寄主 is the biology/medicine technical term for the host organism that a parasite, virus, or fungus lives in or on. Don't confuse with
宿主 (sùzhǔ), which means almost the same thing and is interchangeable in many contexts;
寄主 emphasizes the 'lodging' relationship (
寄 = to lodge / be parasitic on),
宿主 emphasizes 'staying overnight'.
