It could also be a parasite issue.
Did these people treat them for parasites that they are bound to have in the wild?
If not, it's possible the snakes became too stressed in captivity, stress weakened their immune systems, parasite load became too high and boom...dead snakes.
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"What is man without the beasts?
If all the beasts were gone,
men would die from great loneliness of spirit.
For what happens to the beasts,
soon happens to men.
All things are connected."

-Chief Seattle (Duwamish Tribe)

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