Ticks, like spiders and mites, are small crawling bugs with eight legs. Not insects, but arachnids. Ticks are parasitic insects that survive by sucking blood from humans and animals. Because they can feed on a Lyme disease-infected animal (such as a mouse), vectors (carriers) can carry and transmit the Lyme bacterium (Borrelia burgdorferi) to the next animal or person they bite. Tick-borne diseases can cause a wide range of symptoms, and they usually appear within days to weeks of a tick bite. Tick-borne diseases can cause the following symptoms: