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Butterworth NJ, Heffernan L, Hall MD. Is there a sicker sex? Dose relationships modify male-female differences in infection prevalence. Proc Biol Sci 2024; 291:20232575. [PMID: 38196362 PMCID: PMC10777155 DOI: 10.1098/rspb.2023.2575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Accepted: 12/04/2023] [Indexed: 01/11/2024] Open
Abstract
Throughout the animal kingdom, there are striking differences in the propensity of one sex or the other to become infected. However, precisely when we should expect males or females to be the sicker sex remains unclear. A major barrier to answering this question is that very few studies have considered how the susceptibility of males and females changes across the full range of pathogen doses encountered in nature. Without quantifying this 'dose-susceptibility' relationship, we have likely underestimated the scope for sex differences to arise. Here, we use the Daphnia magnia-Pasteuria ramosa system to reveal that sex differences in susceptibility are entirely dose-dependent, with pathogens having a higher probability of successfully establishing an infection in mature males at low doses, but mature females at high doses. The scope for male-female differences to emerge is therefore much greater than previously appreciated-extending to sex differences in the upper limits to infection success, per-propagule infectivity risks and density-dependent pathogen behaviour. Applying this expanded scope across the animal kingdom will help us understand when and why a sicker sex emerges, and the implications for diseases in nature-where sex ratios, age structure and pathogen densities vary drastically.
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Affiliation(s)
- Nathan J. Butterworth
- School of Biological Sciences, Monash University, Wellington Road, Clayton, Victoria 3800, Australia
| | - Lindsey Heffernan
- School of Biological Sciences, Monash University, Wellington Road, Clayton, Victoria 3800, Australia
| | - Matthew D. Hall
- School of Biological Sciences, Monash University, Wellington Road, Clayton, Victoria 3800, Australia
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2
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Snyder PW, Ramsay CT, Harjoe CC, Khazan ES, Briggs CJ, Hoverman JT, Johnson PTJ, Preston D, Rohr JR, Blaustein AR. Experimental evidence that host species composition alters host-pathogen dynamics in a ranavirus-amphibian assemblage. Ecology 2023; 104:e3885. [PMID: 36217286 PMCID: PMC9898091 DOI: 10.1002/ecy.3885] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 08/12/2022] [Accepted: 08/19/2022] [Indexed: 02/06/2023]
Abstract
Losses in biodiversity can alter disease risk through changes in host species composition. Host species vary in pathogen susceptibility and competence, yet how changes in diversity alter host-pathogen dynamics remains unclear in many systems, particularly with respect to generalist pathogens. Amphibians are experiencing worldwide population declines linked to generalist pathogens, such as ranavirus, and thus represent an ideal group to investigate how host species composition affects disease risk. We conducted experiments in which amphibian larvae of three native species (Pacific tree frogs, Pseudacris regilla; Cascades frogs, Rana cascadae; and Western toads, Anaxyrus boreas) were exposed to ranavirus individually (in the laboratory) or as assemblages (in outdoor mesocosms). In a laboratory experiment, we observed low survival and high viral loads in P. regilla compared to the other species, suggesting that this species was highly susceptible to the pathogen. In the mesocosm experiment, we observed 41% A. boreas mortality when alone and 98% mortality when maintained with P. regilla and R. cascadae. Our results suggest that the presence of highly susceptible species can alter disease dynamics across multiple species, potentially increasing infection risk and mortality in co-occurring species.
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Affiliation(s)
- Paul W Snyder
- Integrative Biology, Oregon State University, Corvallis, Oregon, USA
| | - Chloe T Ramsay
- Department of Integrative Biology, University of South Florida, Tampa, Florida, USA
| | - Carmen C Harjoe
- Integrative Biology, Oregon State University, Corvallis, Oregon, USA
| | - Emily S Khazan
- School of Natural Resources and Environment, University of Florida, Gainesville, Florida, USA
| | - Cheryl J Briggs
- Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, California, USA
| | - Jason Todd Hoverman
- Department of Forestry and Natural Resources, Purdue University, West Lafayette, Indiana, USA
| | - Pieter T J Johnson
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, Colorado, USA
| | - Daniel Preston
- Department of Fish, Wildlife and Conservation Biology, Colorado State University, Fort Collins, Colorado, USA
| | - Jason R Rohr
- Department of Integrative Biology, University of South Florida, Tampa, Florida, USA
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3
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Fofana AM, Hurford A. Parasite-induced shifts in host movement may explain the transient coexistence of high- and low-pathogenic disease strains. J Evol Biol 2022; 35:1072-1086. [PMID: 35789020 DOI: 10.1111/jeb.14053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 05/30/2022] [Accepted: 06/02/2022] [Indexed: 11/27/2022]
Abstract
Many parasites induce decreased host movement, known as lethargy, which can impact disease spread and the evolution of virulence. Mathematical models have investigated virulence evolution when parasites cause host death, but disease-induced decreased host movement has received relatively less attention. Here, we consider a model where, due to the within-host parasite replication rate, an infected host can become lethargic and shift from a moving to a resting state, where it can die. We find that when the lethargy and disease-induced mortality costs to the parasites are not high, then evolutionary bistability can arise, and either moderate or high virulence can evolve depending on the initial virulence and the magnitude of mutation. These results suggest, firstly, the coexistence of strains with different virulence, which may explain the transient coexistence of low- and high-pathogenic strains of avian influenza viruses, and secondly, that medical interventions to treat the symptoms of lethargy or prevent disease-induced host deaths can result in a large jump in virulence and the rapid evolution of high virulence. In complement to existing results that show bistability when hosts are heterogeneous at the population level, we show that evolutionary bistability may arise due to transmission heterogeneity at the individual host level.
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Affiliation(s)
- Abdou Moutalab Fofana
- Biology, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada
| | - Amy Hurford
- Biology, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada.,Mathematics and Statistics, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada
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4
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Lopez‐Serna S, Gonzalez‐Quevedo C, Rivera‐Gutierrez HF. Beyond illness: Variation in haemosporidian load explains differences in vocal performance in a songbird. Ecol Evol 2021; 11:18552-18561. [PMID: 35003692 PMCID: PMC8717280 DOI: 10.1002/ece3.8455] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 11/22/2021] [Accepted: 11/26/2021] [Indexed: 02/04/2023] Open
Abstract
In animal communication, signals are expected to evolve to be honest, so that receivers avoid being manipulated by signalers. One way that signals can evolve to be honest is for them to be costly, with only high-quality individuals being able to bear the costs of signal expression. It has been proposed that parasites can introduce costs that affect the expression of sexually selected traits, and there is evidence to support the role of parasitism in modulating animal behavior. If host infection status or intensity is found to relate to differences in signal expression, it may indicate a fitness cost that mediates honesty of signals. Birdsong is a good model for testing this, and physically challenging songs representing complex motor patterns provide a good example of sexually selected traits indicating individual condition. We performed a field study to evaluate the relationship between song performance and avian malaria infection in a common songbird. Previous work on this subject has almost always evaluated avian malaria in terms of binary infection status; however, parasitemia-infection intensity-is rarely assessed, even though differences in parasite load may have profound physiological consequences. We estimated parasitemia levels by using real-time PCR. We found that birds with higher parasitemia displayed lower vocal performance, providing evidence that this song trait is an honest signal of parasitic load of haemosporidian parasites. To our knowledge, this study links parasite load and the expression of a sexually selected trait in a way that has not been addressed in the past. Studies using song performance traits and parasitemia offer an important perspective for understanding evolution of characters via sexual selection.
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Affiliation(s)
- Salome Lopez‐Serna
- Instituto de BiologíaFacultad de Ciencias Exactas y NaturalesGrupo de Ecología y Evolución de VertebradosUniversidad de AntioquiaMedellínColombia
| | - Catalina Gonzalez‐Quevedo
- Instituto de BiologíaFacultad de Ciencias Exactas y NaturalesGrupo de Ecología y Evolución de VertebradosUniversidad de AntioquiaMedellínColombia
| | - Hector Fabio Rivera‐Gutierrez
- Instituto de BiologíaFacultad de Ciencias Exactas y NaturalesGrupo de Ecología y Evolución de VertebradosUniversidad de AntioquiaMedellínColombia
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5
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Weitzman CL, Rostama B, Thomason CA, May M, Belden LK, Hawley DM. Experimental test of microbiome protection across pathogen doses reveals importance of resident microbiome composition. FEMS Microbiol Ecol 2021; 97:6385755. [PMID: 34626186 DOI: 10.1093/femsec/fiab141] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Accepted: 10/07/2021] [Indexed: 01/04/2023] Open
Abstract
The commensal microbes inhabiting a host tissue can interact with invading pathogens and host physiology in ways that alter pathogen growth and disease manifestation. Prior work in house finches (Haemorhous mexicanus) found that resident ocular microbiomes were protective against conjunctival infection and disease caused by a relatively high dose of Mycoplasma gallisepticum. Here, we used wild-caught house finches to experimentally examine whether protective effects of the resident ocular microbiome vary with the dose of invading pathogen. We hypothesized that commensal protection would be strongest at low M. gallisepticum inoculation doses because the resident microbiome would be less disrupted by invading pathogen. Our five M. gallisepticum dose treatments were fully factorial with an antibiotic treatment to perturb resident microbes just prior to M. gallisepticum inoculation. Unexpectedly, we found no indication of protective effects of the resident microbiome at any pathogen inoculation dose, which was inconsistent with the prior work. The ocular bacterial communities at the beginning of our experiment differed significantly from those previously reported in local wild-caught house finches, likely causing this discrepancy. These variable results underscore that microbiome-based protection in natural systems can be context dependent, and natural variation in community composition may alter the function of resident microbiomes in free-living animals.
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Affiliation(s)
- Chava L Weitzman
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24060, USA
| | - Bahman Rostama
- Department of Biomedical Sciences, University of New England, Biddeford - 04005, ME, USA
| | - Courtney A Thomason
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24060, USA.,Division of Remediation, Tennessee Department of Environment and Conservation, Oak Ridge - 37830, TN, USA
| | - Meghan May
- Department of Biomedical Sciences, University of New England, Biddeford - 04005, ME, USA
| | - Lisa K Belden
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24060, USA
| | - Dana M Hawley
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24060, USA
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6
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Wait LF, Kamiya T, Fairlie-Clarke KJ, Metcalf CJE, Graham AL, Mideo N. Differential drivers of intraspecific and interspecific competition during malaria-helminth co-infection. Parasitology 2021; 148:1030-1039. [PMID: 33971991 PMCID: PMC11010048 DOI: 10.1017/s003118202100072x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 04/14/2021] [Accepted: 05/04/2021] [Indexed: 11/05/2022]
Abstract
Various host and parasite factors interact to determine the outcome of infection. We investigated the effects of two factors on the within-host dynamics of malaria in mice: initial infectious dose and co-infection with a helminth that limits the availability of red blood cells (RBCs). Using a statistical, time-series approach to model the within-host ‘epidemiology’ of malaria, we found that increasing initial dose reduced the time to peak cell-to-cell parasite propagation, but also reduced its magnitude, while helminth co-infection delayed peak cell-to-cell propagation, except at the highest malaria doses. Using a mechanistic model of within-host infection dynamics, we identified dose-dependence in parameters describing host responses to malaria infection and uncovered a plausible explanation of the observed differences in single vs co-infections. Specifically, in co-infections, our model predicted a higher background death rate of RBCs. However, at the highest dose, when intraspecific competition between malaria parasites would be highest, these effects of co-infection were not observed. Such interactions between initial dose and co-infection, although difficult to predict a priori, are key to understanding variation in the severity of disease experienced by hosts and could inform studies of malaria transmission dynamics in nature, where co-infection and low doses are the norm.
