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11 Parasites

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Contents

Objectives

When you have completed this chapter you should be able to:

Introduction

11-1 What are parasites?

These are small creatures (animals) which invade and infect (infest) the body. They may be either:

Children with AIDS may be infected with unusual parasites not normally seen in healthy children (e.g. Toxoplasmosis).

11-2 Which are the common intestinal parasites?

In southern Africa the common intestinal parasites are:

Roundworms

11-3 What is a roundworm?

Roundworms are the most common parasites found in the gut of children. The worms are pink and smooth and measure about 25 cm long. They look like pale garden earth worms.

Roundworms produce thousands of eggs a day which are passed in the child’s stool (faeces). The eggs have a very characteristic shape and can be easily recognised if a sample of stool is examined under a microscope.

Roundworms are common in children between the ages of 1 and 5 years.

Roundworms are the most common bowel parasite in many poor countries.

Note
The roundworm is Ascaris lumbricoides. Infection with roundworms is called ascariasis.

11-4 How do children get roundworms?

If human faeces are not disposed of in a hygienic way, or if sewerage sludge is used as a garden fertiliser, children can swallow and get infected by roundworm eggs. Roundworm eggs can survive in soil for years. Playing or crawling in contaminated soil or eating raw vegetables that have not been washed may result in infection. High prevalence rates are common in communities with poor sanitation infrastructure. This is a major public health problem in many parts of South Africa.

Roundworm eggs hatch in the child’s small bowel, and the newly hatched larvae then pass through the bowel wall into the bloodstream and are carried to the alveoli of the lungs. From here they make their way up the bronchi and trachea then get swallowed. In the small bowel the roundworm larvae mature into adult worms where they can live for 2 years.

11-5 Do roundworms in the gut cause clinical problems?

Many children with roundworms appear healthy and have no symptoms. Often the only way the parents know that their children have roundworms, is when worms are seen in the stool. Sometimes worms can be vomited. When the child is ill with a fever, roundworms may make their way up the child’s oesophagus and come out of the nose.

Large numbers of worms in the bowel can cause problems:

Note
Roundworms can also cause bowel perforation, volvulus, intussusception, cholangitis and pancreatic duct obstruction. With heavy infections, bunches of roundworms can be seen in a plain abdominal X-ray. Do not give mebendazole or albendazole if acute abdominal pain is present as treatment increases the worms’ tendency to migrate and may precipitate bowel obstruction. Surgery must be considered if there are signs of obstruction.

11-6 How can roundworms cause chest problems?

The larvae (which hatch out of the eggs in the gut) can causes respiratory symptoms and signs during the time that they are migrating through the lungs. Children with roundworm larvae in the lungs present with a dry cough or wheeze.

Note
A high eosinophil count in the peripheral blood (10% or more) is typical. Chest X-ray may show a pneumonitis.

11-7 How are roundworms treated?

Roundworm infection can be treated with either of:

11-8 How can infection with roundworms be prevented?

Routine deworming every 6 months is recommended for all children between the ages of 1 and 5 years. This is particularly important in communities with poor hygiene and inadequate sanitation (poor toilet facilities) and should done even if there is no history of roundworms in the stool. Medication is usually given at the local primary care clinic or in pre-schools. Deworming has been found to improve the learning capacity and growth of school children.

Mebendazole is the drug of choice. Albendazole is more expensive. The dose for deworming is the same as for treating roundworms. Both these drugs are highly effective for roundworms.

Regular deworming of young children is recommended in communities where roundworms are common.

Whipworms

11-10 What are whipworms?

Whipworms commonly infect the bowel of children in southern Africa. They are short, thin worms (about 4 cm) that attach themselves to the mucosa of the large bowel where they cause bleeding. It is rare to see the worms in the stool.

As with roundworms, eggs are ingested (swallowed) with soil. The eggs hatch in the child’s gut and the larvae attach to the bowel wall. Unlike roundworms, the larvae do not migrate through the lungs.

Note
The whipworm is Trichuris trichiura. The eggs in the stool have a typical ‘tea tray’ appearance.

