Parasites That Do Good for Humans

Parasitism occurs when one organism benefits at the expense of a second, referred to as a host. Parasites often cause diseases in humans, plants and animals, according to Wichita State University researcher Ethne Barnes in her book "Diseases and Human Evolution." However, parasites such as leeches have been used in bloodletting treatments since ancient times, reports University of Johannesburg professor Annemarie Avenant-Oldewage, and there is scientific evidence that suggests other parasites may also be helpful, according to MSNBC.

Leeches

• In the past, blood-sucking leeches were widely used in medicine to treat engorged hemorrhoids, swollen testicles, prolapsed rectums and inflamed vulva, Avenant-Oldewage says. Today, these little worms are used in plastic surgery and arterial revascularization treatments because of their ability to prevent blood clotting and blood vessel dilation.

Wolbachia

• Wolbachia is a bacteria that infects many invertebrates, including between 20 and 75 percent of all insects, according to the website Wolbachia. As the bacteria is inherited, especially among insects, it can be used as pest control, killing human disease carriers such as mosquitoes, according to The University of Melbourne.

Hookworms

• Hookworms have developed an important role during the evolution of our immune systems. According to BBC News, auto-immune disorders such as allergies can be the result of a lack of exposure to microorganisms. Researchers are currently investigating the benefits of hookworms in the prevention and treatment of asthma, type 1 diabetes and inflammatory bowel diseases, BBC says.