Authors

P D Olson²; A Muehlenbachs ¹ Centre for Disease Control, Atlanta, United States;  ² The Natural History Museum

Discussion

In a recently reported case of dwarf tapeworm (Hymenolepis nana) infection in an HIV-positive Columbian man (NEJM 373:1845-52), tumours were found in the lymph nodes, lungs and elsewhere that appeared to comprise non-human cells. Genetic analyses confirmed these to be H. nana cells, and their small size (< 10 um), spherical shape and low cytoplasm/nuclear ratio were all consistent with tapeworm germinative cells or ‘neoblasts' (i.e. flatworm stem cells). With the exception of a degree of syncitia formation (characteristic of tapeworm tissue architecture generally) no cell differentiation was seen. However clonal proliferation and evasive dissemination was evidenced by genetic analysis and the tumours proved fatal. Preliminary genomic analysis comparing the case study with a reference laboratory isolate revealed breaks in genes previously implicated in human cancers (e.g. LAMP2). I describe this case together with previous cases of tapeworm infection in immunocompromised patients in order to illustrate the most likely route of infection and demonstrate the necessity for cross-talk with the host’s immune system for normal development of the parasite. Lastly, I will briefly outline why studying parasites as animals rather than as some unique category of being is essential for understanding their biology and informs applied areas of NTD research.