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hookworms in the intestines
Worms like hookworm and schistosomiasis infect 1.3 billion people a year. Less than one percent lead to death but infection and reinfection lead to long period of discomfort, missed days from school and work, and stunted growth among children.

Websites and Resources Centers for Disease Control and Prevention (CDC) cdc.gov/DiseasesConditions ; World Health Organization (WHO) fact sheets who.int/news-room/fact-sheets ; National Institute of Health (NIH) Library Medline Plus medlineplus/healthtopics ; Merck Manuals (detailed info many diseases) merckmanuals.com/professional/index


An estimated one in five people in the world have hookworms, sharp-toothed parasites that attach themselves to intestinal walls and suck blood. Hookworms crawl up from the ground, penetrate the skin of their hosts and settle in the intestines.

Hookworms eggs hatch in shady area. The worms themselves live in the soil. They enter the body through the skin, often bare feet, and travel through the blood to the lungs and reach the stomach where they are coughed up and swallowed. From the stomach they move to the intestines, where make their home and can reach lengths of four inches (most are less than a half inch). People can be infected by a thousand worms that can live four or five years and can collectively suck up to a cup of blood a day.

There are treatments that can kill the worms. Hookworm is treatable with one or two pills that cost about $1 but people who live in areas where it is found tend to get it repeatedly. The parasites favor damp, cool environments and are particularly common in cotton, rapeseed and tobacco fields. Hookworm can be avoided by the sanitary disposal of human wastes and by wearing shoes.

Affect of Hookworms

Hookworms can stunt growth and cause anemia and lethargy.Hookworm-related ills include increased child mortality, stunted learning capacity and reduced economic production.

Hookworms take hold of certain villages or areas through a cycle of reinfection. Many of those who get the parasites are too poor to afford even flip-flops, and the parasites infect them when they walk barefoot in fields or bend down and touch the soil. Even when the worms are killed with medicines the victims often get reinfected again. Because most houses in infected areas don’t have toilets the worms are constantly re-introduced to the ground, where they can infect others.

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Hookworms sap it victims of energy. Describing a village in Brazil where 80 percent of the inhabitants have hookworms a nurse that lives there told the Washington Post, “The people seem tired all the time, and they never eat. They don’t know what’s wrong with them.” In villages where hookworms have taken hold malnutrition is a problem because victims are too tired to tend their fields and their appetites are low.

Efforts to Get Rid of Hookworm

In the early 1900s, John D. Rockefeller, one of the richest men in the world at that time, tried to eradicate hookworm. He was successful in launching a campaign that wiped it out in the United States, where the parasite was eliminated after World War II, but not globally.

Efforts to develop a vaccine have been slowed by the fact that most victims are poor and drug companies have little incentive to spend the money necessary to develop one. As it stands now vaccines have been developed that successfully fight bacteria and viruses but none have been conceived that prevent parasitic diseases.

Trials for a hookworm vaccine have been conducted near Belo Horizonte in Gerais state in Brazil. The project has been made possible by a $53 million grant from the Bill and Melinda Gates Foundation and other donations from the Rockefeller Foundation and Doctors Without Borders. So far the result have been promising, Renata Diniz, a coordinator of the project, told the Washington Post, “Even after the first treatments, people started telling us they were feeling better, and that got them planting more crops.”

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Tapeworms are kind of fluke (parasitic relatives of flatworms) that have no sense organs or even a digestive system and nourish themselves by absorbing digestive fluids directly through their skin from their hosts.

Tapeworms are found in almost all living creatures. In many cases they cause little damages other than robbing their hosts of food but in some cases can seriously damage their hosts' health by physically injuring tissues or producing waste products that poison them.

Of the 1,500 kinds of tapeworms, three are common in man. One is picked by eating "measly meat." It has a head with suckers that clings to the intestines. Another, which reaches a lengths of 35 feet, is found in infected fish.

Tapeworms are secure as long as their host stays alive. The main problem they have is making sure their young make their way to another host. Many do this by depositing their eggs in their host's excrement, which in turn finds it way into the prey of another animal.

The eggs hatch and grow in this animal which is eaten by another animal, providing a safe home for a new generation. Since the chances of a host animal making their way into the food of another animal, and this animal being consumed by the animal is extremely unlikely, tapeworms often lay millions of eggs.

Tapeworm that live in the human digestive system need to get their larvae into a pig in order to infect another pork-eating human. The chances of this happening are so slim that the tapeworm may lay a million eggs a day and 7 billion eggs in a lifetime.

Flatworms are regarded as the simplest and most basic creature found in the sea. There are 3,000 species of them. Most but not all live the sea. Many are found in reefs, clinging under rocks and hidden in crevasses. Some of those found in coral reefs are quite colorful. Some flatworms cause serious illnesses in humans. Tapeworms and flukes are parasitic flatworms.

Like jellyfish, flatworms have a single opening to their gut which is used to take in food and excrete waste but unlike jellyfish they have a solid body. Flatworms have no gills and breath directly through their skin. Their undersides are covered by cilia, which beat and allow them to move slowly over surfaces. They have a network of nerve fibers but nothing that would qualify as a brain and they don’t have a circulatory system.

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hookworm life cycle

Despite their simplicity, flatworms have amazing powers. Some have been taught to negotiate their way through a maze. Not only that if they are killed and their flesh is feed to another flatworm they too can negotiate the maze.

Image Source: Centers for Disease Control and Prevention cdc.gov/DiseasesConditions

Text Sources: CDC Health Information for International Travel, U.S. Department of Health and Human Services; National Geographic, New York Times, Washington Post, Los Angeles Times, Times of London, The New Yorker, Time, Newsweek, Reuters, AP, Lonely Planet Guides, Compton’s Encyclopedia and various books and other publications.

Last updated May 2022

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