• Rainfall strongly affects infectious Vib

    From ScienceDaily@1:317/3 to All on Thu Mar 3 21:30:42 2022
    Rainfall strongly affects infectious Vibrio bacteria in Ala Wai Canal


    Date:
    March 3, 2022
    Source:
    University of Hawaii at Manoa
    Summary:
    In the Ala Wai Canal in Waikiki, Hawai'i, the abundance of Vibrio
    vulnificus, an infectious bacterium, is strongly influenced by
    the amount of rainfall in the surrounding areas, according to a
    recently published study.



    FULL STORY ==========================================================================
    In the Ala Wai Canal in Waikiki, Hawai'i, the abundance of Vibrio
    vulnificus, an infectious bacterium, is strongly influenced by the amount
    of rainfall in the surrounding areas, according to a recently published
    study by oceanographers at the University of Hawai'i (UH) at Mānoa
    and Hawai'i Pacific University (HPU).


    ========================================================================== Study authors Olivia Nigro, then a graduate student in the oceanography at
    UHM and now an assistant professor at HPU, and Grieg Steward, professor in
    the UHM School of Ocean and Earth Science and Technology (SOEST), first assessed Vibrio in 2006 when Oliver Johnson died from a V. vulnificus
    infection after having cuts and scrapes exposed to Ala Wai Harbor water.

    "His exposure occurred after many days of heavy rainfall, which, given
    our results, suggests this may have been an exacerbating factor,"
    said Steward. "At the time, we realized there was almost no data on
    the ecology of V.vulnificus in the canal, or in Hawai'i generally, and remarkably, very little in tropical waters anywhere." After a quick
    pilot study in 2006 that showed the bacteria are present in high, but
    not unexpected numbers, the team geared up for a year-long study in 2008-
    2009 with better methods to understand the variability in abundance over
    a seasonal cycle.

    At higher latitudes, the abundance of V. vulnificus shows a very strong seasonal cycle -- nearly disappearing in winter when temperatures are
    cold. In Hawai'i, temperatures are warm year-round, so freshwater input
    becomes a more important control.

    "V. vulnificus occurs naturally in warm, brackish waters," said Nigro. "So
    we expect to find this bacterium anywhere that temperatures are warm and freshwater and seawater mix in about equal proportions. When conditions
    are right, the Ala Wai Canal can be a great incubator for this bacterium!"
    The researchers observed that rainfall has a variable effect depending
    on the amount of precipitation.



    ==========================================================================
    "Too little rainfall means much of the canal is saltier than optimum
    for V.

    vulnificus growth, too much rainfall and the canal is fresher than the bacterium likes," said Nigro. "We also found that, because of the flushing effect of intense rainfall, the highest abundance of V. vulnificus shifted
    from within the canal out into the harbor." They observed the highest canal-wide average abundances, among the highest recorded anywhere,
    during a time of modest rainfall, moderate salinities and a moderate
    flushing of the canal.

    The researchers noted that, although rainfall is more frequent in winter
    on average, significant rainfall can also occur in summer, so spikes in V.

    Vulnificus can be a problem any time of year. This makes it challenging
    to predict precisely when and where there will be high concentrations
    of this pathogen. However, based on a few variables -- rainfall and
    resulting salinity and flushing of the canal -- the relative risk of
    exposure to this pathogen could be predicted as an average for the system.

    With additional years of data to better understand how V. vulnificus
    varies in space and time, it may be possible to provide real-time
    predictions of when and where the bacterium is likely to be at unusually
    high concentrations, which is one component in assessing the risk of
    infection.

    "Although V. vulnificus can cause serious or even lethal infections, it
    usually only becomes a problem for individuals with underlying medical
    issues," said Steward. "So people should not panic about incidental
    exposure to canal water.

    But it is wise to wash off with soap and water after exposure and one
    should avoid exposing open wounds to canal water, especially if one
    is immunocompromised." This project was supported by funding to UH
    Mānoa from the National Oceanic and Atmospheric Administration
    through Hawaiʻi Sea Grant and from the National Science Foundation.

    ========================================================================== Story Source: Materials provided
    by University_of_Hawaii_at_Manoa. Original written by Marcie
    Grabowski. Note: Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Olivia D. Nigro, La'Toya I. James-Davis, Eric Heinen De Carlo,
    Yuan-Hui
    Li, Grieg F. Steward. Variable freshwater influences on the
    abundance of Vibrio vulnificus in a tropical urban estuary. Applied
    and Environmental Microbiology, 2022; DOI: 10.1128/AEM.01884-21 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/03/220303095641.htm

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