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[Microbiology](https://durgical.com/en/microbiology/) · [Other parasites of interest](https://durgical.com/en/microbiology/groups/other-parasites-of-interest/)

# Angiostrongylus (A. costaricensis, A. cantonensis)

- Parasite
- For completeness

Rat worms that reach humans through slugs and snails. One inflames the gut of children in the Americas; the other causes meningitis.

Updated 2026-11-01

Also called: rat lungworm (A. cantonensis), angiostrongyliasis

## Key points

- Eosinophilic meningitis after eating snails or slugs: A. cantonensis.
- A child in the Americas with appendicitis and eosinophilia: A. costaricensis in the mesenteric arteries.
- Definitive host: rats; intermediate hosts: slugs and snails.
- In the abdominal form, surgery and histology make the diagnosis.

## At a glance

**Family**
Angiostrongylidae

**Type**
Metastrongylid nematodes

**Size**
Adults from a few millimetres to about two centimetres

## Morphology

- A. costaricensis: adults in the mesenteric arteries of the ileocaecal region; eggs and larvae in the bowel wall.
- A. cantonensis: adults in the rat's pulmonary arteries; in humans they stay as young larvae in the nervous system.

## Transmission

- Eating raw or undercooked snails or slugs, or raw vegetables contaminated with them or their slime.
- A. cantonensis also via raw paratenic hosts (crabs, freshwater shrimp).
- Not spread from person to person.

**Reservoir:** Wild rodents (the cotton rat Sigmodon hispidus for A. costaricensis; Rattus rats for A. cantonensis)

### Isolation precautions

What the care team adds to standard precautions.

- Standard

## Life cycle

- Adults live in the rat's arteries (mesenteric or pulmonary, depending on species).
- First-stage larvae leave in the rat's faeces.
- Slugs and snails swallow them and they mature into infective larvae.
- The rat is infected by eating the mollusc, closing the cycle.
- Humans, accidental hosts, are infected by eating the mollusc or contaminated vegetables.
- A. costaricensis stays in the bowel wall; A. cantonensis migrates to the brain and does not complete its cycle.

## Virulence factors

- A. costaricensis: eggs and larvae cause eosinophilic granulomas, vasculitis and thrombosis in the terminal ileum, caecum and appendix.
- Ischaemia can lead to necrosis, perforation or obstruction.
- A. cantonensis: larvae dying in the nervous system trigger an intense eosinophilic reaction.

## Diseases it causes

- Angiostrongyliasis cantonensis: eosinophilic meningitis
- Abdominal angiostrongyliasis (A. costaricensis): an ileocaecal mass that mimics appendicitis

## Clinical picture

- Abdominal: right lower quadrant pain, fever, vomiting and a palpable mass in children, with leucocytosis and eosinophilia; often operated on as appendicitis.
- Meningeal: severe headache, neck stiffness, nausea, paraesthesiae; most patients recover.

## Diagnosis

- Abdominal: histopathology of the surgical specimen (worms in mesenteric vessels, eosinophilic granulomas); no validated serology.
- Meningeal: cerebrospinal fluid with eosinophils; larvae are rarely seen. CSF PCR is available at reference centres.
- Blood eosinophilia in both.

## Treatment

Abdominal: surgery for complications; anthelmintics such as diethylcarbamazine or levamisole are discouraged because they may worsen inflammation or migration. Meningeal: supportive care with analgesia and corticosteroids; the role of albendazole is still debated.

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

In Pharmacology:

- [Albendazole](https://durgical.com/en/pharmacology/albendazole/)

## Prevention

- Washing vegetables well and not eating raw snails, slugs or freshwater shrimp.
- Handwashing after handling snails, including the giant African snail.
- Rodent and mollusc control in gardens.

## In Colombia

A. costaricensis is present in Colombia: the first case was reported in 1979, a few more followed until 1998, and in 2020 two paediatric cases from Huila and Caquetá were published, both diagnosed by histopathology after surgery.

## Memory aid

The slug leaves a trail on the lettuce and the worm rides along: the Costa Rica species heads for the belly, the Canton species for the head.

## Test yourself

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

## Which parasite is the most frequent cause of eosinophilic meningitis worldwide?

Angiostrongylus cantonensis, the rat lungworm.

## How does A. costaricensis angiostrongyliasis present?

As an abdominal picture in children that mimics appendicitis, with an ileocaecal mass and eosinophilia from granulomas and vasculitis in the bowel wall.

## What are the intermediate hosts of Angiostrongylus?

Slugs and snails; rats are the definitive hosts and humans are accidental.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/microbiology/angiostrongylus/)

## Related

- [Toxocara canis / Toxocara cati](https://durgical.com/en/microbiology/toxocara-canis-toxocara-cati/)
- [Gnathostoma and Anisakis](https://durgical.com/en/microbiology/gnathostoma-and-anisakis/)
- [Strongyloides stercoralis](https://durgical.com/en/microbiology/strongyloides-stercoralis/)

## What the colours mean

**Gram-positive**
Thick peptidoglycan wall: stains purple.

**Gram-negative**
Thin wall with an outer membrane: stains pink.

**Acid-fast**
Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain.

[← Back to the group: Other parasites of interest](https://durgical.com/en/microbiology/groups/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: [CDC - DPDx - Angiostrongyliasis](https://www.cdc.gov/dpdx/angiostrongyliasis/index.html) (CDC, 2024); [Abdominal angiostrongyliasis, report of two cases and analysis of published reports from Colombia](https://www.redalyc.org/journal/843/84364615004/movil/) (Biomédica (Instituto Nacional de Salud), 2020).

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Representative model, for educational purposes only.

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