I do a lot of reptile rescue, primarily with Leos - I will share with you my experience...
The most important factors in recovering a thin Leo is a stress-free environment (or as close to this as possible).
I always start by housing them alone (very important), on paper towels, nonadhesive shelf liner, etc - a substrate with no impaction risk. Three hides (warm, cool, humid), a belly temp of 88-92 degrees.
I have never needed the use of waxworms to fatten up a lizard, nor do i recomend them. Waxworms are likt using twinkies to fatten a person up - it will give extra calories, but not extra nutrition, which is what they really need for healthy weight gain. Well gutloaded, properly supplemented, nutritious feeder insect are more than adequate for adding weight to a thin lizard. I like to use mealworms, silkworms and roaches, and of course crickets as well.
If the lizard is eating on their own then your job is just to keep the husbandry good, properly gutload and supplement the insects and offer food daily. With a proper set up and good feeder insects they will gain weight rapidly.
If they are not eating on there own then the concern is greater and the prognosis is not as good. I start these lizards on a slurry recipe (its posted at the bottom of this message). I use a syringe to dribble small amounts of this slurry onto their nose, oftent imes they will lick this up and force feeding is not necessary. If they take well to this regime i continue this, while also offering live insects until they start to take the insects, then wean them off the slurry.
If they will not accept the slurry then the prognosis is quite poor - you can force feed them small amounts, but it is extremely stressful and should only be tried as a last ditch effort to save them.
A few other things...
- Always get a fecal sample checked. These guys almost always have a heavy parasite load due to the stress of their chronic condition, treatment for these is needed and often leads to improvement in condition and appetite.
- If the lizard appears dehydrated i soak them daily for the first few days in shallow (no higher than the shoulders - lower for weak and debilitated animals) warm water to help rehydrate them.
- I often use a probiotic, Acidophiliz (available at www.reptilesupply.com). This is extremely useful if you end up having to deworm as the dewormer medications often upset the gut and lead to further inappetance before you see an improvement. The probiotic promotes good bacterial growth in the gut and helps them feel better. I will often use it even when i am not using a dewormer as it sometimes helps to "jump start" the system.
- Once you have them all set up in the new tank, give them a few days to settle in before determining whether they will eat or not. If they refuse feeders the first time you offer them, dont jump right to the slurry, give them a little time first. If the lizard is so thin that they cannot wait a few days before feeding then its highly unlikely they will survive anyway. Its also helpful to have a variety of feeders to perk their interest.
I hope this info helps! Could you post a pic of the lizard in question?
Here is the slurry recipe, hope you dont need it!
"In a blender, combine:
1 small can Hill's A/D pet food (available at most vets)
1/4-1/3 cup Ensure (not chocolate)
1 jar baby food squash
1/4-1/3 cup Pedialite
2 tablets or contents of 2 capsules milk thistle (herbal supplement, liver purifier, found at most drug stores.)
1/2 tsp. each calcium powder and herp vitamin powder
1 large handful of mealworms, added slowly while mixture is blending
Puree all ingredients until completely smooth, and pour into ice cube tray(s) and freeze. Store cubes in zip-lock bag in the freezer until ready to use, then thaw out 1 cube at a time and store in fridge for 2-3 days. I use the empty baby food jar for this purpose, washing it thoroughly after each batch.
Using this mixture, draw a full dropper (eye dropper type) and place a drop on the gecko's nose. It will lick it off, and as it does, slowly squeeze out a little at a time. Most geckos love this food, and will lap it up."
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1.1 Bearded Dragons
2.2 Leopard Geckos
1.0 Uromastyx (Mali)
1.1 Corn snakes
0.1 Mexican Black Kingsnake
1.0 Bairds Ratsnake
1.0 Rosy Boa
1.1 Green Anoles
1.1 House Geckos
0.0.2 Flying Geckos
0.0.1 Red Eye Tree Frog