Ascariasis

Ascariasis is a disease caused by a parasitic roundworm named Ascaris lumbricoides. This parasite belongs to a group of diseases called helminthiases. It is also classified as a neglected tropical disease.

Ascariasis is the most common form of soil-transmitted helminthiasis. This means the infection spreads through soil that has been contaminated. While many infections cause no symptoms, the disease can be quite serious. Most people with only a few worms feel nothing at all. However, a small number of people can be heavily infected with many worms.

The life cycle of the worm is a complex journey through the body. It begins when a person ingests infective eggs from contaminated food, water, or soil. These eggs often come from feces. Once swallowed, the eggs hatch into larvae in the intestines. These larvae burrow through the gut wall and enter the bloodstream. From there, they migrate to the lungs.

In the lungs, the larvae penetrate the alveolar walls. They then move up the trachea and are coughed up. The person swallows the larvae a second time. Finally, they pass through the stomach back into the small intestine. There, they mature into adult worms.

This entire process takes about two to three months.

As the larvae migrate, they can cause various health problems. This movement can lead to inflammation of the lungs or the liver. Some people experience a respiratory illness called Loeffler's syndrome. This condition involves pulmonary infiltrates and radiographic shadowing.

Once the worms become adults, they live in the lumen, or the open space, of the small intestine. They stay in place by swimming against the intestinal flow. They take nutrients from the host's partially digested food. They may also secrete enzyme inhibitors to protect themselves from being digested. Adult worms can live for one to two years inside a person.

Heavy infections can lead to dangerous physical complications. A large group of worms can tangle into a mass called a bolus. This can cause a bowel obstruction, which is a blockage in the intestine. This occurs in up to 0.2 per 1,000 people every year.

In extreme cases, worms can cause the intestine to twist or result in gangrene. A worm might also block the biliary tree or the pancreatic duct. This can lead to conditions like acute pancreatitis or cholangitis. In children, the worms can cause malnutrition and poor weight gain. This happens because the worms can cause malabsorption of nutrients. They may erode the villi, which are tiny structures in the intestinal lining.

Ascariasis affects a massive number of people across the globe. Between 0.8 and 1.2 billion people are estimated to have the infection. The most heavily affected regions are sub-Saharan Africa, Latin America, and Asia.

The reproductive capacity of these worms is enormous. A single female worm can produce approximately 200,000 eggs every day. These eggs are very hardy and can survive in the environment for up to 15 years. In 1990, the disease caused about 3,400 deaths annually. By 2010, that number had decreased to approximately 2,700 deaths per year.

Doctors diagnose ascariasis by finding eggs or worms in feces. Under a microscope, the eggs have a unique oval shape. They feature a thick, mamillated shell, which means it is covered in small lumps.

To treat the infection, doctors use medications called ascaricides. The World Health Organization recommends drugs like albendazole and mebendazole. These can be given as a single dose to remove the parasites. Other effective medicines include levamisole and pyrantel pamoate. In some cases, surgery is required to remove a blockage caused by a mass of worms.

Prevention focuses on improving sanitation and hygiene. Better access to clean toilets and proper waste disposal is essential. Handwashing with soap is also a protective measure.

In areas where more than 20% of the population is infected, mass drug administration is recommended. This involves treating everyone at regular intervals, often in schools. This method is very affordable, costing about 2 to 3 cents per person. By managing wastewater and protecting crops from contamination, the spread of these worms can be reduced.