One of these could eat your brain!

A Californian teacher has had the remains of a dead worm removed from her brain during a six-hour operation at the Mayo Clinic in Arizona. She believes she contracted the worm from a pork taco she ate in Mexico, where she owned a coffee ranch and taught University courses.

Note: this is a true story.

When Dawn Becerra ate her taco she didn't think she would end up three years later having a dead worm removed from her brain while she talked to surgeons on the operating table. But that's exactly what happened.

In 1998, Mrs Becerra bought a pork taco from a street vendor, which initially made her ill for three weeks. Eating local food can often give travellers stomach bugs, but Becerra is convinced that her ill-chosen snack carried an unexpected payload.

Doctors at the clinic in Scottsdale, Arizona believe the taco contained Taenia Solium, a parasite that is common in Latin America. It can be transmitted by infected food prepared by someone who has not followed proper sanitation procedures after coming into contact with the creature's eggs, which can be present in human feces.

Once Becerra ingested the parasite, it attached itself as an egg to her intestinal wall. Eventually, the egg developed into the worm, which moved into her blood stream and to her brain. In the brain, Taenia Solium causes little harm until it eventually dies and decays, thereby inflaming surrounding tissue. "It's after the worm dies that the body reacts to something foreign," explained Joseph Sirven, the epilepsy specialist who eventually diagnosed Mrs Becerra's affliction.

But for three years Becerra suffered regular seizures, and her condition was not recognised until November 2000; in April this year brain surgeons at the Mayo Clinic in Phoenix, Arizona, extracted the remains of a dead worm from her brain in a six-hour-long operation.

Mrs Becerra chose to remain conscious throughout the operation and only acupuncture and a mild anaesthetic were used to dull the pain. Becerra, who is bilingual in English and Spanish, feared losing her ability to speak as a result of the procedure. By speaking to her in both English and Spanish as they operated, the doctors were able to ensure that what they were removing was worm not brain.

Despite her composure during the surgery, Mrs Becerra has admitted that she was initially horrified when doctors told her that the only way her siezures could be stopped was to undertake brain surgery and remove he remains of the dead worm.

“The thought of a worm being in your brain is very strange, very difficult to deal with,” she told a local Phoenix television station. “But the thought of brain surgery wasn't easy to deal with either. “All of a sudden, I realised that they were going to cut open my brain and take a worm out. I don't even know if I had cried before this. I guess I have a couple of times, but that realisation was devastating.”

The condition is one of the biggest causes of seizures and epilepsy in Latin America and South-East Asia, but it is unusual in the United States. Sirven said that she had been fortunate because there was only one worm. “If you have enough of these cysts, they can take over the entire brain. Luckily for Dawn, she only had the one.”

The worms, which are borne through undercooked food, travel first to the large intestine and then enter the bloodstream. They settle in locations that are conducive to growth, such as the brain and kidneys.

The diagnosis was made based on Mrs Becerra's certainty that her health problems had followed the consumption of the pork taco and on a brain scan. However, Richard Zimmerman, the neurosurgeon who performed the operation, decided to remove the part of the brain that was causing the seizures so that he could be certain it was not a tumour. Pathology tests subsequently confirmed that it had been a worm.

The worm had destroyed part of Mrs Becerra's brain tissue, but the doctors were able to remove both the worm and the damaged tissue without causing long-term damage to the patient.

Some experts point out that it is difficult to know for certain that one particular taco was the source of the worm, but hey, why spoil a great story.

Mrs Becerra was last reported to be doing well and will not need a checkup for another six months. She is apparently looking forward to her next trip to Mexico, but is planning to bring her own sandwiches.