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Janmaat A, Fung V, Rempel C, Quik R, Kabaluk T, Cory J. Lack of avoidance of the fungal entomopathogen, Metarhizium brunneum, by male Agriotes obscurus beetles. J Invertebr Pathol 2022; 194:107824. [PMID: 36030047 DOI: 10.1016/j.jip.2022.107824] [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: 05/09/2022] [Revised: 08/03/2022] [Accepted: 08/22/2022] [Indexed: 11/24/2022]
Abstract
Fungal entomopathogens can greatly reduce the fitness of their hosts, and it is therefore expected that susceptible insects will be selected to avoid exposure to pathogens. Metarhizium brunneum is a fungal pathogen that can infect Agriotes obscurus, which in its larval form is a destructive agricultural pest and is repelled by the presence of M. brunneum conidia. Due to the subterranean nature of larval A. obscurus, recent research has focused on targeting adult A. obscurus with M. brunneum. No-choice and choice behavioural assays were conducted to determine if male adult A. obscurus avoid M. brunneum mycosed cadavers, or conidia applied to either food or soil. To further investigate the response of A. obscurus beetles to conspecific cadavers, the movement and behaviour of beetles placed at the centre of a semi-circular arrangement of mycosed or control cadavers was examined using motion tracking software. We found little evidence to suggest that A. obscurus male beetles avoid M. brunneum conidia or mycosed conspecific cadavers or alter their behaviour in their presence.
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Affiliation(s)
- Alida Janmaat
- Biology Department, University of the Fraser Valley, Abbotsford, BC, Canada.
| | - Vincent Fung
- Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada
| | - Chera Rempel
- Biology Department, University of the Fraser Valley, Abbotsford, BC, Canada
| | - Rita Quik
- Biology Department, University of the Fraser Valley, Abbotsford, BC, Canada
| | - Todd Kabaluk
- Agriculture and Agri-Food Canada, Agassiz, BC, Canada
| | - Jenny Cory
- Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada
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2
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Guo H, Wang N, Niu H, Zhao D, Zhang Z. Interaction of Arsenophonus with Wolbachia in Nilaparvata lugens. BMC Ecol Evol 2021; 21:31. [PMID: 33610188 PMCID: PMC7896400 DOI: 10.1186/s12862-021-01766-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 02/04/2021] [Indexed: 11/23/2022] Open
Abstract
Background Co-infection of endosymbionts in the same host is ubiquitous, and the interactions of the most common symbiont Wolbachia with other symbionts, including Spiroplasma, in invertebrate organisms have received increasing attention. However, the interactions between Wolbachia and Arsenophonus, another widely distributed symbiont in nature, are poorly understood. We tested the co-infection of Wolbachia and Arsenophonus in different populations of Nilaparvata lugens and investigated whether co-infection affected the population size of the symbionts in their host. Results A significant difference was observed in the co-infection incidence of Wolbachia and Arsenophonus among 5 populations of N. lugens from China, with nearly half of the individuals in the Zhenjiang population harbouring the two symbionts simultaneously, and the rate of occurrence was significantly higher than that of the other 4 populations. The Arsenophonus density in the superinfection line was significantly higher only in the Maanshan population compared with that of the single-infection line. Differences in the density of Wolbachia and Arsenophonus were found in all the tested double-infection lines, and the dominant symbiont species varied with the population only in the Nanjing population, with Arsenophonus the overall dominant symbiont. Conclusions Wolbachia and Arsenophonus could coexist in N. lugens, and the co-infection incidence varied with the geographic populations. Antagonistic interactions were not observed between Arsenophonus and Wolbachia, and the latter was the dominant symbiont in most populations.
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Affiliation(s)
- Huifang Guo
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, No.50, Zhongling street, Nanjing, 210014, Jiangsu, China.
| | - Na Wang
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, No.50, Zhongling street, Nanjing, 210014, Jiangsu, China
| | - Hongtao Niu
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, No.50, Zhongling street, Nanjing, 210014, Jiangsu, China
| | - Dongxiao Zhao
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, No.50, Zhongling street, Nanjing, 210014, Jiangsu, China
| | - Zhichun Zhang
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, No.50, Zhongling street, Nanjing, 210014, Jiangsu, China
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3
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Virulence traits within a community of the fungal entomopathogen Beauveria: Associations with abundance and distribution. FUNGAL ECOL 2020. [DOI: 10.1016/j.funeco.2020.100992] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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4
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Evaluation of direct and indirect transmission of fungal spores in ants. J Invertebr Pathol 2020; 172:107351. [PMID: 32171803 DOI: 10.1016/j.jip.2020.107351] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 02/17/2020] [Accepted: 02/26/2020] [Indexed: 01/17/2023]
Abstract
Parasite transmission plays a central role in disease dynamics, but little is known about the extent to which direct and indirect transmission contributes to disease dynamics in group-living animals. Quantifying transmission by contact or exposure is challenging, as direct measurements of pathogen transmission are often impractical and individual behaviour is largely unknown. Here, we attempt to tackle these twin problems through the use of a generalist entomopathogenic fungus Metarhizium robertsii to study direct and indirect transmission in the black carpenter ant Camponotus pennsylvanicus. We provide evidence that large quantities of fungal conidia (spores) can be acquired over time on the ant's cuticle and significant amounts are shed into the environment, allowing indirect transmission. Unexposed ants in the nest can be infected either through direct (i.e. social contacts) or indirect (i.e. acquisition from the environment) transmission, potentially leading to the same mortality as if all individuals of a nest would have been directly exposed to the pathogen. Our findings highlight the importance of indirect transmission routes in a species of social living organisms.
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Milutinović B, Stock M, Grasse AV, Naderlinger E, Hilbe C, Cremer S. Social immunity modulates competition between coinfecting pathogens. Ecol Lett 2020; 23:565-574. [PMID: 31950595 DOI: 10.1111/ele.13458] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Revised: 10/31/2019] [Accepted: 12/14/2019] [Indexed: 12/18/2022]
Abstract
Coinfections with multiple pathogens can result in complex within-host dynamics affecting virulence and transmission. While multiple infections are intensively studied in solitary hosts, it is so far unresolved how social host interactions interfere with pathogen competition, and if this depends on coinfection diversity. We studied how the collective disease defences of ants - their social immunity - influence pathogen competition in coinfections of same or different fungal pathogen species. Social immunity reduced virulence for all pathogen combinations, but interfered with spore production only in different-species coinfections. Here, it decreased overall pathogen sporulation success while increasing co-sporulation on individual cadavers and maintaining a higher pathogen diversity at the community level. Mathematical modelling revealed that host sanitary care alone can modulate competitive outcomes between pathogens, giving advantage to fast-germinating, thus less grooming-sensitive ones. Host social interactions can hence modulate infection dynamics in coinfected group members, thereby altering pathogen communities at the host level and population level.
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Affiliation(s)
- Barbara Milutinović
- IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400, Klosterneuburg, Austria
| | - Miriam Stock
- IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400, Klosterneuburg, Austria
| | - Anna V Grasse
- IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400, Klosterneuburg, Austria
| | - Elisabeth Naderlinger
- IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400, Klosterneuburg, Austria
| | - Christian Hilbe
- IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400, Klosterneuburg, Austria
| | - Sylvia Cremer
- IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400, Klosterneuburg, Austria
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6
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Brinker P, Weig A, Rambold G, Feldhaar H, Tragust S. Microbial community composition of nest-carton and adjoining soil of the ant Lasius fuliginosus and the role of host secretions in structuring microbial communities. FUNGAL ECOL 2019. [DOI: 10.1016/j.funeco.2018.08.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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7
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Pauli G, Moura Mascarin G, Eilenberg J, Delalibera Júnior I. Within-Host Competition between Two Entomopathogenic Fungi and a Granulovirus in Diatraea saccharalis (Lepidoptera: Crambidae). INSECTS 2018; 9:insects9020064. [PMID: 29899228 PMCID: PMC6023289 DOI: 10.3390/insects9020064] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Revised: 05/30/2018] [Accepted: 06/01/2018] [Indexed: 11/25/2022]
Abstract
We provide insights into how the interactions of two entomopathogenic fungi and a virus play a role in virulence, disease development, and pathogen reproduction for an economically important insect crop pest, the sugarcane borer Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae). In our model system, we highlight the antagonistic effects of the co-inoculation of Beauveria bassiana and granulovirus (DisaGV) on virulence, compared to their single counterparts. By contrast, combinations of Metarhizium anisopliae and B. bassiana, or M. anisopliae and DisaGV, have resulted in additive effects against the insect. Intriguingly, most cadavers that were derived from dual or triple infections, produced signs/symptoms of only one species after the death of the infected host. In the combination of fungi and DisaGV, there was a trend where a higher proportion of viral infection bearing conspicuous symptoms occurred, except when the larvae were inoculated with M. anisopliae and DisaGV at the two highest inoculum rates. Co-infections with B. bassiana and M. anisopliae did not affect pathogen reproduction, since the sporulation from co-inoculated larvae did not differ from their single counterparts.
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Affiliation(s)
- Giuliano Pauli
- Departamento de Entomologia e Acarologia, Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo. Av. Pádua Dias, 11, C.P. 9, CEP 13418-900 Piracicaba, SP, Brazil.
| | - Gabriel Moura Mascarin
- Departamento de Entomologia e Acarologia, Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo. Av. Pádua Dias, 11, C.P. 9, CEP 13418-900 Piracicaba, SP, Brazil.
