{"120711":{"#nid":"120711","#data":{"type":"news","title":"Weakness Can Be an Advantage in Surviving Deadly Parasites, a New Study Shows","body":[{"value":"\u003Cp\u003EWhen battling an epidemic of a deadly parasite, less resistance can sometimes be better than more, a new study suggests.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EA freshwater zooplankton species known as \u003Cem\u003EDaphnia dentifera\u003C\/em\u003E endures periodic epidemics of a virulent yeast parasite that can infect more than 60 percent of the \u003Cem\u003EDaphnia\u003C\/em\u003E population. During these epidemics, the \u003Cem\u003EDaphnia \u003C\/em\u003Epopulation evolves quickly, balancing infection resistance and reproduction.\u003C\/p\u003E\u003Cp\u003EA new study led by Georgia Institute of Technology researchers reveals that the number of vertebrate predators in the water and the amount of food available for \u003Cem\u003EDaphnia \u003C\/em\u003Eto eat influence the size of the epidemics and how these \u201cwater fleas\u201d evolve during epidemics to survive.\u003C\/p\u003E\u003Cp\u003EThe study shows that lakes with high nutrient concentrations and lower predation levels exhibit large epidemics and \u003Cem\u003EDaphnia \u003C\/em\u003Ethat become more resistant to infection by the yeast \u003Cem\u003EMetschnikowia bicuspidata\u003C\/em\u003E. However, in lakes with fewer resources and high predation, epidemics remain small and \u003Cem\u003EDaphnia \u003C\/em\u003Eevolve increased susceptibility to the parasite.\u003C\/p\u003E\u003Cp\u003E\u201cIt\u2019s counterintuitive to think that hosts would ever evolve greater susceptibility to virulent parasites during an epidemic, but we found that ecological factors determine whether it is better for them to evolve enhanced resistance or susceptibility to infection,\u201d said the study\u2019s lead author \u003Ca href=\u0022http:\/\/www.biology.gatech.edu\/people\/meghan-duffy\u0022 target=\u0022_blank\u0022\u003EMeghan Duffy\u003C\/a\u003E, an assistant professor in the \u003Ca href=\u0022http:\/\/www.biology.gatech.edu\u0022 target=\u0022_blank\u0022\u003ESchool of Biology\u003C\/a\u003E at Georgia Tech. \u201cThere is a trade-off between resistance and reproduction because any resources an animal devotes to defense are not available for reproduction. When ecological factors favor small epidemics, it is better for hosts to invest in reproduction rather than defense.\u201d\u003C\/p\u003E\u003Cp\u003EThis study was published in the March 30, 2012 issue of the journal \u003Ca href=\u0022http:\/\/www.sciencemag.org\/lookup\/doi\/10.1126\/science.1215429\u0022 target=\u0022_blank\u0022\u003E\u003Cem\u003EScience\u003C\/em\u003E\u003C\/a\u003E. The research was supported by the National Science Foundation and the James S. McDonnell Foundation.\u003C\/p\u003E\u003Cp\u003EIn addition to Duffy, also contributing to this study were Indiana University Department of Biology associate professor Spencer Hall and graduate student David Civitello; Christopher Klausmeier, an associate professor in the Department of Plant Biology and W.K. Kellogg Biological Station at Michigan State University; and Georgia Tech research technician Jessica Housley Ochs and graduate student Rachel Penczykowski.\u003C\/p\u003E\u003Cp\u003EFor the study, the researchers monitored the levels of nutritional resources, predation and parasitic infection in seven Indiana lakes on a weekly basis for a period of four months. They calculated infection prevalence visually on live hosts using established survey methods, estimated resources by measuring the levels of phosphorus and nitrogen in the water, and assessed predation by measuring the size of uninfected adult \u003Cem\u003EDaphnia\u003C\/em\u003E.\u003C\/p\u003E\u003Cp\u003EThe researchers also conducted infection assays in the laboratory on \u003Cem\u003EDaphnia\u003C\/em\u003E collected from each of the seven lake populations at two time points: in late July before epidemics began and in mid-November as epidemics waned. The assays measured the zooplankton\u2019s uptake of \u003Cem\u003EMetschnikowia bicuspidata\u003C\/em\u003E and infectivity of the yeast once consumed.\u003C\/p\u003E\u003Cp\u003EThe infection assays showed a significant evolutionary response of \u003Cem\u003EDaphnia\u003C\/em\u003E to epidemics in six of the seven lake populations. The \u003Cem\u003EDaphnia\u003C\/em\u003E population became significantly more resistant to infection in three lakes and significantly more susceptible to infection in three other lakes. The hosts in the seventh lake did not show a significant change in susceptibility, but trended toward increased resistance. In the six lake populations that showed a significant evolutionary response, epidemics were larger when lakes had lower predation and higher levels of total nitrogen.\u003C\/p\u003E\u003Cp\u003E\u201c\u003Cem\u003EDaphnia\u003C\/em\u003E became more susceptible to the yeast in lakes with fewer resources and higher vertebrate predation, but evolved toward increased resistance in lakes with increased resources and lower predation,\u201d noted Duffy.\u003C\/p\u003E\u003Cp\u003EThe study\u2019s combination of observations, experiments and mathematical modeling support the researchers\u2019 theoretical prediction that when hosts face a resistance-reproduction tradeoff, they evolve increased resistance to infection during larger epidemics and increased susceptibility during smaller ones. Ultimately, ecological gradients, through their effects on epidemic size, influence evolutionary outcomes of hosts during epidemics.