Parasites: They Have A Number Of Redeeming Features
December 29, 2022 at 5:49 p.m.
By Max [email protected]
The meaning emerged only in the 18th century, in the wake of the scientific revolution. For ancient Greeks and Romans, the term denoted what many of us now assume to be the figurative meaning: a sponger, or a person dining at someone else’s table, at someone else’s expense.
Scott Gardner, Judy Diamond and Gabor Racz, in their new book “Parasites” explain, “They are seen as blood suckers, freeloaders, scroungers, flunkies, deadbeats and the worst kind of groupies. In Bong Joon-ho’s 2019 award-winning film, the main characters first help the members of a wealthy family by tutoring the kids, cooking, housekeeping and driving. Eventually the host family becomes dependent on the help, and only then does the relationship turn toxic, hence the film’s name, Parasite. In all natural and human impacted ecosystems on Earth, parasites are wildly abundant and represent a most successful lifestyle.”
Parasites may live at the expense of their hosts, but both host and parasite are fundamentally changed as a result of the partnership.
Even when the victims aren’t people, there is something about parasites that arouses fascination. The authors of “Parasites” mention the monster in the film “Alien” as a kind of archetype of the gross outs in which the field abounds.
There is also a louse that destroys fishes’ tongues and then lives in their mouths, performing a tongue’s function while gorging itself. The fungus Ophiocordyceps unilateralis, which propagates itself by taking over ant’s bodies, has sufficient notoriety that it appears in the video game “The Last of Us,” where it zombifies people rather than ants. For one of the first times, however, the same authors resist filling their book with nightmarish creatures. They give us a new understanding of parasites, to counter our unalloyed horror and instill a more scientifically nuanced view.
They write about how parasites may keep populations of species in balance, the ways in which they are imperiled by pathogens. But such adaptations can entail costs as well as benefits. The plasmodia that cause malaria have been attacking our red blood cells for millennia, and some people have developed genetic mutations that confers some resistance.
Unfortunately, these mutations are also associated with certain blood cell disorders – sickle cell anemia and thalassemia. Resistance to malaria in other words, appears to come at a price of having blood that is less able to carry oxygen.
The Earliest Parasite
The fossils of the original Pleistocene fauna are scattered throughout North and South America. These remains outline the story of the first peoples — what they ate, the kinds of tools they created, and how they buried their dead. Archaeological sites throughout the Americas also reveal evidence of the constellation of parasites, those that accompanied the migrants. Some, like Enterobius pinworms, were robust travelers and had no problem surviving in tropical or temperate climates.
The incessant partnership between humans and pinworms goes back to a time before the common ancestor of humans and apes. Each human generation passed the parasite on to the next one — like DNA but not like DNA, since the transmission occurred not in the host cells but in the environment as the worm eggs moved among hosts. Pinworms are found in many kinds of primates, the group that includes monkeys and apes, but each species is remarkably specific.
One close relative of the human pinworms infects chimpanzees, while others infect gorillas and orangutans. This suggests that different species of pinworms evolved parallel to the relationships of their hosts.
The pinworm, Enterobius vermicularis, causes one of the most common kinds of intestinal infection among people living in temperate zones such as North America. Their eggs are easily spread among children and people living in institutions via contaminated clothing, food, and surfaces, and they collect under fingernails and in bedding. Once ingested, the eggs hatch and the juveniles molt to adults, completing their life cycle in humans, their only host. Infection rarely results in serious illness.
Because pinworms are relatively host specific, they act as a kind of marker that traces human movements over time. As humans migrated from one area to another, the pinworms came along, leaving traces in coprolites, the fossilized remains of human feces.
Climate Change
According to Gardner, Diamond and Racz, the planet is losing species faster than scientists can name them — much like burning a library without knowing the names of the contents of the books. They note that more than 20 million species may be lost because of our destructive behaviors, which lead to deforestation, spillage of toxic chemicals, and global warming. Our knowledge of earth’s biodiversity is still so partial that many species will become extinct before we even learn of their existence. Given that parasites help keep life in balance, their loss threatens to further destabilize the earth’s ecosystem.
Max Sherman is a medical writer and pharmacist retired from the medical device industry. His new book “Science Snippets” is available from Amazon and other book sellers. It contains a number of previously published columns. He can be reached by email at [email protected].
