Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Parasitic Diseases ?
    ### Response:
    Parasites are living things that use other living things - like your body - for food and a place to live. You can get them from contaminated food or water, a bug bite, or sexual contact. Some parasitic diseases are easily treated and some are not.    Parasites range in size from tiny, one-celled organisms called protozoa to worms that can be seen with the naked eye.
    