Molecular testing for Ascaris (Ascaris lumbricoides) is used for fast, reliable, and safe laboratory diagnosis of ascariasis.
Ascaris (Ascaris lumbricoides) is a large helminthic worm (Nematode) that infects the intestine of humans. It is the most common helminthic infection in humans worldwide, with most cases occurring in the tropics and subtropics. Ascaris infection (ascariasis) is generally rare in developed countries but sporadic cases, especially in rural areas, can occur. Larvae and adult worms live in the small intestine and can cause intestinal disease.
The laboratory diagnosis of the disease includes the examination of the feces for the eggs of the parasite, while in the pulmonary form of the disease, larvae in sputum or gastric fluid can be sought. Rarely, adult worms can be found in the feces.
The molecular testing of feces and other biological materials (sputum, gastric contents), allows the fast, specific, and sensitive method for the diagnosis of ascariasis.
More information about Ascaris
Most people who become infected with Ascaris have no symptoms. Moderate to severe infection causes various symptoms, depending on the organ that has been affected.
Lungs: After the tiny Ascaris eggs are swallowed, they hatch in the small intestine and the larvae migrate through the circulatory or lymphatic system to the lungs. At this stage, signs and symptoms similar to asthma or pneumonia may occur, such as persistent cough, difficulty breathing, and wheezing. After 6 to 10 days in the lungs, the larvae travel to the pharyngeal area, where they cause a reflex cough and then are swallowed.
Intestine: The larvae mature into adult worms in the small intestine and usually live in the intestine until they die (1 to 2 years). In mild or moderate ascariasis, the intestinal infection may cause undetected abdominal pain, nausea, vomiting, diarrhea, or bloody stools. If there is a large number of worms in the intestine (severe ascariasis), severe abdominal pain, fatigue, vomiting, weight loss, malnutrition, and worms in the vomit or stool may occur.
Ascaris is not transmitted directly from person to person. A person should come into contact with soil contaminated with human feces containing Ascaris eggs or contaminated water. In many developing countries, human feces are used as fertilizer and poor sanitation allows human waste to mix with the soil in the fields and near settlements.
Young children often play with dirt and can become infected if they put their hands in their mouths. Unwashed fruits or vegetables grown on contaminated soil can also transmit Ascaris eggs.
The life cycle of Ascaris
Ingestion. Ascaris eggs are not contagious before they come in contact with the soil. People can accidentally swallow contaminated soil through hand-to-mouth contact or by eating fruits and uncooked vegetables grown on contaminated soil.
Immigration. The larvae hatch from eggs in the small intestine and then penetrate the intestinal wall and migrate to the lungs through the bloodstream or lymphatic system. After maturing for about a week in the lungs, the larvae penetrate the airways and reach the throat, where they are swallowed to reach the gastrointestinal tract again.
Maturation. Once they return to the intestine, the parasites develop into male or female worms. Female worms can grow to a length of more than 40 cm and about 6 mm in diameter. Male worms are generally smaller.
Reproduction. Male and female worms mate in the small intestine. Female worms can produce 200.000 eggs a day, which are excreted in the feces. Fertilized eggs must be found in the soil for at least 18 days before becoming infected.
The whole process - from swallowing the eggs to laying the new eggs - takes about two to three months. Ascarids can live inside the human body for 1 to 2 years.
Risk factors for Ascaris infection include:
Age. Most patients with ascariasis are children under 10. Children in this age group are at higher risk because they are more likely to play on dirt.
Warm climate. Ascaris is more prevalent in developing countries with hot temperatures all year round.
Poor hygiene. Ascaris is widespread in developing countries where human feces are mixed with soil.
Mild cases of ascariasis usually have no complications. The most important complications may include:
Poor development. Loss of appetite and poor absorption of nutrients from food in Ascaris-infected children can slow their development.
Intestinal obstruction and perforation. In severe Ascaris infection, the worm mass can block part of the intestine, causing abdominal pain and vomiting. The obstruction can even lead to perforation of the intestinal wall or appendix, causing internal bleeding or appendicitis.
Duct obstruction. In some cases, the worms can block the liver or pancreatic ducts, causing severe pain.
The best defense against ascariasis is good hygiene and common sense.
Rules of good hygiene. Before handling food, wash hands thoroughly with soap and water. Good washing of fresh fruits and vegetables.
Beware of traveling to tropical and subtropical countries. Use only bottled water and avoid raw vegetables. Consume only food that is cooked.
Last update: 02/05 / 2020