Feeding may last for days. During that time, hundreds of proteins in a tick’s saliva act as painkillers—allowing the bloodsuckers to go undetected—and combat a host’s immune response: The proteins change daily, so if a victim produces antibodies against today’s saliva, they're useless a few days later. These compounds also prevent blood clotting and inflammation in the host, which could put an early end to the feast.
Ticks transmit the widest variety of pathogens of any bloodsucking arthropod, including mosquitoes, flies, and fleas. And the effects of tick bites can ripple throughout a food chain: Lions have suffered massive die-offs after eating buffalo infested with tick-borne blood parasites.