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Indirect effects of parasitism: costs of infection to other individuals can be greater than direct costs borne by the host.

ABSTRACT: Parasitic infection has a direct physiological cost to hosts but may also alter how hosts interact with other individuals in their environment. Such indirect effects may alter both host fitness and the fitness of other individuals in the host's social network, yet the relative impact of direct and indirect effects of infection are rarely quantified. During reproduction, a host's social environment includes family members who may be in conflict over resource allocation. In such situations, infection may alter how resources are allocated, thereby redistributing the costs of parasitism between individuals. Here, we experimentally reduce parasite burdens of parent and/or nestling European shags (Phalacrocorax aristotelis) infected with Contracaecum nematodes in a factorial design, then simultaneously measure the impact of an individual's infection on all family members. We found no direct effect of infection on parent or offspring traits but indirect effects were detected in all group members, with both immediate effects (mass change and survival) and longer-term effects (timing of parents' subsequent breeding). Our results show that parasite infection can have a major impact on individuals other than the host, suggesting that the effect of parasites on population processes may be greater than previously thought.

SUBMITTER: Granroth-Wilding HM

PROVIDER: S-EPMC4528545 | biostudies-literature | 2015 Jul

REPOSITORIES: biostudies-literature

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Indirect effects of parasitism: costs of infection to other individuals can be greater than direct costs borne by the host.

Granroth-Wilding Hanna M V HM Burthe Sarah J SJ Lewis Sue S Herborn Katherine A KA Takahashi Emi A EA Daunt Francis F Cunningham Emma J A EJ

Proceedings. Biological sciences 20150701 1811

Parasitic infection has a direct physiological cost to hosts but may also alter how hosts interact with other individuals in their environment. Such indirect effects may alter both host fitness and the fitness of other individuals in the host's social network, yet the relative impact of direct and indirect effects of infection are rarely quantified. During reproduction, a host's social environment includes family members who may be in conflict over resource allocation. In such situations, infect ...[more]

PMID: 26156765

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Project description:BackgroundA good understanding of mosquito ecology is imperative for integrated vector control of malaria. In breeding sites, Anopheles larvae are concurrently exposed to predators and parasites. However, to our knowledge, there is no study on combined effects of predators and parasites on development and survival of larvae and their carry-over effects on adult survivorship and susceptibility to further parasite infection.MethodsThis study focused on effects of the nymphs of the dragonfly Pantala flavescens and the parasitic fungus Beauveria bassiana on Anopheles gambiae, to determine: predation efficacy of nymphs against An. gambiae larvae; development rate of An. gambiae larvae in the presence of one, two or four constrained nymphs; efficacy of B. bassiana against An. gambiae larvae at doses of 3, 6 and 12 mg; and survival of adult mosquitoes exposed to B. bassiana, following pre-exposure to a constrained predator and/or parasite at the larval stage. The experiments consisted of survival bioassays quantified as pupation day, or dead larvae and/or adults.ResultsNymphs had an average predation efficacy of 88.3% (95% CI: 87.5-89.1) at 24 hours, against An. gambiae larvae. The presence of one or two nymphs reduced development time of larvae by 0.65 and 0.35 days, respectively. However, development time of larvae exposed to four nymphs was similar to the control larvae. Larvae exposed to 3, 6 and 12 mg of B. bassiana were 2.0, 2.5 and 3.5 times more likely to die, respectively, compared to control larvae. Adults not pre-exposed, those pre-exposed to predator, parasite, or both were 45.8, 67.4, 50.9 and 112.0 times more likely to die, respectively, compared to control that were unexposed to predator or parasite, at larval and adult stage.ConclusionsThis study shows that both predator and parasite can reduce larval population of An. gambiae, and presence of predator cues decreases development time in breeding sites, as well as, increases the susceptibility of emerging adult to fungus. Predator and parasite both have an additive effect on survival of adults exposed to B. bassiana. Field studies are required for an in-depth understanding of predator and parasite influence on mosquito development time, survival and susceptibility in nature.

Project description:Climate change is affecting interactions among species, including host-parasite interactions. The effects of warming are of particular interest for interactions in which parasite and host physiology are intertwined, such as those between parasitic plants and their hosts. However, little is known about how warming will affect plant parasitic interactions, hindering our ability to predict how host and parasite species will respond to climate change. Here, we test how warming affects aboveground and belowground biomass of a hemiparasitic species (Castilleja sulphurea) and its host (Bouteloua gracilis), asking whether the effects of warming depend on the interaction between these species. We also measured how warming affected the number of haustorial connections between parasite and host. We grew each species alone and together under ambient and warmed conditions. Hosts produced more belowground biomass under warming. However, host biomass was reduced when plants were grown with a hemiparasite. Thus, parasitism negated the benefit of warming on belowground growth of the host. Host resource allocation to roots versus shoots also changed in response to both interaction with the parasite and warming, with hosts producing more root biomass relative to shoot biomass when grown with a parasite and when warmed. As expected, hemiparasite biomass was greater when grown with a host. Warmed parasites had lower root:shoot ratios but only when grown with a host. Under elevated temperatures, hemiparasite aboveground biomass was marginally greater, and plants produced significantly more haustoria. These findings indicate that warming can influence biomass production, both by modifying the interaction between host plants and hemiparasites and by affecting the growth of each species directly. To predict how species will be affected, it is important to understand not only the direct effects of warming but also the indirect effects that are mediated by species interactions. Ultimately, understanding how climate change will affect species interactions is key to understanding how it will affect individual species.