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Affiliation(s)
- L. F. Wait
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, USA
| | - T. Kamiya
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada
| | | | - C. J. E. Metcalf
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, USA
| | - A. L. Graham
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, USA
| | - N. Mideo
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada
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7
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Goodman RM, Carter ED, Miller DL. Influence of Herbicide Exposure and Ranavirus Infection on Growth and Survival of Juvenile Red-Eared Slider Turtles ( Trachemys scripta elegans). Viruses 2021; 13:1440. [PMID: 34452306 PMCID: PMC8402795 DOI: 10.3390/v13081440] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 07/14/2021] [Accepted: 07/19/2021] [Indexed: 11/16/2022] Open
Abstract
Ranaviruses are an important wildlife pathogen of fish, amphibians, and reptiles. Previous studies have shown that susceptibility and severity of infection can vary with age, host species, virus strain, temperature, population density, and presence of environmental stressors. Experiments are limited with respect to interactions between this pathogen and environmental stressors in reptiles. In this study, we exposed hatchling red-eared slider turtles (Trachemys scripta elegans) to herbicide and ranavirus treatments to examine direct effects and interactions on growth, morbidity, and mortality. Turtles were assigned to one of three herbicide treatments or a control group. Turtles were exposed to atrazine, Roundup ProMax®, or Rodeo® via water bath during the first 3 weeks of the experiment. After 1 week, turtles were exposed to either a control (cell culture medium) or ranavirus-infected cell lysate via injection into the pectoral muscles. Necropsies were performed upon death or upon euthanasia after 5 weeks. Tissues were collected for histopathology and detection of ranavirus DNA via quantitative PCR. Only 57.5% of turtles exposed to ranavirus tested positive for ranaviral DNA at the time of death. Turtles exposed to ranavirus died sooner and lost more mass and carapace length, but not plastron length, than did controls. Exposure to environmentally relevant concentrations of herbicides did not impact infection rate, morbidity, or mortality of hatchling turtles due to ranavirus exposure. We also found no direct effects of herbicide or interactions with ranavirus exposure on growth or survival time. Results of this study should be interpreted in the context of the modest ranavirus infection rate achieved, the general lack of growth, and the unplanned presence of an additional pathogen in our study.
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Affiliation(s)
- Rachel M. Goodman
- Biology Department, Hampden-Sydney College, Hampden-Sydney, VA 23943, USA
| | - Edward Davis Carter
- Center for Wildlife Health, University of Tennessee Institute of Agriculture, Knoxville, TN 37996, USA; (E.D.C.); (D.L.M.)
| | - Debra L. Miller
- Center for Wildlife Health, University of Tennessee Institute of Agriculture, Knoxville, TN 37996, USA; (E.D.C.); (D.L.M.)
- Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996, USA
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8
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Herczeg D, Ujszegi J, Kásler A, Holly D, Hettyey A. Host-multiparasite interactions in amphibians: a review. Parasit Vectors 2021; 14:296. [PMID: 34082796 PMCID: PMC8173923 DOI: 10.1186/s13071-021-04796-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Accepted: 05/20/2021] [Indexed: 01/15/2023] Open
Abstract
Parasites, including viruses, bacteria, fungi, protists, helminths, and arthropods, are ubiquitous in the animal kingdom. Consequently, hosts are frequently infected with more than one parasite species simultaneously. The assessment of such co-infections is of fundamental importance for disease ecology, but relevant studies involving non-domesticated animals have remained scarce. Many amphibians are in decline, and they generally have a highly diverse parasitic fauna. Here we review the literature reporting on field surveys, veterinary case studies, and laboratory experiments on co-infections in amphibians, and we summarize what is known about within-host interactions among parasites, which environmental and intrinsic factors influence the outcomes of these interactions, and what effects co-infections have on hosts. The available literature is piecemeal, and patterns are highly diverse, so that identifying general trends that would fit most host–multiparasite systems in amphibians is difficult. Several examples of additive, antagonistic, neutral, and synergistic effects among different parasites are known, but whether members of some higher taxa usually outcompete and override the effects of others remains unclear. The arrival order of different parasites and the time lag between exposures appear in many cases to fundamentally shape competition and disease progression. The first parasite to arrive can gain a marked reproductive advantage or induce cross-reaction immunity, but by disrupting the skin and associated defences (i.e., skin secretions, skin microbiome) and by immunosuppression, it can also pave the way for subsequent infections. Although there are exceptions, detrimental effects to the host are generally aggravated with increasing numbers of co-infecting parasite species. Finally, because amphibians are ectothermic animals, temperature appears to be the most critical environmental factor that affects co-infections, partly via its influence on amphibian immune function, partly due to its direct effect on the survival and growth of parasites. Besides their importance for our understanding of ecological patterns and processes, detailed knowledge about co-infections is also crucial for the design and implementation of effective wildlife disease management, so that studies concentrating on the identified gaps in our understanding represent rewarding research avenues. ![]()
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Affiliation(s)
- Dávid Herczeg
- Lendület Evolutionary Ecology Research Group, Plant Protection Institute, Centre for Agricultural Research, Eötvös Loránd Research Network, Herman Ottó út 15, Budapest, 1022, Hungary.
| | - János Ujszegi
- Lendület Evolutionary Ecology Research Group, Plant Protection Institute, Centre for Agricultural Research, Eötvös Loránd Research Network, Herman Ottó út 15, Budapest, 1022, Hungary
| | - Andrea Kásler
- Lendület Evolutionary Ecology Research Group, Plant Protection Institute, Centre for Agricultural Research, Eötvös Loránd Research Network, Herman Ottó út 15, Budapest, 1022, Hungary.,Department of Systematic Zoology and Ecology, Eötvös Loránd University, Pázmány Péter sétány 1/C, Budapest, 1117, Hungary
| | - Dóra Holly
- Lendület Evolutionary Ecology Research Group, Plant Protection Institute, Centre for Agricultural Research, Eötvös Loránd Research Network, Herman Ottó út 15, Budapest, 1022, Hungary.,Department of Systematic Zoology and Ecology, Eötvös Loránd University, Pázmány Péter sétány 1/C, Budapest, 1117, Hungary
| | - Attila Hettyey
- Lendület Evolutionary Ecology Research Group, Plant Protection Institute, Centre for Agricultural Research, Eötvös Loránd Research Network, Herman Ottó út 15, Budapest, 1022, Hungary.,Department of Ecology, Institute for Biology, University of Veterinary Medicine, Rottenbiller utca 50, Budapest, 1077, Hungary
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9
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FATAL RANAVIRUS INFECTION IN A GROUP OF ZOO-HOUSED MELLER'S CHAMELEONS ( TRIOCEROS MELLERI). J Zoo Wildl Med 2021; 50:696-705. [PMID: 33517641 DOI: 10.1638/2018-0044] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/05/2019] [Indexed: 11/21/2022] Open
Abstract
A group of five juvenile Meller's chameleons (Trioceros melleri) experienced 100% mortality over a period of 1 mo due to ranavirus infection. The index case was found dead without premonitory signs. The three subsequent cases presented with nonspecific clinical signs (lethargy, decreased appetite, ocular discharge) and were ultimately euthanatized. The final case died after initially presenting with skin lesions. Postmortem examination revealed thin body condition in all five animals and mild coelomic effusion and petechiae affecting the tongue and kidneys of one animal. Microscopically, all animals had multifocal necrosis of the spleen, liver, and kidney; four of five animals had necrosis of the nasal cavity; and two of five had necrosis of adrenal tissue, bone marrow, and skin. Numerous basophilic intracytoplasmic inclusions were present in the liver of all animals and nasal mucosa of three of the five animals. Consensus polymerase chain reaction for herpesvirus and adenovirus were negative, whereas ranavirus quantitative polymerase chain reaction was positive. Virus isolation followed by whole genome sequencing and Bayesian phylogenetic analysis classified the isolates as a strain of frog virus 3 (FV3) most closely related to an FV3 isolate responsible for a previous outbreak in the zoo's eastern box turtle (Terrapene carolina carolina) group. This case series documents the first known occurrence of ranavirus-associated disease in chameleons and demonstrates the potential for interspecies transmission between chelonian and squamate reptiles.
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10
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Brannelly LA, McCallum HI, Grogan LF, Briggs CJ, Ribas MP, Hollanders M, Sasso T, Familiar López M, Newell DA, Kilpatrick AM. Mechanisms underlying host persistence following amphibian disease emergence determine appropriate management strategies. Ecol Lett 2020; 24:130-148. [PMID: 33067922 DOI: 10.1111/ele.13621] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 06/18/2020] [Accepted: 09/08/2020] [Indexed: 12/19/2022]
Abstract
Emerging infectious diseases have caused many species declines, changes in communities and even extinctions. There are also many species that persist following devastating declines due to disease. The broad mechanisms that enable host persistence following declines include evolution of resistance or tolerance, changes in immunity and behaviour, compensatory recruitment, pathogen attenuation, environmental refugia, density-dependent transmission and changes in community composition. Here we examine the case of chytridiomycosis, the most important wildlife disease of the past century. We review the full breadth of mechanisms allowing host persistence, and synthesise research on host, pathogen, environmental and community factors driving persistence following chytridiomycosis-related declines and overview the current evidence and the information required to support each mechanism. We found that for most species the mechanisms facilitating persistence have not been identified. We illustrate how the mechanisms that drive long-term host population dynamics determine the most effective conservation management strategies. Therefore, understanding mechanisms of host persistence is important because many species continue to be threatened by disease, some of which will require intervention. The conceptual framework we describe is broadly applicable to other novel disease systems.
