Geckos can carry disease-causing pathogens without showing symptoms. Just because you deworm them doesn't mean that you've eliminated all or even most of the problems. Deworming medications themselves are not full-proof solutions since larvae can migrate and encyst in other parts of the body where they can stay for months, rendering the medication useless. (But the meds were already useless against larvae anyway.) Dewormers are also ineffective against protozoa, and there are a great many varieties that can multiply rapidly within a small enclosure. Coccidia, flagellates, etc. are pretty common particularly with WC specimens.
Can a gecko harbor that kind of stuff without showing symptoms? Heck, yeah! Just because they look healthy doesn't mean squat. Animals, particularly WC, can hide illnesses for long periods of time. That's what they're supposed to do for survival.
For example, I've had two leos since July. Perfectly healthy animals with fantastic appetites, normal, solid poops, inquisitive attitudes, you name it. They were able to gain weight in my care without any problems. Just to be safe, I had fecal tests done on them, and both were confirmed to have pinworms. Ok, fine, I figured. Pinworms are common, and they don't always show symptoms. However, on a follow-up fecal months later, they were diagnosed with hookworms. I -know- they didn't get it from my other leos and it didn't come from the food source; they had to have been carrying the worms the whole time. It really took me by surprise that they had hookworms. I never would have guessed, because they had never showed any symptoms at all. But here they were, suddenly pooping out heaps of white skinny worms that I could see with my own eyes.
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chickabowwow
3.2.3 leopard geckos (Rosie, Locke, Lisa, Caesar, Tommy)
and another group, my het blizards laid some in there hide box, another 