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Exposure to contagious pathogens can result in behavioural changes, which can alter the spread of infectious diseases. Healthy individuals can express generalized social distancing or avoid the sources of infection, while infected individuals can show passive or active self-isolation. Amphibians are globally threatened by contagious diseases, yet their behavioural responses to infections are scarcely known. We studied behavioural changes in agile frog (Rana dalmatina) juveniles upon exposure to a Ranavirus (Rv) using classic choice tests. We found that both non-infected and Rv-infected focal individuals spatially avoided infected conspecifics, while there were no signs of generalized social distancing, nor self-isolation. Avoidance of infected conspecifics may effectively hinder disease transmission, protecting non-infected individuals as well as preventing secondary infections in already infected individuals. On the other hand, the absence of self-isolation by infected individuals may facilitate it. Since infection status did not affect the time spent near conspecifics, it is unlikely that the pathogen manipulated host behaviour. More research is urgently needed to understand under what circumstances behavioural responses can help amphibians cope with infections, and how that affects disease dynamics in natural populations., (© 2024. The Author(s).)

Understanding the epidemiology and transmission dynamics of transboundary animal diseases (TADs) among wild pigs ( Sus scrofa ) will aid in preventing the introduction or containment of TADs among wild populations. Given the challenges associated with studying TADs in free-ranging populations, a surrogate pathogen system may predict how pathogens may circulate and be maintained within wild free-ranging swine populations, how they may spill over into domestic populations, and how management actions may impact transmission. We assessed the suitability of Torque teno sus virus 1 (TTSuV1) to serve as a surrogate pathogen for molecular epidemiological studies in wild pigs by investigating the prevalence, persistence, correlation with host health status and genetic variability at two study areas: Archbold's Buck Island Ranch in Florida and Savannah River Site in South Carolina. We then conducted a molecular epidemiological case study within Archbold's Buck Island Ranch site to determine how analysis of this pathogen could inform transmission dynamics of a directly transmitted virus. Prevalence was high in both study areas (40%, n = 190), and phylogenetic analyses revealed high levels of genetic variability within and between study areas. Our case study showed that pairwise host relatedness and geographic distance were highly correlated to pairwise viral genetic similarity. Molecular epidemiological analyses revealed a distinct pattern of direct transmission from pig to pig occurring within and between family groups. Our results suggest that TTSuV1 is highly suitable for molecular epidemiological analyses and will be useful for future studies of transmission dynamics in wild free-ranging pigs.

Viral outbreaks are a constant threat to aquaculture, limiting production for better global food security. A lack of diagnostic testing and monitoring in resource-limited areas hinders the capacity to respond rapidly to disease outbreaks and to prevent viral pathogens becoming endemic in fisheries productive waters. Recent developments in diagnostic testing for emerging viruses, however, offers a solution for rapid in situ monitoring of viral outbreaks. Genomic epidemiology has furthermore proven highly effective in detecting viral mutations involved in pathogenesis and assisting in resolving chains of transmission. Here, we demonstrate the application of an in-field epidemiological tool kit to track viral outbreaks in aquaculture on farms with reduced access to diagnostic labs, and with non-destructive sampling. Inspired by the "lab in a suitcase" approach used for genomic surveillance of human viral pathogens and wastewater monitoring of COVID19, we evaluated the feasibility of real-time genome sequencing surveillance of the fish pathogen, Infectious spleen and kidney necrosis virus (ISKNV) in Lake Volta. Viral fractions from water samples collected from cages holding Nile tilapia ( Oreochromis niloticus ) with suspected ongoing ISKNV infections were concentrated and used as a template for whole genome sequencing, using a previously developed tiled PCR method for ISKNV. Mutations in ISKNV in samples collected from the water surrounding the cages matched those collected from infected caged fish, illustrating that water samples can be used for detecting predominant ISKNV variants in an ongoing outbreak. This approach allows for the detection of ISKNV and tracking of the dynamics of variant frequencies, and may thus assist in guiding control measures for the rapid isolation and quarantine of infected farms and facilities., Competing Interests: The authors declare there are no competing interests., (©2024 Alathari et al.)

White spot syndrome virus has been a threat to the global shrimp industry since it was discovered in Taiwan in 1992. Thus, shrimp-producing countries have launched regulations to prevent import of WSSV-infected commodity shrimp from endemic areas. Recently, cooked shrimp that is infected with WSSV tested positive by PCR. However, there is no study to determine the infectivity of WSSV in cooked shrimp that tested positive by PCR. In the present study, WSSV-infected shrimp were cooked at boiling temperature for different times including 0, 1, 3, 5, 10 and 30 min. Upon exposure to boiling temperature, WSSV-infected shrimp were fed to SPF shrimp (Litopenaeus vannamei). The result showed experimentally challenged shrimp from 0-min treatment (positive control) indeed got infected with WSSV. However, experimentally challenged shrimp that were fed tissues boiled at 1, 3, 5, 10 and 30 min were not infected with WSSV. Mortality data showed that only the positive control (0-min) treatment displayed high mortality, whereas no mortality was observed in any other treatment category. These findings suggest that cooking shrimp at boiling temperature for at least 1 min might prevent any potential spread of WSSV from endemic countries to other geographical areas where WSSV has not yet been reported., (© 2020 John Wiley & Sons Ltd.)

Torque teno virus (TTV) is the most common component of the human blood virobiota. Little is known, however, about the prevalence of TTV in humans and the most common farm domesticates in Jordan, or the history and modality of TTV transmission across species lines. We therefore tested sera from 396 Jordanians and 171 farm animals for the presence of TTV DNA using nested 5'-UTR-PCR. We then performed phylogenetic, ordination and evolutionary diversity analyses on detected DNA sequences. We detected a very high prevalence of TTV in Jordanians (~96%); much higher than in farm animal domesticates (~29% pooled over species). TTV prevalence in the human participants is not associated with geography, demography or physical attributes. Phylogenetic, ordination and evolutionary diversity analyses indicated that TTV is transmitted readily between humans across the geography of the country and between various species of animal domesticates. However, the majority of animal TTV isolates seem to derive from a single human-to-animal transmission event in the past, and current human-animal transmission in either direction is relatively rare. In conclusion, animal TTV in Jordan is historically derived from human variants; however, ongoing human-animal TTV exchange is minimal and zoonotic infection seems to be of limited importance.