11-11 What are the clinical features of whipworm infection?

Whipworms usually infect children over 5 years of age. If the infection is light there are usually no symptoms or signs. Heavy infection can cause:

Whipworm infection can cause iron deficiency anaemia.

11-12 What is the treatment of whipworm infection?

  1. Prevention through good hand hygiene, washing raw vegetables and the correct disposal of human faeces (as with prevention of roundworms).
  2. Mebendazole or albendazole, as given for roundworms.
  3. Treat iron deficiency anaemia with oral iron.

Pinworms

11-13 What are pinworms?

Pinworm infection is very common. They are small, thin worms (about 4 cm long). Pinworms are especially common where children sleep or play together in crowded conditions. Adult female worms pass out the anus at night to lay eggs on the perineum. Eggs are swallowed from contaminated fingers, clothing or bed linen. Pinworms are common even where hygiene and sanitation are of a high standard. They are also known as threadworms.

Note
The pinworm is Enterobius vermicularis.

11-14 What are the clinical features of pinworm infection?

Perianal itching and scratching at night. This may cause loss of sleep. Secondary infection of the scratched skin is common. In girls the worms may enter the vulva causing irritation and vaginal discharge (vaginitis).

Pinworm infection presents with perianal itching and scratching, especially at night.

11-15 How is pinworm infection diagnosed?

The clinical diagnosis can be confirmed by the parent finding the small worms on the skin around the anus at night. A piece of sticky tape (Sellotape) should be placed against the anus and surrounding skin during the night and then immediately removed. In this way eggs can be collected and identified under a microscope.

11-16 What is the treatment of pinworms?

Mebendazole or albendazole, as used for roundworms.

Hookworms

11-17 What are hookworms?

Hookworms commonly occur in warm, moist climates such as northern KwaZulu-Natal and the Mozambique coast. With poor sanitation, hookworm eggs in the stool contaminate the soil and hatch rapidly. They then infect the feet of barefoot children. Once the skin is penetrated, hookworms behave like roundworms as they enter the bloodstream and travel via the lungs to get into the small bowel. The worms attach to the bowel mucosa and cause bleeding.

Note
There are 2 types of hookworm, Ancylostoma duodenale and Necator americanus.

11-18 What are the clinical features of hookworm infection?

Usually, there are no symptoms unless there is heavy infection. The child may have an unusually large appetite and want to eat sand. In severe cases there may be signs of iron deficiency anaemia.

11-19 How is hookworm infection diagnosed?

Worms and their eggs may be found in the stools.

11-20 What is the treatment of hookworm infection?

Mebendazole or albendazole, as for roundworm infection.

Note
Pyrantel (Combantrin) orally 10 mg/kg as a single dose may also be used.

Tapeworms

11-21 What are tapeworms?

The common tapeworms that infect the human gut are the pork and, to a lesser degree, the beef tapeworm. They are very long (up to 5 metres) segmented worms that grow in the small bowel of humans after eating uncooked or partially cooked meat, which is contaminated with tapeworm cysts. Tapeworm segments filled with eggs are excreted in human stools and later may be swallowed by animals (pigs or cows). The eggs hatch in the animal’s gut and are carried in the bloodstream to the muscles of the animals where they become tapeworm cysts. Eating infected, uncooked meat of these animals completes the life cycle of the tapeworm when the eggs hatch, resulting in adult worms living in the human gut.

Most tapeworms result from eating poorly cooked pork which is infected with tapeworm cysts.

Note
The pork tapeworm is Taenia solium and the beef tapeworm is Taenia saginata.

11-22 How is tapeworm infection diagnosed?

Small segments of the worm are seen in the stool or may be found in the bed. Often there are no other symptoms. However, tapeworms can cause abdominal discomfort, failure to thrive and loss of appetite.

11-23 What is the treatment of tapeworm infection?

Mebendazole orally 100 mg twice daily for 7 days.

11-24 How can tapeworm infection be prevented?

