Hookworms are small intestinal parasites. Two species of them can infect humans and cause hookworm disease.
What is hookworm?
Hookworms are also known as Ancylostomatidae. They are found in humid and warm regions such as the tropics and subtropics. However, they are also found in temperate climates in southern Europe and in mountain and tunnel construction. There are two hookworm species that are capable of parasitic colonization in humans. These are Necator americanus and Ancylostoma duodenale. These two parasite species do not have an intermediate host. In medicine, hookworm infestation is called ankylostomiasis.
Occurrence, distribution, and characteristics
Hookworms represent parasites of the small intestine. They have a round cross-section. While hookworm females reach a length of about one centimeter, males turn out a little shorter. The life cycle of the two human pathogenic hookworm species Ancylostoma duodenale and Necator americanus is approximately the same. Ancylostoma is also known as the pit worm. It is one of the blood-sucking parasites and settles in the jejunum (empty intestine) of humans. Its preferred habitat is North Africa. The males of Ancylostoma duodenale have a posterior end that is flared in the shape of a bell. The females, on the other hand, have a pointed end. Hookworm eggs are excreted from the human body in the feces. Necator americanus also belongs to the blood-sucking parasites. The Latin term “necator” translates as “killer.” The hookworm is equipped with a mouth capsule that has cutting plates. The habitat of the necator is primarily in Southeast Asia, western Africa, and South and Central America. In their development, hookworms go through several stages. The parasite reproduces sexually and lays eggs. There are also five larval stages in succession. In the intestine, hookworm females lay their eggs, which are released into the environment in the stool. After the eggs are excreted, the first larva may hatch. Their diet consists of bacteria within the feces. The first larva is then followed by the development of a second larva, which in turn gives rise to a third that is able to penetrate the soil. There it lies in wait for a suitable host. The hookworm can enter humans by boring into their bare feet. During this process, the larval skin is shed and the fourth larva is formed. Through the blood, the parasite advances to the lungs, where it sheds its skin to form the fifth larval stage. From the lungs, the hookworm travels to the bronchi. From there, the larva is coughed up and swallowed, so that it is transported to the intestine where it attaches itself. In the intestine, the final molt to adult hookworm then takes place. Worms as well as the fifth larva can suck blood from the intestinal villi of their host body. As mentioned above, infestation of humans by hookworms not infrequently occurs through barefoot walking. However, it is equally possible for the parasites to be ingested through the mouth. This happens, for example, when the hookworm is in raw meat. Breast milk is also a possible source of infection, which can result in transmission to the baby. Hookworms can reach an age of up to 15 years. During this time, their diet consists of blood and villous tissue. However, ten times as much blood is sucked by Ancylostoma duodenale as by Necator americanus. In some cases, the hookworms do not immediately penetrate to the intestine, but instead remain in the skeletal muscles during the larval stage. For this reason, there is a risk of recurrence even after successful treatment of hookworm infestation. It is not possible for hookworms to be transmitted from person to person. The eggs of the parasites must spend a certain period of time in the outside world.
Diseases and complaints
Few worm species cause as many infections in tropical and subtropical areas as the hookworm. About 900 million people are affected by the parasites. Approximately 60,000 deaths occur each year. The rural population, small farmers and children, are most often affected by the parasite infestation. The reason for this is considered to be fertilizing with feces.In earlier times, Ancylostoma duodenale also caused infections among miners working in coal mines in Central Europe. This is because the conditions in the tunnels are suitable for the parasites. The course of hookworm disease depends on the number of parasites that enter the intestine. The patient’s state of health also plays a significant role. The first signs of ankylostomiasis are skin reactions and itching. Because hookworm larvae usually migrate toward the lungs during the first week of infestation, this often results in dry cough, bronchitis, and shortness of breath. Pneumonia is likewise conceivable. After the hookworms arrive in the intestine, they develop there into sexually mature specimens. After hooking into the intestinal mucosa, they begin to suck blood, causing bleeding and damage to the mucosa. About four to six weeks after infection, hookworm disease is noticeable by loss of appetite, a bloated abdomen, abdominal pain, and mucous-bloody diarrhea. Treatment for hookworm disease is with worming medications as well as iron supplements to compensate for blood loss.