- Embrapa Meio Ambiente, Rodovia SP-340, km 127.5, S/N-Tanquinho Velho, CEP 13820-000 Jaguariúna, SP, Brazil.
| | - Jørgen Eilenberg
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C., Denmark.
| | - Italo Delalibera Júnior
- Departamento de Entomologia e Acarologia, Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo. Av. Pádua Dias, 11, C.P. 9, CEP 13418-900 Piracicaba, SP, Brazil.
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Konrad M, Pull CD, Metzler S, Seif K, Naderlinger E, Grasse AV, Cremer S. Ants avoid superinfections by performing risk-adjusted sanitary care. Proc Natl Acad Sci U S A 2018; 115:2782-2787. [PMID: 29463746 PMCID: PMC5856517 DOI: 10.1073/pnas.1713501115] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Being cared for when sick is a benefit of sociality that can reduce disease and improve survival of group members. However, individuals providing care risk contracting infectious diseases themselves. If they contract a low pathogen dose, they may develop low-level infections that do not cause disease but still affect host immunity by either decreasing or increasing the host's vulnerability to subsequent infections. Caring for contagious individuals can thus significantly alter the future disease susceptibility of caregivers. Using ants and their fungal pathogens as a model system, we tested if the altered disease susceptibility of experienced caregivers, in turn, affects their expression of sanitary care behavior. We found that low-level infections contracted during sanitary care had protective or neutral effects on secondary exposure to the same (homologous) pathogen but consistently caused high mortality on superinfection with a different (heterologous) pathogen. In response to this risk, the ants selectively adjusted the expression of their sanitary care. Specifically, the ants performed less grooming and more antimicrobial disinfection when caring for nestmates contaminated with heterologous pathogens compared with homologous ones. By modulating the components of sanitary care in this way the ants acquired less infectious particles of the heterologous pathogens, resulting in reduced superinfection. The performance of risk-adjusted sanitary care reveals the remarkable capacity of ants to react to changes in their disease susceptibility, according to their own infection history and to flexibly adjust collective care to individual risk.
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Affiliation(s)
- Matthias Konrad
- Institute of Science and Technology Austria (IST Austria), A-3400 Klosterneuburg, Austria
| | - Christopher D Pull
- Institute of Science and Technology Austria (IST Austria), A-3400 Klosterneuburg, Austria
| | - Sina Metzler
- Institute of Science and Technology Austria (IST Austria), A-3400 Klosterneuburg, Austria
| | - Katharina Seif
- Institute of Science and Technology Austria (IST Austria), A-3400 Klosterneuburg, Austria
| | - Elisabeth Naderlinger
- Institute of Science and Technology Austria (IST Austria), A-3400 Klosterneuburg, Austria
| | - Anna V Grasse
- Institute of Science and Technology Austria (IST Austria), A-3400 Klosterneuburg, Austria
| | - Sylvia Cremer
- Institute of Science and Technology Austria (IST Austria), A-3400 Klosterneuburg, Austria
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9
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Pull CD, Ugelvig LV, Wiesenhofer F, Grasse AV, Tragust S, Schmitt T, Brown MJF, Cremer S. Destructive disinfection of infected brood prevents systemic disease spread in ant colonies. eLife 2018; 7:e32073. [PMID: 29310753 PMCID: PMC5760203 DOI: 10.7554/elife.32073] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2017] [Accepted: 11/17/2017] [Indexed: 01/19/2023] Open
Abstract
In social groups, infections have the potential to spread rapidly and cause disease outbreaks. Here, we show that in a social insect, the ant Lasius neglectus, the negative consequences of fungal infections (Metarhizium brunneum) can be mitigated by employing an efficient multicomponent behaviour, termed destructive disinfection, which prevents further spread of the disease through the colony. Ants specifically target infected pupae during the pathogen's non-contagious incubation period, utilising chemical 'sickness cues' emitted by pupae. They then remove the pupal cocoon, perforate its cuticle and administer antimicrobial poison, which enters the body and prevents pathogen replication from the inside out. Like the immune system of a metazoan body that specifically targets and eliminates infected cells, ants destroy infected brood to stop the pathogen completing its lifecycle, thus protecting the rest of the colony. Hence, in an analogous fashion, the same principles of disease defence apply at different levels of biological organisation.
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Affiliation(s)
- Christopher D Pull
- IST Austria (Institute of Science and Technology Austria)KlosterneuburgAustria
| | - Line V Ugelvig
- IST Austria (Institute of Science and Technology Austria)KlosterneuburgAustria
| | - Florian Wiesenhofer
- IST Austria (Institute of Science and Technology Austria)KlosterneuburgAustria
| | - Anna V Grasse
- IST Austria (Institute of Science and Technology Austria)KlosterneuburgAustria
| | - Simon Tragust
- IST Austria (Institute of Science and Technology Austria)KlosterneuburgAustria
- Evolution, Genetics and BehaviourUniversity of RegensburgRegensburgGermany
| | - Thomas Schmitt
- Department of Animal Ecology and Tropical BiologyUniversity of WürzburgWürzburgGermany
| | - Mark JF Brown
- School of Biological SciencesRoyal Holloway University of LondonEghamUnited Kingdom
| | - Sylvia Cremer
- IST Austria (Institute of Science and Technology Austria)KlosterneuburgAustria
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10
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Cremer S, Pull CD, Fürst MA. Social Immunity: Emergence and Evolution of Colony-Level Disease Protection. ANNUAL REVIEW OF ENTOMOLOGY 2018; 63:105-123. [PMID: 28945976 DOI: 10.1146/annurev-ento-020117-043110] [Citation(s) in RCA: 143] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Social insect colonies have evolved many collectively performed adaptations that reduce the impact of infectious disease and that are expected to maximize their fitness. This colony-level protection is termed social immunity, and it enhances the health and survival of the colony. In this review, we address how social immunity emerges from its mechanistic components to produce colony-level disease avoidance, resistance, and tolerance. To understand the evolutionary causes and consequences of social immunity, we highlight the need for studies that evaluate the effects of social immunity on colony fitness. We discuss the roles that host life history and ecology have on predicted eco-evolutionary dynamics, which differ among the social insect lineages. Throughout the review, we highlight current gaps in our knowledge and promising avenues for future research, which we hope will bring us closer to an integrated understanding of socio-eco-evo-immunology.
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Affiliation(s)
- Sylvia Cremer
- IST Austria (Institute of Science and Technology Austria), Klosterneuburg 3400, Austria; ,
| | - Christopher D Pull
- IST Austria (Institute of Science and Technology Austria), Klosterneuburg 3400, Austria; ,
- Current affiliation: School of Biological Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, United Kingdom;
| | - Matthias A Fürst
- IST Austria (Institute of Science and Technology Austria), Klosterneuburg 3400, Austria; ,
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11
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Affiliation(s)
- Denon Start
- Dept of Ecology and Evolutionary Biology; Univ. of Toronto; Toronto, ON M5S 3B3 Canada
| | - Benjamin Gilbert
- Dept of Ecology and Evolutionary Biology; Univ. of Toronto; Toronto, ON M5S 3B3 Canada
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12
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Pull CD, Cremer S. Co-founding ant queens prevent disease by performing prophylactic undertaking behaviour. BMC Evol Biol 2017; 17:219. [PMID: 29025392 PMCID: PMC5639488 DOI: 10.1186/s12862-017-1062-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Accepted: 09/18/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Social insects form densely crowded societies in environments with high pathogen loads, but have evolved collective defences that mitigate the impact of disease. However, colony-founding queens lack this protection and suffer high rates of mortality. The impact of pathogens may be exacerbated in species where queens found colonies together, as healthy individuals may contract pathogens from infectious co-founders. Therefore, we tested whether ant queens avoid founding colonies with pathogen-exposed conspecifics and how they might limit disease transmission from infectious individuals. RESULTS Using Lasius niger queens and a naturally infecting fungal pathogen Metarhizium brunneum, we observed that queens were equally likely to found colonies with another pathogen-exposed or sham-treated queen. However, when one queen died, the surviving individual performed biting, burial and removal of the corpse. These undertaking behaviours were performed prophylactically, i.e. targeted equally towards non-infected and infected corpses, as well as carried out before infected corpses became infectious. Biting and burial reduced the risk of the queens contracting and dying from disease from an infectious corpse of a dead co-foundress. CONCLUSIONS We show that co-founding ant queens express undertaking behaviours that, in mature colonies, are performed exclusively by workers. Such infection avoidance behaviours act before the queens can contract the disease and will therefore improve the overall chance of colony founding success in ant queens.
