After eating crabs, he vomited every day, and there was no food, which means that crabs may not be fresh, or he may have been poisoned by crabs.

Causing gastrointestinal problems in cats.

In this case, it is best to send the cat to a pet hospital for examination. What medicine should he take, what medicine should he take, what injection should he take, and what injection should he take?

Otherwise, if we go on like this, maybe the cat will die.