PROTOZOAN are organisms that live in the blood, tissues, and intestines, of their host. They are usually very small, generally microscopic, capable of infecting every tissue in the body. The most common protozoan disease is Malaria. Protozoan are usually carried by contaminated water sources and insects (e.g. mosquitoes). Although exceptionally small, these parasites may remain active in the human body for an entire lifetime, causing multiple complications and revisitations, such as malaria fever.
FLUKES (Trematodes), or FLATWORMS, are likely the most common form of parasite found in humans worldwide, including Europe and North America. They are generally flat and oval in shape. They can grow to 3.5 inches in length. They commonly infect human intestines, and can infect other tissues such as the heart, lungs, liver, and kidneys. Flukes are very difficult to get rid of once infected.