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Affiliation(s)
- Christopher D Pull
- IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400, Klosterneuburg, Austria. .,Present address: School of Biological Sciences, Royal Holloway University of London, Egham, TW20 0EX, UK.
| | - Sylvia Cremer
- IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400, Klosterneuburg, Austria
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13
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McLean AHC, Parker BJ, Hrček J, Kavanagh JC, Wellham PAD, Godfray HCJ. Consequences of symbiont co-infections for insect host phenotypes. J Anim Ecol 2017; 87:478-488. [PMID: 28542979 DOI: 10.1111/1365-2656.12705] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2016] [Accepted: 05/08/2017] [Indexed: 01/07/2023]
Abstract
Most animals host communities of symbiotic bacteria. In insects, these symbionts may have particularly intimate interactions with their hosts: many are intracellular and can play important roles in host ecology and evolution, including protection against natural enemies. We investigated how interactions between different species or strains of endosymbiotic bacteria within an aphid host influence the outcome of symbiosis for both symbiont and host. We first asked whether different combinations of facultative symbiont species or strains can exist in stable co-infections. We then investigated whether the benefits that facultative bacteria confer on their hosts (protection against natural enemies) are enhanced, reduced or unaltered by the presence of a co-infecting symbiont. We asked this both for co-infecting symbionts that confer different phenotypes on their hosts (protection against fungal pathogens vs. parasitoid wasps) and symbionts with overlapping functions. Finally, we investigated the additional survival costs to aphids of carrying multiple infections of symbiont species or strains, and compared symbiont titres in double and single infections. We found that stable co-infections were possible between all of the combinations of facultative symbiont species (Regiella insecticola + Hamiltonella defensa, Regiella + Rickettsiella sp., Regiella + Spiroplasma sp.) and strains (Hamiltonella) that we studied. Where symbionts provided protection against different natural enemies, no alteration in protection was observed in the presence of co-infections. Where symbionts provided protection against the same natural enemy, the level of protection corresponded to the higher of the two symbionts present. In some instances, aphid hosts suffered additional survival costs when hosting double infections. In the case of Hamiltonella, however, infection with multiple strains of the same symbiont led to lower symbiont titres than single infections, and actually improved aphid survival. We conclude that the long-term maintenance of symbiont co-infections in aphids is likely to be determined primarily by costs of co-infections and in some instances by redundancy of symbiont benefits.
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Affiliation(s)
| | | | - Jan Hrček
- Department of Zoology, University of Oxford, Oxford, UK
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14
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Clark NJ, Wells K, Dimitrov D, Clegg SM. Co-infections and environmental conditions drive the distributions of blood parasites in wild birds. J Anim Ecol 2016; 85:1461-1470. [DOI: 10.1111/1365-2656.12578] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 07/17/2016] [Indexed: 11/29/2022]
Affiliation(s)
- Nicholas J. Clark
- Environmental Futures Research Institute; School of Environment; Griffith University; Gold Coast Qld 4111 Australia
- Natural Environments Program; Queensland Museum; Institute of Biodiversity and Ecosystem Research; P.O. Box 3300 South Brisbane Qld 4101 Australia
| | - Konstans Wells
- Environmental Futures Research Institute; School of Environment; Griffith University; Gold Coast Qld 4111 Australia
| | - Dimitar Dimitrov
- Institute of Biodiversity and Ecosystem Research at the Bulgarian Academy of Sciences; 2 Gagarin Street Sofia 1113 Bulgaria
| | - Sonya M. Clegg
- Environmental Futures Research Institute; School of Environment; Griffith University; Gold Coast Qld 4111 Australia
- Department of Zoology; Edward Grey Institute of Field Ornithology; University of Oxford; Oxford OX1 3PS UK
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15
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Loreto RG, Hughes DP. Disease in the Society: Infectious Cadavers Result in Collapse of Ant Sub-Colonies. PLoS One 2016; 11:e0160820. [PMID: 27529548 PMCID: PMC4986943 DOI: 10.1371/journal.pone.0160820] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 07/26/2016] [Indexed: 11/19/2022] Open
Abstract
Despite the growing number of experimental studies on mechanisms of social immunity in ant societies, little is known about how social behavior relates to disease progression within the nests of ants. In fact, when empirically studying disease in ant societies, it is common to remove dead ants from experiments to confirm infection by the studied parasite. This unfortunately does not allow disease to progress within the nest as it may be assumed would happen under natural conditions. Therefore, the approach taken so far has resulted in a limited knowledge of diseases dynamics within the nest environment. Here we introduced a single infectious cadaver killed by the fungus Beauveria bassiana into small nests of the ant Camponotus castaneus. We then observed the natural progression of the disease by not removing the corpses of the ants that died following the first entry of the disease. Because some behaviors such as social isolation of sick individuals or the removal of cadavers by nestmates are considered social immune functions and thus adaptations at the colony level that reduce disease spread, we also experimentally confined some sub-colonies to one or two chamber nests to prevent the expression of such behaviors. Based on 51 small nests and survival studies in 1,003 ants we found that a single introduced infectious cadaver was able to transmit within the nest, and social immunity did not prevent the collapse of the small sub-colonies here tested. This was true whether ants did or did not have the option to remove the infectious cadaver. Therefore, we found no evidence that the typically studied social immunity behaviors can reduce disease spread in the conditions here tested.
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Affiliation(s)
- Raquel G. Loreto
- Department of Entomology and Center for Infectious Disease Dynamics, Pennsylvania State University, University Park, 16802 Pennsylvania, United States of America
- CAPES Foundation, Ministry of Education of Brazil, Brasília 70040–020 DF, Brazil
| | - David P. Hughes
- Department of Entomology and Center for Infectious Disease Dynamics, Pennsylvania State University, University Park, 16802 Pennsylvania, United States of America
- Department of Biology, Pennsylvania State University, University Park, 16802 Pennsylvania, United States of America
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Armitage SAO, Fernández-Marín H, Boomsma JJ, Wcislo WT. Slowing them down will make them lose: a role for attine ant crop fungus in defending pupae against infections? J Anim Ecol 2016; 85:1210-21. [PMID: 27136600 PMCID: PMC6084299 DOI: 10.1111/1365-2656.12543] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 04/12/2016] [Indexed: 02/05/2023]
Abstract
Fungus-growing ants (Attini) have evolved an obligate dependency upon a basidiomycete fungus that they cultivate as their food. Less well known is that the crop fungus is also used by many attine species to cover their eggs, larvae and pupae. The adaptive functional significance of this brood covering is poorly understood. One hypothesis to account for this behaviour is that it is part of the pathogen protection portfolio when many thousands of sister workers live in close proximity and larvae and pupae are not protected by cells, as in bees and wasps, and are immobile. We performed behavioural observations on brood covering in the leaf-cutting ant Acromyrmex echinatior, and we experimentally manipulated mycelial cover on pupae and exposed them to the entomopathogenic fungus Metarhizium brunneum to test for a role in pathogen resistance. Our results show that active mycelial brood covering by workers is a behaviourally plastic trait that varies temporally, and across life stages and castes. The presence of a fungal cover on the pupae reduced the rate at which conidia appeared and the percentage of pupal surface that produced pathogen spores, compared to pupae that had fungal cover experimentally removed or naturally had no mycelial cover. Infected pupae with mycelium had higher survival rates than infected pupae without the cover, although this depended upon the time at which adult sister workers were allowed to interact with pupae. Finally, workers employed higher rates of metapleural gland grooming to infected pupae without mycelium than to infected pupae with mycelium. Our results imply that mycelial brood covering may play a significant role in suppressing the growth and subsequent spread of disease, thus adding a novel layer of protection to their defence portfolio.
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Affiliation(s)
- Sophie A O Armitage
- Department of Biology, Centre for Social Evolution, University of Copenhagen, Universitetsparken 15, 2100, Copenhagen, Denmark
| | - Hermógenes Fernández-Marín
- Department of Biology, Centre for Social Evolution, University of Copenhagen, Universitetsparken 15, 2100, Copenhagen, Denmark.,Instituto de Investigaciones Científicas y Servicios de Alta Tecnología, Edificio 219, Ciudad del Saber, Clayton, Panamá City, Panamá,Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancón, Panamá
| | - Jacobus J Boomsma
- Department of Biology, Centre for Social Evolution, University of Copenhagen, Universitetsparken 15, 2100, Copenhagen, Denmark
| | - William T Wcislo
- Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancón, Panamá
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17
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Betts A, Gifford DR, MacLean RC, King KC. Parasite diversity drives rapid host dynamics and evolution of resistance in a bacteria-phage system. Evolution 2016; 70:969-78. [PMID: 27005577 PMCID: PMC4982092 DOI: 10.1111/evo.12909] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Revised: 03/02/2016] [Accepted: 03/11/2016] [Indexed: 12/01/2022]
Abstract
Host–parasite evolutionary interactions are typically considered in a pairwise species framework. However, natural infections frequently involve multiple parasites. Altering parasite diversity alters ecological and evolutionary dynamics as parasites compete and hosts resist multiple infection. We investigated the effects of parasite diversity on host–parasite population dynamics and evolution using the pathogen Pseudomonas aeruginosa and five lytic bacteriophage parasites. To manipulate parasite diversity, bacterial populations were exposed for 24 hours to either phage monocultures or diverse communities containing up to five phages. Phage communities suppressed host populations more rapidly but also showed reduced phage density, likely due to interphage competition. The evolution of resistance allowed rapid bacterial recovery that was greater in magnitude with increases in phage diversity. We observed no difference in the extent of resistance with increased parasite diversity, but there was a profound impact on the specificity of resistance; specialized resistance evolved to monocultures through mutations in a diverse set of genes. In summary, we demonstrate that parasite diversity has rapid effects on host–parasite population dynamics and evolution by selecting for different resistance mutations and affecting the magnitude of bacterial suppression and recovery. Finally, we discuss the implications of phage diversity for their use as biological control agents.
