Helminthiasis (Worm infection)

Introduction

Parasitic worm infestations can arise from different groups:

  1. Nematodes (round worms)
  2. Ascaris
  3. Ancylostoma (hookworm)
  4. Enterobius (pinworm)
  5. Trichiuris (whipworm)
  6. Cestodes (flat worms/tapeworms)
  7. Taenia solium and T. saginata
  8. Trematodes (flukes)
  9. Schistosoma haematobium and S. mansoni

Round worm infestations are associated with rural living and poor hygiene.
It is prevalent among school children and young adults.
It is acquired through soil and faeco-oral contamination.
Flat worms and tape worms are acquired by eating under-cooked contaminated meat or fish.
Bladder worms (S. haematobium) are
acquired by wading through streams and
ponds contaminated with the vector snails.

Clinical features of helminthiasis

This depend on the infecting helminth:

1. Ascariasis

Lung phase:

  • Irritating, non-productive cough
  • Burning substernal discomfort, aggravated by coughing or deep inspiration
  • Dyspnoea
  • Blood-tinged sputum

Intestinal phase:

  • Usually no symptoms Pain
  • Features of small bowel obstruction
  • Features of perforation, Intussusception.
  • Volvulus
  • Biliary tree occlusion: biliary colic, cholecystitis, cholangitis, pancreatitis, intrahepatic abscess

Effects of migration of an adult worm up the oesophagus:

  • Coughing
  • Oral expulsion of the worm

2. Hookworm

  • Most are asymptomatic
  • Maculo-papular dermatitis
  • Mild transient pneumonitis
  • Epigastric pain, often with post-prandial accentuation
  • Diarrhoea
  • Weakness
  • Shortness of breath
  • Skin depigmentation

3. Enterobiasis

  • Perianal pruritus, worse at night owing to the nocturnal migration of the female worms
  • Skin excoriation and bacterial superinfection
  • Abdominal pain
  • Weight loss
  • Vulvo-vaginitis
  • Pelvic/perineal granulomas

4. Trichuriasis

  • Abdominal pain
  • Anorexia
  • Bloody or mucoid diarrhoea
  • Rectal prolapse
  • Growth retardation

5. Strongyloidiasis

  • Distinguished by its ability to replicate in the human host
  • Can thus persist for decades without further exposure of the host to exogenous infective larvae
  • Recurrent urticaria: buttocks and wrists
  • Pruritic raised erythematous skin lesions:
    • advance as rapidly as 10 cm/hour along the course of larval migration
  • The pathognomonic serpiginous eruption
  • Mid-epigastric abdominal pain
  • Nausea
  • Diarrhoea
  • Gastrointestinal bleeding
  • Mild chronic colitis
  • Weight loss
  • Small bowel obstruction
  • Disseminated strongyloidiasis in patients with unsuspected infection who are given glucocorticoids can be fatal

6. Trichinellosis

In the first week after infection (gut invasion):

  • Diarrhoea
  • Abdominal Pain
  • Constipation
  • Nausea
  • Vomiting

In the second week after infection (muscle invasion):

  • Fever
  • Periorbital and facial oedema
  • Haemorrhages (subconjunctival, retinal and nail bed)
  • Maculopapular rash
  • Headache
  • Cough
  • Dyspnoea
  • Dysphagia

7. Tachyarrhythmias

  • Heart failure
  • Encephalitis
  • Pneumonitis

8. Schistosomiasis

See Schistosomiasis under urology

Differential diagnoses

  • Other causes of acute-onset diarrhoea and/or vomiting
  • Other conditions depending on the predominant clinical presentation

Investigations

  • Stool examination for ova and parasites
  • Urine examination: microscopy
  • Haematology: eosinophilia and anaemia may be present
  • Serology and CT scan may be required in some instances

Drug Treatment for helminthiasis

(See detailed Antihelminthics)

1. Hookworm

Mebendazole

  • Adult and child: 100 mg orally every 12 hours for 3 days
  • Iron supplementation may be given if anaemia is present

2. Ascaris

Mebendazole

  • Adult and child: 100 mg orally every 12 hours for 3 days

3. Trichiuris

Mebandazole

  • Adult and child: 100 mg orally every 12 hours for 3 days

4. Enterobius

Pyrantel embonate

  • Adult and child: 10 mg/kg orally once
  • Repeat dose 2 weeks later; several
    treatments may be necessary

5. Trematodes

Praziquantel

  • Adult: 40 mg/kg given orally at once
    • This provides up to 80% cure rates
  • Child over 4 years: 20 mg/kg followed after 4-6 hours a further dose of 20 mg/kg

Praziquantel is effective in all human cases caused by schistosomes

6. Cestodes

Praziquantel

  • Adult:40 mg/kg given orally at once

Or:

  • 20 mg/kg followed by another 20 mg/kg after 4-6 hours
  • Child over 4 years: 20 mg/kg followed after 4-6 hours a further dose of 20 mg/kg (20 mg/kg 3 times daily for one day for S. japonicum infections)

Notable adverse drug reactions, caution and contraindications

  • Avoid mebendazole in pregnant women
  • Side effects of praziquantel include
    abdominal pain, headache, dizziness and skin rashes

Prevention of helminthiasis infections

  • Good personal and food hygiene
  • Access to safe and potable water
  • Regular deworming
  • Adequate cooking of food and meats