Casu marzu: The world’s ‘most dangerous’ cheese

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The Italian island of Sardinia sits in the middle of the Tyrrhenian Sea, gazing at Italy from a distance. Surrounded by a 1,849-kilometer coastline of white sandy beaches and emerald waters, the island’s inland landscape rapidly rises to form hills and impervious mountains.

And it is within these edgy curves that shepherds produce casu marzu, a maggot-infested cheese that, in 2009, the Guinness World Record proclaimed the world’s most dangerous cheese.

Cheese skipper flies, Piophila casei, lay their eggs in cracks that form in cheese, usually fiore sardo, the island’s salty pecorino.

Maggots hatch, making their way through the paste, digesting proteins in the process, and transforming the product into a soft creamy cheese.

Then the cheesemonger cracks open the top – which is almost untouched by maggots – to scoop out a spoonful of the creamy delicacy.

It’s not a moment for the faint-hearted. At this point, the grubs inside begin to writhe frantically.

Some locals spin the cheese through a centrifuge to merge the maggots with the cheese. Others like it au naturel. They open their mouths and eat everything.

If you are able to overcome the understandable disgust, marzu has a flavor that is intense with reminders of the Mediterranean pastures and spicy with an aftertaste that stays for hours.

Some say it’s an aphrodisiac. Others say that it could be dangerous for human health as maggots could survive the bite and and create myiasis, micro-perforations in the intestine, but so far, no such case has been linked to casu marzu.

The cheese is banned from commercial sale, but Sardinians have been eating it, jumping grubs included, for centuries.

“The maggot infestation is the spell and delight of this cheese,” says Paolo Solinas, a Sardinian gastronome.

He says some Sardinians cringe at the thought of casu marzu, but others raised on a lifetime of salty pecorino unabashedly love its strong flavors.

“Some shepherds see the cheese as a unique personal pleasure, something that just a few elects can try,” Solinas adds.

Archaic cuisine

When tourists visit Sardinia, they usually wind up in a restaurant that serves porceddu sardo, a slowly roasted suckling piglet, visit bakers who sell pane carasau, a traditional paper-thin flatbread, and meet shepherds who produce fiore sardo, the island pecorino cheese.

Yet, if you are adventurous enough, it’s possible to find the casu marzu. It shouldn’t be seen as a weird attraction, but a product that keeps alive an ancient tradition and hints at what the future of food might look like.

Giovanni Fancello, a Sardinian journalist and gastronome, has spent his life researching local food history. He’s traced it back to a time when Sardinia was a province of the Roman empire.

“Latin was our language, and it’s in our dialect that we find traces of our archaic cuisine,” Fancello says.

There is no written record of Sardinian recipes until 1909, according to Fancello. That’s when Vittorio Agnetti, a doctor from mainland Modena, traveled to Sardinia and compiled six recipes in a book called “La nuova cucina delle specialità regionali.”

“But we have always eaten worms,” says Fancello. “Pliny the Elder and Aristotle talked about it.”

Ten other Italian regions have their variant of maggot-infested cheese, but while the products elsewhere are regarded as one-offs, casu marzu is intrinsically part of Sardinian food culture.

The cheese has several different names, such as casu becciu, casu fattittu, hasu muhidu, formaggio marcio. Each sub-region of the island has its own way of producing it using different kinds of milk.

‘Magic and supernatural events’

Foodies inspired by the exploits of chefs such as Gordon Ramsay often come in search of the cheese, says Fancello. “They ask us: ‘How do you make casu marzu?’ It’s part of our history. We are the sons of this food. It’s the result of chance, of magic and supernatural events.”

Fancello grew up in the town of Thiesi with his father Sebastiano, who was a shepherd who made casu marzu. Facello shepherded his family’s sheep to grazing grounds around rural Monte Ruju, lost in the clouds, where magic was believed to happen.

He recalls that, for his father, casu marzu was a divine gift. If his cheeses didn’t become infested with maggots, he would be desperate. Some of the cheese he produced stayed for the family, others went to friends or people who asked for it.

Casu Marzu is typically produced at the end of June when local sheep milk begins to change as the animals enter their reproductive time and the grass dries from the summer heat.

If a warm sirocco wind blows on the cheesemaking day, the cheese-transforming magic works even harder. Fancello says it’s because the cheese has a weaker structure, making the fly’s job easier.

After three months, the delicacy is ready.

Mario Murrocu keeps casu marzu traditions alive at his farm, Agriturismo Sa Mandra, near Alghero in the north of Sardinia. He also keeps 300 sheep and hosts guests in his trattoria, and keeps casu marzu traditions alive.

“You know when a form will become casu marzu,” he says. “You see it from the unusual spongy texture of the paste,” Murrocu says.

Nowadays, this isn’t so much down to luck as the ideal conditions that cheesemongers now use to ensure as many casu marzu as possible. They’ve also figured out a way to use glass jars to conserve the cheese, which traditionally never lasted beyond September, for years.

High fines

Though revered, the cheese’s legal status is a gray area.

Casu marzu is registered as a traditional product of Sardinia and therefore is locally protected. Still, it has been deemed illegal by the Italian government since 1962 due to laws that prohibit the consumption of food infected by parasites.

Those who sell the cheese can face high fines running into many thousands of euros, but Sardinians laugh when asked about the prohibition of their beloved cheese.

In recent years, the European Union has begun to study and revive the notion of eating grubs thanks to the concept of novel food, where insects are raised to be consumed.

Research shows that their consumption could help reduce carbon dioxide emissions associated with animal farming and help alleviate the climate crisis.

Editor’s Note: This story was originally published in 2021.

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