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Affiliation(s)
- Alex Betts
- Department of Zoology, University of Oxford, Oxford, OX1 3PS, United Kingdom.
| | - Danna R Gifford
- Department of Zoology, University of Oxford, Oxford, OX1 3PS, United Kingdom
| | - R Craig MacLean
- Department of Zoology, University of Oxford, Oxford, OX1 3PS, United Kingdom
| | - Kayla C King
- Department of Zoology, University of Oxford, Oxford, OX1 3PS, United Kingdom
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18
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Disease Dynamics in Ants: A Critical Review of the Ecological Relevance of Using Generalist Fungi to Study Infections in Insect Societies. ADVANCES IN GENETICS 2016; 94:287-306. [PMID: 27131328 DOI: 10.1016/bs.adgen.2015.12.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
It is assumed that social life can lead to the rapid spread of infectious diseases and outbreaks. In ants, disease outbreaks are rare and the expression of collective behaviors is invoked to explain the absence of epidemics in natural populations. Here, we address the ecological approach employed by many studies that have notably focused (89% of the studies) on two genera of generalist fungal parasites (Beauveria and Metarhizium). We ask whether these are the most representative models to study the evolutionary ecology of ant-fungal parasite interactions. To assess this, we critically examine the literature on ants and their interactions with fungal parasites from the past 114years (1900-2014). We discuss how current evolutionary ecology approaches emerged from studies focused on the biological control of pest ants. We also analyzed the ecological relevance of the laboratory protocols used in evolutionary ecology studies employing generalist parasites, as well as the rare natural occurrence of these parasites on ants. After a detailed consideration of all the publications, we suggest that using generalist pathogens such as Beauveria and Metarhizium is not an optimal approach if the goal is to study the evolutionary ecology of disease in ants. We conclude by advocating for approaches that incorporate greater realism.
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19
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Novak S, Cremer S. Fungal disease dynamics in insect societies: optimal killing rates and the ambivalent effect of high social interaction rates. J Theor Biol 2015; 372:54-64. [PMID: 25728787 DOI: 10.1016/j.jtbi.2015.02.018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Revised: 01/23/2015] [Accepted: 02/14/2015] [Indexed: 12/11/2022]
Abstract
Entomopathogenic fungi are potent biocontrol agents that are widely used against insect pests, many of which are social insects. Nevertheless, theoretical investigations of their particular life history are scarce. We develop a model that takes into account the main distinguishing features between traditionally studied diseases and obligate killing pathogens, like the (biocontrol-relevant) insect-pathogenic fungi Metarhizium and Beauveria. First, obligate killing entomopathogenic fungi produce new infectious particles (conidiospores) only after host death and not yet on the living host. Second, the killing rates of entomopathogenic fungi depend strongly on the initial exposure dosage, thus we explicitly consider the pathogen load of individual hosts. Further, we make the model applicable not only to solitary host species, but also to group living species by incorporating social interactions between hosts, like the collective disease defences of insect societies. Our results identify the optimal killing rate for the pathogen that minimises its invasion threshold. Furthermore, we find that the rate of contact between hosts has an ambivalent effect: dense interaction networks between individuals are considered to facilitate disease outbreaks because of increased pathogen transmission. In social insects, this is compensated by their collective disease defences, i.e., social immunity. For the type of pathogens considered here, we show that even without social immunity, high contact rates between live individuals dilute the pathogen in the host colony and hence can reduce individual pathogen loads below disease-causing levels.
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Affiliation(s)
- Sebastian Novak
- IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400 Klosterneuburg, Austria.
| | - Sylvia Cremer
- IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400 Klosterneuburg, Austria
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20
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Duncan AB, Agnew P, Noel V, Michalakis Y. The consequences of co-infections for parasite transmission in the mosquito Aedes aegypti. J Anim Ecol 2014; 84:498-508. [PMID: 25311642 DOI: 10.1111/1365-2656.12302] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Accepted: 10/01/2014] [Indexed: 11/29/2022]
Abstract
Co-infections may modify parasite transmission opportunities directly as a consequence of interactions in the within-host environment, but also indirectly through changes in host life history. Furthermore, host and parasite traits are sensitive to the abiotic environment with variable consequences for parasite transmission in co-infections. We investigate how co-infection of the mosquito Aedes aegypti with two microsporidian parasites (Vavraia culicis and Edhazardia aedis) at two levels of larval food availability affects parasite transmission directly, and indirectly through effects on host traits. In a laboratory infection experiment, we compared how co-infection, at low and high larval food availability, affected the probability of infection, within-host growth and the transmission potential of each parasite, compared to single infections. Horizontal transmission was deemed possible for both parasites when infected hosts died harbouring horizontally transmitting spores. Vertical transmission was judged possible for E. aedis when infected females emerged as adults. We also compared the total input number of spores used to seed infections with output number, in single and co-infections for each parasite. The effects of co-infection on parasite fitness were complex, especially for V. culicis. In low larval food conditions, co-infection increased the chances of mosquitoes dying as larvae or pupae, thus increasing opportunities for V. culicis' horizontal transmission. However, co-infection reduced larval longevity and hence time available for V. culicis spore production. Overall, there was a negative net effect of co-infection on V. culicis, whereby the number of spores produced was less than the number used to seed infection. Co-infections also negatively affected horizontal transmission of the more virulent parasite, E. aedis, through reduced longevity of pre-adult hosts. However, its potential transmission suffered less relative to V. culicis. Our results show that co-infection can negatively affect parasite transmission opportunities, both directly as well as indirectly via effects on host life history. We also find that transmission is contingent on the combined effect of the abiotic environment.
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Affiliation(s)
- Alison B Duncan
- MIVEGEC, UMR CNRS-IRD-UM1-UM2 5290, Centre IRD, 911 avenue Agropolis, 34394, Montpellier CEDEX 5, France
| | - Philip Agnew
- MIVEGEC, UMR CNRS-IRD-UM1-UM2 5290, Centre IRD, 911 avenue Agropolis, 34394, Montpellier CEDEX 5, France
| | - Valérie Noel
- MIVEGEC, UMR CNRS-IRD-UM1-UM2 5290, Centre IRD, 911 avenue Agropolis, 34394, Montpellier CEDEX 5, France
| | - Yannis Michalakis
- MIVEGEC, UMR CNRS-IRD-UM1-UM2 5290, Centre IRD, 911 avenue Agropolis, 34394, Montpellier CEDEX 5, France
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21
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Abstract
Transmission is a key determinant of parasite fitness, and understanding the dynamics of transmission is fundamental to the ecology and evolution of host-parasite interactions. Successful transmission is often reliant on contact between infected individuals and susceptible hosts. The social insects consist of aggregated groups of genetically similar hosts, making them particularly vulnerable to parasite transmission. Here we investigate how the ratio of infected to susceptible individuals impacts parasite transmission, using the honey bee, Apis mellifera and its microsporidian parasite Nosema ceranae. We used 2 types of infected hosts found simultaneously in colonies; sterile female workers and sexual males. We found a higher ratio of infected to susceptible individuals in groups resulted in a greater proportion of susceptibles becoming infected, but this effect was non-linear and interestingly, the ratio also affected the spore production of infected individuals. The transmission level was much greater in an experiment where the infected individuals were drones than in an experiment where they were workers, suggesting drones may act as intracolonial 'superspreaders'. Understanding the subtleties of transmission and how it is influenced by the phenotype of the infected/susceptible individuals is important for understanding pathogen transmission at population level, and for optimum targeting of parasite control strategies.
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22
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Kay AD, Bruning AJ, van Alst A, Abrahamson TT, Hughes WOH, Kaspari M. A carbohydrate-rich diet increases social immunity in ants. Proc Biol Sci 2014; 281:20132374. [PMID: 24430844 DOI: 10.1098/rspb.2013.2374] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Increased potential for disease transmission among nest-mates means living in groups has inherent costs. This increased potential is predicted to select for disease resistance mechanisms that are enhanced by cooperative exchanges among group members, a phenomenon known as social immunity. One potential mediator of social immunity is diet nutritional balance because traits underlying immunity can require different nutritional mixtures. Here, we show how dietary protein-carbohydrate balance affects social immunity in ants. When challenged with a parasitic fungus Metarhizium anisopliae, workers reared on a high-carbohydrate diet survived approximately 2.8× longer in worker groups than in solitary conditions, whereas workers reared on an isocaloric, high-protein diet survived only approximately 1.3× longer in worker groups versus solitary conditions. Nutrition had little effect on social grooming, a potential mechanism for social immunity. However, experimentally blocking metapleural glands, which secrete antibiotics, completely eliminated effects of social grouping and nutrition on immunity, suggesting a causal role for secretion exchange. A carbohydrate-rich diet also reduced worker mortality rates when whole colonies were challenged with Metarhizium. These results provide a novel mechanism by which carbohydrate exploitation could contribute to the ecological dominance of ants and other social groups.
