Seems a little strange in an ectoparasite, but larval nematodes have been occasionally been found in cestodes, e.g. REGO, A. A. & GIBSON, D. I. (1989) Hyperparasitism by helminths: new records of cestodes and nematodes in proteocephalid cestodes from South American siluriform fishes. Memorias do Instituto Oswaldo Cruz, Rio de Janeiro, 84: 371-376.
Look, please, CESTODES OF CESTODES OF PERUVIAN FRESHWATER STINGRAYS, I'm attaching for you. Interesting if larvae can develop and hatch?
I know about the same fact with parasitic Nematode from Amphibians & Reptiles - Spironoura babei Ha Ky, 1971 (Nematoda: Kathlanidae).
SEY O., MORAVEC F. 1986. An interesting case of hyperparasitism of the nematode Spironoura babei Ha Ky, 1971 (Nematoda: Kathlanidae). Helminthologia-Bratislava 23:173–177.