Project description:Population density and costs of parasite infection may condition the capacity of organisms to grow, survive and reproduce, i.e. their competitive ability. In host-parasite systems there are different competitive interactions: among uninfected hosts, among infected hosts, and between uninfected and infected hosts. Consequently, parasite infection results in a direct cost, due to parasitism itself, and in an indirect cost, due to modification of the competitive ability of the infected host. Theory predicts that host fitness reduction will be higher under the combined effects of costs of parasitism and competition than under each factor separately. However, experimental support for this prediction is scarce, and derives mostly from animal-parasite systems. We have analysed the interaction between parasite infection and plant density using the plant-parasite system of Arabidopsis thaliana and the generalist virus Cucumber mosaic virus (CMV). Plants of three wild genotypes grown at different densities were infected by CMV at various prevalences, and the effects of infection on plant growth and reproduction were quantified. Results demonstrate that the combined effects of host density and parasite infection may result either in a reduction or in an increase of the competitive ability of the host. The two genotypes investing a higher proportion of resources to reproduction showed tolerance to the direct cost of infection, while the genotype investing a higher proportion of resources to growth showed tolerance to the indirect cost of infection. Our findings show that the outcome of the interaction between host density and parasitism depends on the host genotype, which determines the plasticity of life-history traits and consequently, the host capacity to develop different tolerance mechanisms to the direct or indirect costs of parasitism. These results indicate the high relevance of host density and parasitism in determining the competitive ability of a plant, and stress the need to simultaneously consider both factors to understand the selective pressures that drive host-parasite co-evolution.

Project description:BACKGROUND:Migraine is a primary headache disorder which affects all aspects of life. The financial burden of migraine imposed on the society might be substantial. This study aims at estimating the economic cost of migraine in Latvia and Lithuania, including both direct and indirect costs. Direct costs encompass the costs of migraine-related health care resource utilization. Indirect costs are related to productivity loss, the potential or expected earnings lost due to migraine. METHODS:Direct cost is assessed by using the prevalence method, a widely used cost-of-illness approach. The prevalence rate of migraine and the migraine-related health care resource utilization are proxied from the literature, whereas unit cost of medical services and procedures are retrieved from national databases and providers. For estimating the indirect cost of migraine, we follow the human capital approach. We quantify three components of indirect costs: reduced labour force participation, absence from work and reduced productivity while at work. The number of unemployed migraineurs, days missed from work and days lost due to impairment while at work are drawn from the literature. Unemployment rate and average income in Latvia and Lithuania are then inserted to assess indirect costs. RESULTS:We find that the mean per-person total cost of migraine is €801 annually in Latvia, and €721 in Lithuania. In both countries around 30% of total cost is direct cost; cost related to a wide array of migraine-related medical services and interventions. The total cost of migraine is €112.26 million in Latvia, corresponding to 0.42% of Latvia's GDP. The total cost of migraine is €149.62 million in Lithuania, corresponding to 0.35% of Lithuania's GDP. In both countries two thirds of total cost is related to lost workdays due to absenteeism and presenteeism. CONCLUSIONS:The financial burden of migraine imposed on the society is substantial in Latvia and Lithuania. Improvements in care for patients with migraine, such as easier access to structured headache assessment services, wider availability of various procedures and preventive medications would significantly increase direct costs. Nevertheless, this cost increase might be far outweighed by lower migraine-related productivity loss, especially as the prevalence of migraine is the highest in the most productive years of life.

Project description:IntroductionAlcohol consumption is the main risk factor for death and disability in the world population between 15 to 49 years old, is related to more than 200 causes of death, and has an important economic impact on the health and social security systems. In 2016, three million deaths were attributable to alcohol worldwide and 131.4 million DALYs. In Brazil, alcohol consumption per inhabitant was 7.8 liters in 2016; and the prevalence of abusive consumption was 17.1% in 2019.ObjectiveEstimate the costs attributable of alcohol consumption in the Brazilian population 18 years-old and over, in the period 2010 to 2018.MethodsThis is a prevalence-based cost-of-illness study, with a top-down and retrospective approach, including direct costs (hospital and outpatient) and indirect costs (absenteeism from work) related to alcohol consumption. A list of diseases and conditions for which alcohol is a risk factor was used, and the Population Attributable Risk (PAR) was calculated to estimate what portion of the cost of these diseases is attributable to alcohol consumption. Prevalence was calculated by sex and level of alcohol consumption, based on data from the 2019 National Health Survey. Relative risk data were identified by disease/injury and level of daily consumption obtained from the Global Burden Disease study in 2017. The cost data used are from the Brazilian Unified Health System and social security system. All costs were adjusted for inflation for the period and converted to purchasing power parity.ResultsPrevalence data revealed that 73.6% of the Brazilian population reported not consuming alcoholic beverages, which included 62.9% of men and 83.0% of women. The lowest values for the PAR were found at the consumption range of 60 grams per day. Although the 12 grams per day consumption category is the least in terms of the quantity of alcohol consumed, it is one of the main ones in terms of PAR, given the higher prevalence of consumption. The total cost attributable to alcohol between 2010 and 2018 was Int$ 1,487,417,115.43, of which Int$ 737,834,696.89 was for hospital expenses, Int$ 416,052,029.75 for outpatient care, and Int$ 333,530,388.79 due to absenteeism from work.ConclusionFew comprehensive studies of alcohol-related costs have been developed, which suggests a knowledge gap in Brazil and worldwide and indicates the need for more research in this area. Understanding the economic impact of alcohol consumption is essential to help measure this public health problem in all its aspects and encourage implementation of public policies.

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Indirect effects of parasitism: costs of infection to other individuals can be greater than direct costs borne by the host.

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Indirect effects of parasitism: costs of infection to other individuals can be greater than direct costs borne by the host.

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