Behavior out of control: experimental evolution of resistance to host manipulation

Many parasites alter their host's phenotype in a manner that enhances their own fitness beyond the benefits they would gain from normal exploitation. Such host manipulation is rarely consistent with the host's best interests resulting in suboptimal and often fatal behavior from the host's perspective. In this case, hosts should evolve resistance to host manipulation. The cestode Schistocephalus solidus manipulates the behavior of its first intermediate copepod host to reduce its predation susceptibility and avoid fatal premature predation before the parasite is ready for transmission to its subsequent host. Thereafter, S. solidus increases host activity to facilitate transmission. If successful, this host manipulation is necessarily fatal for the host. I selected the copepod Macrocyclops albidus, a first intermediate host of S. solidus, for resistance or susceptibility to host manipulation to investigate their evolvability. Selection on the host indeed increased host manipulation in susceptible and reduced host manipulation in resistant selection lines. Interestingly, this seemed to be at least partly due to changes in the baseline levels of the modified trait (activity) rather than actual changes in resistance or susceptibility to host manipulation. Hence, hosts seem restricted in how rapidly and efficiently they can evolve resistance to host manipulation

Evolutionary ecology of host manipulation by parasites

Many parasites have the ability to change their host’s behavior and/ or appearance in a manner that enhances their fitness. It can be difficult to determine whether this is due to true host manipulation that has evolved for this specific purpose or side-effects e.g. from additional energy drain that shifts the host’s tradeoff between feeding and predation avoidance towards the former. Experimentally, host manipulation has mostly been studied using singly infected hosts in uniform environments. This does not reflect nature. If hosts harbor multiple parasites these parasites might, depending on their aims, be at a conflict over host manipulation or cooperate when it comes to host manipulation. In this thesis I aim to better understand how parasites manipulate their hosts under complex – and hence more natural conditions, such as infections by multiple parasites. To do so, I use two complex-life cycle parasites, the cestode Schistocephalus solidus and both its intermediated hosts, copepods and three-spined sticklebacks and the nematode Camallanus lacustris and its first intermediate copepod host. Both parasites alter the behavior of their hosts in a manner likely to enhance their own fitness. Whether host manipulation by S. solidus in three-spined sticklebacks is due to true host manipulation that has evolved for this purpose or presents a side-effect of increased energy drain is the issue of a long standing debate. With true host manipulation an infective and a not yet infective S. solidus in the same host should be at a conflict over the direction of host manipulation; the infective parasite should enhance the predation risk of its host, but for the not yet infective one any premature predation would be fatal; it should never enhance its host’s risk taking. However, when I experimentally infected sticklebacks in a manner that they harbored one infective and one not yet infective parasite, these were even less risk averse than sticklebacks infected by only an infective parasite. This is only compatible with behavioral changes caused by enhanced energy drain rather than true host manipulation. To verify these findings I tested the effect of hunger status on risk taking in infected sticklebacks. Energy drain should be ineffective in satiated fish but true host manipulation should not. Again the results are more compatible with energy drain rather than true host manipulation. Seemingly adaptive host manipulation need not be caused by mechanisms that have evolved for this specific purpose. I further investigated a conflict between an infective and a not yet infective parasite in copepod hosts. To do so, I experimentally infected copepods with one or two S. solidus and/ or C. lacustris at different time points. Not yet infective S. solidus or C. lacustris reduce their host’s activity, infective ones increase it. If a conflict occurred between different developmental stages of the same species, the infective parasite completely sabotaged host manipulation by the not yet infective one in either species. In an interspecific conflict too, the infective parasite performed better. Camallanus lacustris was however the stronger manipulator. A conflict between an infective C. lacustris and a not yet infective S. solidus resulted in complete sabotage by the infective parasite while such a conflict between an infective S. solidus and a not yet infective C. lacustris resulted in a compromise with regards to host behavior. If there is potential for cooperation, i.e. if multiple S. solidus of the same developmental stage co-occur in the same host, they enhance each other’s