Parasites are organisms that live off other organisms. Parasites live inside the body or on the skin of the host and feeds from the host itself. Parasites enter the human body through food and water that are ingested or transferred from the environment to the skin. Many of these parasites are harmful and cause diseases in humans. It would help to know the symptoms associated with some of these.

 

A study published in the "American Family Physician" journal reports that E. vermicularis is the most prevalent nematode in the U.S. Around 209 million adults and 30 percent of children worldwide are infected by this parasite and show symptoms associated with the infection. This parasite is also present in the intestine and the infection may last four to six weeks in the absence of host autoinfection. Symptoms of the infection include constant perianal and vaginal itching in humans. Prolonged infection can lead to urinary tract infection, appendicitis, and weight loss.

 

The filarial worm causes filariasis in humans that is characterized by symptoms such as swollen feet and lower limbs. The filarial worm is a roundworm that stays beneath the human skin and does not cause any symptoms initially. This parasite circulates in the blood and, upon maturing, enters the lymphatic system and develops while it lives there for more than five years. It affects the lymphatic nodes and causes retention of fluids resulting in swelling.  With prolonged exposure and repeated infection, skin hardening and thickening are also seen.

 

Hookworm is another common parasite that affects humans. Necator americanus is one such species that is found widely in the Americas and Caribbean. The hookworm attaches itself to the intestinal walls and feeds on human blood. This worm consumes up to  a quarter-milliliter of blood per day and can lead to anemia. The infection of this parasite can also result in physical and mental retardation in children.

The Guinea worm is a roundworm that causes Guinea worm disease by entering the stomach and intestine from untreated water. There are no significant visible symptoms when the parasite enters the body. About a year later, when the female guinea worm is mature, it ruptures the skin surface, ideally near the lower limbs preferably while in water and releases numerous larvae too. There are no vaccines or medicines to counter this parasite and this stomach worm is usually removed by winding around a stick once it emerges out of the skin. The ulcer at the ruptured site could be extremely painful and secondary bacterial infections can lead to blood poisoning.