If possible, animals should be slaughtered in a registered abattoir where all meat is inspected to ensure that it is not infected by tapeworm cysts. Cooking meat well kills the cysts. Therefore, avoid eating raw or partially cooked meat. Meat lightly cooked on an open fire may still contain live tapeworm cysts.

Human stools must be disposed of safely so that it cannot be eaten by pigs. This will prevent the pigs from becoming infected with tapeworm cysts. Parts of the Eastern Cape of South Africa are particularly heavily contaminated with tapeworm eggs.

In villages, pigs must be prevented from eating human faeces.

11-25 Can tapeworm cysts enter the brain?

Yes. Sometimes the eggs of the pork tapeworm, which have been passed in human faeces, are swallowed by other humans (instead of by pigs) in food or water contaminated by infected human faeces. The eggs hatch in the child’s gut and are then carried by the bloodstream into all parts of the body including the brain. In the brain they form many small tape worm cysts (neurocysticercosis) which cause fits (convulsions). Tapeworm cysts in the brain are a common cause of fits in children that live in rural areas where toilets are not available. Good sanitation, safe water, handwashing and washed vegetables will reduce the risk of neurocysticercosis.

Swallowed pork tapeworm eggs from human faeces result in tapeworm cysts in the brain.

Note
The tapeworm cysts (cysticerci) are best identified in the brain by MRI or CT scanning. With time they become calcified and can be seen on X-ray. Cysts may also occur in muscles. Antibody tests are of little help. Treatment of neurocysticercosis in hospital is with steroids and Praziquantel.

Hydatid disease

11-26 What is hydatid disease?

This is caused by the dog tapeworm which can occur in the gut of dogs. Eggs, which are passed in the dog’s stool, may be swallowed by sheep and goats, resulting in tapeworm cysts in their muscles. Other dogs can then be infected with tapeworms by eating the raw meat of these sheep or goats.

If eggs of the dog tapeworm are swallowed by humans instead, the eggs hatch in the human gut and are carried by the bloodstream to the liver or lung where they form large cysts (hydatid cysts). These large cysts may cause clinical problems (hydatid disease) and will have to be removed surgically.

Dogs should be dewormed regularly and they should not be allowed to eat raw meat, especially mutton or goat meat which is infected with the cysts of the dog tapeworm. Prevent children eating soil as it may be contaminated with dog tapeworm eggs. Always wash hands before eating. Also wash vegetables well.

Hydatid disease results when children swallow the eggs of the dog tapeworm.

Treatment is with mebendazole or albendazole daily for 6 weeks.

Note
The dog tapeworm is Echinococcus granulosus.

The prevention, diagnosis and treatment of sandworm infection is discussed in chapter 12.

Giardiasis

11-27 What is giardiasis?

Giardiasis is an infection with a single-celled organism (protozoa) called giardia. The cysts of giardia are swallowed in contaminated food or water. Giardia lives in the small bowel and cysts are passed in the stool. The cysts in human stools contaminate the soil and nearby water.

Note
Giardia lamblia is the cause of giardiasis.

11-28 What are the clinical features of giardia infection?

Giardiasis is usually asymptomatic. However, with heavy infection the child develops loose, foul-smelling, watery stools. Abdominal cramps and vomiting are common. Usually the infection resolves in a few days but it may become chronic. Chronic giardiasis may cause chronic diarrhoea with malabsorption leading to failure to thrive and malnutrition.

It is difficult to confirm the diagnosis by finding cysts in the stool. Therefore, diagnosis is usually suspected from the clinical history and confirmed when the symptoms and signs disappear after treatment.

Giardiasis can cause chronic diarrhoea and failure to thrive.

Note
Giardia is a common cause of ‘travellers’ diarrhoea’.

11-29 What is the treatment of giardia infection?

Metronidazole (Flagyl) 500 mg (under 4 years) or 800 mg (4 years or older) daily for 3 days.

It is best to avoid infection with giardia by not drinking contaminated water or eating unwashed vegetables or salad.

Amoebiasis

11-30 What is amoebiasis?

