7 of the most common
Intestinal worms (soil transmitted helminths)
Commonly referred to as intestinal worms. The three most common forms are:
Ascariasis is the most common human worm infection. Infection occurs worldwide and is most prevalent in tropical and subtropical areas where sanitation and hygiene are poor. The parasite lives in the small intestine and children are infected more often than adults. Adult female worms can grow over 12 inches in length, though adult males are smaller. This adversely affects childhood growth and physical fitness and impairs intellectual and cognitive development. There are 1.2 billion people infected with ascariasis and 60,000 deaths are attributed to the disease each year.
Hookworm infection is one of the most common infections of humans with approximately 740 million cases in the developing countries of the tropics. The worms’ larvae enter the body through the skin, and mature as they travel to the small intestine where they attach themselves to the wall and begin to feed. Children and women of reproductive age are the most vulnerable to hookworm due to the associated blood loss resulting in iron-deficiency anaemia and protein malnutrition. Consequently, hookworm infection is one of the most important parasitic maternal-child health problems in the world. It is estimated that hookworm causes a 40% reduction in future wage earnings.
Trichuriasis is caused by a parasite called the human whipworm, a soil-transmitted worm. The worms’ eggs enter the body on food or on hands that have come into contact with soil contaminated with the eggs. It is estimated that 800 million people are infected with the parasite and that 10,000 deaths result each year. The parasites’ eggs hatch in the small intestine and attach to the large intestine, where they cause blood loss and deplete the host of nutrients. This adversely affects childhood growth and physical fitness and impairs intellectual and cognitive development.
Lymphatic Filariasis, more commonly known as elephantiasis, is a parasitic disease caused by thread-like microscopic worms carried from person to person by mosquitos. More than 20% of the world’s population is living at risk of lymphatic filariasis, 120 million people are infected, and 40 million have clinical symptoms. The adult worms live in the human lymph system, which maintains the body’s fluid balance and fights infections. When the parasite dies, it blocks the lymph system, causing disfiguring swelling of legs, the scrotum and the breast. A person once infected cannot be cured, but through the administration of Ivermectin and Albendazole its spread can be prevented. Over time the cycle of infection from one person to another will be broken and the NTD eliminated.
River blindness is an infection caused by a worm parasite, spread by bites from infected blackflies. It derives its name from the fact that transmission occurs most intensely in African villages near rapidly flowing streams. Approximately 37 million people are estimated to be infected with onchocerciasis. People with heavy infections usually have intense itching of the skin, disfiguring dermatitis, eye lesions, and/or subcutaneous nodules. Of the 37 million infected, approximately 500,000 have visual impairment and 270,000 are blind. About 99% of those infected are in Africa. Onchocerciasis is effectively treated with the oral medicine Ivermectin.
Schistosomiasis, sometimes referred to as bilharzia, is caused by a parasitic worm (Schistosoma) which penetrates the skin of people who come in to contact with contaminated water. Fresh water becomes contaminated by Schistosoma eggs when infected people urinate or defecate in the water. Approximately 200 million people are infected. The worms live in the intestine, causing symptoms from blood in the urine to impaired growth, development, and performance. In severe cases, the infection leads to bladder cancer and kidney, liver, and spleen malfunction.
Trachoma, the world’s leading cause of preventable blindness, is a bacteria infection spread by flies, through poor hygiene and direct contact with infectious discharges. Primarily it affects rural populations with limited access to clean water and health care, and disproportionately impacts women and children. 84 million people suffer from active infection and 8 million individuals are visually impaired or irreversibly blind as a result of it. Over time the upper eyelid develops scar tissue eventually turning inward causing the eyelashes to scratch the cornea resulting in blindness. Elimination of the disease is possible through implementation of the World Health Organization approved SAFE strategy, a comprehensive approach that employs surgery, antibiotics (via Pfizer’s donation of Zithromax), facial cleanliness and environmental improvement (clean water and sanitation management) to address the underlying causes of the disease.