• Question: Can parasites inhabit places of extreme temperature differences?

    Asked by Slenneri to Claire, Franco, Koi, Linda, Mark on 20 Jun 2016.
    • Photo: Franco Falcone

      Franco Falcone answered on 20 Jun 2016:

      @Slenneri Yes some parasites have structures which are quite resistant to cold, heat and dryness called cysts, they are a bit like spores. Very resilient. Many parasites include a free-living stage, either in soil or in the water, and in addition to temperature, also have to cope with changes is salinity. It depends on what you call ‘extreme’. If you think about several hundreds of degrees around geothermal vents at the bootom of the sea, I am not sure whether any parasites have adapted to that kind of temperature. I know that some bacteria can withstand temperatures higher than 121 C, they actually thrive under such conditions, but they are free living organisms and not parasites.

    • Photo: Claire Bourke

      Claire Bourke answered on 20 Jun 2016:

      Hi Slenneri,
      as Franco says, some parasites can resist a wide range of temperatures and in many ways adapting from living at the temperature of the outside environment to body temperature (37 degrees Celsius) can be considered quite extreme!

      That said, many parasites and the insects that transmit some of them (also called ‘vectors’) often have quite a restricted temperature range because they have adapted to live in particular environments. For example, mosquitoes live in tropical regions of the world and therefore the Plasmodium parasites that they transmit to humans and cause malaria, tend to also be restricted to these regions. Similarly, schistosomes, the parasitic worms that I study, live inside aquatic snails that are only found in tropical regions too. Some researchers are investigating how increasing temperatures caused by global warming might affect where parasites are found. For example, malaria used to be common in southern europe in the past and perhaps Plasmodium parasites might become more common in Europe again if our climate becomes warmer and a more favourable environment for mosquitoes.

    • Photo: Mark Booth

      Mark Booth answered on 20 Jun 2016:

      Hi Slenneri

      Most parasites have complicated life-cycles that means they must develop through different environments and survive transitions that might include water or soil, mammals, aquatic organisms. These types of parasites tend to have fairly restricted temperature ranges. Vector borne infections have a wider range, and any infection that moves from host to host directly (e.g. blood-borne viruses) have the widest geographical range as they are always in a temperature maintained environment.

    • Photo: Arporn Wangwiwatsin

      Arporn Wangwiwatsin answered on 20 Jun 2016:

      Hi Slenneri,

      Yes, some of them can. And in addition to Franco’s answer on cysts, this question makes me think of parasites that are transmitted by insect vectors (e.g. Plasmodium parasite which cause malaria, or trypanosome which cause sleeping sickness). The parasites get flushed from within the insect into human body when the insect bite human (or other animals) to feed on blood. For this, the parasites need to quickly adapt from the temperature in the insect (~25 ºC) to the temperature in human (~37ºC) in that short amount of time … some parasites prepare for this by having some genes, which they need to use when in human, ready even before they leave the insect.

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