After the L3 larvae have successfully entered the host, they then travel through the subcutaneous venules and lymphatic vessels of the human host. Eventually, the L3 larvae enter the lungs through the pulmonary capillaries and break out into the alveoli. They then travel up the trachea to be coughed and swallowed by the host. After being swallowed, the L3 larvae are then found in the small intestine, where they molt into the L4, or adult worm stage. The entire process from skin penetration to adult development takes about 5–9 weeks. The female adult worms release eggs (N. americanus about 9,000–10,000 eggs/day and A. duodenale 25,000–30,000 eggs/day), which are passed in the feces of the human host. These eggs hatch in the environment within several days and the cycle starts anew. Pathophysiology
Hookworm infection is generally considered to be asymptomatic, but as Norman Stoll described in 1962, it is an extremely dangerous infection because its damage is "silent and insidious." An individual may experience general symptoms soon after infection. Ground-itch, which is an allergic reaction at the site of parasitic penetration and entry, is common in patients infected with N. americanus. Additionally, cough and pneumonitis may result as the larvae begin to break into the alveoli and travel up the trachea. Then once the larvae reach the small intestine of the host and begin to mature, the infected individual will experience diarrhea and other gastrointestinal discomfort. However, the "silent and insidious" symptoms referred to by Stoll are related to chronic, heavy-intensity hookworm infections.
Hookworm infection is an infection by a type of intestinal parasite known as a hookworm. Initially, itching and a rash may occur at the site of infection. Those only affected by a few worms may show no symptoms. Those infected by many worms may experience abdominal pain, diarrhea, weight loss, and tiredness. The mental and physical development of children may be affected. Anemia may result.Two common hookworm infections in humans are ancylostomiasis and necatoriasis, caused by the species Ancylostoma duodenale and Necator americanus respectively. Hookworm eggs are deposited in the stools of infected people. If these end up in the environment, they can hatch into larvae (immature worms), which can then penetrate the skin. One type can also be spread through contaminated food. Risk factors include walking barefoot in warm climates, where sanitation is poor. Diagnosis is by examination of a stool sample with a microscope.The disease can be prevented on an individual level by not walking barefoot in areas where the disease is common. At a population level, decreasing outdoor defecation, not using raw feces as fertilizer, and mass deworming is effective. Treatment is typically with the medications albendazole or mebendazole for one to three days. Iron supplements may be needed in those with anemia.Hookworms infected about 428 million people in 2015. Heavy infections can occur in both children and adults, but are less common in adults. They are rarely fatal. Hookworm infection is a soil-transmitted helminthiasis and classified as a neglected tropical disease.