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Oesophagostomum and Mammomonogamus

  • Parasite
  • For completeness

Two animal roundworms rarely seen in people: one forms lumps in the bowel wall, the other sits in the airway and causes a stubborn cough.

Updated

Also called: Oesophagostomum bifurcum, nodular worm, Mammomonogamus laryngeus, Syngamus laryngeus, gapeworm, syngamosis

Quick facts

Type
Parasite · Nematodes
Gram / shape
Oesophagostomum
Spread
Oesophagostomum · Mammomonogamus
Causes
Oesophagostomiasis · Mammomonogamiasis
Treatment
Oesophagostomum

At a glance

Shape
Oesophagostomum: hookworm-like egg. Mammomonogamus: red male and female joined for life in a Y shape
Family
Chabertiidae (Oesophagostomum); Syngamidae (Mammomonogamus)
Type
Strongylid nematodes of animals; humans are incidental hosts
Size
Small worms, a few millimetres to about 2 cm

Morphology

  • Oesophagostomum eggs cannot be told apart from hookworm eggs on routine stool exams.
  • Oesophagostomum larvae sit inside nodules in the wall of the large bowel.
  • Mammomonogamus: the male stays attached to the female in permanent copulation, forming a Y.

Transmission

  • Oesophagostomum: swallowing infective larvae from soil, water or food contaminated with faeces.
  • Mammomonogamus: presumed ingestion of eggs, larvae or a carrier host (snail, earthworm, arthropod) in raw food or water.
  • Neither spreads directly from person to person.

Reservoir: Oesophagostomum: non-human primates, pigs, sheep and goats; humans in northern Togo and Ghana; Mammomonogamus: cattle, goats, sheep and cats in the tropics

Isolation precautions

What the care team adds to standard precautions.

  • Standard

Life cycle

  1. Oesophagostomum eggs in faeces hatch in soil; larvae moult twice to the infective stage.
  2. The host swallows the larvae, which encyst in the bowel wall and form nodules.
  3. Larvae leave the nodules, mature in the colon lumen and lay eggs about a month later.
  4. Mammomonogamus adults attach to the larynx and trachea of cattle or cats.
  5. Eggs are coughed up, swallowed and passed in faeces; the full cycle is not well known.
  6. A person is infected by swallowing infective stages; worms settle in the larynx or bronchi.

Virulence factors

  • Encysted Oesophagostomum larvae provoke inflammatory nodules, abscesses and masses in the colon wall.
  • Nodules can obstruct the bowel or, rarely, perforate and cause peritonitis.
  • Mammomonogamus attached to the airway mucosa causes irritation, cough and sometimes bleeding.

Diseases it causes

  • Oesophagostomiasis: nodular or tumour-like masses of the large bowel, often mimicking appendicitis
  • Mammomonogamiasis (syngamosis): chronic cough, sensation of a foreign body in the throat, haemoptysis

Clinical picture

  • Oesophagostomum: right lower quadrant pain and fever mimicking appendicitis; painless abdominal mass.
  • Oesophagostomum: intestinal obstruction; rarely skin nodules.
  • Mammomonogamus: weeks of dry cough, foreign-body sensation in the larynx, sometimes haemoptysis or wheezing.
  • Mammomonogamus symptoms often resolve as soon as the worm pair is coughed up.

Diagnosis

  • Oesophagostomum: usually worms in surgical or biopsy specimens; ultrasound shows nodules in the bowel wall.
  • Oesophagostomum eggs on stool exam are read as hookworm; larval culture or PCR separates them.
  • Mammomonogamus: the Y-shaped red worm pair coughed up or seen and removed at bronchoscopy.
  • Mammomonogamus eggs may appear in sputum or stool; eosinophilia may be present.

Treatment

Oesophagostomum: benzimidazoles (albendazole) and surgery for complicated masses. Mammomonogamus: removal of the worms at bronchoscopy; benzimidazoles (albendazole or mebendazole) have been used.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

Prevention

  • Safe water, sanitation and hand hygiene in rural areas.
  • Wash raw vegetables; avoid raw or undercooked food that may carry snails or other carriers.

Test yourself

Think of the answer, then tap the question to see it.

How does human oesophagostomiasis typically present?

With nodules or masses in the large-bowel wall, often mimicking appendicitis or a tumour.

Why is Oesophagostomum easily missed on a stool exam?

Its eggs look like hookworm eggs, so they are reported as hookworm.

What is the characteristic appearance of Mammomonogamus laryngeus?

A red male and female joined in permanent copulation, forming a Y shape.

Which symptom brings patients with Mammomonogamus to the doctor?

A chronic cough, often with a foreign-body sensation in the throat, sometimes with haemoptysis.

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Connections

← Back to the group: Nematodes

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: CDC - DPDx - Oesophagostomiasis (CDC, 2017); Syngamoniasis in Tourist (Emerging Infectious Diseases (PMC), 2005); Reporte del primer caso humano de infección parasitaria por Mammomonogamus laryngeus en Colombia (Biomédica (Instituto Nacional de Salud), 2006).

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Representative model, for educational purposes only.