Amoebiasis is an infection caused by a single-celled organism (protozoa) called an amoeba which infects the large bowel. Amoebae are passed in the stool from where they can contaminate food or water causing infection in others. Therefore, the provision of toilets and a safe water supply are important to prevent amoebiasis.

Note
Entamoeba histolytica is the amoeba which causes amoebiasis.

11-31 What are the clinical features of amoebiasis?

Mild infection is asymptomatic. However, heavy infection causes abdominal discomfort and dysentery with blood and mucus in the stools. Amoebae can also cause abscesses in the liver. This presents with an enlarged tender liver. Severe bowel infection can result in perforation and peritonitis.

Amoebae can be seen microscopically in warm stool. A blood test for antibodies against amoebae is useful in identifying patients with amoebiasis.

11-32 What is the treatment of amoebiasis?

Metronidazole (Flagyl) 200 mg 3 times daily for 5 days. All children with severe dysentery or suspected liver abscess must be referred urgently. A large liver abscess may need to be aspirated.

Clean water, washing hands before eating, avoiding unwashed vegetables and salads, and the safe disposal of human faeces prevents amoebiasis.

11-33 How can infection with many types of intestinal parasite be prevented?

The same basic steps are needed to prevent most intestinal parasites:

  1. The safe disposal of faeces is most important, e.g. water flush toilets or correctly made pit toilets (VIP toilets). Never pass urine or stool near a stream or dam.
  2. Hands should always be washed before preparing and eating food. They should also be washed before eating.
  3. Always use a clean, safe source of water for drinking and washing.
  4. Always wash raw vegetables or salads before eating.
  5. Avoid eating meat which has not been thoroughly cooked.
  6. Prevent pigs from eating human faeces.
  7. Do not leave dog faeces lying around.

Public awareness campaigns are an important method of reducing the number of infected children. Methods of preventing infection with intestinal parasites should be taught and practised at schools.

Safe toilets and clean water will prevent infection with most intestinal parasites.

11-34 What is the treatment of intestinal parasites?

Most intestinal parasites can be effectively treated with oral mebendazole or albendazole. Some require a single dose (roundworms, whipworms and pinworms) but others need a daily dose for a number of days (tapeworms). Giardia and Amoeba infections should be treated with metronidazole (Flagyl).

Regular treatment of children (e.g. deworming for roundworms) is advised for some intestinal parasites in communities where they are common.

It is important that parents are aware of the clinical features of infection with intestinal parasites and can recognise the worms if they are seen.

Bilharzia

11-35 What is bilharzia?

Bilharzia (schistosomiasis) is a disease caused by the bilharzia parasite. About 2 million people are infected with bilharzia in South Africa. There are 2 forms of bilharzia. One affects the bowel while the other affects the bladder. Bilharzia of the bladder is the most common form of bilharzia in children in South Africa.

Eggs of the bladder parasite are passed in the urine. If the urine reaches a source of water, the parasite can infect and multiply in a special snail often found in pools, dams, reservoirs, canals or slow flowing streams. Parasites released from the snail can penetrate the skin of humans. From here the parasites enter the bloodstream and are carried to the bladder. Sometimes they may also reach other organs.

In the bladder wall the parasites cause inflammation, bleeding and eventually scarring. Damage can extend to the rest of the urinary tract, resulting in urinary obstruction with chronic renal failure.

Note
Bilharzia (schistosomiasis) is caused by either Schistosoma haematobium (bladder parasite) or Schistosoma mansoni (bowel parasite).

Bilharzia of the bladder is common in South Africa.

11-36 What are the clinical features of bilharzia of the bladder?

At the time of infection an itchy, papular rash may occur at the site where the parasites enter the skin (called ‘swimmers’ itch’). This may be followed a few weeks later by a flu-like illness.

Mild bladder infection with bilharzia parasites is often asymptomatic. With more severe infection, the classical sign is terminal haematuria (blood seen in the urine towards the end of micturition).

Bilharzia of the bladder usually presents with terminal haematuria.

Note
Bilharzia of the bowel may cause dysentery.

