https://en.wikipedia.org/wiki/Chelonitoxism
Chelonitoxism or chelonitoxication is a type of food poisoning which occasionally results from eating turtles, particularly marine turtles, in the region of the Atlantic, Pacific and Indian Oceans.[1][2] It is considered rare.[3]
...
Chelonitoxism can be deadly, and supportive treatment is the only treatment available; there is no known antidote.[4][5]
...
Symptoms of chelonitoxism begin to show up within hours to a week following ingestion of turtle meat which has not been repeatedly parboiled.[2]
...
Research on the biochemistry of both poisonous turtle tissues and tissues of turtle poisoning patients is scant...