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Affiliation(s)
- Laura A Brannelly
- Veterinary BioSciences, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Werribee, Vic, 3030, Australia
| | - Hamish I McCallum
- Environmental Futures Research Institute and School of Environment and Science, Griffith University, Nathan, Qld., 4111, Australia
| | - Laura F Grogan
- Environmental Futures Research Institute and School of Environment and Science, Griffith University, Nathan, Qld., 4111, Australia.,Forest Research Centre, School of Environment, Science and Engineering, Southern Cross University, Lismore, NSW, 2480, Australia
| | - Cheryl J Briggs
- Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, CA, 93106, USA
| | - Maria P Ribas
- Forest Research Centre, School of Environment, Science and Engineering, Southern Cross University, Lismore, NSW, 2480, Australia.,Wildlife Conservation Medicine Research Group, Departament de Medicina i Cirurgia Animals, Universitat Autònoma de Barcelona, Bellaterra, 08193, Spain
| | - Matthijs Hollanders
- Forest Research Centre, School of Environment, Science and Engineering, Southern Cross University, Lismore, NSW, 2480, Australia
| | - Thais Sasso
- Environmental Futures Research Institute and School of Environment and Science, Griffith University, Nathan, Qld., 4111, Australia
| | - Mariel Familiar López
- School of Environment and Sciences, Griffith University, Gold Coast, Qld., 4215, Australia
| | - David A Newell
- Forest Research Centre, School of Environment, Science and Engineering, Southern Cross University, Lismore, NSW, 2480, Australia
| | - Auston M Kilpatrick
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA, 95064, USA
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11
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Kamiya T, Greischar MA, Schneider DS, Mideo N. Uncovering drivers of dose-dependence and individual variation in malaria infection outcomes. PLoS Comput Biol 2020; 16:e1008211. [PMID: 33031367 PMCID: PMC7544130 DOI: 10.1371/journal.pcbi.1008211] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 07/31/2020] [Indexed: 01/01/2023] Open
Abstract
To understand why some hosts get sicker than others from the same type of infection, it is essential to explain how key processes, such as host responses to infection and parasite growth, are influenced by various biotic and abiotic factors. In many disease systems, the initial infection dose impacts host morbidity and mortality. To explore drivers of dose-dependence and individual variation in infection outcomes, we devised a mathematical model of malaria infection that allowed host and parasite traits to be linear functions (reaction norms) of the initial dose. We fitted the model, using a hierarchical Bayesian approach, to experimental time-series data of acute Plasmodium chabaudi infection across doses spanning seven orders of magnitude. We found evidence for both dose-dependent facilitation and debilitation of host responses. Most importantly, increasing dose reduced the strength of activation of indiscriminate host clearance of red blood cells while increasing the half-life of that response, leading to the maximal response at an intermediate dose. We also explored the causes of diverse infection outcomes across replicate mice receiving the same dose. Besides random noise in the injected dose, we found variation in peak parasite load was due to unobserved individual variation in host responses to clear infected cells. Individual variation in anaemia was likely driven by random variation in parasite burst size, which is linked to the rate of host cells lost to malaria infection. General host vigour in the absence of infection was also correlated with host health during malaria infection. Our work demonstrates that the reaction norm approach provides a useful quantitative framework for examining the impact of a continuous external factor on within-host infection processes.
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Affiliation(s)
- Tsukushi Kamiya
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada
| | - Megan A. Greischar
- Department of Ecology Evolutionary Biology, Cornell University, United States of America
| | - David S. Schneider
- Program in Immunology, Stanford University, Stanford, California, United States of America
- Department of Microbiology and Immunology, Stanford University, Stanford, California, United States of America
| | - Nicole Mideo
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada
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12
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13
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Clay PA, Rudolf VHW. How parasite interaction strategies alter virulence evolution in multi-parasite communities. Evolution 2019; 73:2189-2203. [PMID: 31506940 DOI: 10.1111/evo.13843] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Revised: 06/15/2019] [Accepted: 07/06/2019] [Indexed: 12/11/2022]
Abstract
The majority of organisms host multiple parasite species, each of which can interact with hosts and competitors through a diverse range of direct and indirect mechanisms. These within-host interactions can directly alter the mortality rate of coinfected hosts and alter the evolution of virulence (parasite-induced host mortality). Yet we still know little about how within-host interactions affect the evolution of parasite virulence in multi-parasite communities. Here, we modeled the virulence evolution of two coinfecting parasites in a host population in which parasites interacted through cross immunity, immune suppression, immunopathology, or spite. We show (1) that these within-host interactions have different effects on virulence evolution when all parasites interact with each other in the same way versus when coinfecting parasites have unique interaction strategies, (2) that these interactions cause the evolution of lower virulence in some hosts, and higher virulence in other hosts, depending on the hosts infection status, and (3) that for cross immunity and spite, whether parasites increase or decrease the evolutionarily stable virulence in coinfected hosts depended on interaction strength. These results improve our understanding of virulence evolution in complex parasite communities, and show that virulence evolution must be understood at the community scale.
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14
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Wirth W, Schwarzkopf L, Skerratt LF, Tzamouzaki A, Ariel E. Dose-dependent morbidity of freshwater turtle hatchlings, Emydura macquarii krefftii, inoculated with Ranavirus isolate (Bohle iridovirus, Iridoviridae). J Gen Virol 2019; 100:1431-1441. [PMID: 31483246 DOI: 10.1099/jgv.0.001324] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Ranaviral infections cause mass die-offs in wild and captive turtle populations. Two experimental studies were performed to first determine the susceptibility of an Australian turtle species (Emydura macquarii krefftii) to different routes of infection and second examine the effect of viral titre on the morbidity in hatchlings. All inoculation routes (intracoelomic, intramuscular and oral) produced disease, but the clinical signs, histopathology and time to onset of disease varied with the route. The median infectious and lethal doses for intramuscularly inoculated hatchlings were 102 . 52 (1.98-2.93) and 104.43 (3.81-5.19) TCID50 ml-1, respectively. Clinical signs began 14 to 29 days post-inoculation and the median survival time was 22 days (16-25) across all dose groups. For every 10-fold increase in dose, the odds of developing any clinical signs or severe clinical signs increased by 3.39 [P<0.01, 95 % confidence interval (CI): 1.81-6.36] and 3.71 (P<0.01, 95 % CI: 1.76-7.80), respectively. Skin lesions, previously only reported in ranaviral infection in lizards, were observed in the majority of intramuscularly inoculated hatchlings that developed ranaviral disease. The histological changes were consistent with those in previous reports for reptiles and consisted of necrosis at or near the site of injection, in the spleen, liver and oral cavity. Systemic inflammation was also observed, predominantly affecting necrotic organs. The estimates reported here can be used to model ranaviral disease and quantify and manage at-risk populations.
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Affiliation(s)
- Wytamma Wirth
- College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, QLD, Australia
| | - Lin Schwarzkopf
- College of Science and Engineering, James Cook University, Townsville, QLD, Australia
| | - Lee F Skerratt
- One Health Research Group, Melbourne Veterinary School, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Werribee, Vic, Australia
| | - Anna Tzamouzaki
- College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, QLD, Australia
| | - Ellen Ariel
- College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, QLD, Australia
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15
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Nehring V, Teubner H, König S. Dose-independent virulence in phoretic mites that parasitize burying beetles. Int J Parasitol 2019; 49:759-767. [PMID: 31401062 DOI: 10.1016/j.ijpara.2019.05.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 05/08/2019] [Accepted: 05/23/2019] [Indexed: 01/25/2023]
Abstract
Virulence, the negative impact of parasites on their hosts, typically increases with parasite dose. Parasites and hosts often compete for host resources and more parasites will consume more resources. Depending on the mechanism of competition, increasing host resources can benefit the host. Additional resources can also be harmful when the parasites are the main beneficiaries. Then, the parasites will thrive and virulence increases. While parasite dose is often easy to manipulate, it is less trivial to experimentally scale host resources. Here, we study a system with external host resources that can be easily manipulated: Nicrophorus burying beetles reproduce on vertebrate carcasses, with larger carcasses yielding more beetle offspring. Phoretic Poecilochirus mites reproduce alongside the beetles and reduce beetle fitness. The negative effect of mites could be due to competition for the carrion between beetle and mite offspring. We manipulated mite dose and carcass size to better understand the competition between the symbionts. We found that mite dose itself was not a strong predictor of virulence. Instead, the number of mite offspring determined beetle fitness. At larger doses, there was strong competition among adult parental mites as well as mite offspring. While increasing the carcass size increased both host and parasite fitness, it did surprisingly little to alleviate the negative effect that mites had on beetles. Instead, relative virulence was stronger on large carcasses, indicating that the parasites appropriate more of the additional resources. Our results demonstrate an ecological influence on the selection of parasites on their hosts and suggest that virulence can be dose-independent in principle.
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Affiliation(s)
- Volker Nehring
- Evolutionary Biology & Ecology, Institute of Biology I, University of Freiburg, Hauptstraße 1, 79104 Freiburg, Germany.
| | - Heide Teubner
- Evolutionary Biology & Ecology, Institute of Biology I, University of Freiburg, Hauptstraße 1, 79104 Freiburg, Germany
| | - Sandra König
- Evolutionary Biology & Ecology, Institute of Biology I, University of Freiburg, Hauptstraße 1, 79104 Freiburg, Germany
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16
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Brunner JL, Olson AD, Rice JG, Meiners SE, Le Sage MJ, Cundiff JA, Goldberg CS, Pessier AP. Ranavirus infection dynamics and shedding in American bullfrogs: consequences for spread and detection in trade. DISEASES OF AQUATIC ORGANISMS 2019; 135:135-150. [PMID: 31392966 DOI: 10.3354/dao03387] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
American bullfrogs Lithobates catesbeianus are thought to be important in the global spread of ranaviruses-often lethal viruses of cold-blooded vertebrates-because they are commonly farmed, dominate international trade, and may be 'carriers' of ranavirus infections. However, whether American bullfrogs are easily infected and maintain long-lasting ranavirus infections, or are refractory to or rapidly clear infections, remains unknown. We tracked the dynamics of ranavirus in American bullfrogs through time and with temperature in multiple types of samples and also screened shipments from commercial suppliers to determine whether we could detect subclinical infections. Collectively, we found that tadpoles and juveniles were commonly infected at moderate doses, and while some died, others controlled and appeared to clear their infections. Some individuals, however, harbored subclinical infections for up to 49 d, suggesting that American bullfrogs may be important carriers. Indeed, tadpoles and metamorphosed frogs from 2 of 5 commercial suppliers harbored subclinicial infections. Juveniles at warmer temperatures had less intense but still persistent infections. Because diagnostic performance was strongly related to infection intensity, non-lethal samples (i.e. tail or toe clips, swabs, and environmental DNA) had only a moderate chance of detecting subclinical infections. Even internal tissues may fail to detect subclinical infections. However, viral shedding was correlated with the intensity of infection, so while subclinically infected tadpoles shed virus for 35-49 d, the low levels might lead to little transmission. We suggest that a quantitative focus on virus dynamics within hosts can provide a more nuanced view of ranavirus infections and the risk presented by American bullfrogs in trade.
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Affiliation(s)
- Jesse L Brunner
- School of Biological Sciences, Washington State University, Pullman, WA 99164, USA
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17
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Mihaljevic JR, Greer AL, Brunner JL. Evaluating the Within-Host Dynamics of Ranavirus Infection with Mechanistic Disease Models and Experimental Data. Viruses 2019; 11:E396. [PMID: 31035560 PMCID: PMC6563243 DOI: 10.3390/v11050396] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 04/23/2019] [Accepted: 04/25/2019] [Indexed: 11/30/2022] Open
Abstract
Mechanistic models are critical for our understanding of both within-host dynamics (i.e., pathogen replication and immune system processes) and among-host dynamics (i.e., transmission). Within-host models, however, are not often fit to experimental data, which can serve as a robust method of hypothesis testing and hypothesis generation. In this study, we use mechanistic models and empirical, time-series data of viral titer to better understand the replication of ranaviruses within their amphibian hosts and the immune dynamics that limit viral replication. Specifically, we fit a suite of potential models to our data, where each model represents a hypothesis about the interactions between viral replication and immune defense. Through formal model comparison, we find a parsimonious model that captures key features of our time-series data: The viral titer rises and falls through time, likely due to an immune system response, and that the initial viral dosage affects both the peak viral titer and the timing of the peak. Importantly, our model makes several predictions, including the existence of long-term viral infections, which can be validated in future studies.
