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Invest more and die faster: The life history of a parasite on intensive farms.

ABSTRACT: Organisms are expected to respond to alterations in their survival by evolutionary changes in their life history traits. As agriculture and aquaculture have become increasingly intensive in the past decades, there has been growing interest in their evolutionary effects on the life histories of agri- and aquacultural pests, parasites, and pathogens. In this study, we used salmon lice (Lepeophtheirus salmonis) to explore how modern farming might have affected life history evolution in parasites. We infected salmon hosts with lice from either farmed or unfarmed locations, and monitored life history traits of those parasites in laboratory conditions. Our results show that compared to salmon lice from areas unaffected by salmon farming, those from farmed areas produced more eggs in their first clutch, and less eggs later on; they achieved higher infestation intensities in early adulthood, but suffered higher adult mortality. These results suggest that salmon lice on farms may have been selected for increased investment in early reproduction, at the expense of later fecundity and survival. This call for further empirical studies of the extent to which farming practices may alter the virulence of agricultural parasites.

SUBMITTER: Mennerat A

PROVIDER: S-EPMC5680424 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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Invest more and die faster: The life history of a parasite on intensive farms.

Mennerat Adèle A Ugelvik Mathias Stølen MS Håkonsrud Jensen Camilla C Skorping Arne A

Evolutionary applications 20170621 9

Organisms are expected to respond to alterations in their survival by evolutionary changes in their life history traits. As agriculture and aquaculture have become increasingly intensive in the past decades, there has been growing interest in their evolutionary effects on the life histories of agri- and aquacultural pests, parasites, and pathogens. In this study, we used salmon lice (<i>Lepeophtheirus salmonis</i>) to explore how modern farming might have affected life history evolution in paras ...[more]

PMID: 29151880

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Project description:CONTEXT:Although patient and physician characteristics are thought to be predictive of discretionary interventions at the end of life (EoL), few studies have data on both parties. OBJECTIVE:To test the hypothesis that patient preferences and physician attitudes are both independently associated with discretionary interventions at the EoL. METHODS:We report secondary analyses of data collected prospectively from physicians (n = 38) and patients with advanced cancer (n = 265) in the Values and Options in Cancer Care study. Predictor variables were patient attitudes toward EoL care and physician-reported comfort with medical paternalism, assessed indirectly using a modified version of the Control Preference Scale. We explored whether the magnitude of the physician variable was influenced by the inclusion of particular patient treatment-preference variables (i.e., effect modification). Outcomes were a chemotherapy use score (?14 days before death [scored 2], 15-31 days before death [scored 1], and >31 days [scored 0]) and an emergency department visit/inpatient admission score (two or more admissions in the last 31 days [scored 2], one admission [1], and 0 admissions [0]) in the last month of life. RESULTS:Chemotherapy scores were nearly 0.25 points higher if patients expressed a preference for experimental treatments with unknown benefit at study entry (0.238 points, 95% CI = 0.047-0.429) or reported an unfavorable attitude toward palliative care (0.247 points, 95% CI = 0.047-0.450). A two-standard deviation difference in physician comfort with medical paternalism corresponded to standardized effects of 0.35 (95% CI = 0.03-0.66) for chemotherapy and 0.33 (95% CI = 0.04-0.61) for emergency department visits/inpatient admissions. There was no evidence of effect modification. CONCLUSION:Patient treatment preferences and physician attitudes are independently associated with higher levels of treatment intensity before death. Greater research, clinical, and policy attention to patient treatment preferences and physician comfort with medical paternalism might lead to improvements in care of patients with advanced disease.

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Invest more and die faster: The life history of a parasite on intensive farms.

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Invest more and die faster: The life history of a parasite on intensive farms.

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