Railletina is a genus of tapeworm (cestodes) that parasitizes the birds' intestine worldwide. There are many species of this parasite, but the main four are:

R. echinobothrida and R. tetragona, which affect birds worldwide and are from 23 to 25 cm long.

R. cesticillus (in the picture), which is also present worldwide and is from 11 to 13 cm long.

E. bonini, more frequently found in Europe and the Middle East, which are from 6 to 7 cm long.

Infestation causes intestinal symptoms, emaciation and the liver is friable due to the toxins produced by the parasite.