There are more than 3,200 types of parasites in existence today and at any given time, the human body may be infected with dozens of them. The most common parasite in humans is the worm. Parasites are divided into the following categories: Cestoda, Nematoda, Protozoa, and Trematoda. Some are microscopic while some worms in humans are quite visible to the naked eye. Certain types of parasites are found more often in animals, such as the bloodworm, which typically infects horses. Other types of parasites may affect humans more often. Just a few of the different types of parasites that may infect humans include: tapeworms, (Cestodes); hookworms, pinworms, and roundworms (Nematodes); giardia (Protozoa); and flat worms, (Trematoda).
Did you know that at any given time, the human body might be infected with any number of intestinal worms or parasites? Some are microscopic while others are visible to the naked eye. Some intestinal worms or parasites are found more often in animals – e.g., the bloodworm, which typically infects horses – and others may affect humans more often, such as the roundworm.