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Affiliation(s)
- Joseph R Mihaljevic
- School of Informatics, Computing and Cyber Systems, Northern Arizona University, Flagstaff, AZ 86011, USA.
| | - Amy L Greer
- Department of Population Medicine, University of Guelph, Guelph, ON N1G 2W1, Canada.
| | - Jesse L Brunner
- School of Biological Sciences, Washington State University, Pullman, WA 99163, USA.
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18
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Le Sage MJ, Towey BD, Brunner JL. Do scavengers prevent or promote disease transmission? The effect of invertebrate scavenging on
Ranavirus
transmission. Funct Ecol 2019. [DOI: 10.1111/1365-2435.13335] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Mitchell J. Le Sage
- School of Biological Sciences Washington State University Pullman Washington
| | - Bailey D. Towey
- School of Biological Sciences Washington State University Pullman Washington
| | - Jesse L. Brunner
- School of Biological Sciences Washington State University Pullman Washington
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19
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Mihaljevic JR, Hoverman JT, Johnson PTJ. Co-exposure to multiple ranavirus types enhances viral infectivity and replication in a larval amphibian system. DISEASES OF AQUATIC ORGANISMS 2018; 132:23-35. [PMID: 30530928 DOI: 10.3354/dao03300] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Multiple pathogens commonly co-occur in animal populations, yet few studies demonstrate how co-exposure of individual hosts scales up to affect transmission. Although viruses in the genus Ranavirus are globally widespread, and multiple virus species or strains likely co-occur in nature, no studies have examined how co-exposure affects infection dynamics in larval amphibians. We exposed individual northern red-legged frog Rana aurora larvae to 2 species of ranavirus, namely Ambystoma tigrinum virus (ATV), frog virus 3 (FV3), or an FV3-like strain isolated from a frog-culturing facility in Georgia, USA (RCV-Z2). We compared single-virus to pairwise co-exposures while experimentally accounting for dosage. Co-exposure to ATV and FV3-like strains resulted in almost twice as many infected individuals compared to single-virus exposures, suggesting an effect of co-exposure on viral infectivity. The viral load in infected individuals exposed to ATV and FV3 was also higher than the single-dose FV3 treatment, suggesting an effect of co-exposure on viral replication. In a follow-up experiment, we examined how the co-occurrence of ATV and FV3 affected epizootics in mesocosm populations of larval western chorus frogs Pseudacris triseriata. Although ATV did not generally establish within host populations (<4% prevalence), when ATV and FV3 were both present, this co-exposure resulted in a larger epizootic of FV3. Our results emphasize the importance of multi-pathogen interactions in epizootic dynamics and have management implications for natural and commercial amphibian populations.
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Affiliation(s)
- Joseph R Mihaljevic
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309, USA
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20
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Youker-Smith TE, Boersch-Supan PH, Whipps CM, Ryan SJ. Environmental Drivers of Ranavirus in Free-Living Amphibians in Constructed Ponds. ECOHEALTH 2018; 15:608-618. [PMID: 30094775 PMCID: PMC6245063 DOI: 10.1007/s10393-018-1350-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 06/18/2018] [Accepted: 06/22/2018] [Indexed: 06/08/2023]
Abstract
Amphibian ranaviruses occur globally, but we are only beginning to understand mechanisms for emergence. Ranaviruses are aquatic pathogens which can cause > 90% mortality in larvae of many aquatic-breeding amphibians, making them important focal host taxa. Host susceptibilities and virulence of ranaviruses have been studied extensively in controlled laboratory settings, but research is needed to identify drivers of infection in natural environments. Constructed ponds, essential components of wetland restoration, have been associated with higher ranavirus prevalence than natural ponds, posing a conundrum for conservation efforts, and emphasizing the need to understand potential drivers. In this study, we analyzed 4 years of Frog virus 3 prevalence and associated environmental parameters in populations of wood frogs (Lithobates sylvaticus) and green frogs (Lithobates clamitans) in a constructed pond system. High prevalence was best predicted by low temperature, high host density, low zooplankton concentrations, and Gosner stages approaching metamorphosis. This study identified important variables to measure in assessments of ranaviral infection risk in newly constructed ponds, including effects of zooplankton, which have not been previously quantified in natural settings. Examining factors mediating diseases in natural environments, particularly in managed conservation settings, is important to both validate laboratory findings in situ, and to inform future conservation planning, particularly in the context of adaptive management.
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Affiliation(s)
- Tess E Youker-Smith
- Department of Environmental and Forest Biology, State University of New York College of Environmental Science and Forestry, Syracuse, NY, 13210, USA
| | - Philipp H Boersch-Supan
- Quantitative Disease Ecology and Conservation (QDEC) Lab, Department of Geography, University of Florida, 3128 Turlington Hall, Gainesville, FL, 32601, USA
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, 32610, USA
| | - Christopher M Whipps
- Department of Environmental and Forest Biology, State University of New York College of Environmental Science and Forestry, Syracuse, NY, 13210, USA
| | - Sadie J Ryan
- Quantitative Disease Ecology and Conservation (QDEC) Lab, Department of Geography, University of Florida, 3128 Turlington Hall, Gainesville, FL, 32601, USA.
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, 32610, USA.
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21
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Effects of Emerging Infectious Diseases on Amphibians: A Review of Experimental Studies. DIVERSITY-BASEL 2018. [DOI: 10.3390/d10030081] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Numerous factors are contributing to the loss of biodiversity. These include complex effects of multiple abiotic and biotic stressors that may drive population losses. These losses are especially illustrated by amphibians, whose populations are declining worldwide. The causes of amphibian population declines are multifaceted and context-dependent. One major factor affecting amphibian populations is emerging infectious disease. Several pathogens and their associated diseases are especially significant contributors to amphibian population declines. These include the fungi Batrachochytrium dendrobatidis and B. salamandrivorans, and ranaviruses. In this review, we assess the effects of these three pathogens on amphibian hosts as found through experimental studies. Such studies offer valuable insights to the causal factors underpinning broad patterns reported through observational studies. We summarize key findings from experimental studies in the laboratory, in mesocosms, and from the field. We also summarize experiments that explore the interactive effects of these pathogens with other contributors of amphibian population declines. Though well-designed experimental studies are critical for understanding the impacts of disease, inconsistencies in experimental methodologies limit our ability to form comparisons and conclusions. Studies of the three pathogens we focus on show that host susceptibility varies with such factors as species, host age, life history stage, population and biotic (e.g., presence of competitors, predators) and abiotic conditions (e.g., temperature, presence of contaminants), as well as the strain and dose of the pathogen, to which hosts are exposed. Our findings suggest the importance of implementing standard protocols and reporting for experimental studies of amphibian disease.
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22
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Evaluating the Importance of Environmental Persistence for Ranavirus Transmission and Epidemiology. Adv Virus Res 2018; 101:129-148. [PMID: 29908588 DOI: 10.1016/bs.aivir.2018.02.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
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.
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23
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Martín-Hernández R, Bartolomé C, Chejanovsky N, Le Conte Y, Dalmon A, Dussaubat C, García-Palencia P, Meana A, Pinto MA, Soroker V, Higes M. Nosema ceranaeinApis mellifera: a 12 years postdetectionperspective. Environ Microbiol 2018; 20:1302-1329. [DOI: 10.1111/1462-2920.14103] [Citation(s) in RCA: 94] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Revised: 03/07/2018] [Accepted: 03/11/2018] [Indexed: 12/14/2022]
Affiliation(s)
- Raquel Martín-Hernández
- Laboratorio de Patología Apícola. Centro de Investigación Apícola y Agroambiental de Marchamalo, (CIAPA-IRIAF), Consejería de Agricultura de la Junta de Comunidades de Castilla-La Mancha; Marchamalo Spain
- Instituto de Recursos Humanos para la Ciencia y la Tecnología (INCRECYT-FEDER), Fundación Parque Científico y Tecnológico de Castilla - La Mancha; Spain
| | - Carolina Bartolomé
- Medicina Xenómica, CIMUS, Universidade de Santiago de Compostela. Xenómica Comparada de Parásitos Humanos, IDIS, 15782 Santiago de Compostela; Galicia Spain
| | - Nor Chejanovsky
- Agricultural Research Organization, The Volcani Center; Rishon LeZion Israel
| | - Yves Le Conte
- INRA, UR 406 Abeilles et Environnement; F-84000 Avignon France
| | - Anne Dalmon
- INRA, UR 406 Abeilles et Environnement; F-84000 Avignon France
| | | | | | - Aranzazu Meana
- Facultad de Veterinaria, Universidad Complutense de Madrid; Spain
| | - M. Alice Pinto
- Mountain Research Centre (CIMO), Polytechnic Institute of Bragança; 5300-253 Bragança Portugal
| | - Victoria Soroker
- Agricultural Research Organization, The Volcani Center; Rishon LeZion Israel
| | - Mariano Higes
- Laboratorio de Patología Apícola. Centro de Investigación Apícola y Agroambiental de Marchamalo, (CIAPA-IRIAF), Consejería de Agricultura de la Junta de Comunidades de Castilla-La Mancha; Marchamalo Spain
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24
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Hrynyk MA, Brunetti C, Kerr L, Metcalfe CD. Effect of imidacloprid on the survival of Xenopus tadpoles challenged with wild type frog virus 3. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2018; 194:152-158. [PMID: 29179150 DOI: 10.1016/j.aquatox.2017.11.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2017] [Revised: 11/09/2017] [Accepted: 11/11/2017] [Indexed: 06/07/2023]
Abstract
The sensitivity of amphibians to Ranavirus may be increased by exposure to other environmental stressors, including chemical contaminants. Neonicotinoid insecticides comprise 27% of the global insecticide market and have been detected in wetlands and other aquatic habitats. The present study focused on the effects of exposure of pre-metamorphic Xenopus laevis to the neonicotinoid, imidacloprid (IMI) on sensitivity to frog virus 3 (FV3) infection. It was hypothesized that exposure of tadpoles to IMI at sublethal concentrations of 1 and 500μgL-1 would increase FV3 related mortalities relative to tadpole mortalities in a control treatment with only the virus. However, contrary to the predicted outcome, IMI reduced the rates of mortality following viral challenge, although the total mortalities by the 25th day after infection did not differ among the treatments. These results should not be interpreted as an indication that neonicotinoid insecticides are beneficial to aquatic ecosystems, since these insecticides cause toxic responses at low concentrations to other non-target aquatic organisms.
