• Climate change and extreme weather will

    From ScienceDaily@1:317/3 to All on Tue Feb 15 21:30:40 2022
    Climate change and extreme weather will have complex effects on disease transmission

    Date:
    February 15, 2022
    Source:
    eLife
    Summary:
    Temperature fluctuations such as heatwaves can have very different
    effects on infection rates and disease outcomes depending on the
    average background temperature, says a new report.



    FULL STORY ========================================================================== Temperature fluctuations such as heatwaves can have very different
    effects on infection rates and disease outcomes depending on the average background temperature, says a report published today in eLife.


    ==========================================================================
    The study suggests it will be increasingly difficult to predict the consequences of climate change on host-pathogen interactions as global temperatures rise and extreme weather events become more common.

    Infectious diseases have profound ecological effects on human,
    agricultural and wildlife populations. It is well known that interactions between pathogens and their hosts are sensitive to changes in
    temperature. But what is less well understood is how sudden and extreme temperature variation affects this relationship and how this influences
    overall infection rates and disease outcomes.

    "Climate change is predicted to increase not only average temperatures
    but also temperature fluctuations and the frequency and intensity
    of extreme weather events," explains co-first author Pepijn Luijckx,
    William C. Campbell Lecturer in Parasite Biology, Trinity College Dublin, Ireland. "Yet although studies have quantified the effects of rising
    average temperatures on host and pathogen traits, the influence of
    variable temperature regimes such as heatwaves remains largely unknown." Luijckx and the team examined the effects of different temperatures on
    various traits in a host organism -- a small crustacean called Daphnia
    magna -- and its known gut parasite, Odospora colligata. Transmission
    of the parasite is representative of classic environmental transmission, similar to that seen with diseases such as SARS-CoV-2 and cholera.

    The team looked at how the organisms responded to three distinct
    temperature regimes: a constant temperature, and two variable regimes,
    with daily fluctuations of +/- 3DEGC and three-day heatwaves of 6DEGC
    above ambient temperature. They then measured the crustacean's lifespan, fertility, infection status and the number of parasite spores within
    their gut. Next, they processed the data into a statistical model to
    compare the impact of the three different temperature regimes.

    The team found that daily fluctuations of temperature reduced the
    infectivity and spore burden of the parasite compared to those kept at
    the constant average temperature. However, by contrast, the infectivity
    of parasites after a heatwave was almost the same as the infectivity of
    those maintained at the constant temperature.

    Moreover, the number of spores in the crustacean host increased following
    the three-day 'heatwave' when the background constant temperature
    was 16DEGC, but this burden was reduced at higher temperatures. This
    suggests that the effects of temperature variation differ depending
    on the average background temperature and whether this is close to the
    optimum temperature for the parasite.

    Host fitness and reproductive success were generally reduced in the
    crustacean exposed to either the parasite spores or when experiencing
    variable temperatures. The difference between the host and pathogen
    responses suggest that under some circumstances the parasites were able
    to withstand the sudden change in heat better than their hosts.

    "Our findings show that temperature variation alters the outcome of host- pathogen interactions in complex ways. Not only does temperature variation affect different host and pathogen traits in a distinct way, but the
    type of variation and the average temperature to which it is applied
    also matter," concludes Luijckx. "This means that changing patterns of
    climate variation, superimposed on shifts in mean temperatures due to
    global warming, may have profound and unanticipated effects on disease dynamics." Alongside Pepijn Luijckx, the research team includes co-first author Charlotte Kunze (Carl von Ossietzky University of Oldenburg,
    Germany, and Trinity College Dublin), Andrew Jackson and Ian Donohue
    (both Trinity College Dublin).

    Their study was funded by Science Foundation Ireland and the Irish
    Research Council.

    ========================================================================== Story Source: Materials provided by eLife. Note: Content may be edited
    for style and length.


    ========================================================================== Journal Reference:
    1. Pepijn Luijckx, Charlotte Kunze, Andrew L Jackson, Ian
    Donohue. Alternate
    patterns of temperature variation bring about very different
    disease outcomes at different mean temperatures. eLife, 2022;
    11 DOI: 10.7554/ eLife.72861 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/02/220215113437.htm

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