Summary 8 manipulation but only after they have reached infectivity. I hence show that one parasite can affect host manipulation by both a conspecific and a non-conspecific co-infecting parasite. In nature, parasites are not only faced with other co-infecting parasites but also with differences in the environment their host experiences. Such differences, for example in differences in resource availability might affect host manipulation. Experimentally infected copepods received different feeding treatments. I measured their parasites’ performance in both the first (i.e. copepod) and the second (i.e. stickleback) intermediate host and the behavior of their copepod host. Performance inside the copepod affected performance in the second intermediate fish host. Differences between infected and uninfected copepods (i.e. host manipulation) were larger in a high food environment. Additionally, larger parasites seemed less manipulated. These results could be mediated by changes in host condition, rather than actual differences in host manipulation. Nevertheless, if they lead to differences in the efficiency of host manipulation, they could have ecological consequences.Viele Parasiten verfügen über die Fähigkeit, Verhalten und/oder Aussehen ihres Wirtes zu verändern um dadurch ihre eigene Fitness zu steigern. Es kann schwierig sein festzustellen, ob dies durch echte Wirtsmanipulation geschieht, die zu diesem Zweck evolviert ist, oder ob es eine Begleiterscheinung darstellt, zum Beispiel aufgrund des zusätzlichen Energieentzuges, der den Trade-off des Wirtes zwischen Fressen und Predationsvermeidung zum ersteren hin verschiebt. Experimentell ist Wirtsmanipulation bisher meist unter der Bedingung einer einheitlichen Umwelt und mit Hilfe von Wirten, die nur mit einem Parasiten infiziert worden sind, untersucht worden. Dies spiegelt jedoch nicht die Natur wider. Wenn Wirte mehrere Parasite beherbergen, können diese sich, abhängig von ihren jeweiligen Zielen, in einem Konflikt um Wirtsmanipulation befinden oder in Bezug auf Wirtsmanipulation kooperieren. In dieser Dissertation möchte ich besser verstehen, wie Parasiten ihre Wirte unter komplexen – und daher natürlicheren – Bedingungen, wie zum Beispiel Mehrfachinfektionen – manipulieren. Dazu verwende ich zwei Parasiten mit komplexen Lebenszyklen, den Cestoden Schistocephalus solidus und seine zwei Zwischenwirte Copepoden und dreistachlige Stichlinge, und den Nematoden Camallanus lacustris und seinen ersten Zwischenwirt, Copepoden. Beide Parasiten verändern das Verhalten ihrer Wirte in einer Art, die wahrscheinlich ihre Fitness erhöht. Ob Wirtsmanipulation durch S. solidus in dreistachligen Stichlingen aufgrund von echter Wirtsmanipulation, die zu diesem Zwecke evolviert ist, zu Stande kommt oder eine Begleiterscheinund aufgrund erhöhten Energieentzuges darstellt, ist der Gegenstand einer langanhaltenden Debatte. Im Falle echter Wirtsmanipulation sollten sich ein infektiöser und ein noch nicht infektiöser S. solidus in einem Konflikt um Wirtsmanipulation befinden; der infektiöse Parasit sollte das Predationsrisiko seines Wirtes steigern, aber für den noch nicht infektiösen wäre jegliche vorzeitige Predation fatal; er sollte niemals die Risikobereitschaft seines Wirtes erhöhen. Ich habe Stichlinge experimentell so infiziert, dass sie einen infektiösen und einen noch nicht infektiösen Parasiten beherbergten. Diese waren sogar noch risikofreudiger als die nur mit einem infektiösen Parasiten infizierten Stichlinge. Das ist nur mit Verhaltensänderungen, die durch erhöhten Energieentzug verursacht worden sind, und nicht mit echter Wirtsmanipulation erklärbar. Um diese Ergebnisse zu bestätigen, habe ich den Einfluss des Hungerzustandes auf die Risikobereitschaft infizierter Stichlinge getestet. Energieentzug sollte in satten Fischen wirkungslos sein, aber echte Wirtsmanipulation nicht. Wiederum sind meine Ergebnisse eher mit Energieentzug als mit echter Wirtsmanipulation vereinbar. Scheinbar adaptive Wirtsmanipulation wird nicht zwangsläufig durch Mechanismen verursacht, die zu diesem speziellen Zweck evolviert sind. Darüber hinaus habe ich einen Konflikt zwischen einem infektiösen und einem noch nicht infektiösen Parasiten im Copepoden Wirt untersucht. Dazu habe ich Copepoden zu verschiedenen Zeitpunkten experimentell mit ein oder zwei S. solidus und/ oder C. lacustris infiziert. Noch nicht infektiöse S. solidus oder C. lacustris reduzieren die Predationsanfälligkeit ihres Wirtes, infektiöse erhöhen sie. Wenn ein Konflikt Zusammenfassung 10 zwischen verschiedenen Entwicklungsstadien derselben Art stattfindet, sabotiert der infektiöse Parasit die Wirtsmanipulation des noch nicht infektiösen in beiden Arten vollständig. In einem interspezifischen Konflikt schlug sich der infektiöse Parasite ebenfalls besser. Camallanus lacustris war dabei allerdings der staerkere Manipulateur. Ein Konflikt zwischen einem infektiösen C. Lacustris und einem noch nicht infektiösen S. Solidus resultierte in der vollständigugn unterdrückung durch den infektiösen Parasiten während ein solcher Konflikt zwischen einem infektiösen S. Solidus und