The weather has been so wet for so long leeches are bound to be around in the garden, especially in soaks and overly wet areas. You only need to rub up against a wet bush while you are pruning and they will latch on.
Anyone emptied the spa when not in use this is prefect conditions for leeches to thrive. The solution is salty water.. yes its that simple ! Recently I faced this issue and decided to check out what to do and found this worked for me.
leeches in your garden
1/ you can actually sprinkle salt directly on them and they will generally let go or
2/ put together a salty solution and pour over the little sucka…
3/ still not letting go, strike a match and touch them with the hot tip and hey presto its all gone..
Lifestyle Solutions Centre Pool & Landscaping Blog 