Helminthiasis (Worm infection)

Introduction

Parasitic worm infestations can arise from different groups:

Nematodes (round worms)
Ascaris
Ancylostoma (hookworm)
Enterobius (pinworm)
Trichiuris (whipworm)
Cestodes (flat worms/tapeworms)
Taenia solium and T. saginata
Trematodes (flukes)
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