Ranaviruses began emerging in common frogs ( Rana temporaria ) in the United Kingdom in the late 1980s and early 1990s, causing severe disease and declines in the populations of these animals. Herein, we explored the transmission dynamics of the ranavirus(es) present in common frog populations, in the context of a simple susceptible-infected (SI) model, using parameters derived from the literature. We explored the effects of disease-induced population decline on the dynamics of the ranavirus. We then extended the model to consider the infection dynamics in populations exposed to both ulcerative and hemorrhagic forms of the ranaviral disease. The preliminary investigation indicated the important interactions between the forms. When the ulcerative form was present in a population and the hemorrhagic form was later introduced, the hemorrhagic form of the disease needed to be highly contagious, to persist. We highlighted the areas where further research and experimental evidence is needed and hope that these models would act as a guide for further research into the amphibian disease dynamics.

The pathogenicity of frog virus 3 (FV3)-like ranavirus varies in adult chelonian species at different environmental temperatures, but differences in pathogenicity at different temperatures has yet to be determined in juveniles. Our objective was to determine the susceptibility to FV3-like ranavirus in four species of juvenile chelonians: red-eared sliders (RES; Trachemys scripta elegans), Mississippi map turtles ( Graptemys pseudogeographica kohnii), false map turtles (FMT; Graptemys pseudogeographica), and eastern river cooters ( Pseudemys concinna concinna) at two environmental temperatures. Two simultaneous trials ( n=8 treatment and n=4 controls of each species) were conducted in separate temperature-controlled rooms with animals maintained at 22 C or 27 C. All of the inoculated animals of each species at each temperature died, but no mortality was observed in control animals. Median survival times varied between 8 d and 11 d, based on species and temperature, with RES in the 27 C trial surviving the shortest time and the FMT in the 22 C trial surviving the longest. Combining all species, turtles in the 27 C trial survived for fewer days than those housed at 22 C, despite all turtles in both trials having similar viral copies detected in postmortem tissues. Lesions in inoculated turtles resembled those noted in natural and experimental FV3-like ranavirus infections and included vasculitis, thrombosis, hemorrhage in multiple organs, renal tubular necrosis, and hepatic necrosis. Myositis was not present in any juvenile, infected turtles in this study. This study confirmed that juvenile chelonians have a high susceptibility to ranaviral disease.

Background: Both hepatitis B and C viruses were transmitted through blood transfusion before implementation of donor screening. The existence of additional, yet unknown transfusion transmittable agents causing liver disease could have important public health implications., Methods: Analyses were based on the Scandinavian Donations and Transfusions (SCANDAT2) database. Cox regression models were used to estimate the hazard ratio (HR) of developing chronic liver disease in recipients of blood from donors who later developed any chronic liver disease compared to recipients who received blood transfusion from healthy donors. We also studied whether the risk of liver disease was increased in patients who received units from 'high-risk' donors, defined as donors who had a higher than expected occurrence of liver disease amongst their previous recipients. All analyses were stratified before and after 1992 to account for the effect of screening for hepatitis C virus., Results: A total of 1 482 922 transfused patients were included in the analyses. Analyses showed evidence of transfusion transmission of liver diseases before, but not after the implementation of hepatitis C virus screening in 1992, with HRs for any liver disease of 1.38 [95% confidence interval (CI), 1.30-1.46] and 0.99 (95% CI, 0.91-1.07), before and after 1992, respectively. Similarly, blood components from 'high-risk' donors conferred increased risks before, but not after 1992., Conclusions: Our data provide no evidence for transfusion transmission of agents causing liver disease after the implementation of screening for hepatitis B and C, and suggest that if such transmission does occur, it is rare., (© 2018 The Association for the Publication of the Journal of Internal Medicine.)

Human-mediated disease outbreaks due to poor biosecurity practices when processing animals in wild populations have been suspected. We tested whether not changing nitrile gloves between processing wood frog (Lithobates sylvaticus) tadpoles and co-housing individuals increased pathogen transmission and subsequent diseased-induced mortality caused by the emerging pathogen, ranavirus. We found that not changing gloves between processing infected and uninfected tadpoles resulted in transmission of ranavirus and increased the risk of mortality of uninfected tadpoles by 30X. Co-housing tadpoles for only 15 minutes with 10% of individuals infected resulted in ranavirus transmission and 50% mortality of uninfected tadpoles. More extreme mortality was observed when the co-housing infection prevalence was >10%. Our results illustrate that human-induced disease outbreaks due to poor biosecurity practices are possible in wild animal populations.

Circular replication-associated protein encoding single-stranded DNA (CRESS DNA) viruses are increasingly recognized worldwide in a variety of samples. Representative members include well-described veterinary pathogens with worldwide distribution, such as porcine circoviruses or beak and feather disease virus. In addition, numerous novel viruses belonging to the family Circoviridae with unverified pathogenic roles have been discovered in different human samples. Viruses of the family Genomoviridae have also been described as being highly abundant in different faecal and environmental samples, with case reports showing them to be suspected pathogens in human infections. In order to investigate the genetic diversity of these viruses in European bat populations, we tested guano samples from Georgia, Hungary, Romania, Serbia and Ukraine. This resulted in the detection of six novel members of the family Circoviridae and two novel members of the family Genomoviridae. Interestingly, a gemini-like virus, namely niminivirus, which was originally found in raw sewage samples in Nigeria, was also detected in our samples. We analyzed the nucleotide composition of members of the family Circoviridae to determine the possible host origins of these viruses. This study provides the first dataset on CRESS DNA viruses of European bats, and members of several novel viral species were discovered.

Torque teno viruses [TTVs] are negative sense, single-stranded, DNA viruses, which are distributed globally in several mammalian hosts such as humans, apes, sheep and swine in a species-specific manner. While the pathogenic potential of TTVs is under debate, recent experimental studies in gnotobiotic pigs indicate that swine TTVs, TTSuV1 in particular, can act as a primary or co-infecting pathogen. Hence, determining whether TTSuV1 can infect other mammals would eventually further our understanding of viral pathogenesis, especially in coinfections. In this study, we tested sera from horses, cattle, sheep, dogs and elk for the presence of TTSuV1 DNA using a panel of TTSuV1-specific primers, and assessed the extent of sero-conversion to TTSuV1 in the selected species. We found that TTSuV1 DNA was detected in 46.7% of equines, 70% of canine, 100% of bovine, 40% of ovine and 93.3% of elk samples. However, significant TTSuV1 specific antibody responses were detected only in the bovine, ovine and equine samples but not the canine or elk samples, indicating that these animals could support the replication of TTSuV1. This combined serological and molecular epidemiological profile of TTSuV1 infection in five different species indicates the host range of species-specific TTVs could be wider than initially believed. Further studies are required to understand the health risks to these animal species from TTSuV-1 infection., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Viruses persist outside their hosts in a variety of forms, from naked virions to virus protected in sloughed tissues or carcasses, and for a range of times, all of which affect the likelihood and importance of transmission from the environment. This review synthesizes the literature on environmental persistence of viruses in the genus Ranavirus (family Iridoviridae), which are large double-stranded DNA viruses of ectothermic, often aquatic or semiaquatic vertebrates. Ranaviruses have been associated with mass mortality events in natural and captive settings around the world, and with population and community-wide declines in Europe. Early work suggested ranaviruses are environmentally robust and transmission from the environment should be common. More recent work has shown a large effect of temperature and microbial action on persistence times, although other aspects of the environment (e.g., water chemistry) and aquatic communities (e.g., zooplankton) may also be important. Ranaviruses may persist in the carcasses of animals that have died of infection, and so decomposing organisms and invertebrate scavengers may reduce these persistence times. The question is, do persistence times vary enough to promote or preclude substantial transmission from the environment. We built an epidemiological model with transmission from contacts, free virus in water, and carcasses, to explore the conditions in which environmental persistence could be important for ranavirus epidemiology. Based on prior work, we expected a substantial amount of transmission from the water and that longer persistence times would make this route of transmission dominant. However, neither water-borne nor transmission from carcasses played an important role in the simulated epidemics except under fairly restrictive conditions, such as when there were high rates of virus shedding or high rates of scavenging on highly infectious carcasses. While many aspects of environmental persistence of ranaviruses are being resolved by experiments, key parameters such as viral shedding rates are virtually unknown and will need to be empirically constrained if we are to determine whether environmental persistence and transmission from the environment are essential or insignificant features of Ranavirus epidemiology. We conclude by emphasizing the need to place environmental persistence research in an epidemiological framework., (© 2018 Elsevier Inc. All rights reserved.)