einem noch nicht infektiösen C. Lacustris zu einem Kompromis bezüglich des Wirtverhaltens führte. Wenn Kooperationspotential besteht, d.h. mehrere S. solidus desselben Entwicklungsstadiums im selben Wirt auftreten, verstärken sie ihre Manipulation gegenseitig, aber erst nachdem sie infektiös geworden sind. Ich zeige also, dass ein Parasit die Wirtsmanipulation eines anderen Parasitens derselben oder einer anderen Art beeinflussen kann. In der Natur sind Parasiten nicht nur anderen Parasiten ausgesetzt, die denselben Wirt infizieren, sondern auch Unterschieden in der Umwelt, in der ihr Wirt lebt. Solche Unterschiede, z.B. im Bezug auf Ressourcenverfügbarkeit könnten Wirtsmanipulation beeinflussen. Experimentell infizierte Copepoden haben verschiedene Nahrungstreatments erhalten. Ich habe den Erfolg ihrer Parasiten sowohl im ersten (Copepoden) als auch dem zweiten (Stichling) Zwischenwirt und das Verhalten des Copepoden Wirtes gemessen. Der Erfolg im Copepoden beeinflusste den Erfolg im Fisch. Unterschiede zwischen infizierten und nicht infizierten Copepoden (d.h. Wirtsmanipulation) waren größer in einer Umwelt mit viel Nahrung. Darüber hinaus schienen größere Parasiten weniger zu manipulieren. Diese Ergebnisse könnten durch Veränderungen im Zustand des Wirtes anstatt durch tatsächliche Unterschiede in der Wirtsmanipulation herbeigeführt worden sein. Nichtsdestotrotz könnten diese zu ökologischen Konsequenzen führen, falls daraus Unterschiede in der Effizienz der Wirtsmanipulation resultieren.Contents Summary ............................................................................................................................................................ 7 Zusammenfassung ............................................................................................................................................. 9 Introduction ..................................................................................................................................................... 11 Host manipulation ............................................................................................................. 11 Multiple infections and host manipulation ....................................................................... 14 Study system ..................................................................................................................... 21 Thesis outline ................................................................................................................................................... 25 Chapter I Effects of VIE tagging and partial tissue sampling on the immune response of threespined stickleback Gasterosteus aculeatus .............................................................................. 29 Chapter II An experimentally induced conflict of interest between parasites reveals the mechanism of host manipulation ................................................................................................................ 37 Chapter III When parasites disagree: Evidence for parasite-induced sabotage of host manipulation ........ 53 Chapter IV Inter- and intraspecific conflict over host manipulation .......................................................... 67 Chapter V Growth and ontogeny of the tapeworm Schistocephalus solidus in its copepod first host affects performance in its stickleback second intermediate host ............................................. 81 Chapter VI Does resource availability affect host manipulation? - An experimental test with Schistocephalus solidus ........................................................................................................... 95 Conclusion ...................................................................................................................................................... 107 Acknowledgements ........................................................................................................................................ 111 References ...................................................................................................................................................... 113 Appendices ..................................................................................................................................................... 129 Appendix for chapter II .................................................................................................. 129 Appendix for chapter III ................................................................................................. 141 Appendix for chapter IV ................................................................................................. 153 Appendix for chapter VI ................................................................................................. 162 References for Appendices ............................................................................................. 165 Declaration ..................................................................................................................................................... 16

