A mendicant with defilements ended can’t deliberately take the life of a living creature, take something with the intention to steal, have sex, tell a deliberate lie, or store up goods for their own enjoyment like they did as a lay person. And they can’t make decisions prejudiced by favoritism, hostility, stupidity, or cowardice.
AN 9.7
If an modern arahant were to get infected with intestinal worms (and he know it), would he just bear it because he isn’t a coward, or he’d just use vermifuge?
It really depends on the Arahant from what I’ve heard here in Thailand. Many of the “kruba ajahns” exclusively rely on “Dhamma Medicine” (meditating or perhaps fasting or using other austerities to get through illnesses) while some will follow doctor’s advice and take (some) modern medicines.
I don’t recall hearing any stories about macroscopic parasites though…
Thyme scent (?) has apparently been used as an aromatherapy to convince (!) the worm to leave
I’m sure a thorough search through traditional Buddhist medicinal texts would yield a variety of interesting herbs and specific meditations such an afflicted yogi could try…
I reckon some Arahants would be able to use psychic powers to get them to leave. Not helpful to those who can’t! Maybe they could try to develop them… Though they’d probably lack the motivation.