[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Nematodes](https://durgical.com/en/microbiology/groups/nematodes/) › Trichinella spiralis

[Microbiology](https://durgical.com/en/microbiology/) · [Nematodes](https://durgical.com/en/microbiology/groups/nematodes/)

# Trichinella spiralis

- Parasite
- Exam priority: medium

A tiny worm that comes with undercooked pork or game. Its larvae encyst in muscle and cause fever, muscle pain and swollen eyelids.

Updated 2026-11-01

Also called: trichina

## Key points

- Periorbital oedema + myalgia + eosinophilia after pork or game.
- Larvae encysted in striated muscle.
- Raised CK; late serology.
- Outbreaks in groups who shared the same meat.
- Albendazole or mebendazole, plus corticosteroids when inflammation is severe.

## At a glance

**Shape**
Larva coiled inside a modified muscle cell ('nurse cell')

**Family**
Trichinellidae

**Type**
Tissue nematode (intracellular larva in striated muscle)

**Size**
Adults 1–4 mm; encysted larva about 1 mm

## Morphology

- Larva coiled in a spiral inside the striated muscle fibre.
- Very small adults in the small-bowel mucosa.
- Some species (T. pseudospiralis) do not encyst.

## Transmission

- Eating raw or undercooked meat with encysted larvae: pork, wild boar, bear or other game.
- Homemade sausage, jerky or dried meat from those animals.
- Not spread between people.

**Reservoir:** Domestic cycle: pigs and rodents; Sylvatic cycle: wild boar, bear and other carnivores

### Isolation precautions

What the care team adds to standard precautions.

- Standard

## Life cycle

- A person eats undercooked meat with encysted larvae (pork, wild boar, bear).
- Stomach acid and pepsin release the larvae, which invade the small-bowel mucosa.
- They mature into adults; about a week later the females release newborn larvae.
- The larvae travel in blood and lymph and encyst in striated muscle (diaphragm, masseters, eye muscles).
- In muscle they may calcify; the cycle goes on when a carnivore eats that meat.

## Virulence factors

- Intestinal phase: mucosal invasion with diarrhoea and abdominal pain.
- Migration phase: vasculitis and inflammation with periorbital oedema, fever and splinter haemorrhages.
- Muscle phase: myositis with pain and weakness.
- Serious complications: myocarditis, encephalitis and pneumonitis.

## Diseases it causes

- Trichinellosis (trichinosis) [Trichinellosis →](https://durgical.com/en/conditions/trichinellosis/)

## Clinical picture

- Diarrhoea and abdominal pain in the first week.
- Periorbital and facial oedema, conjunctivitis.
- High fever, severe myalgia and weakness.
- Several diners ill after sharing the same meat.

## Diagnosis

- Marked eosinophilia and raised muscle enzymes (CK).
- EIA serology; antibodies may take 3–5 weeks to appear, so testing is repeated.
- Muscle biopsy showing encysted larvae.
- History of undercooked pork or game.

## Treatment

Benzimidazole antiparasitics (albendazole or mebendazole), most useful early, with corticosteroids when inflammation is severe.

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

In Pharmacology:

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

## Prevention

- Cook meat to a safe internal temperature checked with a thermometer.
- Do not taste raw meat while cooking.
- Freezing does not always kill larvae in game meat; curing, smoking or drying are unreliable.
- Rodent control and proper feeding of pigs.

## Memory aid

Puffy eyes, aching muscles, a pork roast that wasn't done: Trichinella travels from the plate to the muscle.

## Test yourself

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

## Which clinical triad suggests trichinellosis?

Periorbital oedema, myalgia and marked eosinophilia after eating undercooked meat.

## Where do Trichinella larvae encyst?

In striated muscle, especially very active muscles such as the diaphragm, masseters and eye muscles.

## Why does an early negative serology not rule out trichinellosis?

Antibodies can take 3–5 weeks to appear, so the test is repeated.

## Which meats transmit Trichinella?

Pork and game such as wild boar and bear, raw or undercooked.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/microbiology/trichinella-spiralis/)

## Related

- [Taenia solium](https://durgical.com/en/microbiology/taenia-solium/)

## Related conditions

- [Trichinellosis](https://durgical.com/en/conditions/trichinellosis/)

## 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: Nematodes](https://durgical.com/en/microbiology/groups/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 - Trichinellosis](https://www.cdc.gov/dpdx/trichinellosis/index.html) (CDC, 2024); [About Trichinellosis | Trichinellosis (Trichinosis) | CDC](https://www.cdc.gov/trichinellosis/about/index.html) (CDC, 2024).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/trichinella-spiralis/