Raillietina cesticillus is a type of tapeworm that is an internal parasite of chickens and other avian species. R. cesticillus is a 50-150 mm (2-6 in) long flattened, segmented, ribbon-shaped worm that invades the chicken's gastrointestinal system, most commonly found in the duodenum or jejunum.
R. cesticillus has an indirect life cycle, using beetles as intermediate hosts. More than 100 species of beetles can serve as intermediate hosts. Chickens become infected by consuming the R. cesticillus eggs shed in the feces of infected chickens or infected beetles. It takes approximately 2 to 4 weeks to complete the tapeworm life cycle.