Leaky gut is more than likely caused by pathogens that have harbored in the GI tract. The leaky part comes from increased immune reactions due to the pathogen presence. The immune system creates high amounts of oxides that are meant to destroy the pathogens and the side effect from them is perforation of the gut lining.
parasites require specific treatments. There is a possibility that you could be dealing with rogue bacteria and an agressive yeast but I would lean towards parasites. Read Dr. Leo Galland's materials found on his website mdheal.org