Worms

About 25% of all the people on earth are infested by various kinds of worms (helminths). Worm infections are the most prevalent infections in the world. The World Bank estimates that 100 million people may experience stunting or wasting as a result of worm infestation.

Because of their high mobility and lower standards of hygiene, school-age children are particularly vulnerable to these parasites.

Helminths (worms) are worm-like organisms that are usually visible to the naked eye in the adult stage and usually live in the gastrointestinal tract. Some worms can also infect the bloodstream or tissues. Worms live and feed off living hosts, receiving nourishment and protection while disrupting their hosts’ nutrient absorption, causing weakness and disease.

Helminths often find their way into a host through eating infected food, drinking contaminated water and walking on infected soil. Infection is usually more common in areas with poor sanitation, poor personal hygiene or where human faeces are used as fertiliser.

Chronic helminthic infection down-regulates the immune response that is needed to prevent infection by the human immunodeficiency virus (HIV) and Mycobacterium tuberculosis.

Two groups of worms commonly cause gastrointestinal infestations. These are

• nematodes (roundworms) and
• platyhelminthes (flatworms) which include tapeworms.

Roundworm

Over one billion people are thought to be infected with roundworm.

Life cycle

The infection starts by ingesting food or water which contains worm eggs. The eggs hatch in the gut and the larvae are released. These larvae penetrate the gut wall and move into the bloodstream. They reach the lungs, are coughed up and swallowed and thus return to the gut. The larvae then mature into adult worms, which live in the gut and reproduce.

Mature females are 25-35 cm long, with the males a bit smaller. They are about 2 – 6 mm in diameter.

The female lays eggs which are passed in the faeces and stay in the soil until another host ingests them. One female worm can produce nearly 250 000 eggs per day!

Symptoms

As with many worm infections, symptoms are generally mild and vague and may include

• abdominal pain
• nausea
• weight loss
• possibly diarrhoea

Some people develop a cough and mild fever from the larvae moving through the lungs. Large numbers of adult worms in the gut may block the gut itself. Sometimes the worms migrate around the gut and move into structures such as the bile duct and appendix, causing inflammation of the bile duct and appendicitis.

Diagnosis

The diagnosis is made by observing eggs from a stool sample or by identifying worms that have been passed.

Treatment

The most common drugs available to treat roundworm are albendazole (Zentel®) and mebendazole (Vermox®). This treatment is highly effective and is associated with few side-effects.

Prevention

Hygienic disposal of faeces is very important in controlling this and other worm infections.

Tapeworm

As the name suggests, these worms are flat, ribbon-like and segmented. They can reach up to 10 meters in length with over 1000 segments, each segment capable of reproducing. Tapeworms are hermaphroditic – each worm contains both male and female sex organs and one worm is able to reproduce on its own.

Life cycle

The adult worms reproduce in the gut and mature segments break off the worm and migrate out through the anus into the soil. These segments are filled with eggs and are ingested by a herbivorous animal host. In the host animal’s gut, the eggs hatch to release larvae, which move through the gut wall into the tissues. Once in the tissues (e.g. muscle) of the herbivore, the larvae fill with fluid and form a structure called a cysticercus. If a human eats undercooked or raw beef or pork, these cysticerci can hatch and a mature tapeworm can develop in the gut after two to three months.

Humans can become infected by:

• touching contaminated faeces and placing their hands near their mouth
• swallowing food or water containing traces of contaminated faeces
• eating raw contaminated pork, beef or fish

Symptoms

Infections with adult worms normally produce no or mild symptoms, such as

• some abdominal pain
• weight loss
• nausea

However, cysticercosis (cysts in human tissues) can cause a variety of problems, such as epilepsy and fluid on the brain but many people have no symptoms at all. Eventually the cysticerci die and become calcified.

In rare cases, infection with the fish tapeworm can cause vitamin B12 deficiency, because the worm absorbs this vitamin.  Vitamin B12 is required to make red blood cells, so a deficiency can lead to anaemia.

Treatment

Anthelmintic medication:

• kills parasitic worms
• facilitates excretion of the worms in the faeces

Niclosamide (Yomesan®) or praziquantel (Cysticide®) will be prescribed. Praziquantel works by causing severe spasms and paralysis of the worms’ muscles while niclosamide depletes the energy of the worm.