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Affiliation(s)
- Morgan A Hrynyk
- Environmental and Life Sciences Graduate Program, Trent University, 1600 West Bank Dr. Peterborough, Ontario, K9J 7B8, Canada
| | - Craig Brunetti
- Biology Department, Trent University, 1600 West Bank Dr. Peterborough, Ontario, K9J 7B8, Canada
| | - Leslie Kerr
- Biology Department, Trent University, 1600 West Bank Dr. Peterborough, Ontario, K9J 7B8, Canada
| | - Chris D Metcalfe
- The School of the Environment, Trent University, 1600 West Bank Dr. Peterborough, Ontario, K9J 7B8, Canada.
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25
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Lung O, Reimer SA, Goater CP. User-friendly Taqman probe coupled-insulated isothermal PCR (iiPCR) for rapid detection of emerging Ambystoma tigrinum virus (ATV) in western tiger salamanders (Ambystoma mavortium) on a compact, portable instrument. J Virol Methods 2017; 249:21-24. [PMID: 28826930 DOI: 10.1016/j.jviromet.2017.08.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Revised: 08/14/2017] [Accepted: 08/14/2017] [Indexed: 11/26/2022]
Abstract
Portable user-friendly diagnostic tests can benefit detection and surveillance of wildlife diseases. Here, the performance of a compact POCKIT™ Nucleic Acid Analyzer for detection of Ambystoma tigrinum virus (ATV), an emerging Iridovirus that is associated with high host mortality in the western tiger salamander (Ambystoma mavortium) in North America was assessed. Tissue samples from 188 larval tiger salamanders collected from sites in Alberta, Canada were tested by both iiPCR and by conventional PCR. Results of the two assays showed 96.3% agreement. All 176 samples that tested positive by conventional PCR were also positive by iiPCR, while 12 of the samples that were negative by conventional PCR were positive by iiPCR. Comparison of the limits of detection of the two assays shows that the iiPCR assay was more sensitive than conventional PCR and had a LOD95 of 20 copies per reaction. The instrument automatically analyzes and displays results within 40min following nucleic acid extraction. The novel technology could enhance detection of, and response to, wildlife pathogens, particularly those that occur sporadically, cause rapid outbreaks, and/or occur within isolated geographical regions.
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Affiliation(s)
- Oliver Lung
- Canadian Food Inspection Agency, Lethbridge Laboratory, Township Rd. 9-1, Lethbridge, Alberta, T1 K 3Z4, Canada; 4401 University Drive, Department of Biological Sciences, University of Lethbridge, Lethbridge, Alberta, TIK 3M4, Canada.
| | - Stephanie A Reimer
- 4401 University Drive, Department of Biological Sciences, University of Lethbridge, Lethbridge, Alberta, TIK 3M4, Canada
| | - Cameron P Goater
- 4401 University Drive, Department of Biological Sciences, University of Lethbridge, Lethbridge, Alberta, TIK 3M4, Canada
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26
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Brunner JL, Beaty L, Guitard A, Russell D. Heterogeneities in the infection process drive ranavirus transmission. Ecology 2017; 98:576-582. [PMID: 27859036 DOI: 10.1002/ecy.1644] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 09/16/2016] [Accepted: 10/24/2016] [Indexed: 12/14/2022]
Abstract
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.
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Affiliation(s)
- Jesse L Brunner
- School of Biological Sciences, Washington State University, Pullman, Washington, 99164, USA.,Department of Environmental and Forest Biology, SUNY College of Environmental Science and Forestry, Syracuse, New York, 13210, USA
| | - Lynne Beaty
- Department of Environmental and Forest Biology, SUNY College of Environmental Science and Forestry, Syracuse, New York, 13210, USA.,Department of Integrative Biology, Oklahoma State University, Stillwater, Oklahoma, 74078, USA
| | - Alexandra Guitard
- Department of Environmental and Forest Biology, SUNY College of Environmental Science and Forestry, Syracuse, New York, 13210, USA
| | - Deanna Russell
- Department of Environmental and Forest Biology, SUNY College of Environmental Science and Forestry, Syracuse, New York, 13210, USA
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27
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Love CN, Winzeler ME, Beasley R, Scott DE, Nunziata SO, Lance SL. Patterns of amphibian infection prevalence across wetlands on the Savannah River Site, South Carolina, USA. DISEASES OF AQUATIC ORGANISMS 2016; 121:1-14. [PMID: 27596855 DOI: 10.3354/dao03039] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Amphibian diseases, such as chytridiomycosis caused by Batrachochytrium dendrobatidis (Bd) and ranaviral disease caused by ranaviruses, are often linked to global amphibian population declines, yet the ecological dynamics of both pathogens are poorly understood. The goal of our study was to determine the baseline prevalence, pathogen loads, and co-infection rate of Bd and ranavirus across the Savannah River Site (SRS) in South Carolina, USA, a region with rich amphibian diversity and a history of amphibian-based research. We tested over 1000 individuals, encompassing 21 amphibian species from 11 wetlands for both Bd and ranavirus. The prevalence of Bd across individuals was 9.7%. Using wetland means, the mean (±SE) Bd prevalence was 7.9 ± 2.9%. Among toad species, Anaxyrus terrestris had 95 and 380% greater odds of being infected with Bd than Scaphiopus holbrookii and Gastrophryne carolinensis, respectively. Odds of Bd infection in adult A. terrestris and Lithobates sphenocephalus were 75 to 77% greater in metal-contaminated sites. The prevalence of ranavirus infections across all individuals was 37.4%. Mean wetland ranavirus prevalence was 29.8 ± 8.8% and was higher in post-metamorphic individuals than in aquatic larvae. Ambystoma tigrinum had 83 to 85% higher odds of ranavirus infection than A. opacum and A. talpoideum. We detected a 4.8% co-infection rate, with individuals positive for ranavirus having a 5% higher occurrence of Bd. In adult Anaxyrus terrestris, odds of Bd infection were 13% higher in ranavirus-positive animals and odds of co-infection were 23% higher in contaminated wetlands. Overall, we found the pathogen prevalence varied by wetland, species, and life stage.
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Affiliation(s)
- Cara N Love
- Savannah River Ecology Laboratory, University of Georgia, Aiken, South Carolina 29802, USA
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Sainsbury AW, Yu-Mei R, Ågren E, Vaughan-Higgins RJ, Mcgill IS, Molenaar F, Peniche G, Foster J. Disease Risk Analysis and Post-Release Health Surveillance for a Reintroduction Programme: the Pool Frog Pelophylax lessonae. Transbound Emerg Dis 2016; 64:1530-1548. [PMID: 27393743 DOI: 10.1111/tbed.12545] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2015] [Indexed: 11/30/2022]
Abstract
There are risks from disease in undertaking wild animal reintroduction programmes. Methods of disease risk analysis have been advocated to assess and mitigate these risks, and post-release health and disease surveillance can be used to assess the effectiveness of the disease risk analysis, but results for a reintroduction programme have not to date been recorded. We carried out a disease risk analysis for the reintroduction of pool frogs (Pelophylax lessonae) to England, using information gained from the literature and from diagnostic testing of Swedish pool frogs and native amphibians. Ranavirus and Batrachochytrium dendrobatidis were considered high-risk disease threats for pool frogs at the destination site. Quarantine was used to manage risks from disease due to these two agents at the reintroduction site: the quarantine barrier surrounded the reintroduced pool frogs. Post-release health surveillance was carried out through regular health examinations of amphibians in the field at the reintroduction site and collection and examination of dead amphibians. No significant health or disease problems were detected, but the detection rate of dead amphibians was very low. Methods to detect a higher proportion of dead reintroduced animals and closely related species are required to better assess the effects of reintroduction on health and disease.
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Affiliation(s)
- A W Sainsbury
- Institute of Zoology, Zoological Society of London, London, UK
| | - R Yu-Mei
- Royal Veterinary College, London, UK
| | - E Ågren
- National Veterinary Institute, Uppsala, Sweden
| | | | - I S Mcgill
- Institute of Zoology, Zoological Society of London, London, UK.,Prion Interest Group, Brighton, UK
| | - F Molenaar
- Institute of Zoology, Zoological Society of London, London, UK
| | - G Peniche
- Institute of Zoology, Zoological Society of London, London, UK
| | - J Foster
- Amphibian and Reptile Conservation, Wareham, Dorset, UK
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Johnson AJ, Pessier AP, Jacobson ER. Experimental Transmission and Induction of Ranaviral Disease in Western Ornate Box Turtles (Terrapene ornata ornata) and Red-Eared Sliders (Trachemys scripta elegans). Vet Pathol 2016; 44:285-97. [PMID: 17491069 DOI: 10.1354/vp.44-3-285] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
An experimental transmission study was designed to determine whether a causal relationship exists between a Ranavirus (BSTRV) isolated from a Burmese star tortoise that died and the lesions observed in that tortoise. A pilot study was performed with 3 box turtles ( Terrapene ornata ornata) and 3 red-eared sliders (RESs; Trachemys scripta elegans) to assess their suitability in a larger study. Based on the outcome of this study, RESs were selected, and 2 groups of 4 RESs received either an oral (PO) or intramuscular (IM) inoculum containing105 50% Tissue Culture Infecting Dose (TCID50) of a BSTRV-infected cell lysate. One turtle each was mock inoculated PO or IM with the same volume of uninfected cell lysate. Three of four IM-inoculated RESs developed clinical signs (nasal and ocular discharge [3 of 3], oral plaques [1 of 3], conjunctivitis and hyphema [1 of 3] and extreme lethargy [3 of 3]). A Ranavirus was isolated from kidney homogenates of 3 euthanatized turtles; DNA sequences of a portion of the major capsid protein gene were amplified by polymerase chain reaction. Consistent histologic lesions were observed only in IM-inoculated turtles and included fibrinoid vasculitis centered on splenic ellipsoids, multifocal hepatic necrosis, and multicentric fibrin thrombi in a variety of locations, including hepatic sinusoids, glomerular capillary loops, and pulmonary capillaries. Virions compatible with Ranavirus were observed within necrotic cells of the spleen of 1 IM-inoculated turtle using transmission electron microscopy. This study fulfills Koch's postulates, confirming a causal relationship between BSTRV and the clinical and histologic changes in chelonians infected with this virus.
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Affiliation(s)
- A J Johnson
- Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610, USA
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Rothermel BB, Miller DL, Travis ER, Gonynor McGuire JL, Jensen JB, Yabsley MJ. Disease dynamics of red-spotted newts and their anuran prey in a montane pond community. DISEASES OF AQUATIC ORGANISMS 2016; 118:113-127. [PMID: 26912042 DOI: 10.3354/dao02965] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Long-term monitoring of amphibians is needed to clarify population-level effects of ranaviruses (Rv) and the fungal pathogen Batrachochytrium dendrobatidis (Bd). We investigated disease dynamics of co-occurring amphibian species and potential demographic consequences of Rv and Bd infections at a montane site in the Southern Appalachians, Georgia, USA. Our 3-yr study was unique in combining disease surveillance with intensive population monitoring at a site where both pathogens are present. We detected sub-clinical Bd infections in larval and adult red-spotted newts Notophthalmus viridescens viridescens, but found no effect of Bd on body condition of adult newts. Bd infections also occurred in larvae of 5 anuran species that bred in our fishless study pond, and we detected co-infections with Bd and Rv in adult newts and larval green frogs Lithobates clamitans. However, all mortality and clinical signs in adult newts and larval anurans were most consistent with ranaviral disease, including a die-off of larval wood frogs Lithobates sylvaticus in small fish ponds located near our main study pond. During 2 yr of drift fence monitoring, we documented high juvenile production in newts, green frogs and American bullfrogs L. catesbeianus, but saw no evidence of juvenile recruitment in wood frogs. Larvae of this susceptible species may have suffered high mortality in the presence of both Rv and predators. Our findings were generally consistent with results of Rv-exposure experiments and support the purported role of red-spotted newts, green frogs, and American bullfrogs as common reservoirs for Bd and/or Rv in permanent and semi-permanent wetlands.
