Like vampire bats, ticks have an anticoagulant in their saliva to keep the blood of their host from clotting while it feeds. A tick's saliva may contain diseases, thereby transmitting disease organisms to the unknowing host. If left undetected over 2-4 days, the tick will engorge itself with the blood of its host and simply drop off. Most ticks feed and then molt to the next stage in their life cycle. Not all ticks that come in contact with animals carry disease.
Science is constructed of facts as a house is of stones.
But a collection of facts is no more a science than a heap of stones is a house. If you plan to be in a wooded area, wear light-colored clothing that makes it easier to spot a tick that may have crawled on you. Avoid coming in contact with vegetation where ticks may be waiting for a host. Wear long pants tucked inside your socks. When you return home, carefully check your clothes and launder them using hot water to kill any hidden ticks.