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Affiliation(s)
- Adam D Kay
- Department of Biology, University of St. Thomas, , St. Paul, MN, USA, School of Life Sciences, University of Sussex, , Brighton, UK, Graduate Program in EEB, Department of Zoology, University of Oklahoma, , Norman, OK, USA, Smithsonian Tropical Research Institute, , Balboa, Republic of Panama
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23
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Sanitizing the fortress: protection of ant brood and nest material by worker antibiotics. Behav Ecol Sociobiol 2013. [DOI: 10.1007/s00265-013-1664-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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24
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Tragust S, Ugelvig LV, Chapuisat M, Heinze J, Cremer S. Pupal cocoons affect sanitary brood care and limit fungal infections in ant colonies. BMC Evol Biol 2013; 13:225. [PMID: 24125481 PMCID: PMC3854126 DOI: 10.1186/1471-2148-13-225] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Accepted: 08/29/2013] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND The brood of ants and other social insects is highly susceptible to pathogens, particularly those that penetrate the soft larval and pupal cuticle. We here test whether the presence of a pupal cocoon, which occurs in some ant species but not in others, affects the sanitary brood care and fungal infection patterns after exposure to the entomopathogenic fungus Metarhizium brunneum. We use a) a comparative approach analysing four species with either naked or cocooned pupae and b) a within-species analysis of a single ant species, in which both pupal types co-exist in the same colony. RESULTS We found that the presence of a cocoon did not compromise fungal pathogen detection by the ants and that species with cocooned pupae increased brood grooming after pathogen exposure. All tested ant species further removed brood from their nests, which was predominantly expressed towards larvae and naked pupae treated with the live fungal pathogen. In contrast, cocooned pupae exposed to live fungus were not removed at higher rates than cocooned pupae exposed to dead fungus or a sham control. Consistent with this, exposure to the live fungus caused high numbers of infections and fungal outgrowth in larvae and naked pupae, but not in cocooned pupae. Moreover, the ants consistently removed the brood prior to fungal outgrowth, ensuring a clean brood chamber. CONCLUSION Our study suggests that the pupal cocoon has a protective effect against fungal infection, causing an adaptive change in sanitary behaviours by the ants. It further demonstrates that brood removal-originally described for honeybees as "hygienic behaviour"-is a widespread sanitary behaviour in ants, which likely has important implications on disease dynamics in social insect colonies.
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Affiliation(s)
- Simon Tragust
- Evolutionary Biology, IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400 Klosterneuburg, Austria
- Evolution, Behaviour and Genetics, Biology I, University of Regensburg, Universitätsstr. 31, 93040 Regensburg, Germany
- Animal Ecology I, University of Bayreuth, 95440 Bayreuth, Germany
| | - Line V Ugelvig
- Evolutionary Biology, IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400 Klosterneuburg, Austria
- Evolution, Behaviour and Genetics, Biology I, University of Regensburg, Universitätsstr. 31, 93040 Regensburg, Germany
| | - Michel Chapuisat
- Department of Ecology and Evolution, Biophore, UNIL-Sorge, University of Lausanne, 1015 Lausanne, Switzerland
| | - Jürgen Heinze
- Evolution, Behaviour and Genetics, Biology I, University of Regensburg, Universitätsstr. 31, 93040 Regensburg, Germany
| | - Sylvia Cremer
- Evolutionary Biology, IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400 Klosterneuburg, Austria
- Evolution, Behaviour and Genetics, Biology I, University of Regensburg, Universitätsstr. 31, 93040 Regensburg, Germany
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25
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Ben-Ami F, Routtu J. The expression and evolution of virulence in multiple infections: the role of specificity, relative virulence and relative dose. BMC Evol Biol 2013; 13:97. [PMID: 23641899 PMCID: PMC3659053 DOI: 10.1186/1471-2148-13-97] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 04/29/2013] [Indexed: 11/11/2022] Open
Abstract
Background Multiple infections of the same host by different strains of the same microparasite species are believed to play a crucial role during the evolution of parasite virulence. We investigated the role of specificity, relative virulence and relative dose in determining the competitive outcome of multiple infections in the Daphnia magna-Pasteuria ramosa host-parasite system. Results We found that infections by P. ramosa clones (single genotype) were less virulent and produced more spores than infections by P. ramosa isolates (possibly containing multiple genotypes). We also found that two similarly virulent isolates of P. ramosa differed considerably in their within-host competitiveness and their effects on host offspring production when faced with coinfecting P. ramosa isolates and clones. Although the relative virulence of a P. ramosa isolate/clone appears to be a good indicator of its competitiveness during multiple infections, the relative dose may alter the competitive outcome. Moreover, spore counts on day 20 post-infection indicate that the competitive outcome is largely decided early in the parasite’s growth phase, possibly mediated by direct interference or apparent competition. Conclusions Our results emphasize the importance of epidemiology as well as of various parasite traits in determining the outcome of within-host competition. Incorporating realistic epidemiological and ecological conditions when testing theoretical models of multiple infections, as well as using a wider range of host and parasite genotypes, will enable us to better understand the course of virulence evolution.
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Affiliation(s)
- Frida Ben-Ami
- Department of Zoology, George S, Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 6997801, Israel.
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26
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Chouvenc T, Efstathion CA, Elliott ML, Su NY. Resource competition between two fungal parasites in subterranean termites. Naturwissenschaften 2012; 99:949-58. [PMID: 23086391 DOI: 10.1007/s00114-012-0977-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Revised: 10/01/2012] [Accepted: 10/03/2012] [Indexed: 12/24/2022]
Abstract
Subterranean termites live in large groups in underground nests where the pathogenic pressure of the soil environment has led to the evolution of a complex interaction among individual and social immune mechanisms in the colonies. However, groups of termites under stress can show increased susceptibility to opportunistic parasites. In this study, an isolate of Aspergillus nomius Kurtzman, Horn & Hessltine was obtained from a collapsed termite laboratory colony. We determined that it was primarily a saprophyte and, secondarily, a facultative parasite if the termite immunity is undergoing a form of stress. This was determined by stressing individuals of the Formosan subterranean termite Coptotermes formosanus Shiraki via a co-exposure to the virulent fungal parasite Metarhizium anisopliae (Metch.) Sorokin. We also examined the dynamics of a mixed infection of A. nomius and M. anisopliae in a single termite host. The virulent parasite M. anisopliae debilitated the termite immune system, but the facultative, fast growing parasite A. nomius dominated the mixed infection process. The resource utilization strategy of A. nomius during the infection resulted in successful conidia production, while the chance for M. anisopliae to complete its life cycle was reduced. Our results also suggest that the occurrence of opportunistic parasites such as A. nomius in collapsing termite laboratory colonies is the consequence of a previous stress, not the cause of the stress.
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Affiliation(s)
- Thomas Chouvenc
- Department of Entomology and Nematology, Fort Lauderdale Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, 3205 College Avenue, Fort Lauderdale, FL 33314, USA.
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27
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Nutritional limitation and resistance to opportunistic Aspergillus parasites in honey bee larvae. J Invertebr Pathol 2012; 111:68-73. [PMID: 22750047 DOI: 10.1016/j.jip.2012.06.006] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Revised: 05/02/2012] [Accepted: 06/18/2012] [Indexed: 11/24/2022]
Abstract
Honey bees are threatened by land use changes which reduce the availability and diversity of pollen and nectar resources. There is concern that poor nutrition may be involved in recent population declines, either directly or due to indirect effects on immunocompetence. The larval stage is likely to be the most vulnerable to a poor diet, but the effects of larval nutrition on the disease susceptibility of bees are not well known. In this study we used laboratory-reared honey bee larvae to investigate the effects of diet quality on disease susceptibility to the opportunistic fungal parasites Aspergillus flavus, Aspergillus phoenicis and A. fumigatus. Larvae fed on a nutritionally poor diet were found to be significantly more susceptible to A. fumigatus. Larval resistance to A. fumigatus was enhanced by feeding with a diet supplemented with either dandelion or polyfloral pollens. This indicates that dandelion and polyfloral pollens contain elements that enhance resistance to this fungal disease, illustrating an interaction between nutrition and parasitism and emphasising the benefit of diverse floral resources in the environment to maintain honey bee health.
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28
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Mnyone LL, Lyimo IN, Lwetoijera DW, Mpingwa MW, Nchimbi N, Hancock PA, Russell TL, Kirby MJ, Takken W, Koenraadt CJM. Exploiting the behaviour of wild malaria vectors to achieve high infection with fungal biocontrol agents. Malar J 2012; 11:87. [PMID: 22449130 PMCID: PMC3337815 DOI: 10.1186/1475-2875-11-87] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Accepted: 03/26/2012] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Control of mosquitoes that transmit malaria has been the mainstay in the fight against the disease, but alternative methods are required in view of emerging insecticide resistance. Entomopathogenic fungi are candidate alternatives, but to date, few trials have translated the use of these agents to field-based evaluations of their actual impact on mosquito survival and malaria risk. Mineral oil-formulations of the entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana were applied using five different techniques that each exploited the behaviour of malaria mosquitoes when entering, host-seeking or resting in experimental huts in a malaria endemic area of rural Tanzania. RESULTS Survival of mosquitoes was reduced by 39-57% relative to controls after forcing upward house-entry of mosquitoes through fungus treated baffles attached to the eaves or after application of fungus-treated surfaces around an occupied bed net (bed net strip design). Moreover, 68 to 76% of the treatment mosquitoes showed fungal growth and thus had sufficient contact with fungus treated surfaces. A population dynamic model of malaria-mosquito interactions shows that these infection rates reduce malaria transmission by 75-80% due to the effect of fungal infection on adult mortality alone. The model also demonstrated that even if a high proportion of the mosquitoes exhibits outdoor biting behaviour, malaria transmission was still significantly reduced. CONCLUSIONS Entomopathogenic fungi strongly affect mosquito survival and have a high predicted impact on malaria transmission. These entomopathogens represent a viable alternative for malaria control, especially if they are used as part of an integrated vector management strategy.