Diagnosis

The diagnosis can be confirmed by observing tapeworm eggs in a stool sample.

Hookworm

Hookworm infects approximately 700 million people worldwide.

Life cycle

The life cycle of the hookworm begins and ends in the small intestine. Worms in the intestine produce large numbers of eggs which are passed in the faeces. The eggs need warm, moist, shaded soil to hatch into larvae. The larvae can infect a person if they come into contact with human skin, such as someone walking barefoot. They penetrate the skin and are carried to the lungs. The larvae then go through the respiratory tract to the mouth, are swallowed and eventually reach the small intestine. Here they develop into adult worms that are approximately 1cm long. The worms attach themselves to the intestinal wall and suck blood. Adult worms produce thousands of eggs that are passed in the faeces. If the eggs contaminate soil, they can hatch and develop into infective larvae again after five to ten days.

People are usually infected when they walk barefoot on soil that contains human faeces. Hookworm cannot be spread from person to person.

Symptoms

Itching and a rash are usually the first signs of infection. Although many people have no symptoms, others with heavy infection may become anaemic and suffer

• abdominal pain
• diarrhoea
• loss of appetite
• weight loss

Blood loss can also lead to protein deficiency. The degree of anaemia or malnutrition depends on the number of worms infecting the person as well as the amount of iron and protein in the diet. Heavy, chronic infections can cause stunted growth and mental development. It can be fatal, especially among infants.

Diagnosis

Diagnosis is normally made by looking for the eggs under a microscope in a stool specimen.

Treatment

Treatment consists of albendazole or mebendazole which needs to be taken for up to three days. Iron supplementation may also be needed if the patient is anaemic.

Prevention

The main lines of precaution are those dictated by sanitary science:

• Do not defecate in places other than toilets.
• Do not use human excrement or raw sewage as manure in agriculture.
• Do not walk barefoot in known infected areas.

Pinworm (Enterobius vermicularis)

Pinworms occur worldwide and are often seen in children. They are small, thin, white intestinal worms (about 8-13 mm for female and 2-5mm for male worms) which live in the large intestine or rectum of humans.

Life cycle

When an affected person sleeps, the worms leave the intestines through the anus and deposit eggs on the surrounding skin. The eggs can survive up to two weeks on clothing, bedding, toys and other objects. People can become infected if they touch contaminated surfaces and then swallow the eggs. These eggs then hatch in the small intestine and develop into the adult worms after 40 – 50 days. Once matured, the female migrates to the colon and lays eggs around the anus at night.

Symptoms

Main symptoms include

• itching around the anus
• irritability
• restlessness and insomnia caused by the disturbed sleep
• weight loss
• poor appetite
• abdominal pain
• nail biting
• grinding of teeth

Diagnosis

Diagnosis can be made by seeing the worms as they migrate out of the anus to lay their eggs – however, they are often mistaken for bits of thread. The normal method is to press a bit of sticky tape to the anal area early in the morning and examine it for eggs. By doing this a few times, up to 99% of infections can be diagnosed.

Treatment

Treatment consists of a two-dose course of medication, usually albendazole or mebendazole. The second dose must be given two weeks after the first.

General hygiene should be improved – fingernails should be cut short, daily washing of the infected individual’s bedding and sleep garments and regular baths are recommended. Close family members should also be treated.

Treatment does not kill the eggs. Good hygiene is the only way to prevent eggs from spreading and causing another infection.

Threadworm (Strongyloides stercoralis)

Threadworms occur mainly in moist tropical regions, especially in rural areas, institutional settings and lower socio-economic groups.

Life cycle

The larvae in the intestine are excreted in faeces and contaminate soil. From there, some larvae develop into adult worms and continue to breed. Others develop into infective filariform larvae which may penetrate the human skin, usually the feet. They travel to the lungs and from there to the small intestine where they become adult female worms. Female worms lay eggs which become larvae, which once again get passed in the faeces.

Sometimes, however, the larvae mature into filariform larvae while still in the gut and can re-infect the same person by migrating through the mucosa into the bloodstream, into the lungs, etc. This “autoinfection” route can lead to an overwhelming larval invasion. This hyperinfection syndrome is often found in patients with immune defects – such as leukaemia, lymphoma, steroid treatment and HIV infection.