11-37 How is the diagnosis of bilharzia of the bladder confirmed?

By finding the typical bilharzia eggs in the urine under a microscope. It is best to collect urine around midday when most eggs are released. A blood test for antibodies to the parasite is also available.

Note
Eosinophilia in the blood is usually present with bilharzia.

11-38 What is the treatment of bilharzia?

Praziquantel 40 mg/kg orally as a single dose. This treatment can be given at a clinic. Unfortunately, children who live in a bilharzia region may have to be treated repeatedly for bilharzia.

11-39 How can bilharzia be prevented?

Every effort must be made to prevent bilharzia infection. Never pass urine into a stream or pool of water. Standing or slow-moving water such as farm dams and irrigation furrows are the home of the bilharzias snail, especially in the eastern areas of South Africa and in Zimbabwe. Fast-moving streams are usually safe. Swimming or bathing in infected water must be avoided as this is the common way of getting bilharzias. Efforts are being made to kill the snails in high risk areas.

Do not swim in standing water where there are bilharzia snails.

Malaria

11-40 What is malaria?

Malaria is a serious illness caused by a malaria parasite which is transmitted to humans by a special type of mosquito. When a mosquito bites an infected person, human blood containing malaria parasites is taken in by the mosquito. The mosquito becomes infected (but not ill) and can then bite and infect other humans. In the human, the malaria parasite infects both red cells and the liver. Infection of the red cells causes haemolysis, resulting in anaemia. It also causes the red cells to stick together which obstructs small blood vessels. Malaria is a common cause of chronic illness and death in many low lying regions where malaria mosquitoes occur.

Malaria is an important cause of death in many parts of southern Africa.

As falciparum malaria is by far the most common form of malaria in South Africa, other rarer forms of malaria will not be considered.

Note
Almost all malaria in southern Africa is caused by Plasmodium falciparum which is transmitted by female Anopheles mosquitoes (the vector of malaria).

11-41 What are the clinical signs of malaria?

The patient develops an acute illness with fever, shivering rigors and flu-like symptoms 1 to 2 weeks after being bitten by an infected mosquito. Headache, nausea and body pains are common in uncomplicated (mild) malaria. The symptoms and signs of malaria are very non-specific, making the clinical diagnosis difficult to confirm or exclude.

Severe headache, repeated vomiting and drowsiness suggest the development of severe malaria. Mild malaria may become severe and even fatal within hours.

Note
Infection of other organs such as the liver (jaundice), gut (diarrhoea), lungs (respiratory distress) and kidneys (oliguria with renal failure) may occur. Massive haemolysis (blackwater fever) causes anaemia, with dark urine.

Anyone who develops fever in a malaria area, or within 2 weeks of leaving a malaria area, must be suspected of having malaria. Thinking of malaria is the most important step in the clinical diagnosis. As the clinical symptoms and signs of malaria are very varied, it is always important to confirm the clinical suspicion. There are often no clinical signs at presentation.

Suspect malaria in anyone with a flu-like illness who lives in or has recently visited a malaria region.

11-42 How is the diagnosis of malaria confirmed?

  1. Seeing the malaria parasites within red cells in a stained thick blood smear is the traditional ways of confirming the diagnosis. Repeated smears may be needed before malaria is excluded as the smear may be negative early in the infection.
  2. A blood test to detect malaria proteins (rapid antigen test) is also useful in making a rapid diagnosis. It is very reliable to screen for malaria and is available at primary care facilities in malarial areas of South Africa.
  3. It is very important to confirm the diagnosis of malaria as soon as possible and to decide whether the child has uncomplicated or severe malaria.

Most deaths due to malaria are caused by delayed diagnosis or late treatment.

Remember that many other serious conditions may present with the same symptoms and signs as malaria, e.g. bacterial meningitis. Children may also have malaria plus another infection.

11-43 How can you tell whether malaria is uncomplicated or severe?

In uncomplicated malaria the patient:

Note
In uncomplicated malaria the parasite count on a thin blood smear is less than 5%, i.e. less than 5% of red cells containing malaria parasites.

