Ayanokouji put on gloves, leaned back deep in his work chair, and opened a magazine.
As one might expect, it was a science magazine concerning parasites. The cover read “The Journal of Parasitology,” and the contents were all written in English. He was impressed. So she could read English as complex as this at her age.
Flipping through, he found a page with a tag on it. A paper by Norman R. Stoll, titled This Wormy World. He wasn’t sure how to translate it. Did it mean a worm-eaten world? Or a world that was like a worm? No, he couldn’t forget that this was a paper on parasitology. So then, perhaps “this world brimming with parasites” might be most correct.
The sound of showering from the bathroom ceased. About five minutes later, Hiyori appeared, changed into pajamas. Seeing her with a black towel on her head, Ayanokouji muttered a “huh” of some surprise.
“What is it?”, Hiyori asked.
“Oh, it’s nothing big… I just thought that with your silver hair covered like that, you looked like a normal girl.”
Hiyori’s eyes flickered, and she pointed to her head. “Oh, this? Sorry for being a non-normal girl.”
“I’m not saying your hair is bad or anything. It just felt fresh seeing how it would look black.”
“I figure you like girls with black hair, fair skin, polite and without any piercings anyway, Mr. Ayanokouji,” Hiyori said maliciously, sitting cross-legged on the bed.
“I didn’t say anything like that.”
“Then how do you explain all that stuff on your computer?”
“…What do you mean?”
“Kidding. Just wanted to tease you.”
“You can’t make jokes that ominous.”
Ayanokouji sighed, leaning back.
Hiyori suddenly noticed what was in his hand, and her eyes widened. “Hey, that magazine’s…”
“Yeah.” He’d completely forgotten about the magazine until she pointed it out. “Sorry, I’m always just curious what you’re reading. Should I not have gone and touched it?”
“Not really, but… What did you think of it?”
“It was a little tough for me. Are you good at English, Hiyori?”
“Nah. I don’t get very good test scores.”
“But you can read academic papers?”
“Only in this one field. They all have similar composition, so I’ve gotten familiar with it.”
“That’s a big deal. I’d like to tell that to a slacker college student.” Then Ayanokouji aired the question he’d had earlier. “By the way, how do you translate this part?”
Hiyori stood up and came behind Ayanokouji, looking at the part he was pointing at over his shoulder. The sweet smell of shampoo tickled his nose. She was at a distance he’d normally back away from, but since she’d just showered, it was fine.
“You’re an adult and you don’t know something that simple?”, Hiyori said teasingly.
“Adults aren’t quite the fantastic creatures you think they are,” Ayanokouji retorted. “So what does it mean?”
“I think it was translated "this world full of insects” in a book I read once,“ Hiyori mused, as if searching her memory. "It was famously used in 1947 by Norman Stoll to describe the world as one where parasitic diseases run rampant.”
“That’s one horrifying phrase.” Ayanokouji furrowed his brow.
“Incidentally, even over half a decade later, the situation is almost unchanged. People all around the world unconsciously have many types of parasites in their bodies. And Japan’s no exception. Certainly well-known parasitic diseases like ascariasis, schistosomiasis, and malaria have gone away, but parasites naturally lurk in many places in our bodies, waiting for a chance to infect. Or maybe they’ve already infected, but the person never even realizes it.”
Ayanokouji sighed. “Sounds like the mind of a clean freak will never know rest.”
“Unfortunately.”
Hiyori said she’d go dry her hair and left the living room.
Since that day they told each other about their disorders, Hiyori had begun taking showers before she entered the living room. Ayanokouji said she didn’t have to show that much forethought, but Hiyori said “It’s my prerogative, right?” Once she’d washed, she’d put on a fresh change of clothes she brought, enter the living room, lie on the bed, and read, and talk to Ayanokouji if she felt like it.
After returning from the bathroom, it seemed Hiyori still wanted to talk, so rather than lie on the bed, she sat across from Ayanokouji.
Then Ayanokouji asked her. “It looks like you’re always reading books about parasites. What is it about parasites that captivates you so much?”
“…I could tell you, but you might feel sick and faint, okay, Mr. Ayanokouji?”
“If I hear it in this room, I think I’ll be okay.”
“Let’s see…” Hiyori put her hand to her chin and pondered. “Mr. Ayanokouji, have you heard of Diplozoon paradoxum?”
When Ayanokouji shook his head no, Hiyori began explaining the ecology of that parasite. Their lifelong copulation, their appearance coming to resemble a butterfly, their fated love at first sight, the blindness of love, worms that were two peas in a pod.
After talking for a while, Hiyori suddenly became aware of how talkative she was being and her face reddened, but Ayanokouji said “Keep talking,” so she talked a little more.( Chapter 0).
“This earring.” Hiyori parted her hair to show Ayanokouji. “This is modeled after a parasite too.”
“It just looked like a blue flower to me. So there’s a parasite shaped like that?”
“Right. It’s called Kudoa septempunctata, and it belongs to the Myxozoa. These parasites use both fish and annelids as alternating hosts, and each of their spores has six to seven flower-petal-shaped structures called polar capsules, so it looks like a full flower from above. The D. paradoxum keychain is a little exaggerated, but if you dye K. septempunctata blue, it really does look exactly like this earring. Look it up.”
As instructed, Ayanokouji did an image search for “Kudoa septempunctata” with his smartphone. And indeed, many images came up of tiny organisms under a microscope that looked just like Hiyori’s earring.
“The spitting image, right?”
“I’m surprised there’s a parasite this pretty.”
“Well, it causes food poisoning, so it’s a harmful one to humans.”
Ayanokouji put down his phone. “Are there any more interesting parasites like this?”
