Author: Vincent Guo
Editors: Hwi-On Lee, Emily Yu
Artist: Chiara Chen
You have probably encountered a parasite at least once in your life. A parasite’s relationship to its host is called parasitism, where one side benefits from the other. The side that is harmed is called the host, whereas the side that benefits is called the parasite. Parasites cannot live without a host due to their dependence on the host's nutrients to survive. They can also use the host’s body to multiply and reproduce. There are three types of parasites: ectoparasites, helminths, and protozoa. Ectoparasites, which live on the host (e.g. ticks, fleas), are commonly found on animals like dogs and cats, feeding off of the host’s blood. Another type, helminths, live inside the host, such as tapeworms, roundworms, and flukes. They feed off of the nutrients inside the human intestines. Protozoans are very small parasites that cannot be seen by the human eye without a tool like a microscope. They are single-cell organisms, unlike the others which are multicellular organisms.
Parasites have abilities to help them stay alive and reproduce. Some of these parasites can alter the protein on them to avoid detection from our body. Our body uses antibodies to bind to antigens (foreign substances). When the antibody binds to an antigen, our immune system can take them out, but since the parasite changes the protein on them, which is what antibodies bind to, it makes it difficult for the immune system to kill the parasite, turning it into a battle on who can adapt faster. Other parasites can suppress our immune system, allowing it to avoid being killed and reproduce. These types of parasites are very deadly to us. When the parasite suppresses our immune system, our defense against bacteria and disease weakens. This makes us more susceptible to getting sick, and when we are sick, our immune system is too weak to get rid of the disease which makes us die from the disease instead of the parasite. Some parasites affect the hormones of the host. For example, some rats have no fear of their predator, such as a cat, and will purposely let themselves get eaten by the cat. Consequently, the parasites inside the rat are passed to the cat. We also have parasites that affect the behaviors of the host. Zombie ants are caused by a parasitic fungus. When the spores attach to the ant, they try to break into the exoskeleton of the ant. An exoskeleton is a hard cover to protect the organs of an invertebrate. After it manages to break in, it makes the ant move to a certain location and kills it from the inside. Then it grows a stalk on the head of the ant. This stalk will release spores, infecting more ants, which results in an endless cycle. Luckily for humans, this parasite mainly infects ants and does not affect us.
We have medicine that can assist our body in wiping out the parasite, the two most common being antiparasitic drugs and antibiotics. These treatments are used for parasites that live inside the host’s body, but if the parasite is an ectoparasite, shampoo or ointment is more effective. Some of these parasites are found in raw meat, fruits, and vegetables. You can prevent your chance of getting infected with parasites by washing your hands before eating, making sure food is cooked thoroughly and at the right temperature, and washing the knife and area you used to cook the food to prevent contamination. For example, if you use a cutting area and knife to cut raw chicken, you should wash the cutting area and the knife to cut fruit, so you can prevent the potential parasite on the chicken from getting on the apple.
Parasites are essential to our ecosystem. They play a large role in how the ecosystem functions. They help regulate the population and have beneficial effects on the ecosystem. They help decrease the population of the species when the population is too big and the ecosystem can’t handle it anymore. They can also decrease the population of predator species. This allows less competition between species and higher survival rates for those without being infected by the parasite. Even though many parasitic interactions with hosts are harmful, they are still vital to the ecosystem.
Citations:
Admin-Infection. “Exploring the Intricate World of Parasitic Organisms - Unveiling the
Secrets of Nature’s Master Manipulators.” Infection Cycle, 7 Dec. 2023,
“Parasites.” Cleveland Clinic, 1 May 2024, my.clevelandclinic.org/health/diseases/24911-
“Zombie-Ant Fungus.” Encyclopædia Britannica, Encyclopædia Britannica, inc., 23 Sept. 2024,
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