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Epstein B, Storfer A. Comparative Genomics of an Emerging Amphibian Virus. G3 (BETHESDA, MD.) 2015; 6:15-27. [PMID: 26530419 PMCID: PMC4704714 DOI: 10.1534/g3.115.023762] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Accepted: 10/22/2015] [Indexed: 11/18/2022]
Abstract
Ranaviruses, a genus of the Iridoviridae, are large double-stranded DNA viruses that infect cold-blooded vertebrates worldwide. Ranaviruses have caused severe epizootics in commercial frog and fish populations, and are currently classified as notifiable pathogens in international trade. Previous work shows that a ranavirus that infects tiger salamanders throughout Western North America (Ambystoma tigrinum virus, or ATV) is in high prevalence among salamanders in the fishing bait trade. Bait ATV strains have elevated virulence and are transported long distances by humans, providing widespread opportunities for pathogen pollution. We sequenced the genomes of 15 strains of ATV collected from tiger salamanders across western North America and performed phylogenetic and population genomic analyses and tests for recombination. We find that ATV forms a monophyletic clade within the rest of the Ranaviruses and that it likely emerged within the last several thousand years, before human activities influenced its spread. We also identify several genes under strong positive selection, some of which appear to be involved in viral virulence and/or host immune evasion. In addition, we provide support for the pathogen pollution hypothesis with evidence of recombination among ATV strains, and potential bait-endemic strain recombination.
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Affiliation(s)
- Brendan Epstein
- School of Biological Sciences, Washington State University, Pullman, Washington 99164
| | - Andrew Storfer
- School of Biological Sciences, Washington State University, Pullman, Washington 99164
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Echaubard P, Pauli BD, Trudeau VL, Lesbarrères D. Ranavirus infection in northern leopard frogs: the timing and number of exposures matter. J Zool (1987) 2015. [DOI: 10.1111/jzo.12281] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- P. Echaubard
- Genetics and Ecology of Amphibians Research Group (GEARG); Department of Biology; Laurentian University; Sudbury Ontario Canada
- WHO Collaborating Center for Research and Control of Opisthorchiasis; Tropical Disease Research laboratory; Faculty of Medicine; Khon Kaen University; Khon Kaen Thailand
| | - B. D. Pauli
- Environment Canada; Science and Technology Branch, National Wildlife Research Centre; Carleton University; Ottawa Ontario Canada
| | - V. L. Trudeau
- Centre for Advanced Research in Environmental Genomics; Department of Biology; University of Ottawa; Ottawa Ontario Canada
| | - D. Lesbarrères
- Genetics and Ecology of Amphibians Research Group (GEARG); Department of Biology; Laurentian University; Sudbury Ontario Canada
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Crespi EJ, Rissler LJ, Mattheus NM, Engbrecht K, Duncan SI, Seaborn T, Hall EM, Peterson JD, Brunner JL. Geophysiology of Wood Frogs: Landscape Patterns of Prevalence of Disease and Circulating Hormone Concentrations across the Eastern Range. Integr Comp Biol 2015; 55:602-17. [PMID: 26269462 DOI: 10.1093/icb/icv096] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
One of the major challenges for conservation physiologists is to determine how current or future environmental conditions relate to the health of animals at the population level. In this study, we measured prevalence of disease, mean condition of the body, and mean resting levels of corticosterone and testosterone in a total of 28 populations across the years 2011 and 2012, and correlated these measures of health to climatic suitability of habitat, using estimates from a model of the ecological niche of the wood frog's geographic range. Using the core-periphery hypothesis as a theoretical framework, we predicted a higher prevalence and intensity of infection of Batrachochytrium dendrobatidis (Bd) and ranaviruses, two major amphibian pathogens causing disease, and higher resting levels of circulating corticosterone, an indicator of allostatic load incurred from living in marginal habitats. We found that Bd infections were rare (2% of individuals tested), while infections with ranavirus were much more common: ranavirus-infected individuals were found in 92% of ponds tested over the 2 years. Contrary to our predictions, rates of infection with ranaviruses were positively correlated with quality of the habitat with the highest prevalence at the core of the range, and plasma corticosterone concentrations measured when frogs were at rest were not correlated with quality of the habitat, the prevalence of ranavirus, or the intensity of infection. Prevalence and mean viral titers of ranavirus infection were higher in 2012 than in 2011, which coincided with lower levels of circulating corticosterone and testosterone and an extremely early time of breeding due to relatively higher temperatures during the winter. In addition, the odds of having a ranavirus infection increased with decreased body condition, and if animals had an infection, viral titers were positively correlated to levels of circulating testosterone concentration. By resolving these patterns, experiments can be designed to test hypotheses about the mechanisms that produce them, such as whether transmission of the ranavirus and tolerance of the host are greater or whether virulence is lower in populations within core habitats. While there is debate about which metrics serve as the best bioindicators of population health, the findings of this study demonstrate the importance of long-term monitoring of multiple physiological parameters to better understand the dynamic relationship between the environment and the health of wildlife populations over space and time.
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Affiliation(s)
- Erica J Crespi
- *School of Biological Sciences, Washington State University, Pullman, WA 99164, USA;
| | - Leslie J Rissler
- Department of Biological Sciences, University of Alabama, Tuscaloosa, AL 35487, USA
| | - Nichole M Mattheus
- Department of Biological Sciences, University of Alabama, Tuscaloosa, AL 35487, USA
| | - Kristin Engbrecht
- *School of Biological Sciences, Washington State University, Pullman, WA 99164, USA
| | - Sarah I Duncan
- Department of Biological Sciences, University of Alabama, Tuscaloosa, AL 35487, USA
| | - Travis Seaborn
- *School of Biological Sciences, Washington State University, Pullman, WA 99164, USA
| | - Emily M Hall
- *School of Biological Sciences, Washington State University, Pullman, WA 99164, USA
| | - John D Peterson
- *School of Biological Sciences, Washington State University, Pullman, WA 99164, USA; Department of Biology, University of Wisconsin-Platteville, Platteville, WI 538183, USA
| | - Jesse L Brunner
- *School of Biological Sciences, Washington State University, Pullman, WA 99164, USA
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Kimble SJA, Karna AK, Johnson AJ, Hoverman JT, Williams RN. Mosquitoes as a Potential Vector of Ranavirus Transmission in Terrestrial Turtles. ECOHEALTH 2015; 12:334-338. [PMID: 25212726 DOI: 10.1007/s10393-014-0974-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2014] [Revised: 08/19/2014] [Accepted: 08/22/2014] [Indexed: 06/03/2023]
Abstract
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.
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Affiliation(s)
- Steven J A Kimble
- Department of Forestry and Natural Resources, College of Agriculture, Purdue University, 715 West State Street, West Lafayette, IN, USA.
| | - Ajit K Karna
- Department of Comparative Pathobiology, College of Veterinary Medicine, Purdue University, 725 Harrison Street, West Lafayette, IN, USA
| | - April J Johnson
- Department of Comparative Pathobiology, College of Veterinary Medicine, Purdue University, 725 Harrison Street, West Lafayette, IN, USA
| | - Jason T Hoverman
- Department of Forestry and Natural Resources, College of Agriculture, Purdue University, 715 West State Street, West Lafayette, IN, USA
| | - Rod N Williams
- Department of Forestry and Natural Resources, College of Agriculture, Purdue University, 715 West State Street, West Lafayette, IN, USA
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Forzán MJ, Jones KM, Vanderstichel RV, Wood J, Kibenge FSB, Kuiken T, Wirth W, Ariel E, Daoust PY. Clinical signs, pathology and dose-dependent survival of adult wood frogs, Rana sylvatica, inoculated orally with frog virus 3 Ranavirus sp., Iridoviridae. J Gen Virol 2015; 96:1138-1149. [DOI: 10.1099/vir.0.000043] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Accepted: 01/08/2015] [Indexed: 11/18/2022] Open
Affiliation(s)
- María J. Forzán
- Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Canada
- Canadian Wildlife Health Cooperative
| | - Kathleen M. Jones
- Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Canada
| | - Raphaël V. Vanderstichel
- Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Canada
| | - John Wood
- Pisces Molecular LLC, Boulder, Colorado, USA
| | - Frederick S. B. Kibenge
- Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Canada
| | - Thijs Kuiken
- Department of Viroscience, Erasmus University Medical Centre, Rotterdam, The Netherlands
| | - Wytamma Wirth
- School of Veterinary and Biomedical Sciences, James Cook University, Townsville, Australia
| | - Ellen Ariel
- School of Veterinary and Biomedical Sciences, James Cook University, Townsville, Australia
| | - Pierre-Yves Daoust
- Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Canada
- Canadian Wildlife Health Cooperative
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Chen ZY, Chiou PP, Liou CJ, Lai YS. Monoclonal antibody against a putative myristoylated membrane protein encoded by grouper iridovirus 59L gene. DISEASES OF AQUATIC ORGANISMS 2015; 113:215-226. [PMID: 25850399 DOI: 10.3354/dao02834] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Groupers (Epinephelus spp.) are economically important fish species worldwide, and ranaviruses are major viral pathogens causing heavy economic losses in grouper aquaculture. In this study, the 59L gene of grouper iridovirus (GIV-59L) was cloned and characterized. This gene is 1521 bp and encodes a protein of 506 amino acids with a predicted molecular mass of 53.9 kDa. Interestingly, GIV-59L and its homologs are found in all genera of the family Iridoviridae. A mouse monoclonal antibody specific for the C-terminal domain (amino acid positions 254-506) of the GIV-59L protein, GIV-59L(760-1518)-MAb-21, was produced and proved to be well suited for use in a number of GIV immunoassays. RT-PCR, Western blotting, and cycloheximide and cytosine arabinoside drug inhibition analyses indicated that GIV-59L is a viral late gene in GIV-infected grouper kidney cells. Immunofluorescence analysis revealed that GIV-59L protein mainly accumulates in the cytoplasm of infected cells and is finally packed into a whole virus particle. The GIV-59L(760-1518)-MAb-21 characterized in this study could have widespread application in GIV immunodiagnostics and other research on GIV. In addition, the results presented here offer important insights into the pathogenesis of GIV.