In severe malaria the patient may have any of the following:

Note
In severe malaria the parasite count is well over 5% (hyperparasitaemia). The higher the count, the more severe the malaria. Metabolic acidosis may occur.

11-44 What is cerebral malaria?

This is the most dangerous complication of severe malaria as the brain is affected and can lead to rapid death. Young children, pregnant women and people who are HIV infected are particularly susceptible to cerebral malaria. Each year many children die of cerebral malaria in Africa.

Signs of cerebral malaria must always be viewed with great concern:

Confusion is an important sign of potentially fatal cerebral malaria.

Note
In cerebral malaria the large numbers of parasites obstruct the normal blood flow to the brain.

11-45 How is uncomplicated malaria treated?

Early and accurate diagnosis with urgent treatment using the correct drugs is the key to successful management. It is important to differentiate uncomplicated from severe malaria. If possible all patients with malaria are referred to a hospital or clinic where the staff are experience in treating malaria. They must be closely followed up for the first few days. Patients with confirmed malaria are usually treated with Coartem (coartemether, i.e. artemether and lumefantrine). Coartem is a combination of 2 potent, rapidly acting anti-malarial drugs which are well tolerated.

For uncomplicated malaria in children of 5 kg or more, one dose of Coartem should be taken immediately, then again after 8 hours, followed by a twice daily dose for the next 2 days. Each dose is 1 tablet if 5–14 kg, 2 tablets if 15–24 kg, 3 tablets if 25–34 kg and 4 tablets if 35 kg or more. Best taken with food.

For uncomplicated malaria in children less than 5 kg give oral quinine is 10 mg/kg 8 hourly for 7 days PLUS clindamycin 10 mg/kg 12 hourly for 7 days. The quinine tablets are very bitter but can be crushed and taken with jam, or mashed banana.

Drug resistance is a major problem with malarial treatment. Most strains of malaria are now resistant to chloroquine alone or in combination with other drugs. Paracetamol is best for reducing the fever. Make sure the patient is taking enough fluids.

Uncomplicated malaria in older children can also be treated with oral quinine. However, there are some serious side effects of quinine, e.g. myocardial toxicity. Using a combination of drugs for both uncomplicated and severe malaria is more effective and less likely to result in resistance in the community than monotherapy (one drug only).

11-46 How is severe malaria treated?

The preferred treatment of severe malaria is artesunate 2.4 mg/kg intravenously immediately and again after 12 and 24 hours followed by a daily dose until the child can take oral Coartem.

Intravenous drugs must be started immediately and the patient urgently referred to hospital. Do not wait to confirm the diagnosis if severe malaria is suspected. Look for and manage hypoglycaemia, shock or convulsions. The patient should improve clinically within 48 hours and the fever should settle within 5 days.

Rectal artesunate is also an effective emergency treatment.

Note
Severe malaria can also be treated with intravenous quinine. A loading dose of quinine 20 mg/kg diluted in 5% dextrose water (10 ml/kg) must always be given as a slow infusion over 4 hours and never as a bolus. This is followed by 10 mg/kg 8 hourly intravenously over 4 hours. Change to oral Coartem or oral quinine plus clindamycin as soon as possible.

11-47 How is malaria prevented?

  1. Pregnant women and young children under 5 years should not enter a malaria areas if at all possible, especially in the wet season.
  2. Mosquitoes usually bite in the early evening and early morning. Therefore, stay indoors with screens over windows and doors or wear light coloured clothes, long sleeves and trousers with shoes and socks in the evenings and early mornings.
  3. Use a bed net impregnated with insecticide (pyrethroid) at night.
  4. Use insect repellent on the skin and clothes or burn repellent coils or pads or sprays at night.
  5. Antimalarial drug prophylaxis is recommended for short visits to a malaria area.
  6. By reducing the number of mosquitoes.

Preventing mosquito bites is more effective than prophylaxis. Usually both are needed.

Preventing mosquito bites is the most effective way of avoiding malaria.