\u003C\/p\u003E\u003Cp\u003E\u201cWhile the occurrence and magnitude of disease outbreaks can strongly influence host evolution, this study suggests that altering predation pressure on hosts and productivity of ecosystems may also influence this evolution,\u201d added Duffy.\u003C\/p\u003E\u003Cp\u003EThe team plans to repeat the study this summer in the same Indiana lakes to examine whether the relationships between ecological factors, epidemic size and host evolution they found in this study can be corroborated.\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThis work was supported in part by the National Science Foundation (NSF) (Award Nos. DEB-0841679, DEB-0841817, DEB-0845825 and OCE-171 0928819). The content is solely the responsibility of the principal investigators and does not necessarily represent the official views of the NSF.\u003C\/em\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EResearch News \u0026amp; Publications Office\u003Cbr \/\u003E Georgia Institute of Technology\u003Cbr \/\u003E 75 Fifth Street, N.W., Suite 314\u003Cbr \/\u003E Atlanta, Georgia 30308 USA\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EMedia Relations Contacts:\u003C\/strong\u003E Abby Robinson (abby@innovate.gatech.edu; 404-385-3364) or John Toon (jtoon@gatech.edu; 404-894-6986)\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EWriter: \u003C\/strong\u003EAbby Robinson\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EWhen battling an epidemic of a deadly parasite, less resistance can sometimes be better than more. A new study suggests that a lake\u2019s ecological characteristics influence how freshwater zooplankton \u003Cem\u003EDaphnia dentifera\u003C\/em\u003E evolve to survive epidemics of a virulent yeast parasite \u003Cem\u003EMetschnikowia bicuspidate\u003C\/em\u003E. The study found that \u003Cem\u003EDaphnia\u003C\/em\u003E populations evolved either enhanced resistance or susceptibility to infection depending on the nutrient concentration and predation levels in the lake.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"When battling an epidemic of a deadly parasite, less resistance can sometimes be better than more, a new study suggests."}],"uid":"27206","created_gmt":"2012-03-29 15:04:30","changed_gmt":"2016-10-08 03:11:56","author":"Abby Vogel Robinson","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2012-03-29T00:00:00-04:00","iso_date":"2012-03-29T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"120671":{"id":"120671","type":"image","title":"Daphnia-infected-uninfected-Metschnikowia","body":null,"created":"1449178279","gmt_created":"2015-12-03 21:31:19","changed":"1475894478","gmt_changed":"2016-10-08 02:41:18","alt":"Daphnia-infected-uninfected-Metschnikowia","file":{"fid":"194370","name":"6-daphnia-infected-uninfected-metschnikowia.jpg","image_path":"\/sites\/default\/files\/images\/6-daphnia-infected-uninfected-metschnikowia_0.jpg","image_full_path":"http:\/\/hg.gatech.edu\/\/sites\/default\/files\/images\/6-daphnia-infected-uninfected-metschnikowia_0.jpg","mime":"image\/jpeg","size":244577,"path_740":"http:\/\/hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/6-daphnia-infected-uninfected-metschnikowia_0.jpg?itok=6hm4n7Z0"}},"120691":{"id":"120691","type":"image","title":"Daphnia-infected-uninfected-Metschnikowia","body":null,"created":"1449178279","gmt_created":"2015-12-03 21:31:19","changed":"1475894741","gmt_changed":"2016-10-08 02:45:41","alt":"Daphnia-infected-uninfected-Metschnikowia","file":{"fid":"194372","name":"2-daphnia-infected-uninfected-metschnikowia.jpg","image_path":"\/sites\/default\/files\/images\/2-daphnia-infected-uninfected-metschnikowia_0.jpg","image_full_path":"http:\/\/hg.gatech.edu\/\/sites\/default\/files\/images\/2-daphnia-infected-uninfected-metschnikowia_0.jpg","mime":"image\/jpeg","size":117962,"path_740":"http:\/\/hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/2-daphnia-infected-uninfected-metschnikowia_0.jpg?itok=L7XJUtW_"}},"120681":{"id":"120681","type":"image","title":"Downing Lake Indiana","body":null,"created":"1449178279","gmt_created":"2015-12-03 21:31:19","changed":"1475894478","gmt_changed":"2016-10-08 02:41:18","alt":"Downing Lake Indiana","file":{"fid":"194371","name":"downing-lake.jpg","image_path":"\/sites\/default\/files\/images\/downing-lake_0.jpg","image_full_path":"http:\/\/hg.gatech.edu\/\/sites\/default\/files\/images\/downing-lake_0.jpg","mime":"image\/jpeg","size":387747,"path_740":"http:\/\/hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/downing-lake_0.jpg?itok=jCVV356B"}}},"media_ids":["120671","120691","120681"],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"154","name":"Environment"},{"id":"146","name":"Life Sciences and Biology"},{"id":"135","name":"Research"}],"keywords":[{"id":"4896","name":"College of Sciences"},{"id":"9263","name":"daphnia"},{"id":"28811","name":"Daphnia dentifera"},{"id":"8356","name":"epidemic"},{"id":"9262","name":"lake"},{"id":"13456","name":"Meghan Duffy"},{"id":"28821","name":"Metschnikowia bicuspidata"},{"id":"7631","name":"parasite"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003EAbby Robinson\u003Cbr \/\u003E Research News and Publications\u003Cbr \/\u003E \u003Ca href=\u0022mailto:abby@innovate.gatech.edu\u0022\u003Eabby@innovate.gatech.edu\u003C\/a\u003E\u003Cbr \/\u003E 404-385-3364\u003C\/p\u003E","format":"limited_html"}],"email":[],"slides":[],"orientation":[],"userdata":""}}}