Parasite, zombie, leech – these words are often used to describe people in unkind ways. Many of us recoil when ticks, tapeworms, fleas, head lice or bed bugs are even mentioned. Coming across such unwelcome guests – in our hair, on our skin or in our beds – can be a real nightmare.
Some parasites cause horrific deformities and diseases, maiming and killing millions of people and wildlife. Others may help boost immunity or provide the basis of food chains.
