File1262719861.jpg-(17 KB, 441x415, Ascaris lumbricoides.jpg)
Parasites now. Picture is Ascaris, or so it appears to be.
Angiostrongylus cantonensis normally infects rats, but when in a human host through paratenic invertebrates (prawns, crabs and such other seafood) the worms, lost in a host they cannot mature in, migrate to the central nervous system, literally swimming in the cerebrospinal fluid. This is the prime cause of eosiniphilic meningitis and has dire consequences, ending with death if not treated in time. The worms can also enter the eye, where they may cause blindness.
Found in a quarter of our population, Ascaris lumbricoides is the most common macroparasite in humans. While generally harmless, they may grow to prodigious sizes in great numbers (about 400 worms in one person, and an individual worm can grow to about 50cm length), blocking the intestine in a tangled mess of dead worms. They may also attempt to escape through the mouth or anus when disturbed (ie. by anesthetics. )
Dioctophyme renale is called giant kidney worm for obvious reasons, reaching sizes of about a meter and able to demolish the kidney of the host so efficiently that all is left after the worm's death is a hollowed-out cavity. Sometimes it also breaks the kidney and wanders on to other body cavities. It usually prefers the right kidney, and the host obviously dies should both kidneys be affected. Rather rare in humans, its natural host is mustelids, but it can infect freshwater fish as paratenic hosts and pass on to humans. It is more common around Europe.
Loa loa also has a rather explanative name, this time it is the eye worm. The worm does not live exclusively in the eye, merely slithering below the host's skin and occassionally passing through the eyes, which takes a few minutes of great pain. The death of the worm may also cause abscesses and itchy swellings may form wherever it passes through, and it may cause orchitis while passing through the testicles, but the animal is otherwise quite harmless.