digestion and survive in their bodies until becoming a stage three larva. Next, the crustacean is eaten by a fish higher up on the food chain, and the Anisakis continues to mature inside the fish’s body. Then the fish is eaten by a whale, and the Anisakis can pass stage four as a larva and become an adult within the whale’s intestine. The eggs laid by the adult mix in with the whale’s excretions and discharge into the water. This is the life cycle of Anisakis. In its case, the crustacean would be the “first intermediate host,” the fish the “second intermediate host,” and the whale the “final host.” A final host is a parasite’s final destination. If it can’t infect its final host, the parasite can’t reproduce. “…So, back on topic. How many infected by Toxoplasma do you suppose there are worldwide?”, Sanagi questioned. “You say they can infect most warm-blooded animals, so I’m sure it’s a pretty big number. A few hundred million people?” “Over one-third of the population,” Sanagi said readily. “A few billion people.” Kousaka’s eyes went wide. “That many?” “If we restrict it just to Japan today, I guess the ratio might be a little lower. Maybe ten or twenty percent at best.” “Either way, that’s still a lot. …But on the other hand, that’s