He will talk about different sicknesses that an animal may have that do not make it a tereifa (non-kosher due to physical damage). We’re talking about conditions that, even though they may kill the animal, do not cause any sort of damage to the internal organs like the other tereifa that we mentioned. Therefore, the animal would be kosher (people are allowed to eat it).
The Mishnah says that if an animal got very high blood pressure and it became very hard for it to breathe; if an animal breathed in smoke from a fire and was also having a hard time breathing; if an animal got a cold and became sick; if it ate oleander, a herb that is poisonous to animals; if it ate the waste of chickens, which is also poisonous to animals; or if it drank bad water—water that was poisoned by snakes that left their venom in it, was left uncovered, and may have been poisoned by snakes when they put venom in it—the animal is kosher. Even though it may be sick and is going to die, the sickness or poison it has does not affect the organs and make it a tereifa.
So we learn from here that an animal becomes a tereifa only when there is actual damage to it. In all these cases, it is not only kosher, but people are allowed to eat it; it is considered safe. When an animal eats poison, it is not dangerous for a person who eats the animal afterward. As we mentioned, oleander and the waste of chickens are poisonous only to animals, but human beings would not be in danger if they ate an animal that had consumed those items. And mayim hara'im, the water that may have been poisoned, is changed in form by digestion inside the animal, and the venom is no longer dangerous to people.
If the animal ate actual poison that is dangerous to people as well, or was bitten by a poisonous snake, you are allowed to eat the animal in terms of its being a tereifa. In other words, it is not unkosher; the issur is that it’s forbidden to eat the animal because it’s dangerous to life. A person could die from the poison or from this type of snake venom. That could be a major problem for a person. In those types of situations, uniquely, since it is not healthy for the human being eating it, it would be halakhically asur (forbidden) as well.
In the previous case, where we said there was water, that was water into which the snake had put venom. Here, we’re talking about an animal that was bitten directly by a poisonous snake. It remains dangerous even after the animal digested it, and therefore it is not allowed to be eaten.