Spent several hours looking into leechs and leech-proof socks. They do make them. Easy to get in Malaysian Borneo and one maker in Australia.
They are a close weave cotton the shape of a Santa stocking, calf high with a string or elastic at the top. MYO.
Other options to try are knee high stockings or compression socks as an extra layer to block them.
So you tuck your trousers into your socks, these go over the top then put on your shoes and gaiters.
Theory is the weave is too small for them to wriggle through or to latch on through. Gives you time to find them and they may just gather in your shoe.
Alternatively/ additionally you can slather on DEET or use eucalyptus oil, tobacco dilution or tiger balm.
Most leeches here are land based. They sense vibrations and body heat and come marching on. Some hang out on foliage waiting for a passer by.
First aid is to apply pressure, it make take a few hours until your blood clots. Importantly if you get one in your eye do not remove it as you can damage the eye. Wait until it has finished and lets go.
Methods for removal are don't worry about it just wait, scrape off with a thin card or rub and roll them off. Using poison spray, salt or pulling can cause the leach to spew first, increasing the chance of bacteria from its stomach or of mouth parts being left in you.
The initial blood flow can help cleanse the wound. Leeches don't carry viruses.
'yes officer, those are my stockings in the glovebox'