Paediatrics chapters
Roundworm, hookworm and pinworm
The three common intestinal worms of children: Ascaris (roundworm), Ancylostoma and Necator (hookworm) and Enterobius (pinworm): how each is caught, the clinical picture, how to diagnose it and the anthelmintic treatment.
- Ascaris (roundworm) eggs are swallowed from soil; larvae pass through the lungs (cough, eosinophilia, transient infiltrates: Loeffler syndrome) and adults live in the small bowel, causing pain, distension, malnutrition and, with heavy loads, intestinal or biliary obstruction; eggs or adult worms are seen in stool or vomit.
- Hookworm larvae penetrate the skin of bare feet (ground itch); adults suck blood in the small intestine, giving iron-deficiency (microcytic hypochromic) anaemia, eosinophilia and hypoalbuminaemia; eggs are found in fresh stool.
- Pinworm (Enterobius) causes nocturnal perianal itching; eggs are picked up by sticky tape pressed on the perianal skin in the morning; treat the whole family with albendazole, mebendazole or pyrantel and repeat after 2 weeks.
On this page
Overview
Intestinal worms are among the commonest infections of Pakistani children. Three are examined repeatedly:
- Ascaris lumbricoides (roundworm).
- Ancylostoma duodenale and Necator americanus (hookworm).
- Enterobius vermicularis (pinworm, threadworm).
Roundworm and hookworm are soil-transmitted: their eggs need days to weeks in the soil before they can infect, so they flourish where there is open defecation. Pinworm spreads directly from hands, clothes and dust. All three respond to albendazole, mebendazole or pyrantel.
Life cycles at a glance
| Worm | How it enters | Route in the body | Where the adult lives | Eggs found |
|---|---|---|---|---|
| Ascaris | Swallowing eggs from soil (dirty hands, raw vegetables) | Larvae hatch in the small bowel, penetrate the wall, travel by blood to the lungs, climb the airways, are swallowed | Small intestine (moving loose in the lumen) | Stool |
| Hookworm | Larvae penetrate the skin (bare feet in damp soil); A. duodenale also by mouth | Blood and lymph to the lungs, up the trachea, swallowed | Small intestine (attached to the wall, sucking blood) | Fresh stool |
| Pinworm | Swallowing eggs from hands, clothes, bedding, dust | Hatch in the stomach; larvae mature in the caecum; no lung phase | Caecum and colon; females go to the perianal skin at night to lay eggs | Perianal skin (rarely stool) |
"Ascaris and hookworm take a lung tour; pinworm goes straight to the bottom": only the first two cause lung symptoms and eosinophilic infiltrates.
Roundworm (Ascaris lumbricoides)
Key facts
- The commonest helminth infection worldwide (Nelson).
- Large worms: adult females are about 20-35 cm long, pink and round (Park).
- Peak in pre-school and young children (Akbar: 1-6 years); associated with pica.
- Eggs survive in soil for months to years.
Clinical features
Most children are asymptomatic. With heavier infection:
| Phase | Features |
|---|---|
| Lung (larval migration) | Cough, blood-stained sputum, wheeze, fever, eosinophilia and transient (fleeting) infiltrates on chest X-ray: Loeffler syndrome |
| Intestinal (adult worms) | Vague abdominal pain, distension, nausea, poor appetite, malnutrition and growth retardation |
| Complications of heavy loads | Intestinal obstruction from a worm bolus (also volvulus, intussusception), biliary obstruction (worms entering the bile duct: jaundice, cholangitis, pancreatitis), bowel perforation, worms vomited or passed per rectum |
A child from a poor area with colicky pain, vomiting and a palpable mass and history of passing worms may have Ascaris intestinal obstruction.
Diagnosis
- Eggs in stool on microscopy.
- Adult worms passed in stool or vomit (long, pink, round).
- Eosinophilia on the blood count (mainly during the larval phase).
- Imaging (ultrasound or barium) can show worms in the bowel or bile duct.
Treatment
| Drug | Dose |
|---|---|
| Albendazole | 400 mg single dose for children over 2 years (Park; Akbar gives 200-400 mg) |
| Mebendazole | 100 mg twice daily for 3 days |
| Pyrantel pamoate | 10 mg/kg single dose (maximum 1 g) |
| Piperazine, levamisole | Alternatives (levamisole is given as a single dose) |
- Intestinal obstruction: admit for nasogastric decompression and IV fluids; involve surgeons if it does not settle or the bowel is compromised.
- Treat associated malnutrition.
Hookworm (Ancylostoma duodenale, Necator americanus)
Key facts
- Larvae live in warm, damp, shaded soil; infection follows walking barefoot.
- Adults are small (about 1 cm) and attach to the jejunal mucosa, sucking blood.
- An occupational disease of farming communities; in children it adds to poor nutrition.
Clinical features
- Ground itch: intense itching, papules or vesicles where larvae entered, usually the soles or between the toes.
- Lung migration is usually silent.
- Intestinal phase: abdominal pain, anorexia, indigestion, fullness, diarrhoea.
- Major effect: iron-deficiency anaemia. Akbar puts blood loss at about 0.2-0.5 mL per A. duodenale worm per day; with heavy loads this exceeds dietary iron.
- Chronic heavy infection: hypoalbuminaemia and oedema from protein loss, heart failure from severe anaemia, pica, poor growth and learning.
Iron-deficiency anaemia plus eosinophilia in a child who walks barefoot in villages: think hookworm.
