Ascariasis

Ascariasis is a disease caused by the parasitic roundworm Ascaris lumbricoides. Infections have no symptoms in more than 85% of cases, especially if the number of worms is small. Symptoms increase with the number of worms present and may include shortness of breath and fever at the beginning of the disease. These may be followed by symptoms of abdominal swelling, abdominal pain, and diarrhea. Children are most commonly affected, and in this age group the infection may also cause poor weight gain, malnutrition, and learning problems. Infection occurs by ingesting food or drink contaminated with Ascaris eggs from feces. The eggs hatch in the intestines, the larvae burrow through the gut wall, and migrate to the lungs via the blood. There they break into the alveoli and pass up the trachea, where they are coughed up and may be swallowed. The larvae then pass through the stomach a second time into the intestine, where they become adult worms. It is a type of soil-transmitted helminthiasis and part of a group of diseases called helminthiases. Prevention is by improved sanitation, which includes improving access to toilets and proper disposal of feces. Handwashing with soap appears protective. In areas where more than 20% of the population is affected, treating everyone at regular intervals is recommended. Reoccurring infections are common. There is no vaccine. Treatments recommended by the World Health Organization are the medications albendazole, mebendazole, levamisole, or pyrantel pamoate. Other effective agents include tribendimidine and nitazoxanide. About 0.8 to 1.2 billion people globally have ascariasis, with the most heavily affected populations being in sub-Saharan Africa, Latin America, and Asia. This makes ascariasis the most common form of soil-transmitted helminthiasis. As of 2010 it caused about 2,700 deaths a year, down from 3,400 in 1990. Another type of Ascaris infects pigs. Ascariasis is...