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Affiliation(s)
- Ladslaus L Mnyone
- Biomedical and Environmental Group, Ifakara Health Institute, P.O. Box 53, Off Mlabani Passage, Ifakara, Tanzania
- Laboratory of Entomology, Wageningen University and Research Centre, P.O. Box 8031, 6700 EH Wageningen, The Netherlands
- Pest Management Centre, Sokoine University of Agriculture, P.O. Box 3110, Morogoro, Tanzania
| | - Issa N Lyimo
- Biomedical and Environmental Group, Ifakara Health Institute, P.O. Box 53, Off Mlabani Passage, Ifakara, Tanzania
- Faculty of Biomedical and Life Sciences, University of Glasgow, 120 University Place, G12 8TA Glasgow, UK
| | - Dickson W Lwetoijera
- Biomedical and Environmental Group, Ifakara Health Institute, P.O. Box 53, Off Mlabani Passage, Ifakara, Tanzania
| | - Monica W Mpingwa
- Biomedical and Environmental Group, Ifakara Health Institute, P.O. Box 53, Off Mlabani Passage, Ifakara, Tanzania
| | - Nuru Nchimbi
- Biomedical and Environmental Group, Ifakara Health Institute, P.O. Box 53, Off Mlabani Passage, Ifakara, Tanzania
| | | | - Tanya L Russell
- Biomedical and Environmental Group, Ifakara Health Institute, P.O. Box 53, Off Mlabani Passage, Ifakara, Tanzania
- The University of Queensland, School of Population Health, Australian Centre for Tropical and International Health, Brisbane 4006, Australia
- Vector Group, Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK
| | - Matthew J Kirby
- Biomedical and Environmental Group, Ifakara Health Institute, P.O. Box 53, Off Mlabani Passage, Ifakara, Tanzania
- Laboratory of Entomology, Wageningen University and Research Centre, P.O. Box 8031, 6700 EH Wageningen, The Netherlands
| | - Willem Takken
- Laboratory of Entomology, Wageningen University and Research Centre, P.O. Box 8031, 6700 EH Wageningen, The Netherlands
| | - Constantianus JM Koenraadt
- Laboratory of Entomology, Wageningen University and Research Centre, P.O. Box 8031, 6700 EH Wageningen, The Netherlands
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29
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Vojvodic S, Boomsma JJ, Eilenberg J, Jensen AB. Virulence of mixed fungal infections in honey bee brood. Front Zool 2012; 9:5. [PMID: 22444792 PMCID: PMC3384236 DOI: 10.1186/1742-9994-9-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2011] [Accepted: 03/23/2012] [Indexed: 11/16/2022] Open
Abstract
Introduction Honey bees, Apis mellifera, have a diverse community of pathogens. Previous research has mostly focused on bacterial brood diseases of high virulence, but milder diseases caused by fungal pathogens have recently attracted more attention. This interest has been triggered by partial evidence that co-infection with multiple pathogens has the potential to accelerate honey bee mortality. In the present study we tested whether co-infection with closely related fungal brood-pathogen species that are either specialists or non-specialist results in higher host mortality than infections with a single specialist. We used a specially designed laboratory assay to expose honey bee larvae to controlled infections with spores of three Ascosphaera species: A. apis, the specialist pathogen that causes chalkbrood disease in honey bees, A. proliperda, a specialist pathogen that causes chalkbrood disease in solitary bees, and A. atra, a saprophytic fungus growing typically on pollen brood-provision masses of solitary bees. Results We show for the first time that single infection with a pollen fungus A. atra may induce some mortality and that co-infection with A. atra and A. apis resulted in higher mortality of honey bees compared to single infections with A. apis. However, similar single and mixed infections with A. proliperda did not increase brood mortality. Conclusion Our results show that co-infection with a closely related fungal species can either increase or have no effect on host mortality, depending on the identity of the second species. Together with other studies suggesting that multiple interacting pathogens may be contributing to worldwide honey bee health declines, our results highlight the importance of studying effects of multiple infections, even when all interacting species are not known to be specialist pathogens.
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Affiliation(s)
- Svjetlana Vojvodic
- Center for Social Evolution, Department of Agriculture and Ecology Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK 1871 Frederiksberg C, Denmark.
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Krkošek M, Connors BM, Lewis MA, Poulin R. Allee Effects May Slow the Spread of Parasites in a Coastal Marine Ecosystem. Am Nat 2012; 179:401-12. [DOI: 10.1086/664458] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Evison SEF, Roberts KE, Laurenson L, Pietravalle S, Hui J, Biesmeijer JC, Smith JE, Budge G, Hughes WOH. Pervasiveness of parasites in pollinators. PLoS One 2012; 7:e30641. [PMID: 22347356 PMCID: PMC3273957 DOI: 10.1371/journal.pone.0030641] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2011] [Accepted: 12/24/2011] [Indexed: 11/18/2022] Open
Abstract
Many pollinator populations are declining, with large economic and ecological implications. Parasites are known to be an important factor in the some of the population declines of honey bees and bumblebees, but little is known about the parasites afflicting most other pollinators, or the extent of interspecific transmission or vectoring of parasites. Here we carry out a preliminary screening of pollinators (honey bees, five species of bumblebee, three species of wasp, four species of hoverfly and three genera of other bees) in the UK for parasites. We used molecular methods to screen for six honey bee viruses, Ascosphaera fungi, Microsporidia, and Wolbachia intracellular bacteria. We aimed simply to detect the presence of the parasites, encompassing vectoring as well as actual infections. Many pollinators of all types were positive for Ascosphaera fungi, while Microsporidia were rarer, being most frequently found in bumblebees. We also detected that most pollinators were positive for Wolbachia, most probably indicating infection with this intracellular symbiont, and raising the possibility that it may be an important factor in influencing host sex ratios or fitness in a diversity of pollinators. Importantly, we found that about a third of bumblebees (Bombus pascuorum and Bombus terrestris) and a third of wasps (Vespula vulgaris), as well as all honey bees, were positive for deformed wing virus, but that this virus was not present in other pollinators. Deformed wing virus therefore does not appear to be a general parasite of pollinators, but does interact significantly with at least three species of bumblebee and wasp. Further work is needed to establish the identity of some of the parasites, their spatiotemporal variation, and whether they are infecting the various pollinator species or being vectored. However, these results provide a first insight into the diversity, and potential exchange, of parasites in pollinator communities.
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Affiliation(s)
- Sophie E. F. Evison
- Institute of Integrative and Comparative
Biology, University of Leeds, Leeds, United Kingdom
| | - Katherine E. Roberts
- Institute of Integrative and Comparative
Biology, University of Leeds, Leeds, United Kingdom
| | - Lynn Laurenson
- National Bee Unit, Food and Environment
Research Agency, York, United Kingdom
| | | | - Jeffrey Hui
- Center for Infection and Immunity, Columbia
University, New York, New York, United States of America
| | - Jacobus C. Biesmeijer
- Institute of Integrative and Comparative
Biology, University of Leeds, Leeds, United Kingdom
- Netherlands Centre for Biodiversity NCB
Naturalis, Leiden, The Netherlands
| | - Judith E. Smith
- School of Environment and Life Sciences,
University of Salford, Salford, United Kingdom
| | - Giles Budge
- National Bee Unit, Food and Environment
Research Agency, York, United Kingdom
| | - William O. H. Hughes
- Institute of Integrative and Comparative
Biology, University of Leeds, Leeds, United Kingdom
- * E-mail:
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Graystock P, Hughes WOH. Disease resistance in a weaver ant, Polyrhachis dives, and the role of antibiotic-producing glands. Behav Ecol Sociobiol 2011. [DOI: 10.1007/s00265-011-1242-y] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Abstract
OBJECTIVE Unravelling the determinants of parasite life-history traits in natural settings is complex. Here, we deciphered the relationships between biotic, abiotic factors and the variation in 4 life-history traits (body size, egg presence, egg number and egg size) in the fish ectoparasite Tracheliastes polycolpus. We then determined the factors affecting the strength of the trade-off between egg number and egg size. METHODS To do so, we used 4-level (parasite, microhabitat, host and environment) hierarchical models coupled to a field database. RESULTS Variation in life-history traits was mostly due to individual characteristics measured at the parasite level. At the microhabitat level (fins of fish hosts), parasite number was positively related to body size, egg presence and egg number. Higher parasite number on fins was positively associated with individual parasite fitness. At the host level, host body size was positively related to the individual fitness of the parasite; parasites were bigger and more fecund on bigger hosts. In contrast, factors measured at the environmental level had a weak influence on life-history traits. Finally, a site-dependent trade-off between egg number and egg size existed in this population. CONCLUSION Our study illustrates the importance of considering parasite life-history traits in a hierarchical framework to decipher complex links between biotic, abiotic factors and parasite life-history traits.
