"Unclean" in Levitical law is not about health.
IT is according to scripture when it comes to Lev 11.
2 “Speak to the sons of Israel, saying, ‘These are the creatures which you may eat from all the animals that are on the earth.
2 “Speak to the children of Israel, saying, ‘These
are the animals which you may eat among all the animals that
are on the earth: 3 Among the animals, whatever divides the hoof, having cloven hooves
and chewing the cud—
that you may eat. 4 Nevertheless these you shall not eat
29 These also shall be unclean unto you among the creeping things that creep upon the earth; the weasel, and
the mouse, and the tortoise after his kind,
30 And the ferret, and the chameleon, and the lizard, and the snail, and
the mole.
...
39 ‘And if any animal
which you may eat dies, he who touches its carcass shall be unclean until evening.
39 ‘Also if one of the animals dies
which you have for food, the one who touches its carcass becomes unclean until evening
46 ‘This
is the law of the animals and the birds and every living creature that moves in the waters, and of every creature that creeps on the earth, 47 to distinguish between the unclean and the clean,
and between the animal that may be eaten and the animal that may not be eaten.’ ”
46 This is the law regarding the animal and the bird, and every living thing that moves in the waters and everything that swarms on the earth, 47
to make a distinction between the unclean and the clean, and
between the edible creature and the creature which is not to be eaten.
==============
In Lev 11 even a clean animal is "not to be eaten" if it dies of itself and you simply come upon the carcass
