Ascariasis

Published by Bupa's health information team, November 2008.

This factsheet is for people who have ascariasis, or who would like information about it.

Ascariasis is an infection caused by the worm Ascaris lumbricoides. A. lumbricoides is a parasitic roundworm that lives in the small intestine.

Ascariasis is very common worldwide. It is thought to affect up to a quarter of the world's population. The infection is most common in Africa, Central and South Eastern Asia and South America.

• About Ascariasis
• Symptoms of ascariasis
• Complications of ascariasis
• Diagnosis of ascariasis
• Treatment of ascariasis
• After your treatment
• Questions and answers
• Sources

About Ascariasis

Ascariasis is caused by an infection with the parasitic worm A. lumbricoides. Parasites live off other animals, causing them harm.

A. lumbricoides is a type of roundworm. It is well adapted to living in the human body. It goes through several different stages in its lifecycle inside the body.

How is ascariasis spread?

A. lumbricoides is spread by eating food contaminated by eggs from an infected person's faeces. The eggs can survive in soil for months or even years. From the soil the eggs can become attached to fruit or vegetables and are then eaten accidentally. The eggs are microscopic and not visible to the naked eye.

Once the eggs have passed from the stomach into the small intestine they hatch, releasing microscopic larvae. The larvae travel through the wall of your intestine and enter the blood stream, which carries them to your liver and heart.

After one to seven days the larvae reach your lungs. Here they pass through the lining of your lungs, and then travel up your windpipe to the back of your throat. You then swallow the larvae, which pass through your stomach and back into the small intestine where they develop into adult worms, living off half-digested food. Female worms can grow between 20cm and 35cm long; male worms are smaller and more slender than female worms, at around 10cm to 30cm in length. The adult worms are white in colour and have a similar size and appearance to an earthworm.

The worms mate in your small intestine and the females produce eggs that are passed in faeces, and the lifecycle begins again.

People who get severely infected may have hundreds, even thousands, of worms living inside them.

The infection is most common among young children in poor areas, because of their low hygiene standards and undeveloped immune system.

Symptoms of ascariasis

Ascariasis doesn't usually cause any symptoms. However if you are infected with many worms ascariasis can cause symptoms as follows.

• The main effect of ascariasis is a general slowing of growth and weight gain. Children can lose up to 10 percent of the protein they eat, and may become deficient in vitamin A and C. Children with severe ascariasis can develop malnutrition
.
• If large numbers of larvae enter the lungs it can cause a cough and make it difficult for you to breathe. This is known as Loeffler's syndrome. You may also have a fever and allergic symptoms such swollen lips or asthma. Severe Loeffler's syndrome can cause pneumonia (a build up of fluid in the lungs).
• The most common symptoms of ascariasis are caused by adult worms. These include vague abdominal pains, nausea and colic. The more worms you have the worse these symptoms are likely to be.

Complications of ascariasis

Ascariasis can rarely cause a number of complications, some of which are severe.

• If you are infected with lots of worms, they might block your small intestine completely. This can be serious. If this happens you may need an operation to clear the blockage.
• Larvae sometimes travel elsewhere in the body than the lungs. If they reach your brain or spinal cord they can cause other symptoms such as epilepsy, insomnia or meningitis.
• Adult worms may travel to other areas of your body causing other, sometimes serious, problems. They can enter and block the bile duct from your liver, causing jaundice or other liver problems. They can also block your pancreatic duct, causing the pancreas to become inflamed (pancreatitis).
• The worms can enter the appendix or burst the wall of the intestine. This can be life-threatening. The worms can also travel into the stomach and be vomited up, or even travel up the oesophagus (pipe that carries food from your mouth to your stomach) to come out of the nose. If they enter the windpipe they can sometimes cause suffocation.
• In rare cases the worm can travel into the eustachian tubes - the tubes connecting your throat to the middle ear. This can happen during a fever, or when you're under general anaesthesia.

Diagnosis of ascariasis

Ascariasis is diagnosed by the presence of worms or eggs in a faecal sample. These can be tested for in a laboratory. Blood tests also show an increase in antibody levels and an increase in one of the types of white blood cells when the worms are in the larval phase.

If you have a barium meal X-ray, the adult worms are sometimes visible as string-like shadows.

Treatment of ascariasis

Medicines

Ascariasis can be easily treated with the right medicine. The infection is dealt with when the worms are in the adult stage of their life cycle.

A one-off dose of a drug called albendazole or the alternative drug levamisole is thought to be the best way to treat ascariasis. This is taken in a tablet form. Other drugs that might be used include piperazine and mebendazole, which is taken twice a day for three days.

If your breathing is affected by larvae in your lungs (See symptoms), a drug called prednisolone is used to control the inflammation in your lungs. The adult worm infection can then be treated two to three weeks later.

If your intestines become blocked by worms, your doctor may be able to clear them in hospital using liquid paraffin and the drug piperazine, which kills the worms. You will also be given fluids through a tube into your veins to keep you hydrated.

Surgery

If your intestines become blocked by the worms and other treatments options haven't worked (see Medicines), you may need surgery to clear the blockage.

After your treatment

Improved hygiene measures will help stop re-infection. This includes better methods of disposing of faeces in the area, and not using human manure for fertilising crops -a common way that ascariasis is spread in developing countries.

Sources

• Eddleston M, Davidson R, Wilkinson R, et al. Oxford Handbook of Tropical Medicine. 2nd ed. Oxford: Oxford University Press, 2005
• Kasper DL, Braunwald E, Fauci AS, et al. Harrison's Principles of Internal Medicine. 16th ed. New York: McGraw-Hill, 2005:1254-1257
• Ascaris lumbricoides. University of Cambridge Department of Pathology Schistosome Research Group. www.path.cam.ac.uk, accessed 15 May 2008
• Ascaris infection. Division of Parasitic Diseases. www.cdc.gov, accessed 15 May 2008
• Joint Formulary Committee, British National Formulary. 55th ed. London: British Medical Association and Royal Pharmaceutical Society of Great Britain, 2008 :356-357

This information was published by Bupa's health information team and is based on reputable sources of medical evidence. It has been peer reviewed by Bupa doctors. The content is intended for general information only and does not replace the need for personal advice from a qualified health professional.

Publication date: November 2008