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Ben-Ami F, Rigaud T, Ebert D. The expression of virulence during double infections by different parasites with conflicting host exploitation and transmission strategies. J Evol Biol 2011; 24:1307-16. [PMID: 21481055 DOI: 10.1111/j.1420-9101.2011.02264.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
In many natural populations, hosts are found to be infected by more than one parasite species. When these parasites have different host exploitation strategies and transmission modes, a conflict among them may arise. Such a conflict may reduce the success of both parasites, but could work to the benefit of the host. For example, the less-virulent parasite may protect the host against the more-virulent competitor. We examine this conflict using the waterflea Daphnia magna and two of its sympatric parasites: the blood-infecting bacterium Pasteuria ramosa that transmits horizontally and the intracellular microsporidium Octosporea bayeri that can concurrently transmit horizontally and vertically after infecting ovaries and fat tissues of the host. We quantified host and parasite fitness after exposing Daphnia to one or both parasites, both simultaneously and sequentially. Under conditions of strict horizontal transmission, Pasteuria competitively excluded Octosporea in both simultaneous and sequential double infections, regardless of the order of exposure. Host lifespan, host reproduction and parasite spore production in double infections resembled those of single infection by Pasteuria. When hosts became first vertically (transovarilly) infected with O. bayeri, Octosporea was able to withstand competition with P. ramosa to some degree, but both parasites produced less transmission stages than they did in single infections. At the same time, the host suffered from reduced fecundity and longevity. Our study demonstrates that even when competing parasite species utilize different host tissues to proliferate, double infections lead to the expression of higher virulence and ultimately may select for higher virulence. Furthermore, we found no evidence that the less-virulent and vertically transmitting O. bayeri protects its host against the highly virulent P. ramosa.
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Affiliation(s)
- F Ben-Ami
- Department of Zoology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.
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Staves PA, Knell RJ. Virulence and competitiveness: testing the relationship during inter- and intraspecific mixed infections. Evolution 2011; 64:2643-52. [PMID: 20394652 DOI: 10.1111/j.1558-5646.2010.00999.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Understanding the reasons why different parasites cause different degrees of harm to their hosts is an important objective in evolutionary biology. One group of models predicts that if hosts are infected with more than one strain or species of parasite, then competition between the parasites will select for higher virulence. While this idea makes intuitive sense, empirical data to support it are rare and equivocal. We investigated the relationship between fitness and virulence during both inter- and intraspecific competition for a fungal parasite of insects, Metarhizium anisopliae. Contrary to theoretical expectations, competition favored parasite strains with either a lower or a higher virulence depending on the competitor: when in interspecific competition with an entomopathogenic nematode, Steinernema feltiae, less virulent strains of the fungus were more successful, but when competing against conspecific fungi, more virulent strains were better competitors. We suggest that the nature of competition (direct via toxin production when competing against the nematode, indirect via exploitation of the host when competing against conspecific fungal strains) determines the relationship between virulence and competitive ability.
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Affiliation(s)
- Peter A Staves
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, United Kingdom.
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Mnyone LL, Koenraadt CJ, Lyimo IN, Mpingwa MW, Takken W, Russell TL. Anopheline and culicine mosquitoes are not repelled by surfaces treated with the entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana. Parasit Vectors 2010; 3:80. [PMID: 20799937 PMCID: PMC2939606 DOI: 10.1186/1756-3305-3-80] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Accepted: 08/27/2010] [Indexed: 11/25/2022] Open
Abstract
Background Entomopathogenic fungi, Metarhizium anisopliae and Beauveria bassiana, are promising bio-pesticides for application against adult malaria mosquito vectors. An understanding of the behavioural responses of mosquitoes towards these fungi is necessary to guide development of fungi beyond the 'proof of concept' stage and to design suitable intervention tools. Methods Here we tested whether oil-formulations of the two fungi could be detected and avoided by adult Anopheles gambiae s.s., Anopheles arabiensis and Culex quinquefasciatus. The bioassays used a glass chamber divided into three compartments (each 250 × 250 × 250 mm): release, middle and stimulus compartments. Netting with or without fungus was fitted in front of the stimulus compartment. Mosquitoes were released and the proportion that entered the stimulus compartment was determined and compared between treatments. Treatments were untreated netting (control 1), netting with mineral oil (control 2) and fungal conidia formulated in mineral oil evaluated at three different dosages (2 × 1010, 4 × 1010 and 8 × 1010 conidia m-2). Results Neither fungal strain was repellent as the mean proportion of mosquitoes collected in the stimulus compartment did not differ between experiments with surfaces treated with and without fungus regardless of the fungal isolate and mosquito species tested. Conclusion Our results indicate that mineral-oil formulations of M. anisopliae and B. bassiana were not repellent against the mosquito species tested. Therefore, both fungi are suitable candidates for the further development of tools that aim to control host-seeking or resting mosquitoes using entomopathogenic fungi.
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Affiliation(s)
- Ladslaus L Mnyone
- Biomedical and Environmental Group, Ifakara Health Institute, P,O, Box 53, Off Mlabani Passage, Ifakara, Tanzania.
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Morelos-Juárez C, Walker TN, Lopes JF, Hughes WO. Ant farmers practice proactive personal hygiene to protect their fungus crop. Curr Biol 2010; 20:R553-4. [DOI: 10.1016/j.cub.2010.04.047] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Cheun HI, Cho SH, Lee JH, Lim YY, Jeon JH, Yu JR, Kim TS, Lee WJ, Cho SH, Lee DY, Park MS, Jeong HS, Chen DS, Ji YM, Kwon MH. Infection status of hospitalized diarrheal patients with gastrointestinal protozoa, bacteria, and viruses in the Republic of Korea. THE KOREAN JOURNAL OF PARASITOLOGY 2010; 48:113-20. [PMID: 20585526 DOI: 10.3347/kjp.2010.48.2.113] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2010] [Revised: 04/15/2010] [Accepted: 04/21/2010] [Indexed: 11/23/2022]
Abstract
To understand protozoan, viral, and bacterial infections in diarrheal patients, we analyzed positivity and mixed-infection status with 3 protozoans, 4 viruses, and 10 bacteria in hospitalized diarrheal patients during 2004-2006 in the Republic of Korea. A total of 76,652 stool samples were collected from 96 hospitals across the nation. The positivity for protozoa, viruses, and bacteria was 129, 1,759, and 1,797 per 10,000 persons, respectively. Especially, Cryptosporidium parvum was highly mixed-infected with rotavirus among pediatric diarrheal patients (29.5 per 100 C. parvum positive cases), and Entamoeba histolytica was mixed-infected with Clostridium perfringens (10.3 per 100 E. histolytica positive cases) in protozoan-diarrheal patients. Those infected with rotavirus and C. perfringens constituted relatively high proportions among mixed infection cases from January to April. The positivity for rotavirus among viral infection for those aged < or = 5 years was significantly higher, while C. perfringens among bacterial infection was higher for > or = 50 years. The information for association of viral and bacterial infections with enteropathogenic protozoa in diarrheal patients may contribute to improvement of care for diarrhea as well as development of control strategies for diarrheal diseases in Korea.
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Affiliation(s)
- Hyeng-Il Cheun
- Department of Malaria and Parasitic Diseases, Korea National Institute of Health, Korea Centers for Disease Control and Prevention, Seoul, Korea.
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Choisy M, de Roode J. Mixed Infections and the Evolution of Virulence: Effects of Resource Competition, Parasite Plasticity, and Impaired Host Immunity. Am Nat 2010; 175:E105-18. [DOI: 10.1086/651587] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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40
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Abstract
Social insects have evolved a suite of sophisticated defences against parasites. In addition to the individual physiological immune response, social insects also express ‘social immunity’ consisting of group-level defences and behaviours that include allogrooming. Here we investigate whether the social immune response of the leaf-cutting ant Acromyrmex echinatior reacts adaptively to the virulent fungal parasite, Metarhizium anisopliae. We ‘immunized’ mini-nests of the ants by exposing them twice to the parasite and then compared their social immune response with that of naive mini-nests that had not been experimentally exposed to the parasite. Ants allogroomed individuals exposed to the parasite, doing this both for those freshly treated with the parasite, which were infectious but not yet infected, and for those treated 2 days previously, which were already infected but no longer infectious. We found that ants exposed to the parasite received more allogrooming in immunized mini-nests than in naive mini-nests. This increased the survival of the freshly treated ants, but not those that were already infected. The results thus indicate that the social immune response of this leaf-cutting ant is adaptive, with the group exhibiting a greater and more effective response to a parasite that it has previously been exposed to.
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Affiliation(s)
- Tom N Walker
- Institute of Integrative and Comparative Biology, University of Leeds, Leeds, UK
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41
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Kleindorfer S, Dudaniec RY. Love thy neighbour? Social nesting pattern, host mass and nest size affect ectoparasite intensity in Darwin’s tree finches. Behav Ecol Sociobiol 2009. [DOI: 10.1007/s00265-008-0706-1] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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42
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Alizon S. Decreased overall virulence in coinfected hosts leads to the persistence of virulent parasites. Am Nat 2008; 172:E67-79. [PMID: 18582168 DOI: 10.1086/588077] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Multiple infections are known to affect virulence evolution. Some studies even show that coinfections may decrease the overall virulence (the disease-induced mortality of a coinfected host). Yet, epidemiological studies tend to overlook the overall virulence, and within-host models tend to ignore epidemiological processes. Here, I develop an epidemiological model where overall virulence is an explicit function of the virulence of the coinfecting strains. I show that in most cases, a unique strain is evolutionarily stable (in accordance with the model I use here). However, when the overall virulence is lower than the virulence of each of the coinfecting strains (i.e., when coinfections decrease virulence), the evolutionary equilibrium may be invaded by highly virulent strains, leading to the coexistence of two strains on an evolutionary timescale. This model has theoretical and experimental implications: it underlines the importance of overall virulence and of epidemiological feedbacks on virulence evolution.
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Affiliation(s)
- Samuel Alizon
- Department of Mathematics and Statistics, Queen's University, Jeffery Hall, Kingston, Ontario K7L 3N6, Canada.
