfrogs. The factor that makes FV3 problematic for bullfrogs is its lethality and the symptoms it produces in infected individuals. FV3’s deadly symptoms include organ failure in mainly the kidney and liver, hemorrhaging throughout the body, and cell necrosis. (Blaustein et al. 2012, Miller et al. 2011) These symptoms can result in the death of the host within a couple of days to a few weeks. (Miller et al. 2011) For most parasites, this lethality would present a problem because the parasite needs a host to live. This would lead one to think that FV3’s lethality may seem like a negative for FV3 in that the host dies, but the virus is able to persist in a host’s corpse for extended amounts of time. During this time, if another bullfrog consumes any of the infected tissue of an infected corpse, the virus can easily be contracted. (Miller et al. 2011) This is yet another factor that makes FV3 such a dynamic parasite. Other than the lethal symptoms, FV3 may also produce severely crippling symptoms as well. These symptoms may not immediately kill the host, but maim them to the point that their fitness is greatly reduced. Symptoms such as these include bloated limbs which reduce mobility and anorexia. (Miller et al. 2011) These symptoms greatly decrease bullfrog fitness because a bullfrog that cannot swim properly is easy prey and a bullfrog that won’t eat will eventually die. Also, the probability that a male bullfrog with impaired mobility will mate successfully is low due to the fact that it cannot compete with other males to garner the attraction of a mate. All of these factors of transmission efficiency, lethality, and survivability present a threat to the global communities that bullfrogs live in. FV3 requires human attention because of its potential to harm not just bullfrogs and amphibians, but the entire communities that they inhabit. It has been found that the horizontal transmission of FV3 has been able to infect not only bullfrogs, but amphibians of other species and other aquatic species as well. (Blaustein et al. 2012) When bullfrogs that were infected die, their bodies still retain the virus. If the frog died inside of a pond or lake, the water then becomes infected as well because the virus can sustain itself in an aquatic environment. This has been found to be responsible for the infection of not only amphibians, but also some fish. (Mazzoni et al. 2009, Miller et al. 2007) The disease has the same pathological effect on fish as it does on bullfrogs, and is a threat to the diversity of species in aquatic environments that bullfrogs inhabit. This threat is perpetuated by the fact that American Bullfrogs are a heavily traded commodity. In Brazil, FV3 was found in a bullfrog farm and was responsible for a mass mortality event that devastated the farm. (Mazzoni et al. 2009) This was due to the lack of screening prior to the shipping of the bullfrogs from the U.S. to Brazil. The trade of infected bullfrogs is a very effective means of transportation for FV3 as it becomes a global threat with the ability to pass beyond the borders of other countries without hindrance. Noting the die-offs and the threat that FV3 poses to aquatic environments across the globe, I propose that government organizations such as the U.S. FTC require screenings of bullfrog exports and imports exports to lower the occurrence of FV3 globally. FV3 is a very effective and dangerous threat. Its high transmission efficiency and ability to move across the globe make it a necessary problem to deal with. American bullfrogs may be the main target of FV3 in the U.S., but it has the potential to destroy entire communities and must be dealt with. References Blaustein, A.R., Gervasi, S.S., Johnson, P.T.J., Hoverman, J.T., Belden, L.K., Bradley, P.W., Xie, G.Y. 2012. Ecophysiology meets conservation: understanding the role of disease in amphibian population declines. Philosophical Transactions of the Royal Society Biological Sciences 367: 1688-1707. Miller, D.L., Gray, M.J., Storfer, A. 2011. Ecopathology of ranaviruses infecting amphibians. MDPI Viruses 3: 2351-2373. Mazzoni, R., Mesquita, A.J., Fleury, L.F.F., de Brito, W.M.E.D., Nunes, I.A., Robert, J., Morales, H., Coelho, A.S.G., Barthasson, D.L., Galli, L., Catroxo, M.H.B. 2009. Mass mortality associated with a frog virus 3-like Ranavirus infection in farmed tadpoles Rana catesbeiana from Brazil. Dis Aquat Organ. 86: 181-191. Miller, D.L., Rajeev, S., Gray, M.J., Baldwin, C.A. 2007. Frog virus 3 infection, cultured american bullfrogs. Emerging Infectious Diseases 13: 342-343. Hoverman, J.T., Gray, M.J., Miller, D.L., Haislip, N.A. 2011. Widespread occurrence of ranavirus in pondbreeding amphibian populations. Ecohealth 9: 36-48.