"So, naturalists observe, a flea has smaller fleas that on him prey; and these have smaller still to bite ’em; and so proceed ad infinitum."
- Jonathan Swift

October 6, 2010

October 6 - Hymenolepis nana

Hymenolepis nana, or the dwarf tapeworm (only 40 mm long!), is thought to be the most common human cestode on the planet. Unusual amongst tapeworms, H. nana does not require an intermediate host, but can be passed simply from one person (or rodent) to another via the ingestion of eggs that are shed in the feces, and auto-infection occurs in parts of the world where the worms are common. This direct life cycle is thought to be a recent adaptation in this species as the life cycle can be completed via an intermediate such as a flour beetle, much like its cousin, H. microstoma that you met way in the beginning of the year.

Image from the CDC Public Health Image Library.


  1. your blog is so awesome!!!
    i love reading and learning about parasites!
    i also enjoyed the show " monsters inside me" which led me to finding your blog.
    i didnt know there where so many parasites in the world.. and each one is different and special in its way..that is amazing.
    but i wonder how do you know so much about parasites.. are you a parasytologist or something?

  2. Glad you like the blog. Yes, I am a parasitologist - see the sidebar, which has a little biography. But, I also rely on lots of information from journals and colleagues.

  3. i wish i can be a parasitologist one day.. but there is no university that teaches parasytologia in my country.. perhaps i should fly to US or europe to learn.. anyway,can i ask a parasite related question?