(CNN) The woman who came into the emergency room in Dijon, France, said she had been having difficulty riding her horse for three months. Her symptoms had only gotten worse, from weakness to falls to feeling electric shocks in both legs.

After a battery of tests, doctors discovered a parasitic worm hiding out in her spine.

When Drs. Marine Jacquier and Lionel Piroth of the Centre Hospitalier Universitaire de Dijon conducted an MRI exam of her spine, they found an abnormal lobed lump in her ninth thoracic vertebra, they wrote along with an image published recently in the New England Journal of Medicine. Further testing revealed the tapeworm, Echinococcus granulosus, to have caused the woman's symptoms.

When they first saw the MRI scan, "to be perfectly honest, we couldn't imagine it could be echinococcosis," Piroth said. He submitted the image to the journal in order to educate physicians about the possibility of this disease, which is uncommon both in France and in the area of the woman's body it was found.

Echinococcus worms mainly cause two diseases in humans: cystic echinococcosis and alveolar echinococcosis. The disease is zoonotic, meaning it is transferred to humans by animals, in this case dogs, which in turn are infected by ungulates like cattle or sheep. According to the World Health Organization , which lists echinococcosis as a neglected tropical disease, more than 1 million people worldwide are affected with echinococcosis at any given time.

But while the disease is certainly neglected, it is not solely tropical, said Dr. Dominique Vuitton, a professor emeritus at the University of Franche-Comté and a member of the WHO Collaborating Centre for Prevention and Treatment of Human Echinococcosis. Almost every nation worldwide has seen cases of the disease, added Vuitton, who was not involved in the woman's treatment.

Although it is uncommon to see Echinococcus in developed countries, the parasite causes disease in up to 10% of the population in endemic countries such as Argentina, Peru and China, according to WHO. In hyperendemic regions of South America, between 20% and 95% of slaughtered livestock have the disease.

The doctors reported that the 35-year-old woman had no history of foreign travel but owned a cat and had contact with cattle, offering insight into where the woman might have been infected with the worm cattle -- but according to Dr. Christina Coyle, director of the tropical medicine clinic at Jacobi Hospital and a professor of medicine at the Albert Einstein College of Medicine, the cat and cattle are red herrings, since the disease is typically spread to humans by dogs.

Humans can become hosts to the parasite when they ingest its eggs, which are present in the feces of an infected dog, according to the US Centers for Disease Control and Prevention . Piroth said the woman did not report any contact with dogs, nor had she traveled to any region where the disease is endemic, such as Corsica.

"We have no real idea of how she was contaminated," he said, suggesting that she may have eaten food or vegetables contaminated by an infected dog.

Once swallowed, the eggs hatch and migrate through the circulatory system into various organs, starting with the liver. Vuitton said that approximately 65% of the lesions (which betray the worm's location) develop in the liver, 20% in the lungs and the rest elsewhere, including the brain, bone and occasionally the vertebrae.

Most people with Echinococcosis are asymptomatic, Coyle said. When the parasite develops in the liver, the cysts tend to grow over many years; in this woman's case, however, the cyst displaced her spine as it grew -- and caused her symptoms.

The MRI scan of the woman's back was notable to the experts; Piroth said the lesion looked like "a little flower," and Vuitton said the image was "very, very nice" because it showed the woman's cyst very clearly.

However, she was "amazed" that the journal published the doctors' note without requiring more specific identification of the worm's species and information as to where the woman might have been exposed to it.

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After discovering the woman's cyst, doctors surgically removed the lesion and placed the patient on the antiparasitic medication albendazole. Nine months later, the woman had no residual symptoms or signs of recurrence, according to the report.

Vuitton said that albendazole is the only medicine offered to treat patients and that nearly 20% of patients who take it experience side effects that can include liver toxicity. The drug must be used in tandem with surgery, and even then, it is not 100% effective.

"After 40 years of use of albendazole, we have nothing new that is really efficient against the disease, and that is really an issue," she said.

According to WHO, prevention programs focus on regulating the slaughtering of animals and deworming dogs and sheep, which are the definitive hosts of the disease.