This quantitative risk assessment provided an analytical framework to estimate white spot syndrome virus (WSSV) transmission risks in the following different scenarios: (1) partial harvest from rearing ponds and (2) post-harvest transportation, assuming that the introduction of contaminated water with viral particles into shrimp culture ponds is the main source of viral transmission risk. Probabilities of infecting shrimp with waterborne WSSV were obtained by approaching the functional form that best fits (likelihood ratio test) published data on the dose-response relationship for WSSV orally inoculated through water into shrimp. Expert opinion defined the ranges for the following uncertain factors: (1) the concentrations of WSSV in the water spilled from the vehicles transporting the infected shrimp, (2) the total volume of these spills, and (3) the dilution into culture ponds. Multiple scenarios were analysed, starting with a viral load (VL) of 1×10 2 mL -1 in the contaminated water spilled that reached the culture pond, whose probability of infection of an individual shrimp (P i ) was negligible (1.7×10 -7 ). Increasing the VL to 1×10 4.5 mL -1 and 1×10 7 mL -1 yielded results into very low (P i =5.3×10 -5 ) and high risk (P i =1.6×10 -2 ) categories, respectively. Furthermore, different pond stocking density (SD) scenarios (20 and 30 post-larvae [PL]/m 2 ) were evaluated, and the probability of infection of at least one out of the total number of shrimp exposed (P N ) was derived; for the scenarios with a low VL (1×10 2 mL -1 ), the P N remained at a negligible risk level (P N , 2.4×10 -7 to 1.8×10 -6 ). For most of the scenarios with the moderate VL (1×10 4.5 mL -1 ), the P N scaled up to a low risk category (P N , 1.1×10 -4 to 5.6×10 -4 ), whereas for the scenarios with a high VL (1×10 7 mL -1 ), the risk levels were high (P N , 2.3×10 -2 to 3.5×10 -2 ) or very high (P N , 1.1×10 -1 to 1.6×10 -1 ) depending on the volume of contaminated water spilled in the culture pond (VCWSCP, 4 or 20L). In the sensitivity analysis, for a SD of 30 PL/m 2 , it was shown that starting with a VL of 1×10 5 mL -1 and a VCWSCP of 12L, the P N was moderate (1.05×10 -3 ). This was the threshold for greater risks, given the increase in either the VCWSCP or VL. These findings supported recommendations to prevent WSSV spread through more controlled transportation and partial harvesting practices., (Copyright © 2017 Elsevier B.V. All rights reserved.)

In this review we provide an overview of the diversity of large DNA viruses known to be pathogenic for invertebrates. We present their taxonomical classification and describe the evolutionary relationships among various groups of invertebrate-infecting viruses. We also indicate the relationships of the invertebrate viruses to viruses infecting mammals or other vertebrates. The shared characteristics of the viruses within the various families are described, including the structure of the virus particle, genome properties, and gene expression strategies. Finally, we explain the transmission and mode of infection of the most important viruses in these families and indicate, which orders of invertebrates are susceptible to these pathogens., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Background: TTV has been detected in almost every human tissue type or body fluid reaching near 100% prevalence. Several studies report mother-to-child postnatal transmission of TTV in infancy but the risk of transplacental transmission of TTV is still unclear., Methods: The blood and plasma collected postpartum from 100 mother-child pairs were analyzed using TTV-specific qPCR. Samples were collected from the peripheral vein of the mother and the umbilical cord., Results: Eighty four percent of pregnant women were TTV positive (median titers: 8 × 10 4 copies/mL; range: 10 3 - 3 × 10 7 ). The TTV load in plasma was approximately 100 times lower than in whole blood. TTV was not detected in any of cord blood samples., Conclusions: Our data demonstrate the lack of transplacental transmission of TTV (or effective prenatal inhibition of viral proliferation). The presence of the virus in infants may be associated with mother-to-child transmission through breast feeding or other routes of transmission.

Megalocytiviruses cause high mortality diseases that have seriously impacted aquaculture, with the most frequent outbreaks occurring in East and South-East Asia. The international trade of juvenile fish for food and ornamental aquaculture has aided the spread of these viruses, which have spread to Europe and Australia and other regions. Australian freshwater fishes were examined for susceptibility to infection with the exotic megalocytivirus, dwarf gourami iridovirus (DGIV), which belongs to a group with the type species, Infectious spleen and kidney necrosis virus (ISKNV). Fish were held at 23 ± 1 °C and challenged by intraperitoneal (IP) injection or by cohabitation with Murray cod, Maccullochella peelii (Mitchell) infected with DGIV. A species was deemed to be susceptible to DGIV based on evidence of viral replication, as determined by qPCR, and megalocytic inclusion bodies observed histologically. Horizontal transmission occurred between infected Murray cod and golden perch, Macquaria ambigua (Richardson), Macquarie perch, Macquaria australasica (Cuvier) and Murray cod. This indicated that DGIV shed from infected fish held at 23 °C can survive in fresh water and subsequently infect these naïve fish. Further, DGIV administered IP was highly pathogenic to golden perch, Macquarie perch and Murray cod. Compared to these species, the susceptibility of southern pygmy perch, Nannoperca australis (Gunther) was lower. Freshwater catfish (dewfish), Tandanus tandanus (Mitchell), were not susceptible under the experimental conditions based on the absence of clinical disease, mortality and virus replication. This study showed the potential risks associated with naïve and DGIV-infected fish sharing a common water source., (© 2016 John Wiley & Sons Ltd.)