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Ben-Ami F, Mouton L, Ebert D. THE EFFECTS OF MULTIPLE INFECTIONS ON THE EXPRESSION AND EVOLUTION OF VIRULENCE IN ADAPHNIA-ENDOPARASITE SYSTEM. Evolution 2008; 62:1700-1711. [DOI: 10.1111/j.1558-5646.2008.00391.x] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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44
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Ben-Ami F, Regoes RR, Ebert D. A quantitative test of the relationship between parasite dose and infection probability across different host-parasite combinations. Proc Biol Sci 2008; 275:853-9. [PMID: 18198145 DOI: 10.1098/rspb.2007.1544] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Epidemiological models generally assume that the number of susceptible individuals that become infected within a unit of time depends on the density of the hosts and the concentration of parasites (i.e. mass-action principle). However, empirical studies have found significant deviations from this assumption due to biotic and abiotic factors, such as seasonality, the spatial structure of the host population and host heterogeneity with respect to immunity and susceptibility. In this paper, we examine the effect of the dose level of the bacterial endoparasite Pasteuria ramosa on the infection rate of its host, the water flea Daphnia magna. Using seven host clones and two parasite isolates, we measure the fraction of infected hosts after exposure to eight different parasite doses to determine whether there is variation in the infection process across different host clone-parasite isolate combinations. In five combinations, a pronounced dose-dependent infection pattern was found. Using a likelihood approach, we compare the infection data of these five combinations to the fit of three mathematical models: a mass-action model, a parasite antagonism model (i.e. an increase in the parasite dose leads to an under-proportionate increase in the infection rate per host) and a heterogeneous host model. We found that the host heterogeneity model, in which we assumed the existence of non-inherited phenotypic differences in host susceptibilities to the parasite, provides the best fit. Our analysis suggests that among 5 out of the 14 host clone-parasite isolate combinations that resulted in appreciable infections, non-genetic host heterogeneity plays an important role.
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Affiliation(s)
- Frida Ben-Ami
- Zoologisches Institut, Evolutionsbiologie, Universität Basel, Vesalgasse 1, 4051 Basel, Switzerland.
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45
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Devi UK, Reineke A, Rao UCM, Reddy NRN, Khan APA. AFLP and single-strand conformation polymorphism studies of recombination in the entomopathogenic fungus Nomuraea rileyi. ACTA ACUST UNITED AC 2007; 111:716-25. [PMID: 17604614 DOI: 10.1016/j.mycres.2007.03.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2006] [Revised: 01/18/2007] [Accepted: 03/02/2007] [Indexed: 11/30/2022]
Abstract
In most putative asexual fungi analysed through population genetic studies, recombination has been detected. However, the mechanism by which it is achieved is still not known. A parasexual cycle is known to occur in asexual fungi but there is no evidence, as yet, of its prevalence in natural populations. This study was undertaken to investigate the possibility of a parasexual cycle mediating recombination in the mitosporic fungus Nomuraea rileyi. The genotypic diversity in isolates sampled from an epizootic population from South India was studied through AFLP. The AFLP data were subjected to analysis of molecular variance (AMOVA) and cluster analysis. Great genetic variation was observed in the population including the isolates from a single insect. To assess the occurrence of recombination in the population, single-strand conformation polymorphism (SSCP) of partial regions of two mitochondrial (mt) genes (rRNA genes of LSU and SSU) and a nuclear gene (beta tubulin) was performed. The SSCP data were analysed using MP, the tree length permutation test, and multilocus analysis. Recombination was inferred from the SSCP analysis. The occurrence of isolates with diverse genotypes in a single insect; the fact that fungi multiply as hyphal bodies (cell wall-less) in the insect haemolymph; and the inference of recombination in mitochondrial genes (suggesting cytomixis), all indicate that recombination is accomplished by fusion of hyphal bodies of different isolates infecting the insect.
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Affiliation(s)
- Uma K Devi
- Department of Botany, Andhra University, Visakhapatnam, 530 003, Andhra Pradesh, India.
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Kurtz J, Hammerschmidt K. Resistance against heterogeneous sequential infections: experimental studies with a tapeworm and its copepod host. J Helminthol 2007; 80:199-206. [PMID: 16768863 DOI: 10.1079/joh2006349] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Parasite heterogeneity is thought to be an important factor influencing the likelihood and the dynamics of infection. Previous studies have demonstrated that simultaneous exposure of hosts to a heterogeneous mixture of parasites might increase infection success. Here this view is extended towards the effect of parasite heterogeneity on subsequent infections. Using a system of the tapeworm Schistocephalus solidus and its copepod intermediate host, heterogeneity of the tapeworm surface carbohydrates is investigated, i.e. structures that are potentially recognized by the invertebrate host's immune system. With lectin labelling, a significant proportion of variation in surface carbohydrates is related to differences in worm sibships (i.e. families). Tapeworm sibships were used for experimental exposure of copepods to either homogeneous combinations of tapeworm larvae, i.e. worms derived from the same sibship or heterogeneous mixtures of larvae, and copepods were subsequently challenged with an unrelated larva to study re-infection. Contrary to expectation, neither an effect of parasite heterogeneity on the current infection, nor on re-infection were found. The effect of parasitic heterogeneity on host immunity is therefore complex, potentially involving increased cross-protection on the one hand, with higher costs of raising a more heterogeneous immune response on the other.
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Affiliation(s)
- J Kurtz
- Department of Evolutionary Ecology, Max Planck Institute of Limnology, August-Thienemann-Str. 2, 24306 Plön, Germany.
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Abstract
Much evolutionary theory assumes that parasite virulence (i.e. parasite-induced host mortality) is determined by within-host parasite reproduction and by the specific parasite genotypes causing infection. However, many other factors could influence the level of virulence experienced by hosts. We studied the protozoan parasite Ophryocystis elektroscirrha in its host, the monarch butterfly, Danaus plexippus. We exposed monarch larvae to wild-isolated parasites and assessed the effects of within-host replication and parasite genotype on host fitness measures, including pre-adult development time and adult weight and longevity. Per capita replication rates of parasites were high, and infection resulted in high parasite loads. Of all host fitness traits, adult longevity showed the clearest relationship with infection status, and decreased continuously with increasing parasite loads. Parasite genotypes differed in their virulence, and these differences were maintained across ecologically relevant variables, including inoculation dose, host sex and host age at infection. Thus, virulence appears to be a robust genetic parasite trait in this system. Although parasite loads and genotypes had strong effects on virulence, inoculation dose, host sex and age at infection were also important. These results have implications for virulence evolution and emphasize the need for a detailed understanding of specific host-parasite systems for addressing theory.
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Affiliation(s)
- J C de Roode
- Department of Environmental Studies, Emory University, Atlanta, GA 30322, USA.
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48
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Abstract
Polyandry is often difficult to explain because benefits of the behaviour have proved elusive. In social insects, polyandry increases the genetic diversity of workers within a colony and this has been suggested to improve the resistance of the colony to disease. Here we examine the possible impact of host genetic diversity on parasite evolution by carrying out serial passages of a virulent fungal pathogen through leaf-cutting ant workers of known genotypes. Parasite virulence increased over the nine-generation span of the experiment while spore production decreased. The effect of host relatedness upon virulence appeared limited. However, parasites cycled through more genetically diverse hosts were more likely to go extinct during the experiment and parasites cycled through more genetically similar hosts had greater spore production. These results indicate that host genetic diversity may indeed hinder the ability of parasites to adapt while cycling within social insect colonies.
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Affiliation(s)
- W O H Hughes
- Department of Population Biology, Institute of Biology, University of Copenhagen, Copenhagen, Denmark.
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Devi KU, Rao CUM. Allee effect in the infection dynamics of the entomopathogenic Fungus Beauveria bassiana (Bals) Vuill. on the beetle, Mylabris pustulata. Mycopathologia 2006; 161:385-94. [PMID: 16761186 DOI: 10.1007/s11046-006-0020-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2005] [Accepted: 01/24/2006] [Indexed: 10/24/2022]
Abstract
Successful infection by Beauveria bassiana as with all other entomopathogenic fungi, is accomplished only at a high conidial dose while, theoretically, a single conidium should be sufficient. Indeed, this is a major deterrent in its use as a biocontrol agent. High pathogen load for infection is required by organisms which display 'Allee' effect. In such organisms, a threshold exists for pathogen dose, below which no infection can be caused. B. bassiana has a semelparous life cycle and, therefore, its infection dynamics are expected to conform to the mass action principle with a linear relationship between dose and successful infection observable as mortality of the insect. Whether the need for a high conidial dose to induce insect mortality by B. bassiana is due to the operation of Allee effect was examined. A sample of 34 isolates was bioassayed on Mylabris pustulata (Coleoptera: Meloidae) at four conidial concentrations. With more than half of the isolates in the sample, the lowest dose tested (10(4) conidia/insect) did not cause insect mortality. Thus, a threshold pathogen load is required to cause successful infection. In these isolates, the dose-mortality relationship was sigmoid. Allee effect is thus identified in the infection dynamics of B. bassiana-M. pustulata system. The isolates that induced mortality at the lowest dose tested are concluded to be highly virulent with a lower threshold dose required for successful infection. With some isolates, at high conidial dose, the infection rate decreased either due to a decrease in the proportion of insects showing mycosis, to the speed of death, or both. Such a response could result from intra scramble competition arising from overload of pathogen at very high dose.
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Affiliation(s)
- K Uma Devi
- Department of Botany, Andhra University, Visakhapatnam, AP, India.
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