Hookworms
Hookworms are parasitic roundworms that infect the small intestines of their human hosts, with two primary species causing infections: Ancylostoma duodenale (Old World hookworm) and Necator americanus (New World hookworm). These worms are prevalent in rural tropical and subtropical regions, including parts of Asia, East Africa, South America, and the southeastern United States, although improved hygiene has reduced their incidence in some areas. Hookworm infections affect an estimated one-fifth of the global population and are classified as neglected tropical diseases by the World Health Organization.
Transmission occurs through direct skin contact with contaminated soil or ingestion of larvae in contaminated food. Once inside the host, hookworms attach to the intestinal lining and feed on blood, leading to symptoms such as anemia, fatigue, and digestive issues. Severe cases can result in significant health complications, particularly in children, including developmental delays. Prevention strategies focus on proper sanitation and wearing shoes in endemic areas. Treatment typically involves antiparasitic medications and may also require iron supplements or more intensive medical intervention for severe infections. Researchers are also exploring vaccine development as a potential long-term solution to prevent hookworm infections.
Hookworms
- TRANSMISSION ROUTE: Direct contact, ingestion
Definition
Hookworms are parasitic, threadlike roundworms (nematodes) that infect the small intestines of their host. Two hookworm species are known to infect humans: Ancylostoma duodenale, also known as Old World hookworm, and Necator americanus, also known as New World or American hookworm. Ancylostoma ceylanicum and Ancylostoma braziliense are two other species of hookworm that have been known to infect humans, although this is uncommon. Listed as one of the neglected tropical diseases (NDT) by the World Health Organization, hookworm infection is estimated to affect about one-fifth of the world’s population.
Natural Habitat and Features
Hookworms are most often found in rural areas of tropical and subtropical countries, such as those in Asia, East Africa, South America, and the southeastern United States. The presence of hookworms in the American South, however, has been greatly reduced with proper hygiene and sanitation. The eggs are deposited in the soil from human feces because of poor sanitation or using human feces as fertilizer. For the eggs to develop into larvae, the soil must be warm, shaded, sandy, or loamy and have sufficient moisture. The eggs hatch into larvae that can penetrate the skin and enter their human host in one to two days. Ingestion of larvae from contaminated food is also possible.
Once inside the host, the larvae migrate through the body through the circulatory system and the lungs to the small intestines, where they adhere to the intestinal lining with their teeth or cutting plates. The worms will feed on their host’s blood and proteins.
The worm will have reached the adult reproductive stage six weeks after initial host penetration. The oval eggs exit the body with the passage of stools. Depending on the species, each female can generate thousands of eggs daily. Hookworm life spans an average of one to two years, and some live up to ten years.
N. americanus is 6 to 12 millimeters (mm) long and has a round body. Males are typically smaller than females. A. duodenale is slightly larger at 8 to 13 mm long and has an S shape at its front end.
Pathogenicity and Clinical Significance
The larvae's penetration of the skin causes an allergic reaction around the site of entry, known as ground itch. Larvae's migration through the body may also cause mild pulmonary distress, such as asthma, bronchitis, or coughing.
Minor hookworm infections are typically asymptomatic. When many worms are present, the most critical pathology is human blood loss, which leads to iron deficiency anemia. Heavy infestation may also result in extreme fatigue, lethargy, fever, malnutrition, and digestive disruptions such as nausea, abdominal pain, diarrhea, and discolored stools. Severe infection in children can cause developmental delays.
Hookworm infections may be prevented through sanitary disposal of human feces and by wearing shoes in areas where hookworm larvae are likely to be found. Despite efforts to control and eradicate hookworms, they remain a worldwide public health concern. In the face of hookworm’s prevalence and disruption to daily life, and because of concern over building resistance to drugs, the Human Hookworm Vaccine Initiative, composed of educational and research institutions worldwide, worked to develop a vaccine against hookworm infection. Several promising vaccine candidates have shown efficacy against hookworm infections in clinical trials by demonstrating the ability to produce a beneficial immune system response to hookworm infections.
Drug Susceptibility
Hookworm infections may be treated with albendazole, mebendazole, and pyrantel pamoate. To ensure the parasites have been eradicated, stools should be reexamined two weeks after initial drug therapy. Iron supplements may also be necessary. More severe infections will require longer courses of treatment, and serious cases may involve blood transfusions and hospitalizations.
Bibliography
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