Transmission is central to our understanding and efforts to control the spread of infectious diseases. Because transmission generally requires close contact, host movements and behaviors can shape transmission dynamics: random and complete mixing leads to the classic density-dependent model, but if hosts primarily interact locally (e.g., aggregate) or within groups, transmission may saturate. Manipulating host behavior may thus change both the rate and functional form of transmission. We used the ranavirus-wood frog (Lithobates sylvaticus) tadpole system to test whether transmission rates reflect contacts, and whether the functional form of transmission can be influenced by the distribution of food in mesocosms (widely dispersed, promoting random movement and mixing vs. a central pile, promoting aggregations). Contact rates increased with density, as expected, but transmission rapidly saturated. Observed rates of transmission were not explained by observed contact rates or the density-dependent model, but instead transmission in both treatments followed models allowing for heterogeneities in the transmission process. We argue that contacts were not generally limiting, but instead that our results are better explained by heterogeneities in host susceptibility. Moreover, manipulating host behavior to manage the spread of infectious disease may prove difficult to implement., (© 2016 by the Ecological Society of America.)

Many new and emerging RNA and DNA viruses are zoonotic or have zoonotic origins in an animal reservoir that is usually mammalian and sometimes avian. Not all zoonotic viruses are transmissible (directly or by an arthropod vector) between human hosts. Virus genome sequence data provide the best evidence of transmission. Of human transmissible virus, 37 species have so far been restricted to self-limiting outbreaks. These viruses are priorities for surveillance because relatively minor changes in their epidemiologies can potentially lead to major changes in the threat they pose to public health. On the basis of comparisons across all recognized human viruses, we consider the characteristics of these priority viruses and assess the likelihood that they will further emerge in human populations. We also assess the likelihood that a virus that can infect humans but is not capable of transmission (directly or by a vector) between human hosts can acquire that capability.

Most viral infections encountered in resource-rich countries are relatively trivial and transient with perhaps fever, malaise, myalgia, rash (exanthema) and sometimes mucosal manifestations (enanthema), including oral in some. However, the apparent benignity may be illusory as some viral infections have unexpected consequences - such as the oncogenicity of some herpesviruses and human papillomaviruses. Infections are transmitted from various human or animal vectors, especially by close proximity, and the increasing movements of peoples across the globe, mean that infections hitherto confined largely to the tropics now appear worldwide. Global warming also increases the range of movement of vectors such as mosquitoes. Thus recent decades have seen a most dramatic change with the emergence globally also of new viral infections - notably human immunodeficiency viruses (HIV) - and the appearance of some other dangerous and sometimes lethal infections formerly seen mainly in, and reported from, resource-poor areas especially in parts of Asia, Latin America and Africa. This study offers a brief update of the most salient new aspects of the important viral infections, especially those with known orofacial manifestations or other implications for oral health care., (© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Infection with Torque teno viruses (TTVs) is not restricted to humans. Different domestic and wild animal species are naturally infected with species-specific TTVs worldwide. Due to the global spread of the infection, it is likely that essentially all animals are naturally infected with species-specific TTVs, and that co-evolution of TTVs with their hosts probably occurred. Although TTVs are potentially related to many diseases, the evidence of the widespread infection in healthy human and nonhuman hosts raised doubts about their pathogenic potential. Nonetheless, their role as superimposed agents of other diseases or as triggers for impairment of immune surveillance is currently under debate. The possible contribution of animal TT viruses to interspecies transmission and their role as zoonotic agents are currently topics of discussion.

Ranaviruses are significant pathogens of amphibians, reptiles, and fishes, contributing to mass mortality events worldwide. Despite an increasing focus on ranavirus ecology, our understanding of ranavirus transmission, especially among reptilian hosts, remains limited. For example, experimental evidence for oral transmission of the virus in chelonians is mixed. Consequently, vector-borne transmission has been hypothesized in terrestrial turtle species. To test this hypothesis, mosquitoes captured during a 2012/2013 ranavirus outbreak in box turtles from southwestern Indiana were pooled by genus and tested for ranavirus DNA using qPCR. Two of 30 pools tested positive for ranavirus. Additionally, an individual Aedes sp. mosquito observed engorging on a box turtle also tested positive for ranavirus. Although our approach does not rule out the possibility that the sequenced ranavirus was simply from virus in bloodmeal, it does suggests that mosquitoes may be involved in virus transmission as a mechanical or biological vector among ectothermic vertebrates. While additional studies are needed to elucidate the exact role of mosquitoes in ranavirus ecology, our study suggests that a greater focus on vector-borne transmission may be necessary to fully understand ranaviral disease dynamics in herpetofauna.

Background: A new Marseilleviridae virus family member, giant blood Marseille-like (GBM) virus, was recently reported in persons from France in the serum of an infant with adenitis, in the blood of 4% of healthy blood donors, and in 9% of multiply transfused thalassemia patients. These results suggested the presence of a nucleocytoplasmic large DNA virus potentially transmissible by blood product transfusion., Study Design and Methods: To investigate this possibility we tested the plasma from 113 US blood donors and 74 multiply transfused Cameroon patients for GBM viral DNA using highly sensitive polymerase chain reaction (PCR) assays., Results: GBM DNA was not detected by nested PCR in any of these 187 human specimens., Conclusions: Further testing is required to confirm the occurrence of human GBM virus infections., (© 2015 AABB.)

Human torque teno viruses (TTVs) are new, emerging infectious agents, recently assigned to the family Anelloviridae. The first representative of the genus, torque teno virus (TTV), was discovered in 1997, followed by torque teno mini virus (TTMV) in 2000, and torque teno midi virus (TTMDV) in 2007. These viruses are characterized by an extremely high prevalence, with relatively uniform distribution worldwide and a high level of genomic heterogeneity, as well as an apparent pan-tropism at the host level. Although these viruses have a very high prevalence in the general population across the globe, neither their interaction with their hosts nor their direct involvement in the etiology of specific diseases are fully understood. Since their discovery, human anelloviruses, and especially TTV, have been suggested to be associated with various diseases, such as hepatitis, respiratory diseases, cancer, hematological and autoimmune disorders, with few arguments for their direct involvement. Recent studies have started to reveal interactions between TTVs and the host's immune system, leading to new hypotheses for potential pathological mechanisms of these viruses. In this review article, we discuss the most important aspects and current status of human TTVs in order to guide future studies.