Symptoms

Threadworm infection is frequently asymptomatic. Symptoms which may be present include

• itching
• urticarial rashes in the buttocks and waist areas
• mild diarrhoea alternating with constipation
• abdominal pains
• nausea and vomiting
• cough with bloodstained sputum

People who have massive larval invasion due to hyperinfection often have more severe symptoms. These include severe abdominal pain, diffuse involvement of the lung and sometimes associated bacterial infections with shock and severe sepsis. This form of the infection can be fatal.

Diagnosis

The diagnosis is made by finding larvae in stool or duodenal fluid.

Treatment

The infection is usually treated with the medication piperazine (Piprine®), mebendazole or albendazole. In people with the hyperinfection syndrome, treatment may be life-saving.

Prevention

Prevention of the disease requires careful attention to personal hygiene in endemic areas, including hand-washing after defecating and before handling food. Other precautions include wearing shoes when walking outside.

Whipworm

This roundworm is a slender, whip-shaped worm about 4 cm long.  It occurs mainly in the subtropics and tropics, especially in areas where sanitation is poor. It causes about 500 million infections per year. Children are usually infected.

Life cycle

Whipworm eggs are deposited in the soil where they mature and become infective. People become infected when they handle contaminated soil and touch their mouths without washing their hands. They can also be infected when they eat food that contains the eggs.

The larvae hatch in the small intestine. On reaching adulthood, the worms move to the large intestine where they burrow into the intestinal lining. Female worms lay eggs which are excreted in the faeces.

Symptoms

If the infection is light, there may be few or no symptoms. Moderate infection causes

• abdominal pain
• loss of appetite
• nausea and vomiting
• diarrhoea

Heavy infection causes bleeding from the intestine, severe abdominal cramps, anaemia and can also result in appendicitis. Rectal prolapse could be a complication of whipworm infection.

Diagnosis

As with most worm infections, diagnosis is best made by examining a stool sample for the ova, which have a very characteristic shape.

Treatment

Light, moderate and heavy infections can be treated with the anthelmintics such as albendazole or mebendazole.

Prevention

Whipworm infection can be prevented by good personal hygiene, e.g. washing hands, proper cleaning of fruit and vegetables and good sanitation.

Hygiene method

Strict hygiene measures can be used to clear up a worm infection and reduce the likelihood of re-infection. Everyone in the household must follow this regimen.

• Wash all sleepwear, bed linen, towels and cuddly toys after diagnosis.
• Thoroughly vacuum and dust the whole house, paying particular attention to the bedrooms. Continue to vacuum regularly and thoroughly.
• Carefully clean the bathroom and kitchen by damp-dusting surfaces and washing the cloth frequently in hot water. Continue to clean bathroom and kitchen surfaces regularly and thoroughly.
• Avoid shaking any material that may have eggs on it, such as clothing or bed sheets, as this may transfer the eggs to other surfaces.
• Do not eat food in the bedroom because one may swallow eggs that have been shaken off the bedclothes.
• Keep the fingernails short.
• Discourage nail biting and finger sucking. In particular, make sure that children do not suck their thumb.
• Wash the hands frequently and scrub under the fingernails, particularly before eating, after going to the toilet and before and after changing a nappy.
• Wear close-fitting underwear at night and change the underwear every morning.
• Wearing cotton gloves at night may help prevent scratching while asleep.
• Bath or shower regularly, particularly first thing in the morning and make sure to clean around the anus and vagina to remove any eggs.
• Ensure that everyone in the household has their own face cloth and towel. Avoid sharing towels.
• Keep toothbrushes in a closed cupboard and rinse them thoroughly before use.

Even after the infestation has cleared up, continue with good general hygiene measures, such as washing the hands after going to the toilet. Children can easily pick up another worm infection from friends or at school and good hygiene may help prevent another outbreak.

Sometimes mass treatment campaigns of children are carried out to try to reduce the worm burden in the population. Since children are most at risk, the World Health Organisation (WHO) currently recommends mass treatment of children > 1 year old without prior diagnosis when the prevalence is > 20% and treatment twice a year when the prevalence is > 50%.