Red worm in toilet

Hi,

hope you can help me with a problem.
In our basement toilet we keep finding red worm (every couple of weeks). This toilet is used by at least 5 adults occasionaly.

Is this possible to come from cesspool or can be more serius problem? In other toilets we didnt find any.

worm is identical to this one I found on internet link posted

//www.curezone.org/ig/i.asp?i=32268


Thank you for the answer.