Why the Parasite is Here?

...I Knew the Parasite is here." Suddenly new information invaded Jon's mind. He learned that the Parasite that had infected his mother was from another world. Jon learned that it's purpose on Earth was to infect humans and use them as slaves and breeders. Jon learned that the Parasite does not directly control it's host rather it influences them, making the host completely subservient to it's master and loyal to the Parasites cause. Jon learned that the Parasite could mutate and transform it's host in ways that would help propagate the species. Jon also learned that there are other Parasites in town and a Hive Queen, the leader of the invasion, hidden somewhere in town too.