We investigated mass mortalities of koi, Cyprinus carpio Linnaeus, 1758, experienced in South Indian fish farms by virus isolation, electron microscopy, PCR detection, sequencing of capsid protein gene and transmission studies. Samples of moribund koi brought to the laboratory suffered continuous mortality exhibiting swimming abnormalities, intermittent surfacing and skin darkening. Irido-like virus was isolated from the infected fish in the indigenous snakehead kidney cell line (SNKD2a). Icosahedral virus particles of 100 to 120 nm were observed in the infected cell cultures, budding from the cell membrane. Virus transmission and pathogenicity studies revealed that horizontal transmission occurred associated with mortality. PCR analysis of infected fish and cell cultures confirmed the presence of Ranavirus capsid protein sequences. Sequence analysis of the major capsid protein gene showed an identity of 99.9% to that of largemouth bass virus isolated from North America. Detection and successful isolation of this viral agent becomes the first record of isolation of a virus resembling Santee-Cooper Ranavirus from a koi and from India. We propose the name koi ranavirus to this agent., (© 2014 John Wiley & Sons Ltd.)

This report documents an emerging trend of identification of Megalocytivirus-like inclusions in a range of ornamental fish species intercepted during quarantine detention at the Australian border. From September 2012 to February 2013, 5 species of fish that had suffered mortality levels in excess of 25% whilst in the post-entry quarantine and had Megalocytivirus-like inclusion bodies in histological sections were examined by PCR. The fish had been imported from Singapore, Malaysia and Sri Lanka. Ninety-seven of 111 individual fish from affected tanks of fish tested were positive for the presence of Megalocytivirus by PCR. Sequence analysis of representative PCR products revealed an identical sequence of 621 bp in all cases which was identical to a previously characterized Megalocytivirus (Sabah/RAA1/2012 strain BMGIV48). Phylogenetic analysis of available Megalocytivirus major capsid protein (MCP) sequences confirmed the existence of 3 major clades of Megalocytivirus. The virus detected in this study was identified as a member of Genotype II. The broad host range and pathogenicity of megalocytiviruses, coupled to the documented spread of ornamental fish into the environment, render this a significant and emerging biosecurity threat to Australia., (© 2014 John Wiley & Sons Ltd.)

Viruses are ubiquitous organisms, but their role in the ecosystem and their prevalence are still poorly understood. Mimiviruses are extremely complex and large DNA viruses. Although metagenomic studies have suggested that members of the family Mimiviridae are abundant in oceans, there is a lack of information about the association of mimiviruses with marine organisms. In this work, we demonstrate by molecular and virological methods that oysters are excellent sources for mimiviruses isolation. Our data not only provide new information about the biology of these viruses but also raise questions regarding the role of oyster consumption as a putative source of mimivirus infection in humans.

Transmission is an essential process that contributes to the survival of pathogens. Ranaviruses are known to infect different classes of lower vertebrates including amphibians, fishes and reptiles. Differences in the likelihood of infection among ectothermic vertebrate hosts could explain the successful yearlong persistence of ranaviruses in aquatic environments. The goal of this study was to determine if transmission of a Frog Virus 3 (FV3)-like ranavirus was possible among three species from different ectothermic vertebrate classes: Cope's gray treefrog (Hyla chrysoscelis) larvae, mosquito fish (Gambusia affinis), and red-eared slider (Trachemys scripta elegans). We housed individuals previously exposed to the FV3-like ranavirus with naïve (unexposed) individuals in containers divided by plastic mesh screen to permit water flow between subjects. Our results showed that infected gray treefrog larvae were capable of transmitting ranavirus to naïve larval conspecifics and turtles (60% and 30% infection, respectively), but not to fish. Also, infected turtles and fish transmitted ranavirus to 50% and 10% of the naïve gray treefrog larvae, respectively. Nearly all infected amphibians experienced mortality, whereas infected turtles and fish did not die. Our results demonstrate that ranavirus can be transmitted through water among ectothermic vertebrate classes, which has not been reported previously. Moreover, fish and reptiles might serve as reservoirs for ranavirus given their ability to live with subclinical infections. Subclinical infections of ranavirus in fish and aquatic turtles could contribute to the pathogen's persistence, especially when highly susceptible hosts like amphibians are absent as a result of seasonal fluctuations in relative abundance.

Background: Emerging viral infections in humans are appearing at an increasing rate. Recently, we identified a new Marseillevirus, named Giant Blood Marseillevirus (GBM), by performing viral metagenomics on asymptomatic blood donors., Objectives: To study and compare the prevalence of Marseillevirus between asymptomatic blood donors and thalassemia patients., Design: Here, we present a combined molecular and serological study on 174 asymptomatic blood donors and 22 patients with thalassemia who receive repeated blood transfusions to estimate the prevalence of Marseillevirus in these two populations., Results: We identified Marseillevirus genomic DNA in 4% of donors, whereas 9.1% of the thalassemia patients were positive for this virus. Moreover, IgG seropositivity was detected in 22.7% of patients in the thalassemia group, whereas this seropositivity was observed in 12.6% of the blood donor population., Conclusion: These results suggest that Marseillevirus infection is not rare in healthy persons and may be transmitted by transfusion, thus raising speculation regarding the long-term consequences of this viral infection, particularly in patients requiring repeated blood transfusions., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Chronic viral infections can infect sperm and are considered a risk factor in male infertility. Recent studies have shown that the presence of HIV, HBV or HCV in semen impairs sperm parameters, DNA integrity, and in particular reduces forward motility. In contrast, very little is known about semen infection with human papillomaviruses (HPV), herpesviruses (HSV), cytomegalovirus (HCMV), and adeno-associated virus (AAV). At present, EU directives for the viral screening of couples undergoing assisted reproduction techniques require only the evaluation of HIV, HBV, and HCV. However, growing evidence suggests that HPV, HSV, and HCMV might play a major role in male infertility and it has been demonstrated that HPV semen infection has a negative influence on sperm parameters, fertilization, and the abortion rate. Besides the risk of horizontal or vertical transmission, the negative impact of any viral sperm infection on male reproductive function seems to be dramatic. In addition, treatment with antiviral and antiretroviral therapies may further affect sperm parameters. In this review we attempted to focus on the interactions between defined sperm viral infections and their association with male fertility disorders. All viruses considered in this article have a potentially negative effect on male reproductive function and dangerous infections can be transmitted to partners and newborns. In light of this evidence, we suggest performing targeted sperm washing procedures for each sperm infection and to strongly consider screening male patients seeking fertility for HPV, HSV, and HCMV, both to avoid viral transmission and to improve assisted or even spontaneous fertility outcome., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Cyprinid herpesvirus 3 (CyHV-3), a member of the family Alloherpesviridae is the causative agent of a lethal, highly contagious and notifiable disease in common and koi carp. The economic importance of common and koi carp industries together with the rapid spread of CyHV-3 worldwide, explain why this virus became soon after its isolation in the 1990s a subject of applied research. In addition to its economic importance, an increasing number of fundamental studies demonstrated that CyHV-3 is an original and interesting subject for fundamental research. In this review, we summarized recent advances in CyHV-3 research with a special interest for studies related to host-virus interactions.

