Parasitologists study parasites. Imagine all your life devoted to freeloaders. Parasitology is an interdisciplinary field. To study these critters you need to know a good bit about microbiology, immunology, biochemistry, and other life sciences. Billions of parasitic infections occur in humans every year.
Infections can be fatal, however, most result in few if any symptoms.
Parasites are a major health concern. Approximately 30 percent of the world's population is infected with the worm called Ascaris lumbricoides . Parasites can be found everywhere. A common misconception is that these parasitic infections only occur in hot tropical areas of the world. If you have ever visited a tropical country you may also bring back a parasite along with your souvenirs.