Three main types of parasites--protozoa, helminths and extoparasites--cause illness and disease in humans. Protozoa, tiny one-celled organisms, live and multiply in the human intestine and bloodstream. Helminths are parasitic worms that reside in the intestinal tract. Ectoparasites include ticks, lice, fleas and mites that burrow into the skin and feed on the host's blood.
Typhus
Murine typhus, a bacterial disease spread by lice or fleas, produces symptoms such as nausea, vomiting, headache, abdominal pain, high fever and a dull red rash. Antibiotic treatment includes doxycycline or tetracycline. The National Institutes of Health reports the death rate for untreated murine typhus as less than 2 percent. Endemic typhus symptoms include delirium, severe headache, severe muscle pain, high fever, cough and chills. Expect infected patients to require oxygen and intravenous fluids. If left untreated, 10 to 60 percent of patients infected with endemic typhus die.
Giardia Infections
Giardiasis is a parasitic disease caused by the giardia intestinalis. The giardia parasite thrives in the intestine or on fecal-infected soil, water or food. Symptoms of giardia infection include diarrhea, greasy stools, nausea, gas and abdominal cramps. The CDC reports giardia as a common cause of waterborne disease. Possible contaminates include raw vegetables, bathroom surfaces, water from lakes or streams, contaminated uncooked food, recreational water such as hot tubs and swimming pools, and contact with a person with giardiases.
Parasitic Roundworm Diseases
Parasitic roundworm eggs make an entry into the human body from the soil to the mouth by hand transfer or directly through the skin. Human intestines provide a home for the adult roundworm. Parasitic diseases caused by the roundworm include ascariasis, hookworm disease, pinworm infection, strongyloidiasis, trichinosis and whipworm disease. The National Institute of Allergy and Infectious Diseases reports that poor personal hygiene remains the primary cause of roundworm diseases.
Toxoplasmosis
The CDC explains that toxoplasmosis, caused by the protozoan parasite Toxoplasma gondii, infects an estimated 22.5 percent of people age 12 and older. Foodborne transmission occurs because of eating undercooked meat contaminated with the parasite and eating food touched by contaminated utensils such as knives and cutting boards. Animal to human transmission occurs when the oocyst form of the parasite is ingested, such as by failure to wash hands thoroughly after cleaning an infected cat's litter box.
Scabies
The human itch mite burrows into the skin and lays its eggs. Itching and a skin rash are the first symptoms to indicate an infestation. Up to two months may pass before the first signs of infestation appear. During the two months before symptoms, scabies is contagious. Common places for the scabies rash to appear include the wrist, waist, armpit, shoulder blades and elbow. Complications from scabies include a bacterial skin infection and inflammation of the kidneys. Crusted scabies may contain as many as two million mites and is highly contagious.
