That is VERY awesome!! Might also show something for research. Is it necessarily true that it is completely passed from snake to snake...or does a snake perhaps show symptomatically because of stress and then die from it? If all 3 tests come back negative then perhaps most snakes harbor the spore, but never show symptoms.
It is true that snakes can harbor/carry Crypto without succumbing to it. Then, some factors (yes, it is believed that stress is just one factor) could allow Crypto to quickly rise, in amount, due to a weakened immune system. Thus, wreaking havoc upon the snake. Which, of course, causes the snake to succumb to it.
However... No, not all snakes are carriers of (or "harboring") Crypto. Studies have shown Crypto free snakes.
I believe that Crypto exists in a fair number of snakes, in captivity, but, still, that there are also many that are crypto free. However, with the careless actions (&/or perhaps their belief that "it can't happen to me") of keepers, Crypto can/will continue to rise. After all, we know that many owners/keepers do not keep a strict policy of using disposable gloves &/or or washing hands between snakes, or having each snake with its own fecal (&/or dirty substrate) scooping utensil assigned to it, or quarantine, etc.
BTW Quarantining snakes is only effective, against crypto, ~if~ a snake shows clinical signs during that time (since snakes, that carry Crypto, can show symptoms <or succumb to it> either very quickly <within months> or it could take years) &/or if the snake is tested during the quarantine period.
It is passed from snake to snake... infecting another however is not -that- easy- the transmission is done fecal-orally.
Mode of transmission is by direct contact with infected fecal matter, infected objects, or (depending) an infected animal. Of course, a snake can keep re-infecting itself with its own fecal matter, etc., too.
So, while it is not as easy to transmit, as some other things (i.e. virus, airborne, etc.), it is, or can be, made easier by keepers who are "lenient" with their husbandry (feeding, cleaning, handling, etc.).