Fire still works to get rid of them just tested it
Leech

Player-written tips for taming, using, and fighting the Leech in ARK: Survival Ascended & Evolved.
They suck to get on you fight from long range
If you have a leech attached to your tame on mobile, there should be a grab button when you look at the tame. Press that button and the leech will basically just disappear.
The ones that are brown are “diseased “ and will give you swamp fever.
If your looking for leach blood get scuba and go the the swamp cave with a bary then begin the extermination
These are so annoying I try starting on any map there is always someone running around spreading swamp fever
To Get rid of it you have stand on top of a lit camp fire and it will fall off and die but you will not see the corpse
If you have a freind you can smack each other with a torch
I had a leech stuck on me and I couldn’t get it off even using fire from a cooking pot, campfire or a forge.
Remove it with an argentavis or jump on fire
Like most animals like this leeches can be tamed using a fish basket on aberration they are not tameable on mobile or switch but they are on PC or consule
To get a leech of your tame simply go select that creature’s inventory and you’ll see a new option. It says “hold to remove leech”.
Be careful if you see a red leech. It is diseased and will give you a debuff which reduces health, stamina, speed and some others. the way to cure it is with lesser antidote
Jump in a fire to kill the leech
They can latch onto pretty much all creatures if you get one when mounted on a dino make sure to check if the dino has the leech before setting yourself on fire chances are you don't have the leech your tame does
Mobile players only:
Leeches are super rare and I'm pretty sure swamp fever isn't a thing (not 100%). If you get butted you need to jump into a campfire and for tames you can just use the grab option to remove them
When in the swamp be wary of small moving organisms they are not as big as they seem
I ensure my raft has a campfire and fuel. Just be sure to watch your screen, I sometimes don't notice they got me until way too late!
WARNING: on mobile they do stick to swamp original creatures so if you go passing by make sure to bring 3 lesser antidotes in case of diseased leech one for you one for your tame and the third in case one spoils
I can never find these things even though I was driving a raft across a swamp