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E-book Ranaviruses : Lethal Pathogens of Ectothermic Vertebrates

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Penilaian

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The family Iridoviridae currently contains fi ve genera, two of which infect invertebrates ( Iridovirus and Chloriridovirus ) and three that infect only ectother-mic vertebrates ( Lymphocystivirus , Megalocytivirus , and Ranavirus ; Jancovich et al. 2015a ). Lymphocy stiviruses and megalocytiviruses only infect fi sh, whereas, as indicated above, ranaviruses target fi sh, amphibians, and reptiles. Infection of “higher” vertebrates (i.e., birds and mammals) has not been reported. However, this block likely refl ects a temperature limit above which the virus cannot replicate (approximately 32 °C), and not a lack of suitable cellular recep-tors, as ranaviruses can replicate in mammalian cell lines (e.g., baby hamster kidney) when incubated at 30 °C. Ranaviruses also cause apoptotic cell death in mammals even if the pathogen has been inactivated by heat or radiation (Grayfer et al. 2015 ). Thus, ranaviruses represent a group of pathogens that possesses a wide host range and the potential to affect diverse populations of vertebrate species around the globe. The question frequently arises, “Are ranaviruses a signifi cant threat to wildlife?” We believe the answer is, “Yes,” but that the seriousness of the threat is dependent upon a number of factors. Brunner et al. ( 2015 ) describe how ranaviruses could contribute to species declines using epidemiological theory and results from math-ematical simulations. However, because there have been very few long-term longi-tudinal studies on populations with reoccurring ranavirus die-offs, data necessary to address population and species declines are scarce. Recent studies are beginning to address this defi ciency. Stephen Price and colleagues recently reported ranavirus-induced declines in three amphibian species at several sites in northern Spain (Price et al. 2014 ). Amber Teacher and colleagues analyzed an 11-year dataset in England, and found about an 80 % decline in common frog abundance at ranavirus die-off sites (Teacher et al. 2010 ). Jim Petranka and several other ecologists have observed no recruitment in consecutive years at sites with ranavirus die-offs (Petranka et al. 2003 ; Wheelwright et al. 2014 ). Julia Earl showed in closed popula-tions of wood frogs that reoccurring outbreaks of ranavirus could result in popula-tion extinction in as quickly as 5 years (Earl and Gray 2014 ). These studies suggest that several elements are in place (e.g., high susceptibility among several host spe-cies, possible density-independent transmission) for ranaviruses to cause local pop-ulation extinction and thereby contribute to species declines. However, to date, species extinction due to ranaviral disease has not been reported. This uncertainty emphasizes the need for more intensive investigations in ranavirus surveillance and population monitoring, which is outlined in Gray et al. ( 2015 ). Importantly, we should not sit idly until there is defi nitive evidence of species extinctions due to ranavirus. The writing is on the wall suggesting its potential threat, especially con-sidering that many rare species are hosts for ranaviruses. For example, the highly endangered Chinese giant salamander ( Andrias davidianus , Geng et al. 2010 ), gopher tortoise ( Gopherus polyphemus , Westhouse et al. 1996 ), dusky gopher frog ( Lithobates sevosus , Sutton et al. 2014 ), and boreal toad ( Anaxyrus boreas boreas , J. Chaney, M. Gray, and D. Miller, University of Tennessee, unpublished data) are very susceptible to ranaviral disease. Additional investigations are needed to iden-tify other rare species that are highly susceptible (Gray et al. 2015 ). In captivity, 100 % mortality of hosts is commonly observed likely due to abundant hosts, guaranteed transmission, and stress associated with these environments (Waltzek et al. 2014 ). Several species of economic (e.g., bullfrogs, Mazzoni et al. 2009 ; grouper, Qin et al. 2001 ) and conservation concern (e.g., pallid sturgeon, Waltzek et al. 2014 ; Chinese giant salamander, Geng et al. 2010 ; Cunningham et al. 2015 ) have experienced cata-strophic losses in captivity due to ranaviruses. Given this preliminary information on the possible effects of ranaviruses on highly susceptible hosts, we believe it is reasonable to consider this pathogen a serious threat to the biodiversity of ectother-mic vertebrate species.

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Ketersediaan

Informasi Detail

Judul Seri

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No. Panggil

591.7 ALL r

Penerbit

Switzerland : Springer Nature., 2015

Deskripsi Fisik

254 hlm

Bahasa

English

ISBN/ISSN

9783319137551

Klasifikasi

591.7

Tipe Isi

text

Tipe Media

computer

Tipe Pembawa

online resource

Edisi

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Subjek

Animal Ecology

Info Detail Spesifik

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Pernyataan Tanggungjawab

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Versi lain/terkait

Lampiran Berkas

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