Diagnosis
- Fresh stool for hookworm eggs (fresh, because eggs hatch quickly).
- Blood film: microcytic, hypochromic anaemia and eosinophilia.
- Low ferritin, low albumin in chronic disease.
Treatment
| Drug | Dose |
|---|---|
| Albendazole | 400 mg single dose (over 2 years) |
| Mebendazole | 100 mg twice daily for 3 days |
| Pyrantel pamoate | 10 mg/kg single dose |
Plus iron (and folic acid) to correct the anaemia; transfusion only for severe, decompensated anaemia. Treat hypoproteinaemia and malnutrition.
Giving iron alone to a child with hookworm anaemia corrects the count only for a while; deworm as well, and stop reinfection with footwear and latrines.
Pinworm (Enterobius vermicularis)
Key facts
- Very common at all income levels, especially in children; crowding helps spread.
- Eggs on hands, under nails, on clothes, bedding and in house dust are swallowed.
- At night the gravid females migrate to the perianal skin to lay eggs, which stay infective for about 2 days.
- Scratching carries eggs under the nails back to the mouth: autoinfection, and spread to the family.
Clinical features
- Nocturnal perianal itching (pruritus ani) with disturbed sleep, restlessness, irritability.
- Excoriation of perianal skin; secondary infection.
- In girls, worms may wander to cause vulvovaginitis (and rarely salpingitis).
- Sometimes poor appetite and vague abdominal pain; worms may be found in an appendix removed at surgery.
Diagnosis
- Adhesive (cellophane) tape test: press sticky tape on the perianal skin first thing in the morning, before washing or defecation, then examine it on a slide for eggs.
- Adult worms (small, white, thread-like) may be seen at the anus at night or in stool.
- Stool microscopy is usually negative because eggs are laid on the skin, not in the bowel lumen.
Do not answer "stool examination for ova" for pinworm; the test of choice is the perianal tape test in the morning.
Treatment
| Drug | Dose (single dose, repeat after 2 weeks) |
|---|---|
| Albendazole | 400 mg (Nelson) |
| Mebendazole | 100 mg |
| Pyrantel pamoate | 11 mg/kg in Nelson, up to 1 g; Akbar gives 10 mg/kg for other worms |
- Repeat after 2 weeks to kill worms hatched from eggs swallowed after the first dose.
- Treat all family members at the same time.
- Hygiene: trim and clean fingernails, wash hands, avoid scratching, change and wash underwear and bedding.
"Tape in the morning, treat the family, repeat in a fortnight."
Prevention and control
- Sanitary latrines and an end to open defecation: the single most important step for soil-transmitted worms.
- Footwear to stop hookworm larvae entering the skin.
- Hand washing before eating and after the toilet; short clean nails.
- Wash, cook or peel vegetables; safe drinking water.
- Periodic deworming of at-risk children (Park): WHO advises treating all at-risk people in endemic areas without testing, once a year when worm prevalence in the community is over 20% and twice a year when it is over 50%. It is often linked with school health or child health programmes; check the current national guideline for local practice.
Albendazole is avoided under 2 years and in pregnancy in Park's text; mebendazole is given from 2 years.
Expect: Ascaris as the commonest helminth, acquired by swallowing eggs, with Loeffler syndrome (cough, eosinophilia, fleeting infiltrates), intestinal and biliary obstruction and worms in vomit; hookworm larvae penetrating bare feet, ground itch, blood sucking in the jejunum, microcytic hypochromic anaemia, eosinophilia and hypoalbuminaemia, fresh stool for eggs; pinworm with nocturnal perianal itch, the morning adhesive tape test, vulvovaginitis in girls, single-dose treatment repeated after 2 weeks and treatment of the whole family; drugs and doses (albendazole 400 mg once, mebendazole 100 mg twice daily for 3 days, pyrantel 10 mg/kg); and prevention with latrines, footwear and deworming.
Quick revision
- Ascaris: swallowed eggs → lungs (Loeffler) → small bowel; obstruction, biliary ascariasis; eggs in stool.
- Hookworm: larvae through skin (ground itch) → lungs → jejunum; iron-deficiency anaemia, eosinophilia, low albumin.
- Hookworm diagnosis: fresh stool eggs; microcytic hypochromic film; treat worm and anaemia.
- Pinworm: nocturnal perianal itch; tape test in the morning; stool usually negative.
- Pinworm: single dose, repeat at 2 weeks, treat family, cut nails.
- Albendazole 400 mg once (over 2 years); mebendazole 100 mg twice daily for 3 days; pyrantel 10 mg/kg once.
- Prevention: latrines, shoes, hand washing, periodic deworming.
Written by The House Job from standard references (Basis of Paediatrics by Pervez Akbar; Nelson Essentials of Paediatrics; Park's Preventive and Social Medicine).
FAQ
Why does pinworm treatment need a second dose?
The drugs kill adult worms but not all eggs. Eggs swallowed around the time of the first dose grow into new worms, so a repeat dose after 2 weeks clears them.
Which worms cause lung symptoms?
Ascaris and hookworm, because their larvae pass through the lungs. Ascaris most often causes Loeffler syndrome: cough, eosinophilia and fleeting shadows on the chest X-ray.
Why is stool microscopy poor for pinworm?
The female lays her eggs on the perianal skin, not into the faeces, so eggs are best collected with adhesive tape from the skin in the morning.
How much blood does hookworm take?
Akbar gives about 0.2-0.5 mL per worm per day for A. duodenale, so a heavy load steadily drains iron and causes microcytic anaemia.