Malaria prophylaxis is needed by all who enter a malaria area (a region where malaria occurs), even if it is only a one day visit. The risk of becoming infected by malaria is particularly high in the rainy season when mosquitoes are common. Full compliance is very important. However, prophylaxis is never 100% effective.

  1. Malanil or malarone (atovaquone plus proguanil) daily for children of 10 kg or more. It is well tolerated but expensive.
  2. Mefloquine (Larium) once weekly for children of 5 kg or more.
  3. Doxycycline daily for older children (over 8 years).

It is best for all children under 5 years, especially children under 5 kg, not to enter a malaria area as they are at high risk for severe infection. Chloroquine alone, chloroquine with proguanil, and Coartem should not be used for prophylaxis.

Note
Malanil daily ¼ tablet if 5–20 kg, ½ tablet if 21–30 kg, ¾ tablet if 31–45 kg and 1 tablet if over 45 kg starting one day before entering and stopping one week after leaving a malaria area. Mefloquine weekly ¼ tablet if 5–20 kg, ½ tablet if 21–30 kg, ¾ tablet if 31–45 kg and 1 tablet if over 45 kg starting one week before entering and stopping 4 weeks after leaving a malaria area. Doxycycline 100 mg daily starting 1 day before entering and stopping 4 weeks after leaving a malaria area.

Seasonal Intermittent Treatment of children in malaria regions decreases the incidence of clinical malaria.

11-49 How can the number of mosquitoes be reduced?

  1. By reducing the mosquito population with the use of controlled spraying around homes with insecticides. This is done by government-employed teams.
  2. By reducing pools of water where mosquitoes can breed.
Note
Malarial mosquitoes have become resistant to many insecticides. The controlled use of DDT is very effective but remains controversial due to the risk of environmental pollution and dangers to other animals and possibly the newborn infant.

Case study 1

A mother brings her 5-year-old son to the clinic because he has passed 2 roundworms with his stool. He is generally well but the mother complains that he scratches his anus at night which keeps him awake.

1. How do children get roundworms?

They ingest the roundworm eggs after playing in sand or soil. If human faeces are not disposed of correctly they can contaminate soil in the village, garden or playground. Eggs can survive for years in soil and may also contaminate pools of water or raw vegetables. This is a common public health problem.

2. Can roundworms cause clinical problems?

Usually not. However, with heavy infections children may complain of abdominal pain or discomfort and lose their appetite. Roundworms can cause bowel obstruction or block a bile duct. The larvae of roundworms pass through the lungs and can cause coughing and wheezing.

3. How should this child be treated?

With a single oral dose of mebendazole or albendazole. The mother should be told how to avoid reinfection.

A deworming programme is recommended in regions where roundworms are common.

5. What is a common cause of perianal itch at night in children?

Pinworms. These are short worms that infect the gut and leave the anus at night, causing irritation to the skin around the anus. They can also cause a vaginal discharge in girls.

6. How can the diagnosis be confirmed?

A strip of Sellotape should be stuck onto the child’s skin over and next to the anus and then immediately removed. Pinworm eggs will stick to the Sellotape. These can then be seen under a microscope. The treatment is the same as for roundworms.

Case study 2

A malnourished child from a rural village presents at the local clinic after passing a piece of tapeworm in her stool. Pigs run free and eat human faeces. There are also a number of dogs in the village.

1. What are the common types of tapeworms in children?

The pork or beef tapeworms. Pig tapeworms are more common.

2. What is the clinical presentation of tapeworms?

Infected children are often asymptomatic. However, tapeworms can cause poor appetite, abdominal discomfort and weight loss. This child’s malnutrition may be partly explained by the tapeworm.

3. How did this child get infected with a tapeworm?

Probably by eating uncooked or partially cooked pork. Tapeworm eggs get passed in the stool and then may be eaten by pigs if toilets are not available. The eggs hatch in the pig’s gut and then travel in the bloodstream to the muscles where they form cysts. If these cysts in the meat are eaten by humans, they hatch out in the gut to form a tapeworm.