An experimental conflict of interest between parasites reveals the mechanism of host manipulation

Parasites can increase their host’s predation susceptibility. It is a long-standing puzzle, whether this is caused by host manipulation, an evolved strategy of the parasite, or by side effects due to, for example, the parasite consuming energy from its host thereby changing the host’s trade-off between avoiding predation and foraging toward foraging. Here, we use sequential infection of three-spined sticklebacks with the cestode Schistocephalus solidus so that parasites have a conflict of interest over the direction of host manipulation. With true manipulation, the not yet infective parasite should reduce rather than enhance risk taking because predation would be fatal for its fitness; if host behavior is changed by a side effect, the 2 parasites would add their increase of predation risk because both drain energy. Our results support the latter hypothesis. In an additional experiment, we tested both infected and uninfected fish either starved or satiated. True host manipulation should act independently of the fish’s hunger status and continue when energy drain is balanced through satiation. Starvation and satiation affect the risk averseness of infected sticklebacks similarly to that of uninfected starved and satiated ones. Increased energy drain rather than active host manipulation dominates behavioral changes of S. solidus-infected sticklebacks

Guillain-Barré syndrome: a century of progress

In 1916, Guillain, Barré and Strohl reported on two cases of acute flaccid paralysis with high cerebrospinal fluid protein levels and normal cell counts — novel findings that identified the disease we now know as Guillain–Barré syndrome (GBS). 100 years on, we have made great progress with the clinical and pathological characterization of GBS. Early clinicopathological and animal studies indicated that GBS was an immune-mediated demyelinating disorder, and that severe GBS could result in secondary axonal injury; the current treatments of plasma exchange and intravenous immunoglobulin, which were developed in the 1980s, are based on this premise. Subsequent work has, however, shown that primary axonal injury can be the underlying disease. The association of Campylobacter jejuni strains has led to confirmation that anti-ganglioside antibodies are pathogenic and that axonal GBS involves an antibody and complement-mediated disruption of nodes of Ranvier, neuromuscular junctions and other neuronal and glial membranes. Now, ongoing clinical trials of the complement inhibitor eculizumab are the first targeted immunotherapy in GBS

North America's net terrestrial CO2 exchange with the atmosphere 1990–2009

Scientific understanding of the global carbon cycle is required for developing national and international policy to mitigate fossil fuel CO2 emissions by managing terrestrial carbon uptake. Toward that understanding and as a contribution to the REgional Carbon Cycle Assessment and Processes (RECCAP) project, this paper provides a synthesis of net land–atmosphere CO2 exchange for North America (Canada, United States, and Mexico) over the period 1990–2009. Only CO2 is considered, not methane or other greenhouse gases. This synthesis is based on results from three different methods: atmospheric inversion, inventory-based methods and terrestrial biosphere modeling. All methods indicate that the North American land surface was a sink for atmospheric CO2, with a net transfer from atmosphere to land. Estimates ranged from −890 to −280 Tg C yr−1, where the mean of atmospheric inversion estimates forms the lower bound of that range (a larger land sink) and the inventory-based estimate using the production approach the upper (a smaller land sink). This relatively large range is due in part to differences in how the approaches represent trade, fire and other disturbances and which ecosystems they include. Integrating across estimates, "best" estimates (i.e., measures of central tendency) are −472 ± 281 Tg C yr−1 based on the mean and standard deviation of the distribution and −360 Tg C yr−1 (with an interquartile range of −496 to −337) based on the median. Considering both the fossil fuel emissions source and the land sink, our analysis shows that North America was, however, a net contributor to the growth of CO2 in the atmosphere in the late 20th and early 21st century. With North America's mean annual fossil fuel CO2 emissions for the period 1990–2009 equal to 1720 Tg C yr−1 and assuming the estimate of −472 Tg C yr−1 as an approximation of the true terrestrial CO2 sink, the continent's source : sink ratio for this time period was 1720:472, or nearly 4:1

Effect of acute kidney injury requiring extended dialysis on 28 day and 1 year survival of patients undergoing interventional lung assist membrane ventilator treatment

