[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Apicomplexans](https://durgical.com/en/microbiology/groups/apicomplexans/) › Sarcocystis spp.

# Sarcocystis spp.

- Parasite
- For completeness

A coccidian parasite acquired from undercooked beef or pork (intestinal form) or from food contaminated with animal feces (muscle form).

Updated Nov 13, 2026

Also called: sarcocystosis, Sarcocystis hominis, Sarcocystis suihominis

## Quick facts

**Type**
Parasite · [Apicomplexans](https://durgical.com/en/microbiology/groups/apicomplexans/)

**Gram / shape**
Thin-walled oocysts with two sporocysts in stool

**Spread**
Intestinal form · Muscular form

**Causes**
Intestinal sarcocystosis · Muscular sarcocystosis

**Treatment**
The intestinal form usually needs no specific treatment

On this page

- The basics Key points
- At a glance
- Morphology
- Transmission
- Life cycle
- Memory aid
- What the colours mean

- Clinical Virulence factors
- Diseases it causes
- Clinical picture
- Diagnosis

- Treatment Treatment
- Prevention

- Study Test yourself

- Connections Connections

## Key points

- Humans are definitive hosts for S. hominis (beef) and S. suihominis (pork): intestinal infection.
- Humans are dead-end intermediate hosts for other species: muscle cysts with myositis.
- Fever, myalgia, eosinophilia and high CK after travel: think trichinellosis and muscular sarcocystosis.
- Stool shows sporocysts that autofluoresce.

## At a glance

**Shape**
Thin-walled oocysts with two sporocysts in stool; sarcocysts full of bradyzoites in muscle

**Family**
Sarcocystidae

**Type**
Intracellular coccidian protozoan (apicomplexan) with two hosts

**Stain**
Wet mount of stool (sporocysts autofluoresce under UV); histology of muscle biopsy

**Size**
Oocysts about 15 to 20 µm

## Morphology

- Oocyst with a fragile wall and two sporocysts, each with four sporozoites; free sporocysts are often seen.
- Sarcocyst: an elongated cyst inside a muscle fiber, packed with banana-shaped bradyzoites.
- Close relatives of Toxoplasma and Cystoisospora.

## Transmission

- Intestinal form: eating raw or undercooked beef (S. hominis) or pork (S. suihominis) with sarcocysts.
- Muscular form: swallowing sporocysts from the feces of a carnivore (for example in water or food); here the human is a dead-end intermediate host.
- Not spread from person to person.

**Reservoir:** Cattle and pigs (intermediate hosts of the human intestinal species); Wild carnivores and their prey for the species that cause muscle disease

### Isolation precautions

What the care team adds to standard precautions.

- Standard

## Life cycle

- Cattle or pigs swallow sporocysts shed in human stool.
- Sporozoites multiply in blood vessel endothelium (schizogony) for two generations.
- Merozoites enter muscle fibers and form sarcocysts full of bradyzoites.
- A person eats undercooked meat with sarcocysts.
- Bradyzoites invade the intestinal wall and form gametes; fertilization gives oocysts.
- Oocysts sporulate in the gut wall and are passed in stool, often as free sporocysts.

## Virulence factors

- Intestinal form: mild damage to the intestinal lining.
- Muscular form: cysts in muscle and heart fibers with inflammation (eosinophilic myositis, vasculitis).

## Diseases it causes

- Intestinal sarcocystosis: often silent or mild and self-limited; nausea, abdominal pain and diarrhea a few hours after eating raw meat. [Acute (viral) gastroenteritis →](https://durgical.com/en/conditions/acute-gastroenteritis/)
- Muscular sarcocystosis: fever, myalgia, weakness and transient swelling, with eosinophilia and raised creatine kinase; outbreaks have occurred in travelers to Southeast Asia.

## Clinical picture

- Suspect the muscular form in a returning traveler with fever, myalgia, eosinophilia and high CK without another cause.
- Its main differential diagnosis is trichinellosis.

## Diagnosis

- Intestinal: oocysts or sporocysts in stool; they are shed in small numbers and are easy to miss; species cannot be told apart by morphology.
- Muscular: sarcocysts on muscle biopsy; eosinophilic myositis supports but does not confirm it.
- Molecular and serologic tests are not widely available.

## Treatment

The intestinal form usually needs no specific treatment. For the muscular form there is no proven therapy; albendazole has been reported in a case and corticosteroids may relieve symptoms.

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

- Cooking beef and pork thoroughly; freezing reduces risk.
- Safe drinking water and washing raw vegetables in endemic areas.
- Keeping human feces away from cattle and pig pastures.

## Memory aid

«Sarco = flesh»: eat the flesh and it stays in the gut; eat the carnivore's feces and it settles in your flesh.

## Test yourself

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

## How does a person get intestinal sarcocystosis?

By eating raw or undercooked beef (S. hominis) or pork (S. suihominis) that contains sarcocysts.

## What is the human's role in muscular sarcocystosis?

A dead-end intermediate host: sporocysts from carnivore feces reach the muscles and form cysts.

## Which findings suggest muscular sarcocystosis in a traveler?

Fever, myalgia and weakness with eosinophilia and raised creatine kinase, with no other explanation.

## How is the muscular form confirmed?

By finding sarcocysts in a muscle biopsy.

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

## 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.

## Connections

## Related 6

- [Toxoplasma gondii](https://durgical.com/en/microbiology/toxoplasma-gondii/)
- [Cyclospora cayetanensis and Cystoisospora belli](https://durgical.com/en/microbiology/cyclospora-cayetanensis-and-cystoisospora-belli/)
- [Cryptosporidium spp.](https://durgical.com/en/microbiology/cryptosporidium-spp/)
- [Trichinella spiralis](https://durgical.com/en/microbiology/trichinella-spiralis/)
- [Taenia saginata](https://durgical.com/en/microbiology/taenia-saginata/)
- [Taenia solium](https://durgical.com/en/microbiology/taenia-solium/)

## Related conditions 1

- [Acute (viral) gastroenteritis](https://durgical.com/en/conditions/acute-gastroenteritis/)

[← Back to the group: Apicomplexans](https://durgical.com/en/microbiology/groups/apicomplexans/)

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

Sources: [CDC - DPDx - Sarcocystosis](https://www.cdc.gov/dpdx/sarcocystosis/index.html) (CDC, 2024); [Clinical Care of Sarcocystosis | Sarcocystosis | CDC](https://www.cdc.gov/sarcocystosis/hcp/clinical-care/index.html) (CDC, 2024).

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Representative model, for educational purposes only.

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