The transmission of lymphocystis disease virus (LCDV) to gilthead seabream, Sparus aurata L., larvae was investigated using fertilized eggs from a farm with previous reports of lymphocystis disease. LCDV genome was detected by PCR-hybridization in blood samples from 17.5% of the asymptomatic gilthead seabream broodstock analysed. Using the same methodology, eggs spawned from these animals were LCDV positive, as well as larvae hatched from them. The presence of infective viral particles was confirmed by cytopathic effects development on SAF-1 cells. Whole-mount in situ hybridization (ISH) and immunohistochemistry (IHC) showed the presence of LCDV in the epidermis of larvae hatched from LCDV-positive eggs. When fertilized eggs were disinfected with iodine, no viral DNA was detected either in eggs (analysed by PCR-hybridization) or in larvae (PCR-hybridization and ISH). These results suggest the vertical transmission of LCDV, the virus being transmitted on the egg surface. Larvae hatched from disinfected eggs remain LCDV negative during the endotrophic phase, as showed by PCR-hybridization, ISH and IHC. After feeding on LCDV-positive rotifers, viral antigens were observed in the digestive tract, which suggests that viral entry could be achieved via the alimentary canal, and that rotifers can act as a vector in LCDV transmission to gilthead seabream larvae., (© 2012 Blackwell Publishing Ltd.)

The koi herpesvirus (KHV) has spread worldwide since its discovery in 1998 and causes disease and mortality in koi and common carp populations with a high impact on the carp production industry. Many investigations have been conducted to examine ways of distribution and to identify possible transmission vectors. The answers, however, raise many new questions. In the present study, different wild fish species taken from carp ponds with a history of KHV infection were examined for their susceptibility to the virus. In the tissue of these fish, the virus load was determined and it was tested whether a release of the virus could be induced by stress and the virus then could be transferred to naive carp. Wild fish were gathered from carp ponds during acute outbreaks of virus-induced mortality in summer and from ponds stocked with carp carrying a latent KHV infection. From these ponds, wild fish were collected during the harvesting process in autumn or spring when the ponds were drained. We found that regardless of season, temperature variation, age and infection status of the carp stock, wild fish from carp ponds and its outlets could be tested positive for the KHV genome using real-time PCR with a low prevalence and virus load. Furthermore, virus transfer to naive carp was observed after a period of cohabitation. Cyprinid and non-cyprinid wild fish can therefore be considered as an epidemiological risk for pond carp farms., (© 2012 Blackwell Publishing Ltd.)

Objectives: Torque teno mini virus (TTMV) is classified as the Betatorquevirus genus of Anelloviridae. Little is known about the prevalence of TTMV in humans. Worldwide, cervical cancer is the second most common cancer affecting women. This study aimed to estimate the TTMV infection frequency in cervicitis cases and cervical tumors including intraepithelial neoplasia (CIN), squamous cell carcinoma (SCC) and adenocarcinoma, and the possible role of this virus in the etiology of them in an Isfahan population., Methods: 79 cervicitis cases and 42 tumors were collected from histopathological files of Al-Zahra Hospital in Isfahan, Iran. DNA was extracted and subjected to nested polymerase chain reaction., Results: Totally 62% of the tested samples were positive for TTMV. It was positive in 52.4% of adenocarcinoma, 68.4% of CIN and 100% SCC cases. In cervicitis, 48% of the cases were positive. In the phylogenetic construct two of the cervical tumor isolates and two of the cervicitis isolates were placed in the same cluster with already reported isolates from Japan (EF538880 and AB041962). Also, three of the cervical tumors isolated (JQ734980, JQ734981 and JQ734982) were placed in another cluster., Conclusion: The presence of the virus in cervical tissues suggests possible sexual transmission of the virus., (Copyright © 2013 S. Karger AG, Basel.)

Infections during pregnancy have been suggested to be involved in childhood leukemias. We used high-throughput sequencing to describe the viruses most readily detectable in serum samples of pregnant women. Serum DNA of 112 mothers to leukemic children was amplified using whole genome amplification. Sequencing identified one TT virus (TTV) isolate belonging to a known type and two putatively new TTVs. For 22 mothers, we also performed TTV amplification by general primer PCR before sequencing. This detected 39 TTVs, two of which were identical to the TTVs found after whole genome amplification. Altogether, we found 40 TTV isolates, 29 of which were putatively new types (similarities ranging from 89% to 69%). In conclusion, high throughput sequencing is useful to describe the known or unknown viruses that are present in serum samples of pregnant women., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Emerging infectious diseases are a significant threat to global biodiversity. While historically overlooked, a group of iridoviruses in the genus Ranavirus has been responsible for die-offs in captive and wild amphibian, reptile and fish populations around the globe over the past two decades. In order to share contemporary information on ranaviruses and identify critical research directions, the First International Symposium on Ranaviruses was held in July 2011 in Minneapolis, MN, USA. Twenty-three scientists and veterinarians from nine countries examined the ecology and evolution of ranavirus-host interactions, potential reservoirs, transmission dynamics, as well as immunological and histopathological responses to infection. In addition, speakers discussed possible mechanisms for die-offs, and conservation strategies to control outbreaks.

This study was performed to clarify the sow-to-fetus transmission pathway of Torque teno sus virus (TTSuV) types 1 (TTSuV1) and 2 (TTSuV2). For this purpose, detection of TTSuV1 and TTSuV2 (TTSuVs) in sera of 6 sows (Sows 1-6) at parturition and in sera of their newborn piglets immediately after birth without suckling colostrum was performed by nested polymerase chain reaction (nPCR). These sows were bred using semen that had tested negative for TTSuVs. In a TTSuV1- and TTSuV2-positive sow (Sow 1), TTSuV1 and TTSuV2 were detected in 4 and 5 of 12 newborn littermates, respectively. In a TTSuV1-positive sow (Sow 2), TTSuV1 was detected in 1 of 8 newborn littermates. In 4 TTSuV1- and TTSuV2-negative sows (Sows 3-6), TTSuV1 was detected in 6 out of the 25 newborn piglets of 3 sows (Sows 3-5), while TTSuVs were not detected in all 13 piglets of 1 sow (Sow 6). In addition, to investigate the possibility of a sow-to-piglet transmission pathway of TTSuV via colostrum, TTSuV1 and TTSuV2 in sera of 12 newborn piglets from Sows 1-3 were examined by nPCR. Immediately after birth without suckling colostrum, TTSuV1 and TTSuV2 were not detected in 10 and 8 of 12 newborn piglets, respectively; however, at 24 hr after suckling colostrum, TTSuV1 was detected in 6 piglets, while TTSuV2 was not detected in any piglets. These results confirmed the existence of a sow-to-fetus transmission pathway of TTSuV during normal pregnancy and suggested a possibility of sow-to-piglet transmission of TTSuV via colostrum.

