Hookworm is a gastrointestinal parasitic infection. It is estimated that one billion people worldwide may be infected by hookworm. The infection is most commonly found in tropical and sub-tropical climates. The adult worm is about one centimeter long.
There are four different hookworm species that can infect man. These species are Necator americanus, Ancylostoma duodenale, Ancylostoma ceylanicum and Ancylostoma braziliense. Necator americanus and Ancylostoma duodenale only infect humans while the other two species can also infect animal hosts. The mode of infection and life cycle is the similar for all four species.
The eggs laid by adult hookworms pass out of the body in the feces. Where fecal matter contaminates moist soil the hookworm eggs can develop into larval forms which will burrow through intact skin to infect a new host. After entering a host the larval hookworm migrates via the blood stream to the lungs. The larvae leave the lungs via the airway to the back of the throat where they are swallowed into the intestinal tract. On reaching the small intestine the larvae mature into adult hookworms.
The symptoms caused by hookworm infection may start with an itchy skin rash at the site the larva had penetrated the skin. This is sometimes known as known as ground itch. The migration of the larvae in the lungs induces coughing accompanied by the production of blood stained sputum. Once the larvae leave the lungs and move to the intestines many patients have no further symptoms particularly if they only have a light infection.
Where symptoms of the gastrointestinal phase of hookworm infection are present they may include: abdominal pain, bloody stools, diarrhea, fatigue, fever, gas, loss of appetite, nausea and vomiting. Blood loss in heavy infestation may lead to iron deficient anemia with a resulting pale pallor. Other complications sometimes seen in long term or heavy infections include nutritional deficiencies, protein loss and a build up of fluid in the abdominal cavity (this is known as ascites).
Infections with hookworm are rarely life threatening. The debilitation they can cause may lead their host open to severe disease from other pathogens that they would otherwise have been able to fight. This is particularly a problem with hookworm infections in young children.
Diagnosis of hookworm infection is made by looking for the characteristic microscopic eggs in a stool sample. Occasionally the adult worms may be seen in the feces.
Hookworm infections can be treated with one of the anti-helminthic drugs such as albendazole, mebendazole or pyrantel pamoate. The drug Ivermectin, while useful for many other worm infections, is ineffectual in treating hookworm infections.
Infection with hookworm may be prevented by the provision of improved sanitation. As the larva frequently penetrates the foot travelers and people living in endemic areas may reduce their likelihood of catching hookworm by wearing adequate footwear.