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Affiliation(s)
- Zhi-Yu Chen
- Department of Biotechnology and Animal Science, National Ilan University, Yilan, Taiwan
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Earl JE, Gray MJ. Introduction of ranavirus to isolated wood frog populations could cause local extinction. ECOHEALTH 2014; 11:581-592. [PMID: 24962849 DOI: 10.1007/s10393-014-0950-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Revised: 02/25/2014] [Accepted: 03/31/2014] [Indexed: 06/03/2023]
Abstract
Amphibian declines and extinction have been attributed to many causes, including disease such as chytridiomycosis. Other pathogens may also contribute to declines, with ranavirus as the most likely candidate given reoccurring die-offs observed in the wild. We were interested in whether it is possible for ranavirus to cause extinction of a local, closed population of amphibians. We used susceptibility data from experimental challenges on different life stages combined with estimates of demographic parameters from a natural population to predict the likelihood of extinction using a stage-structured population model for wood frogs (Lithobates sylvaticus). Extinction was most likely when the larval or metamorph stage was exposed under frequent intervals in smaller populations. Extinction never occurred when only the egg stage was exposed to ranavirus. Under the worst-case scenario, extinction could occur in as quickly as 5 years with exposure every year and 25-44 years with exposure every 2 years. In natural wood frog populations, die-offs typically occur in the larval stage and can reoccur in subsequent years, indicating that our simulations represent possible scenarios. Additionally, wood frog populations are particularly sensitive to changes in survival during the pre-metamorphic stages when ranavirus tends to be most pathogenic. Our results suggest that ranavirus could contribute to amphibian species declines, especially for species that are very susceptible to ranavirus with closed populations. We recommend that ranavirus be considered in risk analyses for amphibian species.
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Affiliation(s)
- Julia E Earl
- National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville, TN, 37996, USA,
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Brenes R, Miller DL, Waltzek TB, Wilkes RP, Tucker JL, Chaney JC, Hardman RH, Brand MD, Huether RR, Gray MJ. Susceptibility of fish and turtles to three ranaviruses isolated from different ectothermic vertebrate classes. JOURNAL OF AQUATIC ANIMAL HEALTH 2014; 26:118-126. [PMID: 24895866 DOI: 10.1080/08997659.2014.886637] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Ranaviruses have been associated with mortality of lower vertebrates around the world. Frog virus 3 (FV3)-like ranaviruses have been isolated from different ectothermic vertebrate classes; however, few studies have demonstrated whether this pathogen can be transmitted among classes. Using FV3-like ranaviruses isolated from the American bullfrog Lithobates catesbeianus, eastern box turtle Terrapene carolina carolina, and Pallid Sturgeon Scaphirhynchus albus, we tested for the occurrence of interclass transmission (i.e., infection) and host susceptibility (i.e., percent mortality) for five juvenile fish and three juvenile turtle species exposed to each of these isolates. Exposure was administered via water bath (10(3) PFU/mL) for 3 d and survival was monitored for 28 d. Florida softshell turtles Apalone ferox experienced no mortality, but 10% and 20% of individuals became infected by the turtle and fish isolate, respectively. Similarly, 5% of Mississippi map turtles Graptemys pseudogeographica kohni were subclinically infected with the turtle isolate at the end of the experiment. Channel Catfish Ictalurus punctatus experienced 5% mortality when exposed to the turtle isolate, while Western Mosquitofish Gambusia affinis experienced 10% mortality when exposed to the turtle and amphibian isolates and 5% mortality when exposed to the fish isolate. Our results demonstrated that interclass transmission of FV3-like ranaviruses is possible. Although substantial mortality did not occur in our experiments, the occurrence of low mortality and subclinical infections suggest that fish and aquatic turtles may function as reservoirs for FV3-like ranaviruses. Additionally, our study is the first to report transmission of FV3-like ranaviruses between fish and chelonians.
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Affiliation(s)
- Roberto Brenes
- a Department of Biology , Carroll University , 100 North East Avenue, Waukesha , Wisconsin 53186 , USA
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Transmission of ranavirus between ectothermic vertebrate hosts. PLoS One 2014; 9:e92476. [PMID: 24667325 PMCID: PMC3965414 DOI: 10.1371/journal.pone.0092476] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2014] [Accepted: 02/22/2014] [Indexed: 11/22/2022] Open
Abstract
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.
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Becker JA, Tweedie A, Gilligan D, Asmus M, Whittington RJ. Experimental infection of Australian freshwater fish with epizootic haematopoietic necrosis virus (EHNV). JOURNAL OF AQUATIC ANIMAL HEALTH 2013; 25:66-76. [PMID: 23339340 DOI: 10.1080/08997659.2012.747451] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The ranavirus, epizootic hematopoietic necrosis virus (EHNV), is endemic to southern Australia with natural outbreaks resulting in mass mortality events in wild Redfin Perch Perca fluviatilis (also known as Eurasian Perch) and less severe disease in farmed Rainbow Trout Oncorhynchus mykiss. To further investigate the host range for EHNV, 12 ecologically or economically important freshwater fish species from southeastern Australia were exposed experimentally to the virus. A bath-challenge model at 18 ± 3°C was employed with limited use of intraperitoneal inoculation to determine if a species was likely to be susceptible to EHNV. Of the species tested, Murray-Darling Rainbowfish Melanotaenia fluviatilis and Dewfish Tandanus tandanus (also known as Freshwater Catfish) were considered to be potentially susceptible species. EHNV was isolated from approximately 7% of surviving Eastern Mosquitofish Gambusia holbrooki, indicating this widespread alien fish species is a potential carrier. The infection of Silver Perch Bidyanus bidyanus and Macquarie Perch Macquaria australasica and the lack of infection in Murray Cod Maccullochella peelii peelii and Golden Perch Macquaria ambigua ambigua after exposure to EHNV via water confirmed earlier data from Langdon (1989). Five other species of native fish were potentially not susceptible to the virus or the fish were able to recover during the standard 35-d postchallenge observation period. Overall, it appeared that EHNV was less virulent in the present experimental model than in previous studies, but the reasons for this were not identified. Received May 21, 2012; accepted November 1, 2012.
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Affiliation(s)
- Joy A Becker
- University of Sydney, Camden , New South Wales, Australia.
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Haislip N, Hoverman J, Miller D, Gray M. Natural stressors and disease risk: does the threat of predation increase amphibian susceptibility to ranavirus? CAN J ZOOL 2012. [DOI: 10.1139/z2012-060] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Emerging infectious diseases have been identified as threats to biodiversity, yet our understanding of the factors contributing to host susceptibility to pathogens within natural populations remains limited. It has been proposed that species interactions within communities affect host susceptibility to pathogens, thereby contributing to disease emergence. In particular, predation risk is a common natural stressor that has been hypothesized to compromise immune function of prey through chronic stress responses possibly leading to increased susceptibility to pathogens. We examined whether predation risk experienced during the development of four larval anuran species increases susceptibility (mortality and infection) to ranaviruses, a group of viruses responsible for amphibian die-offs. Using controlled laboratory experiments, we exposed each species to a factorial combination of two virus treatments (no virus or virus) crossed with three predator-cue treatments (no predators, larval dragonflies, or adult water bugs). All four amphibian species reduced activity by 22%–48% following continuous exposure to predator cues. In addition, virus exposure significantly reduced survival by 17%–100% across all species. However, exposure to predator cues did not interact with the virus treatments to elevate mortality or viral load. Our results suggest that the expression of predator-induced plasticity in anuran larvae does not increase ranaviral disease risk.
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Affiliation(s)
- N.A. Haislip
- Center for Wildlife Health, Department of Forestry, Wildlife, and Fisheries, University of Tennessee, Knoxville, TN 37996, USA
| | - J.T. Hoverman
- Center for Wildlife Health, Department of Forestry, Wildlife, and Fisheries, University of Tennessee, Knoxville, TN 37996, USA
| | - D.L. Miller
- Center for Wildlife Health, Department of Forestry, Wildlife, and Fisheries, University of Tennessee, Knoxville, TN 37996, USA
- Veterinary Diagnostic and Investigational Laboratory, College of Veterinary Medicine, University of Georgia, Tifton, GA 31793, USA
- Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996, USA
| | - M.J. Gray
- Center for Wildlife Health, Department of Forestry, Wildlife, and Fisheries, University of Tennessee, Knoxville, TN 37996, USA
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Ecopathology of ranaviruses infecting amphibians. Viruses 2011; 3:2351-2373. [PMID: 22163349 PMCID: PMC3230856 DOI: 10.3390/v3112351] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2011] [Revised: 11/03/2011] [Accepted: 11/10/2011] [Indexed: 12/19/2022] Open
Abstract
Ranaviruses are capable of infecting amphibians from at least 14 families and over 70 individual species. Ranaviruses infect multiple cell types, often culminating in organ necrosis and massive hemorrhaging. Subclinical infections have been documented, although their role in ranavirus persistence and emergence remains unclear. Water is an effective transmission medium for ranaviruses, and survival outside the host may be for significant duration. In aquatic communities, amphibians, reptiles and fish may serve as reservoirs. Controlled studies have shown that susceptibility to ranavirus infection and disease varies among amphibian species and developmental stages, and likely is impacted by host-pathogen coevolution, as well as, exogenous environmental factors. Field studies have demonstrated that the likelihood of epizootics is increased in areas of cattle grazing, where aquatic vegetation is sparse and water quality is poor. Translocation of infected amphibians through commercial trade (e.g., food, fish bait, pet industry) contributes to the spread of ranaviruses. Such introductions may be of particular concern, as several studies report that ranaviruses isolated from ranaculture, aquaculture, and bait facilities have greater virulence (i.e., ability to cause disease) than wild-type isolates. Future investigations should focus on the genetic basis for pathogen virulence and host susceptibility, ecological and anthropogenic mechanisms contributing to emergence, and vaccine development for use in captive populations and species reintroduction programs.
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Hoverman JT, Gray MJ, Haislip NA, Miller DL. Phylogeny, life history, and ecology contribute to differences in amphibian susceptibility to ranaviruses. ECOHEALTH 2011; 8:301-19. [PMID: 22071720 DOI: 10.1007/s10393-011-0717-7] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2011] [Revised: 09/27/2011] [Accepted: 10/11/2011] [Indexed: 05/23/2023]
Abstract
Research that identifies the potential host range of generalist pathogens as well as variation in host susceptibility is critical for understanding and predicting the dynamics of infectious diseases within ecological communities. Ranaviruses have been linked to amphibian die-off events worldwide with the greatest number of reported mortality events occurring in the United States. While reports of ranavirus-associated mortality events continue to accumulate, few data exist comparing the relative susceptibility of different species. Using a series of laboratory exposure experiments and comparative phylogenetics, we compared the susceptibilities of 19 amphibian species from two salamander families and five anurans families for two ranavirus isolates: frog virus 3 (FV3) and an FV3-like isolate from an American bullfrog culture facility. We discovered that ranaviruses were capable of infecting 17 of the 19 larval amphibian species tested with mortality ranging from 0 to 100%. Phylogenetic comparative methods demonstrated that species within the anuran family Ranidae were generally more susceptible to ranavirus infection compared to species from the other five families. We also found that susceptibility to infection was associated with species that breed in semi-permanent ponds, develop rapidly as larvae, and have limited range sizes. Collectively, these results suggest that phylogeny, life history characteristics, and habitat associations of amphibians have the potential to impact susceptibility to ranaviruses.
