ASCARIS LUMBRICOIDES

An estimated 807-1,221 million people in the world are infected with Ascaris lumbricoides (sometimes called just "Ascaris"). Ascaris, hookworm, and whipworm are known as soil-transmitted helminths (parasitic worms). Together, they account for a major burden of disease worldwide. Ascariasis is now uncommon in the United States.

Ascaris lives in the intestine and Ascaris eggs are passed in the feces of infected persons. If the infected person defecates outside (near bushes, in a garden, or field) or if the feces of an infected person are used as fertilizer, eggs are deposited on soil. They can then mature into a form that is infective. Ascariasis is caused by ingesting eggs. This can happen when hands or fingers that have contaminated dirt on them are put in the mouth or by consuming vegetables or fruits that have not been carefully cooked, washed or peeled.

People infected with Ascaris often show no symptoms. If symptoms do occur they can be light and include abdominal discomfort. Heavy infections can cause intestinal blockage and impair growth in children. Other symptoms such as cough are due to migration of the worms through the body. Ascariasis is treatable with medication prescribed by your health care provider.

FAQS

What is ascariasis?

Ascaris is an intestinal parasite of humans. It is the most common human worm infection. The larvae and adult worms live in the small intestine and can cause intestinal disease.

How is ascariasis spread?

Ascaris lives in the intestine and Ascaris eggs are passed in the feces of infected persons. If the infected person defecates outside (near bushes, in a garden, or field), or if the feces of an infected person are used as fertilizer, then eggs are deposited on the soil. They can then mature into a form that is infective. Ascariasis is caused by ingesting infective eggs. This can happen when hands or fingers that have contaminated dirt on them are put in the mouth or by consuming vegetables or fruits that have not been carefully cooked, washed or peeled.

Who is at risk for infection?

Infection occurs worldwide in warm and humid climates, where sanitation and hygiene are poor, including in temperate zones during warmer months. Persons in these areas are at risk if soil contaminated with human feces enters their mouths or if they eat vegetables or fruit that have not been carefully washed, peeled or cooked. Ascariasis is now uncommon in the United States.

What are the symptoms of ascariasis?

People infected with Ascaris often show no symptoms. If symptoms do occur they can be light and include abdominal discomfort. Heavy infections can cause intestinal blockage and impair growth in children. Other symptoms such as cough are due to migration of the worms through the body.

How is ascariasis diagnosed?

Health care providers can diagnose ascariasis by taking a stool sample and using a microscope to look for the presence of eggs. Some people notice infection when a worm is passed in their stool or is coughed up. If this happens, bring in the worm specimen to your health care provider for diagnosis.

How can I prevent infection?

• Avoid contact with soil that may be contaminated with human feces, including with human fecal matter ("night soil") used to fertilize crops.
• Wash your hands with soap and warm water before handling food.
• Teach children the importance of washing hands to prevent infection.
• Wash, peel, or cook all raw vegetables and fruits before eating, particularly those that have been grown in soil that has been fertilized with manure.

Transmission of infection to others can be prevented by:

• not defecating outdoors, and by
• effective sewage disposal systems.

What is the treatment for ascariasis?

Anthelminthic medications (drugs that rid the body of parasitic worms), such as albendazole and mebendazole, are the drugs of choice for treatment. Infections are generally treated for 1-3 days. The recommended medications are effective.

What is preventive treatment?

In developing countries, groups at higher risk for soil-transmitted helminth infections (hookworm, Ascaris, and whipworm) are often treated without a prior stool examination. Treating in this way is called preventive treatment (or "preventive chemotherapy"). The high-risk groups identified by the World Health Organization are preschool and school-age children, women of childbearing age (including pregnant women in the 2nd and 3rd trimesters and lactating women) and adults in occupations where there is a high risk of heavy infections. School-age children are often treated through school-health programs and preschool children and pregnant women at visits to health clinics.

What is mass drug administration (MDA)?

The soil-transmitted helminths (hookworm, Ascaris, and whipworm) and four other "neglected tropical diseases" (river blindness, lymphatic filariasis, schistosomiasis and trachoma) are sometimes treated through mass drug administrations. Since the drugs used are safe and inexpensive or donated, entire risk groups are offered preventive treatment. Mass drug administrations are conducted periodically (often annually), commonly with drug distributors who go door-to-door. Multiple neglected tropical diseases are often treated simultaneously using MDAs.

EPIDEMIOLOGY & RISK FACTORS

Ascaris infection is one of the most common intestinal worm infections. It is found in association with poor personal hygiene, poor sanitation, and in places where human feces are used as fertilizer.

Geographic Distribution

The geographic distributions of Ascaris are worldwide in areas with warm, moist climates and are widely overlapping. Infection occurs worldwide and is most common in tropical and subtropical areas where sanitation and hygiene are poor.

BIOLOGY

Causal Agent:

Ascaris lumbricoides is the largest nematode (roundworm) parasitizing the human intestine. (Adult females: 20 to 35 cm; adult male: 15 to 30 cm.)

Life Cycle:

Adult worms live in the lumen of the small intestine. A female may produce approximately 200,000 eggs per day, which are passed with the feces. Unfertilized eggs may be ingested but are not infective. Fertile eggs embryonate and become infective after 18 days to several weeks, depending on the environmental conditions (optimum: moist, warm, shaded soil). After infective eggs are swallowed, the larvae hatch, invade the intestinal mucosa, and are carried via the portal, then systemic circulation to the lungs. The larvae mature further in the lungs (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed. Upon reaching the small intestine, they develop into adult worms. Between 2 and 3 months are required from ingestion of the infective eggs to oviposition by the adult female. Adult worms can live 1 to 2 years.

Life cycle image and information courtesy of DPDx.

DISEASE

People infected with Ascaris often show no symptoms. If symptoms do occur they can be light and include abdominal discomfort. Heavy infections can cause intestinal blockage and impair growth in children. Other symptoms such as cough are due to migration of the worms through the body. Ascariasis is treatable with medication prescribed by your health care provider.

DIAGNOSIS

The standard method for diagnosing ascariasis is by identifying Ascaris eggs in a stool sample using a microscope. Because eggs may be difficult to find in light infections, a concentration procedure is recommended.

PREVENTION AND CONTROL

The best way to prevent ascariasis is to always:

• Avoid ingesting soil that may be contaminated with human feces, including where human fecal matter ("night soil") or wastewater is used to fertilize crops.
• Wash your hands with soap and warm water before handling food.
• Teach children the importance of washing hands to prevent infection.
• Wash, peel, or cook all raw vegetables and fruits before eating, particularly those that have been grown in soil that has been fertilized with manure.

For more information view the source:Center for Disease Control

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