A worm that stays with you for 17 years? Well, that's almost a pet!
Loa Loa is the causative agent for Loiasis and is a Nematode (roundworm) that inhabits the subcutaneous tissue of your skin. The disease is found mostly in central and west Africa. The adults are slender, white animals between 3-7 cm long and move around freely in your tissue.
The females produce microfilariae, microscopically small worms which are being released into the bloodstream and from there picked up by various biting flies of the genus Chrysops. After the microfilariae are being inoculated into human skin, it takes them about one year to mature into an adult, which can live up to 17 years in the host.
Try to find a golden retriever that lives that long.
The wanderings of the worm seldom produce any symptoms, but sometimes so called Calabar swellings appear (named after a town in eastern Nigeria), painful and itchy swellings up to 10 cm long, probably associated with a blow to the worm and the release of irritating substances.
The most dramatic, frightening and probably traumatic symptoms appear when the animal passes under one of the patient's conjunctivae: There is an irritating feeling of "something in the eye", and the patient looks in the mirror, just to see a large worm moving with a vigorous thrashing movement between the sclera and the conjunctiva. The worm takes about 1/2 hour to move through the eye, and after 2 days the irritating symptoms subside again. That's mostly the time when the patient calls a doctor.
Therapy is either by surgical removal of the worm (especially during eye transit) or diethylcarbamazine (DEC), but that stuff seems to be quite toxic, so albendazole is used as well, but I'd prefer prevention instead of having a worm in my eye.