Known for plaguing pets like dogs and cats, fleas and ticks
are parasites that live on mammals, birds, and even reptiles and amphibians. Fleas are insects, whereas ticks are arachnids. Both fleas and ticks live off the blood they suck from their hosts. They are known for transmitting diseases such as Lyme disease, encephalitis, and tick fever, and for spreading bacteria, viruses, and protozoa. They can also cause or activate allergies. Ticks remain attached to their hosts for longer stretches of time, while fleas bite and move about their hosts.