A woman who went to hospital complaining of feeling weak and experiencing electric shocks in her legs was told she had tapeworm larvae in her spine.
The 35-year-old from France had been struggling to ride her horse during the past three months and had fallen over unusually often.
When doctors did an MRI scan they found she had a parasite infection on one of her vertebrae, which they say came from a tapeworm which lives in dogs and sheep.
The unnamed woman had to have surgery to remove the insect larvae from her back and was given medication to stop the infection returning.
Doctors did not say how the woman contracted the parasite, but it is transmitted through food or drinking water contaminated by dog faeces, or by direct contact with animals with worms.
She made a full recovery and showed no signs or lasting effects of the infection after nine months.
The infection caused unusual symptoms, including weakness in the French woman's foot, which were getting worse over time.
According to the World Health Organisation, people can be infected for years before they start to show any symptoms, but the larvae do not grow into full tapeworms inside people.
Animals which usually host the tapeworms include dogs, sheep, foxes and cows.
Doctors said the woman has a pet cat – which could have harboured the tapeworm – and also rides a horse and lives near cows.
She went to hospital in Dijon, a city about 180 miles south-east of Paris, where she was diagnosed with cystic echinococcosis, also known as hydatid disease.
The parasites may affect a million people around the world
Hydatid disease is thought to affect around one million people worldwide but the majority of cases affect people's liver or lungs.
Less commonly it can infect the nerves, bones, kidneys, spleen, muscles, and eyes, according to the WHO.
Symptoms depend on where the infection is but the woman was likely experiencing the feeling of electric shocks and struggling to use her legs because the parasite was pressing on nerves in her spine.
The tapeworm larvae infect people by causing cysts to grow inside the body but the worms do not actually grow in humans.
Parasite infects people through contaminated food and drink
Instead, people become infected by accident when they swallow the parasites in food or drink contaminated by dog faeces, such as fruits or vegetables picked from fields where dogs have been.
Hydatid disease can be expensive and difficult to treat, according to the World Health Organisation.
Prevention of the infection is based on deworming dogs and sheep which are the main hosts of the worms.
Inspecting food and slaughterhouses can also reduce the spread of infection, and the WHO is considering vaccinating lambs against the parasites.