Casu Marzu: World's Most Dangerous Cheese

The name of this Sardinian speciality literally translates to “rotten cheese.” And if that’s not enough to scare you away, how about a few thousand wriggling maggots?

That’s right. Casu Marzu, otherwise known as walking cheese, is an Italian sheep’s milk variety with a little something extra. You could say it’s alive. Very alive.

Casu Marzu begins as Pecorino Sardo (Fiore Sardo), a cheese that’s typically soaked in brine, smoked, and left to ripen in the cheese cellars of central Sardinia. But to produce Casu Marzu, cheese makers set the Pecorino Sardo outside in the open – uncovered – and allow cheese flies (scientifically named Piophila casei) to lay eggs inside of it.

As the eggs hatch into a myriad of white transparent maggots, they feed on the cheese. By doing so, they produce enzymes that promote fermentation and cause fats within the Casu Marzu to decompose.

Sometimes, cuts are made into the rind of Pecorino Sardo and already-hatched maggots are introduced into the cheese. This speeds the whole cheese making process along.

Casu Marzu has been declared illegal and not in compliance with EU hygienic standards. It is banned by Italian health laws and not sold in shops. In addition to numerous anecdotal reports of allergic reaction (including burning, crawling skin sensations that last for days), there is increasing concern of risk for enteric myiasis, or intestinal larval infection.

Once ingested, it’s possible for the Piophila casei larvae to pass through the human stomach without dying (sometimes stomach acids aren’t enough to kill them). In that case, the maggots may take up residency in the intestines for some time. They can cause serious lesions and bore through intestinal walls, resulting in abdominal pain, nausea, vomiting, and bloody diarrhea.