Again she looked briefly from Søren to Henrik, and didn’t appear to have much faith in their ability to keep up with her. She seemed to be contemplating something; then she rose and produced a whiteboard, which descended silently from the ceiling. She grabbed a felt-tip pen and accompanied her explanation with simple drawings.
“Inside the pig, the egg hatches and the bloodstream transports the larva until it attaches itself to muscle tissue, nervous tissue, or subcutaneous connective tissue, where it develops into a cysticercus, a dormant cyst, whose further development isn’t triggered until the pig is eaten—by humans, for example.” Her hands flew across the board. “Inside the human stomach, the cysticercus wakes up from hibernation, attaches itself to the intestines where it grows into a tapeworm, thus completing its life cycle.”
Søren felt nauseated. He stared at his notepad, where he had scribbled down a few words. He was about to say something, but Dr. Bjerregaard beat him to it. She put the cap back on her pen.
“A tapeworm is harmless and won’t necessarily cause its host to fall ill,” she said. “As a result, you can host even very long tapeworms for a long period of time without knowing that you’re infected. In the vast majority of cases, the tapeworm is discovered by chance, during an operation or an autopsy. They normally grow six to eight feet long, and when a tapeworm is discovered, the host is given medication that kills the tapeworm and it’s expelled from the host with feces. Unpleasant, certainly, but as I said, quite harmless.”
Søren was close to retching. At the same time his brain was troubled by a discrepancy.
“I’m not sure I quite understand,” he stuttered. “Professor Helland didn’t have a tapeworm, but carried . . .” Søren checked his notes, “cysticercus.” Dr. Bjerregaard waited patiently.
“That’s correct. However, I haven’t finished my explanation,” she said calmly. “The life cycle of parasites is a complex area, even for a great many biologists, and in order for you, as lay people, to understand what I’m telling you, I need to give you some basic information.” She suddenly looked at the two men as though she was enjoying herself tremendously.
“Yes, of course. Sorry,” Søren said. Henrik looked sick.
Søren expected Dr. Bjerregaard to launch into the second half of her disgusting lecture, but she merely said, “The logical conclusion is . . . ?” She looked sternly at the two men.
“That Helland ate shit,” Henrik blurted out. “Gross.”
Søren glared at Henrik.
“It means,” he said, addressing Dr. Bjerregaard, “that Helland somehow ingested a tapeworm egg.” On realizing the implications, he fell silent.
“Or, to be precise, 2,600 eggs,” Dr. Bjerregaard interjected. “If that’s the number of cysticerci Bøje found in the tissue of the diseased, then it would equal 2,600 eggs.”
Søren managed to suppress his revulsion to such an extent that he could follow her logic. “But he didn’t ingest a whole . . .” he checked his notes again, “proglottid?”
“That would be impossible to know.”
Søren detected a microscopic smile at the corner of her mouth.
“If the proglottid carried more than forty thousand eggs, you would have expected many more than 2,600 cysticerci. However, there might be several factors why only 2,600 managed to develop.” She shrugged. “The point is Lars Helland acted as the intermediate host, and that happens very rarely in these latitudes. During my thirty years here, I’ve only come across three cases of human intermediate host infection, and they were all discovered in people who had recently returned from countries with a high prevalence of Taenia solium, such as Latin America, non-Islamic Asia, and Africa. Do you know if Helland spent time in a high-risk country?”
“We’ll be checking that. The parasite theory is still very new to us,” he said, by way of apology, and continued, “How can you tell how long the cysticerci have been in Helland’s tissue?”
“The host body forms calcium capsules around the cysticercus, to protect itself from the foreign object, and in the capsule, the cysticercus awaits its next developmental stage. You can determine the exact age of the cysticercus by measuring the thickness of the calcium shell. This would normally take place in pigs, which will be eaten sooner or later, and this places an upper limit on how calcified the capsule becomes. However, humans are unlikely to be eaten, aren’t they? The growth of the cysticercus is generally very slow, and as Helland’s cysticerci were fairly large, I would estimate that they’d developed over a long period of time. The capsules were thick and the cysticerci would undoubtedly have demanded more and more room. To begin with, they would have caused Professor Helland only mild irritation, but in time they would have become a pathological condition, and I can’t imagine how he coped with it. Cysticerci have a preference for the central nervous system, and from records—from Mexico, for example, where the occurrence of humans infected with cysticerci is high—82 percent of cysticerci had attached themselves to nerve tissue. Otherwise they prefer muscular and subcutaneous tissue, in that order.”