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Affiliation(s)
- Jason T Hoverman
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309, USA.
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Waterborne infectivity of the Ranavirus frog virus 3 in Xenopus laevis. Virology 2011; 417:410-7. [PMID: 21783222 DOI: 10.1016/j.virol.2011.06.026] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Revised: 06/28/2011] [Accepted: 06/29/2011] [Indexed: 10/18/2022]
Abstract
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.
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Haislip NA, Gray MJ, Hoverman JT, Miller DL. Development and disease: how susceptibility to an emerging pathogen changes through anuran development. PLoS One 2011; 6:e22307. [PMID: 21799820 PMCID: PMC3142128 DOI: 10.1371/journal.pone.0022307] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2011] [Accepted: 06/23/2011] [Indexed: 01/31/2023] Open
Abstract
Ranaviruses have caused die-offs of amphibians across the globe. In North America, these pathogens cause more amphibian mortality events than any other pathogen. Field observations suggest that ranavirus epizootics in amphibian communities are common during metamorphosis, presumably due to changes in immune function. However, few controlled studies have compared the relative susceptibility of amphibians to ranaviruses across life stages. Our objectives were to measure differences in mortality and infection prevalence following exposure to ranavirus at four developmental stages and determine whether the differences were consistent among seven anuran species. Based on previous studies, we hypothesized that susceptibility to ranavirus would be greatest at metamorphosis. Our results did not support this hypothesis, as four of the species were most susceptible to ranavirus during the larval or hatchling stages. The embryo stage had the lowest susceptibility among species probably due to the protective membranous layers of the egg. Our results indicate that generalizations should be made cautiously about patterns of susceptibility to ranaviruses among amphibian developmental stages and species. Further, if early developmental stages of amphibians are susceptible to ranaviruses, the impact of ranavirus epizootic events may be greater than realized due to the greater difficulty of detecting morbid hatchlings and larvae compared to metamorphs.
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Affiliation(s)
- Nathan A. Haislip
- Department of Forestry, Wildlife, and Fisheries, Center for Wildlife Health, University of Tennessee, Knoxville, Tennessee, United States of America
| | - Matthew J. Gray
- Department of Forestry, Wildlife, and Fisheries, Center for Wildlife Health, University of Tennessee, Knoxville, Tennessee, United States of America
| | - Jason T. Hoverman
- Department of Forestry, Wildlife, and Fisheries, Center for Wildlife Health, University of Tennessee, Knoxville, Tennessee, United States of America
- * E-mail:
| | - Debra L. Miller
- Department of Forestry, Wildlife, and Fisheries, Center for Wildlife Health, University of Tennessee, Knoxville, Tennessee, United States of America
- Veterinary Diagnostic and Investigational Laboratory, College of Veterinary Medicine, University of Georgia, Tifton, Georgia, United States of America
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Lorenz LM, Koella JC. The microsporidian parasite Vavraia culicis as a potential late life-acting control agent of malaria. Evol Appl 2011; 4:783-90. [PMID: 25568022 PMCID: PMC3352544 DOI: 10.1111/j.1752-4571.2011.00199.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Accepted: 06/14/2011] [Indexed: 01/16/2023] Open
Abstract
Microsporidian parasites are being considered as alternatives to conventional insecticides for malaria control. They should reduce malaria transmission by shortening the lifespan of female mosquitoes and thus killing them before they transmit malaria. As the parasite replicates throughout the mosquito's life, it should have little detrimental effects on young mosquitoes, thus putting less selection pressure on the hosts to evolve resistance. Here, we examined these expectations for the microsporidian Vavraia culicis on Anopheles gambiae Giles sensu stricto mosquitoes under varying environmental conditions. Infection by the microsporidian delayed pupation by 10%, decreased fecundity by 23% and reduced adult lifespan by 27%, with higher infectious doses causing greater effects. The decrease of lifespan was mostly because of an increase of the mortality rate with age. Similarly, the parasite's effect on mosquito fecundity increased with the mosquitoes’ age. Neither infection nor food availability affected juvenile survival. Thus, as V. culicis reduced the longevity of A. gambiae (s.s.), yet affected mortality and fecundity of the young mosquitoes only slightly, the microsporidian is a promising alternative to insecticides for effective malaria control that will impose little evolutionary pressure for resistance.
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Affiliation(s)
- Lena M Lorenz
- Division of Biology, Imperial College London Silwood Park Campus, Ascot, UK ; Department of Disease Control, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine London, UK
| | - Jacob C Koella
- Division of Biology, Imperial College London Silwood Park Campus, Ascot, UK
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48
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Kerby JL, Hart AJ, Storfer A. Combined effects of virus, pesticide, and predator cue on the larval tiger salamander (Ambystoma tigrinum). ECOHEALTH 2011; 8:46-54. [PMID: 21523490 DOI: 10.1007/s10393-011-0682-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2010] [Revised: 02/21/2011] [Accepted: 02/22/2011] [Indexed: 05/30/2023]
Abstract
Emerging diseases and environmental contamination are two of the leading hypotheses for global amphibian declines. Yet few studies have examined the influence of contaminants on disease susceptibility, and even fewer have incorporated the role of natural stressors such as predation. We performed a factorial study investigating the interaction of the insecticide carbaryl, dragonfly predator cue, and the emerging pathogen Ambystoma tigrinum virus (ATV) on fitness correlates and disease susceptibility in tiger salamander larvae. Four week old larvae were exposed for 22 days in a 2 (0, 500 μg/l carbaryl) × 2 (control, predator cue water) × 2 (0, 1 × 10(4) pfu ATV) factorial designed laboratory study. Results show significant impacts to survival of larvae for both virus and predator cue treatments, as well as an interactive effect between the two, in which predator cue strongly exacerbated disease-driven mortality. There was a clear pattern of reduced survival with the addition of stressors, with those where all three stressors were present exhibiting the worst effects (a decrease in survival from 93 to 60%). On those that survived, we also detected several sub-lethal impacts in mass, SVL, and development. Predator cue and pesticide treatments significantly reduced both SVL and mass. Virus and predator treatments significantly slowed development. Stressors also exhibited opposing effects on activity. Predator cue caused a significant reduction in activity, whereas virus caused a significant increase in activity over time. These results highlight the importance of examining combined natural and introduced stressors to understand potential impacts on amphibian species. Such stressors may contribute to the emergence of ATV in particular regions, raising concerns about the influence of pesticides on disease emergence in general.
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Affiliation(s)
- Jacob L Kerby
- Biology Department, University of South Dakota, 414 E. Clark St, Vermillion, SD 57069, USA.
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49
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de Roode JC, de Castillejo CLF, Faits T, Alizon S. Virulence evolution in response to anti-infection resistance: toxic food plants can select for virulent parasites of monarch butterflies. J Evol Biol 2011; 24:712-22. [PMID: 21261772 DOI: 10.1111/j.1420-9101.2010.02213.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Host resistance to parasites can come in two main forms: hosts may either reduce the probability of parasite infection (anti-infection resistance) or reduce parasite growth after infection has occurred (anti-growth resistance). Both resistance mechanisms are often imperfect, meaning that they do not fully prevent or clear infections. Theoretical work has suggested that imperfect anti-growth resistance can select for higher parasite virulence by favouring faster-growing and more virulent parasites that overcome this resistance. In contrast, imperfect anti-infection resistance is thought not to select for increased parasite virulence, because it is assumed that it reduces the number of hosts that become infected, but not the fitness of parasites in successfully infected hosts. Here, we develop a theoretical model to show that anti-infection resistance can in fact select for higher virulence when such resistance reduces the effective parasite dose that enters a host. Our model is based on a monarch butterfly-parasite system in which larval food plants confer resistance to the monarch host. We carried out an experiment and showed that this environmental resistance is most likely a form of anti-infection resistance, through which toxic food plants reduce the effective dose of parasites that initiates an infection. We used these results to build a mathematical model to investigate the evolutionary consequences of food plant-induced resistance. Our model shows that when the effective infectious dose is reduced, parasites can compensate by evolving a higher per-parasite growth rate, and consequently a higher intrinsic virulence. Our results are relevant to many insect host-parasite systems, in which larval food plants often confer imperfect anti-infection resistance. Our results also suggest that - for parasites where the infectious dose affects the within-host dynamics - vaccines that reduce the effective infectious dose can select for increased parasite virulence.
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Affiliation(s)
- J C de Roode
- Biology Department, Emory University, Atlanta, GA 30322, USA.
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50
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Echaubard P, Little K, Pauli B, Lesbarrères D. Context-dependent effects of ranaviral infection on northern leopard frog life history traits. PLoS One 2010; 5:e13723. [PMID: 21060894 PMCID: PMC2965661 DOI: 10.1371/journal.pone.0013723] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2010] [Accepted: 10/01/2010] [Indexed: 12/22/2022] Open
Abstract
Pathogens have important effects on host life-history traits, but the magnitude of these effects is often strongly context-dependent. The outcome of an interaction between a host and an infectious agent is often associated with the level of stress experienced by the host. Ranavirus causes disease and mortality in amphibian populations in various locations around the world, but most known cases of ranaviral infection have occurred in North America and the United Kingdom. While Ranavirus virulence has been investigated, the outcome of Ranavirus infection has seldom been related to the host environment. In a factorial experiment, we exposed Northern leopard frog (Lithobates pipiens, formerly Rana pipiens) tadpoles to different concentrations of Ranavirus and investigated the effect of host density on certain life-history traits, namely survival, growth rate, developmental stage and number of days from virus exposure to death. Our results suggest a prominent role of density in driving the direction of the interaction between L. pipiens tadpoles and Ranavirus. We showed that increasing animal holding density is detrimental for host fitness as mortality rate is higher, day of death earlier, development longer and growth rate significantly lower in high-density tanks. We observed a linear increase of detrimental effects when Ranavirus doses increased in low-density conditions, with control tadpoles having a significantly higher overall relative fitness. However, this pattern was no longer observed in high-density conditions, where the effects of increasing Ranavirus dose were limited. Infected and control animals fitness were consequently similar. We speculate that the host may eventually diverts the energy required for a metabolic/immune response triggered by the infection (i.e., direct costs of the infection) to better cope with the increase in environmental "stress" associated with high density (i.e., indirect benefits of the infection). Our results illustrate how the net fitness of organisms may be shaped by ecological context and emphasize the necessity of examining the direct/indirect costs and benefits balance to fully understand host-pathogen interactions.
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Affiliation(s)
- Pierre Echaubard
- Genetics and Ecology of Amphibians Research Group (GEARG), Department of Biology, Laurentian University, Sudbury, Canada
| | - Kevin Little
- Genetics and Ecology of Amphibians Research Group (GEARG), Department of Biology, Laurentian University, Sudbury, Canada
| | - Bruce Pauli
- Environment Canada, Science and Technology Branch, National Wildlife Research Centre, Carleton University, Ottawa, Canada
| | - David Lesbarrères
- Genetics and Ecology of Amphibians Research Group (GEARG), Department of Biology, Laurentian University, Sudbury, Canada
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