Yet another case where D3 isn't the cause.
This is
exactly what I have been doing with supplementation, and sometimes even a little more than a month apart and yet two of my montanes recently broke with edema.
I understand that but fortunately what has worked for me is extremely safe to test out - more hydration, severely limiting phosphorus in food, and sunlight. All things that are good for chameleons anyway and nothing that should cause harm regardless of the cause. For increased hydration hornworms especially help and you can drip some extra water into her mouth while she's chewing on bugs if she'll let you get close to her while eating.
Of course D3 isn't always the cause of edema since there are many causes of organ malfunction and/or damage. It's not surprising in the least that there are other causes of edema. However, as a rule, I first determine whether any supplemental D3 was given to the chameleon, either through dusting or through a commercial gutload because so many of those products do contain D3 and often, a lot of it. Again, before ruling out hypervitaminosis D3, it is very important to know what your feeders were gutloaded with by the supplier before you received them because, in many instances, insects suppliers use gutloads that contain D3 and other fat soluble vitamins that insects can store in their tissues (at least two weeks as suggested by the CiN experiment).
If only a couple of neonates develop edemas, that doesn't rule out hypervitaminosis D3 as a possible cause because metabolisms vary between animals. The safest way to provide adequate D3 is by exposing our chameleons to sunlight. Lamps that produce UVB are usually safe enough if the levels produced are not in excess, but when using them, there is always the concern that a particular neonate (raised in a group setting) might not be getting enough UVB. For instance, some individuals might not be spending as much time in the ideal UVB and/or temperature locations in an enclosure due to dominance issues, etc.. Under that scenario (a group setting), the animals will presumably metabolize vitamins and minerals differently. To make sure all the neonates are getting enough D3, we sometimes dust with it once or twice a month or else we gutload our feeders with a vitamin fortified formula we feel is safe to use (particularly one containing low levels of D3). When we take that approach, however, we must be prepared to immediately back off vitamin supplementation in general on the individuals that develop the edemas. When quick action is taken at the first slightest sign of any edema, it's been my experience those edemas will disappear completely. Presumably, no permanent damage had been done. Of course, when providing supplemental D3, it's also important to provide it in the "proper" ratio to other vitamins, particularly preformed vitamin A.
If hypervitaminosis D3 can definitely be ruled out (no D3 even in the gutload of the keeper or the insect supplier), then I would look into other causes of what might have caused it. That's just my way of doing things and it's been working very well for me, although it took me many years before I consistently used that approach. Although my mind can be changed with more evidence, for the time being, I'm definitely in the camp that believes that most cases of reported edemas can be traced to hypervitaminosis D3, although I have no doubt there are many causes.
Because there are so many products out there (commercial gutloads and powdered supplements) that are highly fortified with vitamins, many of which do not even provide how many I.U. (international units) per kg of each vitamin they contain for us to make valuable comparisons. IMO we shouldn't be surprised when keepers run into problems with their animals when using those products.
Perry