This review deals with the aetiology and the diagnosis of bovine viral abortion. While the abortion rates on beef and dairy cattle farms usually do not exceed 10%, significant economic losses because of abortion storms may be encountered. Determining the cause of abortions is usually a challenge, and it generally remains obscure in more than 50% of the necropsy submitted foetuses. Bovine viral diarrhoea virus and bovine herpesvirus-1 are the most common viruses causally associated with bovine abortions in farmed cattle globally. Rift Valley fever virus and bluetongue virus are important insect-transmitted abortogenic viruses. The geographic distribution of these two viruses is primarily dependent on the distribution of the insect vector, but direct transmission is possible. Recent global warming and subsequent insect vector expansion, coupled with the increase in international trade of animals and animal products, have been important factors in recent geographic advances of those two viruses. Bovine herpesviruses-4 and 5 in cattle, as well as other less frequent vector-borne viruses including epizootic haemorrhagic disease virus, Aino virus, Wesselsbron virus and lumpy skin disease virus, are discussed., (© 2011 Blackwell Verlag GmbH.)

Background: Porcine torque teno sus virus (TTSuV) is a small icosahedral and non-enveloped virus which contains a single-stranded (ssDNA), circular and negative DNA genome and infects mainly vertebrates and is currently classified into the 'floating' genus Anellovirus of Circoviridae with two species. Viral DNA of both porcine TTSuV species has a high prevalence in both healthy and diseased pigs worldwide and multiple infections of TTSuV with distinct genotypes or subtypes of the same species has been documented in the United States, Europe and Asia. However, there exists no information about histopathological lesions caused by infection with porcine TTSuV2., Methods: Porcine liver tissue homogenate with 1 ml of 6.91 × 107 genomic copies viral loads of porcine TTSuV2 that had positive result for torque teno sus virus type 2 and negative result for torque teno sus virus type 1 and porcine pseudorabies virus type 2 were used to inoculate specific pathogen-free piglets by intramuscular route and humanely killed at 3,7,10,14,17,21 and 24 days post inoculation (dpi), the control pigs were injected intramuscularly with 1 ml of sterile DMEM and humanely killed the end of the study for histopathological examination routinely processed, respectively., Results: All porcine TTSuV2 inoculated piglets were clinic asymptomatic but developed myocardial fibroklasts and endocardium, interstitial pneumonia, membranous glomerular nephropathy, and modest inflammatory cells infiltration in portal areas in the liver, foci of hemorrhage in some pancreas islet, a tiny amount red blood cells in venule of muscularis mucosae and outer longitudinal muscle, rarely red blood cells in the microvasculation and infiltration of inflammatory cells (lymphocytes and eosinophils) of tonsil and hilar lymph nodes, infiltration of inflammatory lymphocytes and necrosis or degeneration and focal gliosis of lymphocytes in the paracortical zone after inoculation with porcine TTSuV2-containing tissue homogenate., Conclusions: Analysis of these presentations revealed that porcine TTSuV2 was readily transmitted to TTSuV-negative swine and that infection was associated with characteristic pathologic changes in specific pathogen-free piglets inoculated with porcine TTSuV2. Those results indicated no markedly histopathological changes happened in those parenchymatous organs, especially the digestive system and immune system when the specific pathogen-free pigs were infected with porcine TTSuV2, hence, to some extent, it was not remarkable pathological agent for domestic pigs at least. So, porcine TTSuV2 could be an unrecognized pathogenic viral infectious etiology of swine. This study indicated a directly related description of lesions responsible for TTSuV2 infection in swine.

Ranaviruses like frog virus 3 (FV3) are responsible for emerging infectious diseases spreading worldwide to fish, amphibian and reptilian species. We have developed, in Xenopus laevis, an experimental model to investigate viral transmission. We show that FV3 released in water by immunocompromised infected adults can infect adult and larval stages of Xenopus within 3h of exposure. Time course of virus load and viral transcription in different tissues suggests that early waterborne FV3 infection through the digestive tract leads to dissemination in the kidney. Finally, a fraction of adult macrophages becomes infected following exposure to waterborne FV3 as visualized by fluorescence microscopy using macrophage- and FV3-specific antibodies. Little cytopathicity and apoptosis were detected in infected macrophages, which is consistent with our proposition that macrophages are permissive to FV3. These data highlight the efficiency of FV3 infectivity by the water route and the ability of FV3 to adapt to its hosts., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Little is known about the viruses infecting most species. Even in groups as well-studied as Drosophila, only a handful of viruses have been well-characterized. A viral metagenomic approach was used to explore viral diversity in 83 wild-caught Drosophila innubila, a mushroom feeding member of the quinaria group. A single fly that was injected with, and died from, Drosophila C Virus (DCV) was added to the sample as a control. Two-thirds of reads in the infected sample had DCV as the best BLAST hit, suggesting that the protocol developed is highly sensitive. In addition to the DCV hits, several sequences had Oryctes rhinoceros Nudivirus, a double-stranded DNA virus, as a best BLAST hit. The virus associated with these sequences was termed Drosophila innubila Nudivirus (DiNV). PCR screens of natural populations showed that DiNV was both common and widespread taxonomically and geographically. Electron microscopy confirms the presence of virions in fly fecal material similar in structure to other described Nudiviruses. In 2 species, D. innubila and D. falleni, the virus is associated with a severe (∼80-90%) loss of fecundity and significantly decreased lifespan.

Background: Anellovirus species Torque teno virus (TTV), Torque teno mini virus (TTMV), and Torque teno midi virus (TTMDV) and flavivirus GBV-C are highly prevalent and genetically diverse chronic human viral infections that have not yet been associated with disease., Study Design and Methods: To determine if these commensal viruses are transmitted by blood transfusions, we genetically analyzed viral species in cryopreserved samples from blood donors and corresponding pre- and posttransfusion samples from recipients enrolled in the Transfusion-Transmitted Viruses Study cohort., Results: All 24 individuals in 12 donor-recipient pairs were infected with TTV, while 16 were infected with TTMV, 15 with TTMDV, and four with GBV-C. None of the 12 informative cases of TTV transfusion or eight cases of TTMV transfusion, where the donor and recipient viruses could be genetically differentiated, resulted in detectable transmissions in which the donor viruses were detected in the recipient by direct sequencing of the polymerase chain reaction products. Of the five informative cases of TTMDV transfusion, including two cases of transfusion into TTMDV-negative recipients, one case of superinfection was seen with both the recipient and the donor viral variants detected in the transfusion recipient for at least 11 days posttransfusion. Three donor-recipient pairs were informative for GBV-C transmission with only one transfusion into a GBV-C-negative recipient resulting in a transiently detected infection., Conclusions: Transmission of the common commensal anelloviruses and GBV-C during transfusion was detected in 2 of 12 already infected or uninfected recipients. Underestimation of the true rate of viral transmission may be due to limitations in detecting donor viral variants present as minority variants in the already infected transfusion recipients., (© 2010 American Association of Blood Banks.)