4. What is used to treat intestinal tapeworms?

Oral mebendazole twice daily for 7 days.

5. Can tapeworms affect the brain?

Yes. If eggs of the pork tapeworm are passed in human faeces and then later get swallowed by another human rather than a pig, they can hatch in the gut of that person and then travel in the bloodstream to the brain where they form many small cysts. This is called neurocysticercosis and usually presents with convulsions. Neurocysticercosis is common in communities where there are pigs and human faeces are not disposed of safely.

6. What problems can be caused by the dog tapeworm?

If eggs of the dog tapeworm are ingested by humans they hatch in the gut, enter the bloodstream and are carried to organs such as the liver and lungs where they grow into large (hydatid) cysts. Therefore it is important that children do not play in areas where dog faeces are left to mix with the soil or pools of water.

Hydatid disease can be treated with oral daily mebendazole or albendazole for 6 weeks. Large cysts may have to be removed surgically.

Case study 3

A month after returning from holiday on a farm in the Eastern Cape, a 14-year-old child presents with a 3-week story of loose stools, and terminal haematuria for 2 days. While on holiday he swam in a farm dam.

1. What is the common cause of terminal haematuria?

Blood in the urine towards the end of micturition is typical of bilharzia. The bilharzia parasite settles in the wall of the bladder where it causes inflammation and bleeding.

2. When did the infection probably occur?

When he swam in the farm dam. The special bilharzia snail is common in the eastern parts of South Africa where it lives in standing or slow-moving water such as farm dams or irrigation furrows. If someone with bilharzia passes urine into the water the snails can become infected. The parasites released from the snails can then penetrate the skin of anyone walking or playing in the water.

3. Can bilharzia be treated?

Yes. It can be treated very effectively with praziquantel. It is best to first confirm the diagnosis by seeing bilharzia parasites in a urine sample collected around midday. Chronic bilharzia infection can lead to damage of the urinary system causing renal failure.

4. What is the probable cause of the diarrhoea for the past 3 weeks?

The child may have a bowel infection with giardia, which causes diarrhoea. Although it is often acute it may last for weeks or months. Giardia is common where a safe water supply and adequate toilets are not present.

5. Which drug is used to treat giardiasis?

Metronidazole (Flagyl).

Case study 4

Two weeks after returning from a malaria area, a 10-year-old child presents with headache, shivering and vomiting. The mother gave her some paracetamol for the fever. A few hours later the child becomes confused and cannot stand up. The family did not take malarial prophylaxis because they planned to be in the area for 2 days only.

1. Do you think this child has malaria?

Yes. Malaria has an incubation period of 1 to 2 weeks and presents with fever and a flu-like illness.

2. How severe is the infection?

At presentation it was uncomplicated, with fever and vomiting. However, within hours she was confused and could not stand. This indicates severe, probably cerebral malaria. Malaria can progress from uncomplicated to severe within hours if not treated.

3. How can the diagnosis be confirmed?

By examining a blood smear or performing a malaria rapid antigen test.

4. What is the correct treatment?

She must be admitted to hospital urgently as cerebral malaria can be fatal. She needs to be treated immediately with intravenous artesunate. Uncomplicated malaria can be adequately treated with oral Coartem provided the clinical diagnosis has been confirmed.

5. How can malaria be prevented while on holiday?

The only way to confidently avoid malaria is not to enter a malaria area. However, malaria can usually be avoided by making efforts not to be bitten by mosquitoes and by taking malaria prophylaxis. Insecticide impregnated bed nets are very effective. Also keeping indoors after sunset with mosquito screens on the door and windows. Wear long trousers and sleeves, and shoes and socks if going out in the evening or early morning, when mosquitoes are most active.

6. What malaria prophylaxis should be taken?

The choice is atovaquone and proguanil (Malanil) for children of 10kg or more, or mefloquine (Larium) for children of 5 kg or more. Children over 8 years can also use doxycycline. The medication must be taken correctly, including for the correct period after leaving the malaria area. Prophylaxis must be taken even for a one day visit.

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