<p>Abstract</p> <p>Background</p> <p>Extracorporeal lung assist devices are increasingly used in the intensive care unit setting to improve extracorporeal gas exchange mainly in patients with acute respiratory distress syndrome. ARDS is frequently accompanied by acute kidney injury; however it is so far unknown how the combination of these two conditions affects long term survival of critically ill patients.</p> <p>Methods</p> <p>In a retrospective analysis of a tertiary care hospital we evaluated all patients undergoing interventional lung assist (iLA) treatment between January 1^st2005 and December 31^st2009. Data from all 61 patients (31 F/30 M), median age 40 (28 to 52) years were obtained by chart review. Follow up data up to one year were obtained.</p> <p>Results</p> <p>Of the 61 patients undergoing iLA membrane ventilator treatment 21 patients had acute kidney injury network (AKIN) stage 3 and were treated by extended dialysis (ED). Twenty-eight day survival of all patients was 33%. While patients without ED showed a 28 day survival of 40%, the survival of patients with ED was only 19%. Patients on ED were not different in respect to age, weight, Horowitz index and underlying disease.</p> <p>Conclusions</p> <p>AKI requiring ED therapy in patients undergoing iLA treatment increases mortality in ICU patients. Patients in whom iLA was placed as a bridge to lung transplantation and that were successfully transplanted showed the best outcome. Future studies have to clarify whether it is possible to identify patients that truly benefit from the combination of these two extracorporeal treatment methods.</p

Developing Telemental Health Partnerships Between State Medical Schools and Federally Qualified Health Centers: Navigating the Regulatory Landscape and Policy Recommendations

BackgroundFederally Qualified Health Centers (FQHCs) deliver care to 26 million Americans living in underserved areas, but few offer telemental health (TMH) services. The social missions of FQHCs and publicly funded state medical schools create a compelling argument for the development of TMH partnerships. In this paper, we share our experience and recommendations from launching TMH partnerships between 12 rural FQHCs and 3 state medical schools.ExperienceThere was consensus that medical school TMH providers should practice as part of the FQHC team to promote integration, enhance quality and safety, and ensure financial sustainability. For TMH providers to practice and bill as FQHC providers, the following issues must be addressed: (1) credentialing and privileging the TMH providers at the FQHC, (2) expanding FQHC Scope of Project to include telepsychiatry, (3) remote access to medical records, (4) insurance credentialing/paneling, billing, and supplemental payments, (5) contracting with the medical school, and (6) indemnity coverage for TMH.RecommendationsWe make recommendations to both state medical schools and FQHCs about how to overcome existing barriers to TMH partnerships. We also make recommendations about changes to policy that would mitigate the impact of these barriers. Specifically, we make recommendations to the Centers for Medicare and Medicaid about insurance credentialing, facility fees, eligibility of TMH encounters for supplemental payments, and Medicare eligibility rules for TMH billing by FQHCs. We also make recommendations to the Health Resources and Services Administration about restrictions on adding telepsychiatry to the FQHCsâ Scope of Project and the eligibility of TMH providers for indemnity coverage under the Federal Tort Claims Act.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149739/1/jrh12323_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149739/2/jrh12323.pd

p66 Shc and tyrosine-phosphorylated Shc in primary breast tumors identify patients likely to relapse despite tamoxifen therapy

INTRODUCTION: Shc adapter proteins are secondary messenger proteins involved in various cellular pathways, including those mediating receptor tyrosine kinase signaling and apoptosis in response to stress. We have previously reported that high levels of tyrosine-phosphorylated Shc (PY-Shc) and low levels of its inhibitory p66 Shc isoform are strongly prognostic for identifying both early node-negative and more advanced, node-positive, primary breast cancers with high risk for recurrence. Because aberrant activation of tyrosine kinases upstream of Shc signaling proteins has been implicated in resistance to tamoxifen – the most widely prescribed drug for treatment of estrogen receptor-positive breast cancer – we hypothesized that Shc isoforms may identify patients at increased risk of relapsing despite tamoxifen treatment. METHODS: Immunohistochemical analyses of PY-Shc and p66 Shc were performed on archival primary breast cancer tumors from a population-based cohort (60 patients, 9 relapses) and, for validation, an independent external cohort (31 patients, 13 relapses) in which all patients received tamoxifen as a sole systemic adjuvant prior to relapse. RESULTS: By univariate and multivariate analyses, the Shc proteins were very strong and independent predictors of treatment failure in both the population-based cohort (interquartile hazard ratio = 8.3, 95% confidence interval [CI] 1.8 to 38, P = 0.007) and the validating cohort (interquartile relative risk = 12.1, 95% CI 1.7 to 86, P = 0.013). CONCLUSION: These results suggest that the levels of PY-Shc and p66 Shc proteins in primary tumors identify patients at high risk for relapsing despite treatment with tamoxifen and therefore with further validation may be useful in guiding clinicians to select alternative adjuvant treatment strategies