“Hmm, well, let’s change course a little for the next one.” Hiyori folded her arms and thought for a while. “Since you’re such a clean freak, even without studying parasites, I’m sure you know Toxoplasma gondii?”
“Yeah, naturally.” Finally, a name he recognized. “They’re parasites that transmit from cats to humans, right?”
Hiyori nodded. “Yeah. They’re famous as the cause of toxoplasmosis. Their final hosts are cats, but they can infect most warm-blooded animals, which of course includes people.”
“Final host?”, Ayanokouji asked, an unfamiliar term coming up quickly.
“The host that’s the parasite’s final destination,” Hiyori explained in layman’s terms.
Some kinds of parasite will infect different hosts in various stages of growth. For instance, Anisakis, nematodes that are the cause of anisakiasis, first incubate in water, then are preyed upon by crustaceans such as krill. They avoid 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?”, Hiyori 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,” Hiyori said readily. “A few billion people.”
Ayanokouji’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 proof that Toxoplasma is harmless to humans, right? If that weren’t the case, I’d think there would be a big panic by now.”
“Yeah. It’s no problem if it infects healthy people. And so far, it’s been deemed harmless to anyone but those with immunodeficiency and pregnant women. But lately, there’s been talk about the possibility of them altering people’s actions and personalities.”
Hiyori poked at her forehead.
“There’s been interesting research about the effects of giving Toxoplasma gondii to a host. Male rats who are infected with these protozoa stop fearing cats, who should be their predators. Apparently the Toxoplasma controls the rat, using it as an intermediate host, to make it easier to be eaten by its final host, the cat.”
“It controls the host?” Ayanokouji’s voice cracked in horror. Wasn’t that just like Heinlein’s book The Puppet Masters?
“When they dissected the infected rat, the area around the cerebral limbic system had a huge number of cysts. And when they analyzed the DNA of Toxoplasma gondii, they found the presence of genes relating to the creation of dopamine. I don’t know the exact mechanisms, but it seems like Toxoplasma can control a host for the convenience of its own reproduction. In fact, parasites controlling their hosts is a common thing. Dicrocoelium and Leucochloridium are famous examples. Both are known to cause suicide or starvation in intermediate hosts.”
Ayanokouji thought a little, then spoke. “So you mean something similar could happen in human brains infected by Toxoplasma?”
“That’s right. Recent research shows that a man infected with Toxoplasma gondii shows a more favorite reaction to the smell of cats than a man who isn’t infected. However, it seems the opposite was shown in women.”
“That’s strange. There’s a gender difference in the effects of parasites?”
“I haven’t heard much about it with other parasites, but it’s a trend I see with Toxoplasma research. There are results showing that infection by Toxoplasma gondii causes men to become antisocial and be disliked by women, while women become social and are liked by men. There was also a report that for women, there were 1.5% more who attempted suicide among the infected than the uninfected.”
“So Toxoplasma might induce suicide in women?” Ayanokouji shuddered. “And over a third of the world’s population is infected with a parasite like that?”
“It’s just a possibility. It’s not proven.”
“…Even so, it makes me shiver,” Ayanokouji said with a sour look. “They say Pasteur became a germaphobe because of his studies in microbiology, so I feel like the more I learn about things I can’t see with the naked eye, the harder it’ll be to live in this world.”
“I’ve got plenty more spine-chilling stories where that came from. Want to hear?”
Ayanokouji shook his head. “No, let’s change the subject. Hiyori, do you have any interests besides parasitology?”
“Hmm… It’s a secret.” Hiyori put her finger to her lips mischievously.
“Is it a hobby you can’t tell people about?”
“It’s a girly hobby.”
“Normally you would be public about the girly hobby and hide the parasite-loving.”
“Standards for embarrassment will vary,” Hiyori retorted with displeasure. “You tell me, Mr. Ayanokouji. What captivated you about making viruses?”
Ayanokouji told the story of acquiring an interest in malware. How a text message about the end of the world saved him somewhat. How he wondered if he could make something similar himself. How he found once he started that he was unexpectedly suited for it, and it even ended up being what he lived for.
“I think I kind of understand feeling saved by a message about the end of the world,” Hiyori agreed. “By the way, what kind of virus were you making?”
“Do you know about the first computer virus recognized in Japan, Hiyori?”
“Nah.”
“Japan’s first domestic virus was developed in 1989. It was a sort of playful virus called Japanese Christmas that just displayed a festive message on computers on December 25th. Similarly, the malware I made will activate on Christmas Eve. Though I think the damage it’ll bring about will be a little more serious.”
Hiyori moved her chin just a few millimeters, urging him to continue.
“Strictly speaking, what I made is a worm that isolates people,” Ayanokouji explained, trying to break it down. “Infected smartphones can’t do any communication from the evening of Christmas Eve to Christmas night. I figured it would mess up couples trying to meet up all over Japan. …Funny, isn’t it?”
But Hiyori didn’t laugh.
The moment she heard Ayanokouji’s words, her eyes widened and she became still, as if struck by a bolt of lightning.
“What’s wrong?”, Ayanokouji asked. Hiyori’s eyes remained fixed on his throat, and she didn’t reply. And perhaps her eyes didn’t see anything.
Hiyori didn’t move for a while, silently pondering. As if she’d found a crack in the world, she kept staring at the same point in space. If you listened closely, maybe you could hear the gears rapidly spinning in her head.
Maybe something in my words disturbed Hiyori, Ayanokouji realized. But he couldn’t identify anything that had such power in what he’d said.
In the end, Hiyori never explained why she suddenly went silent, and awkwardly changed the subject. But even while chatting about different subjects, it seemed her attention was still focused on “something” from earlier.
It only figured that she would be disturbed. Because the malware Ayanokouji created, as it happened, was just so similar to something else she knew of.