Coccidia - According to the Leopard Gecko Manual coccidia "are tiny protozoan parasites that invade the intestinal llining in order to reproduce." Basically they then lay a very small "egg-like structure" called an oocyst. They oocyst is than past on to the fecal matter into the geckos envirement so other geckos can catch it. Coccidia than leads to deyhydration, anorexia, and allows other bacteria to invade. For treatment, go to a vet as soon as suspected. But, coccidia spread can be avoided by quarantining any new leos you get, until making sure they are healthy. This is a very contagious parasite. And has been known to wipe out whole entire colonies

Hyoicalcemia (Metabolic Bone Disease) - This is probobly one of the best known leo diseases. It happens when your gecko doesn't get enough calcium supplemented with appropriate levels of of vitamin D3. To avoid this disease dust the insects that you feed your gecko with the appropriate supplements. (You can dust juveniles every day and adults every other day with calcium carbonate) But once a week, a calcium/D3 supplement should replace the calcium carbonate. If you notice signs Hypocalcemia (which include, lthargy, weaknes, painful movement, a softened or "rubbery" jaw and swollen or disorted limbs) then the D3 dustings can be increased. But stop when inprovement is noted because too much D3 can cause soft tissue mineralization. Feeding pinkie mice every two weeks also gives your gecko an excellent source of vitamins and minerals. If you feed too many pinkie mice to your gecko it will cause obesity. So don't over do it.