Hookworms: the intestinal vampires
This is the second most common intestinal roundworm in humans worldwide, with an estimated half a billion people infected at any one time.
There are two species that are human pathogens; Ancylostoma duodenale which is found in Africa, India, Europe and China, and Necator americanus, which is found in the Americas. However, many areas are endemic for both species.
Hookworm disease caused by N. americanus is the prevailing species in the southeastern United States.
You get hookworm in areas of unsanitary conditions where people defecate on the ground and the climate is favorable. Warm, moist climates and sandy soil are the environments hookworms thrive in. Infective larvae can survive up to a month in the soil under ideal conditions.
Hookworm is not an issue in cold climates because the larvae cannot survive.
People get infected by walking barefoot over contaminated soil where the hookworm larvae can penetrate the skin. It is a particular problem in farmers in developing nations worldwide. Also, small children get it by sitting bare-butt on the ground that has hookworm.
Ancylostoma duodenale may also be acquired orally, transmammary and transplacentally.
After the larvae penetrate the skin, it is carried in the bloodstream to the heart and then the lungs. Here they climb the windpipe and are swallowed to the intestines where they mature to adults.
In the intestines, the adults attach and suck blood. The blood loss can be significant depending on the amount of worms present. A. duodenale drinks more blood per worm (0.2-0.3 ml) per day than N. americanus (0.03 ml), and are therefore more pathogenic.
The symptoms you may see depends on what stage of infection the person is in. During invasion when the larvae initially penetrate the skin, there may be a severe allergic reaction known as “ground itch”.
While the larvae are migrating through the lungs, an infected person may experience a mild pneumonia with a cough.
When adults are in the intestines, symptoms may include diarrhea, pain, and nausea.
In very heavy infections, blood loss can reach 100 ml per day resulting in iron deficiency anemia and weakness due to blood loss.
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In addition, protein deficiencies, enlarged liver and spleen and developmental disorders like mental, physical and sexual may occur in severe hookworm disease.
People can be infected by animal hookworms, but most just penetrate the skin and wander in tissue just below skin (cutaneous larval migrans). They cannot complete their life cycle and do not cause hookworm disease.
There is one species, Ancylostoma caninum, which nearly complete its life cycle, whose larvae may migrate to the human intestine, causing eosinophilic enteritis.
Hookworm can be diagnosed by finding the characteristic eggs microscopically in stool. Hookworm can be treated with anti-parasitic drugs like albendazole, mebendazole or pyrantel pamoate. You will likely be put on iron supplements also. Cutaneous larva migrans is a self-limiting infection but can be treated with albendazole or ivermectin.
The primary way of preventing infection is simple: wear shoes.
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