Roundworms (also known as Ascaris lumbricoides) belong to a large group of worms called nematodes. Roundworms are common human parasites that live in the intestine (guts).
Roundworm is rare in developed countries such as the UK. It is most common in warm, moist climates, so the most likely time to contract roundworms is when travelling abroad.
A female roundworm living in a personís intestines lays eggs that are passed out in faeces. The eggs can survive for over three years in suitable conditions, such as moist soil. The eggs can get into food or water, or onto a personís hands, through poor sanitation, using human excrement as a fertilizer, or inadequate personal hygiene. The infection spreads in humans by eating food or drinking water containing worm eggs.
Eggs that have been eaten hatch in the small intestine and become larvae. The larvae penetrate the bowel lining and are carried in the blood to the lungs, where they grow to about the size of a pinhead. They then migrate up the air passages to back of the throat and are swallowed.
When they return to the small intestine, the larvae mature into adult worms and start to reproduce. Mature worms can live for up to 2 years in the intestine.
Roundworms are pale pink in colour and have a long cylindrical body, between 20 and 30 cm long.
Many cases of roundworm infestation produce no symptoms, or a mild abdominal pain. In the early stages, there may be effects from worm larvae in the lungs, such as fever, wheezing and coughing, or pneumonitis (inflammation of the lungs).
When there is a heavy worm infestation, common symptoms include:
abdominal discomfort and pain,
nausea or vomiting.
Occasionally, serious complications occur, such as blockages of the intestine
Roundworm eggs can be detected by microscopic examination of a stool sample. It usually takes around 2 months between the ingestion of eggs to the first appearance of fresh eggs in stools.
Occasionally, larvae are found in the sputum (coughed up phlegm-like substance), during the stage when they are in the lungs.
In cases of heavy infestation, the adult worm may be seen in the faeces.
Roundworms can be treated with a combination of drugs and hygiene measures. Treatments with medicines usually work well. They kill or paralyse the worms, which are then passed out of the body with the stools.
Mebendazole is a worm-killing drug that is usually the first choice of drug treatment for adults and children older than 2 years. It is taken as a tablet or a drink, for three days, is the normal treatment. Side effects are minimal, but in people with heavy infestations it can cause abdominal pain or diarrhoea while it removes the worms. This medication is available on prescription.
Piperazine paralyses the worms and is recommended if intestinal or biliary obstruction is suspected. It is often given in conjunction with senna, which is a laxative. It has some common side effects such as vomiting and diarrhoea, but is safe for use in children from 3 months onwards. It is not however suitable for those with epilepsy, decreased kidney function, liver disease, or women who are pregnant or breast- feeding. Piperazine is available on prescription.
A person can be reinfected after drug treatment if they swallow more worm eggs, so it is important to maintain high levels of hygiene (see Prevention).
Your GP can advise if you are pregnant or breast feeding or your baby is under three months old.
Drug treatments for roundworm are not recommended in pregnancy, but the infection cannot spread to an unborn baby. Pregnant women should take hygiene measures and receive drug treatment after giving birth, unless complications occur.
There are other medicines that are licensed outside the UK, where roundworms are more common.
In heavy infestations, of up to 100 worms, pneumonia or obstruction of the bowel may result.
If there are many worms in the bowel, a blockage may occur in the intestines or biliary tract (bile ducts and gall bladder). Sometimes adult worms migrate to other parts of the body, such as the lungs and liver, and cause severe complications such as appendicitis. A large number of larvae in the lungs may cause pneumonia.
source NHSDirect 151204