The meaning emerged only in the 18th century, in the wake of the scientific revolution. For ancient Greeks and Romans, the term denoted what many of us now assume to be the figurative meaning: a sponger, or a person dining at someone else’s table, at someone else’s expense.
Scott Gardner, Judy Diamond and Gabor Racz, in their new book “Parasites” explain, “They are seen as blood suckers, freeloaders, scroungers, flunkies, deadbeats and the worst kind of groupies. In Bong Joon-ho’s 2019 award-winning film, the main characters first help the members of a wealthy family by tutoring the kids, cooking, housekeeping and driving. Eventually the host family becomes dependent on the help, and only then does the relationship turn toxic, hence the film’s name, Parasite. In all natural and human impacted ecosystems on Earth, parasites are wildly abundant and represent a most successful lifestyle.”
Parasites may live at the expense of their hosts, but both host and parasite are fundamentally changed as a result of the partnership.
Even when the victims aren’t people, there is something about parasites that arouses fascination. The authors of “Parasites” mention the monster in the film “Alien” as a kind of archetype of the gross outs in which the field abounds.
There is also a louse that destroys fishes’ tongues and then lives in their mouths, performing a tongue’s function while gorging itself. The fungus Ophiocordyceps unilateralis, which propagates itself by taking over ant’s bodies, has sufficient notoriety that it appears in the video game “The Last of Us,” where it zombifies people rather than ants. For one of the first times, however, the same authors resist filling their book with nightmarish creatures. They give us a new understanding of parasites, to counter our unalloyed horror and instill a more scientifically nuanced view.
They write about how parasites may keep populations of species in balance, the ways in which they are imperiled by pathogens. But such adaptations can entail costs as well as benefits. The plasmodia that cause malaria have been attacking our red blood cells for millennia, and some people have developed genetic mutations that confers some resistance.
Unfortunately, these mutations are also associated with certain blood cell disorders – sickle cell anemia and thalassemia. Resistance to malaria in other words, appears to come at a price of having blood that is less able to carry oxygen.
The Earliest Parasite
The fossils of the original Pleistocene fauna are scattered throughout North and South America. These remains outline the story of the first peoples — what they ate, the kinds of tools they created, and how they buried their dead. Archaeological sites throughout the Americas also reveal evidence of the constellation of parasites, those that accompanied the migrants. Some, like Enterobius pinworms, were robust travelers and had no problem surviving in tropical or temperate climates.
The incessant partnership between humans and pinworms goes back to a time before the common ancestor of humans and apes. Each human generation passed the parasite on to the next one — like DNA but not like DNA, since the transmission occurred not in the host cells but in the environment as the worm eggs moved among hosts. Pinworms are found in many kinds of primates, the group that includes monkeys and apes, but each species is remarkably specific.
One close relative of the human pinworms infects chimpanzees, while others infect gorillas and orangutans. This suggests that different species of pinworms evolved parallel to the relationships of their hosts.
The pinworm, Enterobius vermicularis, causes one of the most common kinds of intestinal infection among people living in temperate zones such as North America. Their eggs are easily spread among children and people living in institutions via contaminated clothing, food, and surfaces, and they collect under fingernails and in bedding. Once ingested, the eggs hatch and the juveniles molt to adults, completing their life cycle in humans, their only host. Infection rarely results in serious illness.
Because pinworms are relatively host specific, they act as a kind of marker that traces human movements over time. As humans migrated from one area to another, the pinworms came along, leaving traces in coprolites, the fossilized remains of human feces.
Climate Change
According to Gardner, Diamond and Racz, the planet is losing species faster than scientists can name them — much like burning a library without knowing the names of the contents of the books. They note that more than 20 million species may be lost because of our destructive behaviors, which lead to deforestation, spillage of toxic chemicals, and global warming. Our knowledge of earth’s biodiversity is still so partial that many species will become extinct before we even learn of their existence. Given that parasites help keep life in balance, their loss threatens to further destabilize the earth’s ecosystem.
Max Sherman is a medical writer and pharmacist retired from the medical device industry. His new book “Science Snippets” is available from Amazon and other book sellers. It contains a number of previously published columns. He can be reached by email at [email protected].
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