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July 27, 2026Sources cited
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Casu marzu

Casu marzu is a traditional Sardinian sheep’s-milk cheese known for containing live larvae of the cheese fly, which contribute to its fermentation and soft texture.

By Ethan Anderson| Reviewed by Olivia Bennett, Standards & Fact-Checking Lead| Updated July 27, 2026|2 min read| Fact-checked

Casu marzu is a traditional Sardinian sheep’s-milk cheese known for containing live larvae of the cheese fly, which contribute to its fermentation and soft texture. The name means “rotten cheese” in Sardinian, and the cheese is associated with Sardinian culinary heritage as well as food-safety controversy. Commercial sales are illegal in Italy, and it is also banned in several other countries, including the United States.

Origin and meaning

Casu marzu comes from Sardinia, an island in Italy. Its name means “rotten cheese” in Sardinian, reflecting the cheese’s unusual fermentation process.

Production

The cheese is made from sheep’s milk and starts as a pecorino-type cheese. Cheese fly larvae are allowed to hatch in it, and their activity changes the texture and flavour.

Culinary significance

Casu marzu is regarded by some Sardinians as part of local food culture and heritage. Outside Sardinia, it is widely known for its unusual appearance and reputation.

Because of food-safety concerns, commercial sales of casu marzu are illegal in Italy. It has also been banned in several other countries, including the United States.

Key facts

  • Casu marzu is a Sardinian cheese made from sheep’s milk.
  • Its production involves live larvae of the cheese fly, which break down the cheese’s fats and proteins.
  • The cheese is usually described as an offshoot of pecorino sardo.
  • Commercial sales are illegal in Italy, and the cheese is banned in several other countries.
  • It is considered controversial because of health concerns.
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Canadian context

Casu marzu is mainly relevant to Canadian readers as an example of regional Italian food culture and food-safety regulation. It is not a traditional Canadian food, and it is generally known in Canada as a novelty or extreme-food example.

Frequently asked questions

What is casu marzu?
A traditional Sardinian sheep’s-milk cheese made with live cheese fly larvae that help ferment and soften it.
What does casu marzu mean?
It means “rotten cheese” in Sardinian.
What cheese is it based on?
It is an offshoot of pecorino sardo, often described as fiore sardo or a similar sheep’s-milk pecorino.
Why is casu marzu controversial?
Its production involves live larvae, which raises food-safety concerns and has led to legal restrictions on sale.
Is casu marzu legal to sell?
Commercial sales are illegal in Italy, and it is banned in several other countries, including the United States.
Where is casu marzu from?
It originates from Sardinia, Italy.

References

  1. Encyclopaedia Britannica — https://www.britannica.com/topic/casu-marzu
    Supports: Traditional Sardinian sheep’s-milk cheese; live larvae aid fermentation; sales illegal in Italy; banned in several countries including the United States.
  2. National Geographic — https://www.nationalgeographic.com/culture/article/maggot-cheese-casu-marzu-sardinia-italy
    Supports: Meaning of the name in Sardinian; larvae of Piophila casei hatch in the cheese; cultural significance in Sardinia.
  3. Slow Food Foundation — https://www.fondazioneslowfood.com/en/ark-of-taste-slow-food/casu-marzu-2/
    Supports: Seasonal Sardinian production; base cheese; Piophila casei; creamy texture; health-risk and marketing restrictions.