In article , A.Malhotra
writes

It is
completely harmless to mammals (as are all British leeches with the
exception of the endangered species Hirudo medicinalis) but because of
its habit of finding its way into sewage systems and swimming against
the flow of water we regularly used to get specimens sent to us from
doctors. In one case a mother took her 2 children out of the bath and
pulled the plug out. When she went to clean the bath a few minutes later
there were two fat leeches in the bottom of the bath. She put 2 leeches
and 2 children together raced to the nearest hospital!

Why? Getting bitten by a leech (if thats what's implied actually happened)
is hardly a life-threatening emergency. Although you do imply it doesn't
bite mammals....so what was the problem?

Ignorance! :-)
I think she assumed that they'd come out of the children ;-)

btw - it's not me implying that it doesn't bite mammals, I was simply
quoting from Edward's web page, and as a professional oligochaetologist
(albeit retired) he's infinitely more qualified to comment than I am!

Edward taking over from here on:

Incidentally, Hirudo medicinalis is not the only UK species that is capable
of feeding on mammalian blood

It is also extremely rare in the UK, so rare that it is a
protected species. It is only known from 3 or 4 British sites. It is
relatively eay to recognise by the two longitudinal thin stripes running
along the top of its body.

....the much more common horse leech does too.

No it doesn't, not even blood of any sort. It feeds on aquatic
and soil invertebrates.
--
Kay Easton

Edward's earthworm page:
http://www.scarboro.demon.co.uk/edward/index.htm