Biosecurity is an extremely important part of reptile keeping, and is often overlooked. If you are buying an animal from an ethical breeder you are unlikely to run into issues, but it's always best practice to quarantine regardless. If your animal is from a pet shop, has traveled a long distance, or is a rescue you will want to take quarantine more seriously.
What is a quarantine enclosure?
A quarantine enclosure is a toned-down version of an animal's permanent enclosure. You can use the animal's permanent setup, but be sure that you will be able to sterilise it completely should the animal get sick, so they don't reinfect themselves.
The substrate for a quarantine enclosure should be paper towels. This makes it easy for you to see any issues with bodily fluids (runny or parasite-ridden poop, vomit, complete lack of poop, etc).
Enrichment and clutter can and should still be offered, just be aware that things may need to be thrown away / sterilised should your gecko get sick.
Where should I put my quarantine enclosure?
If you don't have other reptiles, then you can put it wherever you want.
However, if you do have other reptiles, it's very important that your new animal is as far away from them as possible, ideally in a separate room.
How long should quarantine last?
Quarantine should be a minimum of 6 weeks and a clear parasite test.
What is a parasite test?
Parasites are one of the biggest problems encountered in quarantine. Despite what many people think, most parasites are harmless and should not be treated. Like most animals (humans included!), Leopard Geckos have a natural bioload of parasites which is kept in check by their immune systems. The only time parasites tend to become an issue is when an animal has had a stressful experience (e.g. being shipped or changing owners) which causes their immune systems to falter and the balance to be compromised. This is partially why wild-caught animals tend to be quite sickly and require treatment, despite the fact that they were presumably healthy in the wild.
We use Veterinary Parasitology Online to do all of our parasite testing. I recommend this test. After ordering they will send out a small parcel containing a sterile tub, which you then add fresh feces to. You then mail it back to them and receive your results via email. They offer online appointments via Zoom which I highly recommend.
It is likely your gecko will have a small bioload of parasites, and the consensus we have come to with various exotic vets is that it is not worth treating them unless they are affecting the health of the animal, as dewormers are often more detrimental to the geckos health than the parasites are.
Because the stress of coming to a new home will increase your geckos bioload, it's recommended that you wait 4 weeks to test your gecko so you don't get an inaccurate result. After 4 weeks their immune system will have recovered, and they will have settled in.
It is never recommended to try and treat parasites yourself, it is extremely dangerous and irresponsible to do so. All medication should be given under the advice of an exotic vet.
The basic facts
Quarantine for 6 weeks
Paper towels as substrate
Keep the new animal away from other reptiles
Track your animal's weight and feeding schedule
Parasite test your gecko after 4 weeks