Armillifer and Linguatula
- Parasite
- For completeness
Worm-like parasites related to crustaceans that live in the airways of snakes and dogs. People are infected by eggs or by eating raw organs.
Also called: tongue worms, pentastomids, Linguatula serrata, Armillifer armillatus
Quick facts
- Type
- Parasite · Other parasites of interest
- Gram / shape
- Elongated
- Spread
- Visceral infection · Handling
- Causes
- Visceral pentastomiasis · Nasopharyngeal linguatulosis
- Treatment
- No antiparasitic drug is proven
At a glance
- Shape
- Elongated, ringed, tongue-like body; Armillifer nymphs curl into a C shape
- Family
- Porocephalidae (Armillifer, Porocephalus); Linguatulidae (Linguatula)
- Type
- Pentastomids: highly modified crustaceans (arthropods), worm-like endoparasites
- Size
- Nymphs a few millimetres to over 1 cm; adults several centimetres
Morphology
- Four hooks around the mouth, which explain the old name: five mouths (penta-stoma).
- Body ringed by annuli; Armillifer has prominent thick rings.
- Nymphs encyst in tissues and later calcify.
Transmission
- Visceral infection: swallowing eggs from respiratory secretions or faeces of snakes or dogs, or from contaminated water, food or hands.
- Handling, cooking or eating snake meat is a major risk for Armillifer in Africa and Asia.
- Nasopharyngeal infection: eating raw or undercooked liver, lungs or trachea of sheep, goats or cattle with Linguatula nymphs.
Reservoir: Large snakes such as pythons and vipers (Armillifer, Porocephalus); Dogs and other canids (Linguatula); Rodents, sheep, goats and cattle as intermediate hosts
Isolation precautions
What the care team adds to standard precautions.
- Standard
Life cycle
- Adults live in the airways of the final host: lungs of snakes or nasal passages of dogs.
- Eggs leave in respiratory secretions or faeces and contaminate soil, water and food.
- An intermediate host swallows the eggs; larvae hatch in the gut and cross into the organs.
- Larvae moult into nymphs that encyst in liver, lungs, peritoneum and lymph nodes.
- The final host is infected by eating the intermediate host, and nymphs migrate to its airways.
- Humans are accidental intermediate hosts (eggs) or accidental final hosts (raw organs with nymphs).
Virulence factors
- Most visceral infections are silent; the nymphs die and calcify.
- Heavy infections cause inflammation, abscesses, obstruction or bleeding in liver, peritoneum, lung and eye.
- Masses can mimic cancer or tuberculosis on imaging.
- Live nymphs attaching in the throat cause acute swelling, the halzoun or marrara syndrome.
Diseases it causes
- Visceral pentastomiasis (Armillifer, Linguatula nymphs in liver, peritoneum, lungs)
- Nasopharyngeal linguatulosis (halzoun, marrara) after eating raw offal
- Ocular pentastomiasis: a nymph in the anterior chamber or orbit
Clinical picture
- Usually an incidental finding: C- or horseshoe-shaped calcifications on an abdominal or chest X-ray.
- Abdominal pain, ascites or a liver mass in heavy infections.
- Halzoun: within hours of eating raw liver, throat pain, cough, sneezing and swelling of the pharynx and face.
- Eye: pain, reduced vision or a moving parasite seen inside the eye.
Diagnosis
- Imaging: calcified C-shaped nymphs in liver and peritoneum.
- Histopathology or identification of nymphs removed at surgery or endoscopy.
- Serology is not widely available.
Treatment
No antiparasitic drug is proven. Most cases need no treatment; surgical or endoscopic removal for symptomatic or heavy infections and for nymphs in the eye.
Drug class only; doses and regimens are set by the clinician from the current guideline.
Prevention
- Handwashing after handling snakes or dogs; avoid eating or handling raw snake meat.
- Cook offal (liver, lungs) of sheep, goats and cattle thoroughly.
- Safe drinking water in areas with snakes or many dogs.
Test yourself
Think of the answer, then tap the question to see it.
Which final hosts do Armillifer and Linguatula use?
Large snakes for Armillifer and dogs or other canids for Linguatula serrata.
What is the classic imaging finding in visceral pentastomiasis?
C- or horseshoe-shaped calcified nymphs in the liver, peritoneum or lungs on X-ray.
What causes halzoun or marrara syndrome?
Eating raw or undercooked offal with Linguatula nymphs, which attach in the pharynx and cause acute swelling.
How is pentastomiasis treated?
There is no proven antiparasitic drug; most cases need nothing, and symptomatic nymphs are removed surgically.
Connections
← Back to the group: Other parasites of interest
Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Diagnosis of Human Visceral Pentastomiasis (PLoS Neglected Tropical Diseases, 2009); Linguatula serrata Tongue Worm in Human Eye, Austria (Emerging Infectious Diseases (CDC), 2011).
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Representative model, for educational purposes only.