Deficient disaccharidase & inflammation in small intestine

My son is 14 and has had severe GI symptoms for over a year. Symptoms started in Aug 2015, working at a zoo. Previously he never had any stomach issues, not even the stomach flu as a kid. Started having severe diarrhea & a lot pain for a day (5-25 times in a 12 hour period) this would happen 1 month. Sometimes vomiting would occur. Then he would go back to normal for the rest of the time. All labs and stool samples came back normal. They decided to treat him for a parasite because of symptoms and that he was working at the zoo when symptoms began. He was treated with Albendazole and Flagy and for almost 2 months was symptom free with normal bowel movements. Then symptoms reoccured, he had a couple times with blood and mucus. Had a CT scan that showed thickening of the ileum and mesenteric adenitis. EGD and Colonoscopy that was normal, except for his disaccharidase levels being low- the GI doc we were seeing didn't really think this was a big deal. His symptoms continued to get worse and became daily. Pain increased and he would sit on the toilet with just globs of mucus coming out. They tried some antispasm medication that did nothing. They scoped him again, the GI doctor said that the clean out wasn't ideal on the first one. This time he had 11 ulcers- 9 in his colon and 2 in his stomach, also they saw patches of inflammation. They put him on prednisone for a 6 week run including the taper. The biopies came back as normal, except again the dissacharidase being low . The GI group we were at told us that he had a Eosinophilic Gastroenteritis. After about a week on the predisone, he started doing really good and became basically symptom free. We ended up getting a second opinion as we felt that we weren't getting anywhere. This doctor had us taper more quickly off of the predinsone because she reviewed the Eosinophilic levels and they were actually normal. Once he had to taper off the predisone, symptoms came back. My son's symptom have become spending most of the day in the bathroom pooping "soft serve", lots of mucus- sometimes it is bloody. He has had a couple times of blood in his stool throughout all of this. They did a pill cam, which showed nothing. He was scoped for a 3rd time by our new GI doc and she found inflammation in the duodenum, where the disaccharidase enzymes are, his disaccharidase levels are now extremely low. His lactase is now zero, all of the other ones are very low as well. He felt really good for a couple of days after this scope, we don't know if it was from his system being cleaned out & he was also given Decadron during the procedure. This doctor is finally taking these disaccharidase levels seriously and obviously it is causing a lot of his symptoms since he can not properly digest any sugars or carbohydrates. They are trying to figure out what the cause of this damage to the duodenom and the dissacharidase deficiency. Our doctor says it is most likely from an infection (bacteria or parasite probably from the zoo) or an atypical presentation of Crohns. He seems to really respond to anti inflammatories. We are so ready for answers as this has pretty much taken over our lives. Our son is so behind in school as he has is spending so much time in the bathroom pooping. Anyone have any experience with any of this? Thank you for any help you can provide.