The aim of this study was to estimate the presence of Torque teno sus virus (TTV) species in pig foetuses in order to assess the possible relationship between swine TTV infection and abortion in swine. A total of 98 abortion cases and foetuses collected from 55 pregnant sows at slaughterhouse were analysed by PCR for the presence of Torque teno sus virus 1 (TTV1) and Torque teno sus virus 2 (TTV2). All foetuses were necropsied and relevant tissues were collected, pooled, and submitted to DNA extraction. The overall prevalence of swine TTV1 and TTV2 in aborted foetuses (n = 98) was 17.0% and 29.6%, respectively. For slaughterhouse collected foetuses (n = 55), 10.9% were TTV1 PCR positive and 40.0% were positive for TTV2. There were no statistically significant differences when comparing prevalence of swine TTVs by type of sample (aborted versus slaughterhouse collected foetuses) or by gestation stage. The present work represents the first description of swine TTV infection in pig foetuses at different stages of gestation. Results obtained confirm that vertical transmission is an important route of TTVs dissemination. In addition, data obtained suggest that swine TTVs should not be considered as infectious agents responsible for abortion occurrence., (Copyright 2010 Elsevier Inc. All rights reserved.)

Oysters Crassostrea gigas were placed at water supply canals of three shrimp farms in Guasave, Mexico where WSSV outbreaks occur. Animals were sampled through April-August and September-December to detect WSSV DNA. By using three different PCR protocols, only oysters from a farm undergoing a WSSV outbreak were found WSSV-positive in gills and digestive gland. Two WSSV amplicons were sequenced and they corresponded over 99% to WSSV genome segments. Results showed that oysters can capture WSSV particles suspended in water. Susceptibility of oysters to WSSV infection and their role as a carrier remain to be determined., ((c) 2010 Elsevier Inc. All rights reserved.)

The mechanism of death in densovirus infected mosquitoes remains unexplored. This study investigated the cellular consequences of densovirus infection in Aedes aegypti mosquitoes after a second generation challenge with a densovirus isolated from adult Aedes albopictus mosquitoes in Thailand (AThDNV). Specimens were analyzed by TUNEL assay, fluorescent in situ hybridization (FISH) and a calorimic assay to detect activation of caspase 3-like activity. After challenge, moribund mosquitoes showed considerable evidence of TUNEL positive cells. The caspase 3-like activity assay showed that the presence of TUNEL positive cells was associated with increased levels of activated caspase 3-like activity in AThDNV infected mosquitoes., ((c) 2010 Elsevier Inc. All rights reserved.)

Global wildlife trade exacerbates the spread of nonindigenous species. Pathogens also move with hosts through trade and often are released into naïve populations with unpredictable outcomes. Amphibians are moved commercially for pets, food, bait, and biomedicine, and are an excellent model for studying how wildlife trade relates to pathogen pollution. Ranaviruses are amphibian pathogens associated with annual population die-offs; multiple strains of tiger salamander ranaviruses move through the bait trade in the western United States. Ranaviruses infect amphibians, reptiles, and fish and are of additional concern because they can switch hosts. Tiger salamanders are used as live bait for freshwater fishing and are a potential source for ranaviruses switching hosts from amphibians to fish. We experimentally injected largemouth bass with a bait trade tiger salamander ranavirus. Largemouth bass became infected but exhibited no signs of disease or mortality. Amphibian bait ranaviruses have the potential to switch hosts to infect fish, but fish may act as dead-end hosts or nonsymptomatic carriers, potentially spreading infection as a result of trade.

Viruses in three genera of the family Iridoviridae (iridoviruses) affect finfish. Ranaviruses and megalocytiviruses are recently emerged pathogens. Both cause severe systemic disease, occur globally and affect a diversity of hosts. In contrast, lymphocystiviruses cause superficial lesions and rarely cause economic loss. The ranavirus epizootic haematopoietic necrosis virus (EHNV) from Australia was the first iridovirus to cause epizootic mortality in finfish. Like other ranaviruses, it lacks host specificity. A distinct but closely related virus, European catfish virus, occurs in finfish in Europe, while very similar ranaviruses occur in amphibians in Europe, Asia, Australia, North America and South America. These viruses can be distinguished from one another by conserved differences in the sequence of the major capsid protein gene, which informs policies of the World Organisation for Animal Health to minimize transboundary spread of these agents. However, limited epidemiological information and variations in disease expression create difficulties for design of sampling strategies for surveillance. There is still uncertainty surrounding the taxonomy of some putative ranaviruses such as Singapore grouper iridovirus and Santee-Cooper ranavirus, both of which cause serious disease in fish, and confusion continues with diseases caused by megalocytiviruses. In this review, aspects of the agents and diseases caused by ranaviruses are contrasted with those due to megalocytiviruses to promote accurate diagnosis and characterization of the agents responsible. Ranavirus epizootics in amphibians are also discussed because of possible links with finfish and common anthropogenic mechanisms of spread. The source of the global epizootic of disease caused by systemic iridoviruses in finfish and amphibians is uncertain, but three possibilities are discussed: trade in food fish, trade in ornamental fish, reptiles and amphibians and emergence from unknown reservoir hosts associated with environmental change.

Ranaviruses are known to cause mortality in a variety of anuran species and have the potential to significantly impact wild and captive frog populations. In this study, 16 captive frogs and toads from the Louisville Zoological Garden were examined for the presence of ranavirus; this group included 14 Cope's grey tree frogs (Hyla chrysoscelis), an American toad (Bufo americanus), and a southern toad (Bufo terrestris). All animals were wild caught and were evaluated via polymerase chain reaction (PCR), while animals that died were also assessed via histologic study to understand the role of ranaviral disease in these specimens. Of the animals that died, 82% were positive for ranavirus via PCR. Multiple swab samples collected over time from live tree frogs were positive for ranavirus via PCR. These findings reveal that ranaviral infection in captive adult anurans may occur without clinical signs or consistent histopathologic lesions.