Any organism that lives on or in another organism is known as a parasite. Generally, these parasitic organisms draw their sustenance from either the host or from the food consumed by the host. However, all parasites depend on their hosts for survival. A parasite depends on its host for food, and to grow and multiply.

More often than not, parasite infections cause harm to their hosts. While parasites themselves may not kill the host, they can cause several problems and diseases, some of which can result in the death of the host. Unlike predators, parasites are usually much smaller than their hosting organisms. However, some parasites can exceed over thirty meters in length.ย 

Types of Parasites

Protozoa: These are single-celled organisms that need the host to multiply.ย 

Helminths: The parasites in this group are the worm parasites such as tapeworm, roundworm, pinworm, etc.ย 

Ectoparasites: This group lives on rather than in their hosts and includes parasites such as fleas and lice.

Parasites in Humans

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Contrary to what a vast majority of us think, humans all over the world are susceptible to parasitic infections.

While it may be true that people in developing and /or poor countries are more prone to parasitic infections, data shows that people living in developed countries also suffer from parasites. You can visit this article here for detailed information on parasites that affect humans and their treatment.

While numerous parasites affect humans, given below are some diseases and the parasites that are responsible for them.ย 

Diseases Caused Due to Protozoa


Acanthamoebiasis โ€“ Affecting the skin, eyes, and brains, this tiny amoeba is found in soil and water, all over the world.ย 

Balantidiasis โ€“ A single-cell parasite, Balatidium coli, generally infects pigs but is known to cause infections in the intestines of humans as well. The parasite infections spread through drinking contaminated water or through direct contact with pigs.

Coccidiosis โ€“ Found throughout the world, Coccidia enters humans through the fecal-oral route and affects the intestines.ย 

Amoebiasis โ€“ More prevalent in the tropics and places with high population density combined with poor sanitation and hygiene, Amoebiasis affects the intestines. It is caused by the parasite Entamoeba histolytica that enters through the fecal-oral route.

Cyclosporiasis โ€“ Prevalent all over the world, this disease is caused by Cystoisospora belli that enters humans through the fecal-oral route. Affecting the epithelial cells of the small intestine, this disease is preventable and curable.

Leishmaniasis โ€“ Transmitted by parasites of the Leishmania family, which use certain types of sandflies as vectors, this disease can be fatal. It affects the viscera, skin, and/or the mucous membrane of the mouth, throat, and nose.

Primary amoebic meningoencephalitis (PAM) โ€“ A fatal disease caused by breathing contaminated soil and water, it affects the brain and nervous system of the host. Fatality can occur within one to eighteen days of infection. The parasite responsible for this disease is Naegleria fowleri, a free-living ameba.ย 

Malaria โ€“ Caused by different types of plasmodium that are transmitted by the Anopheles mosquito, this disease is highly prevalent in tropical regions.ย 

Toxoplasmosis โ€“ Parasite infection occurs through contact with contaminated cat feces and from ingesting raw or undercooked goat, lamb, pork, or milk. Occurring all over the world, this disease affects the eyes, brain, heart, and liver.

Trichomoniasis โ€“ Trichomoniasis is a sexually transmitted infection caused by Trichomonas vaginalis, a parasite that is found in both males and females. However, while generally there are no symptoms in males, it affects the urogenital tract in females.

Diseases Caused by Helminths

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Anisakiasis โ€“ This health condition can be attributed to the worms that encroach into the stomach walls or intestines. The worms can be transferred via undercooked and fresh fish and/or squid.ย 

Roundworm: Ascariasis is a parasite infection caused by roundworms and does not reveal any symptoms. However, the signs and symptoms of this parasite infection can be noticed in the fecal remains of the infected person. The contamination usually incurs via the consumption of contaminated drinks or food.ย 

Raccoon roundworm: The disease Baylisascaris can be contracted through raccoon stools. Baylisascaris can impact the lungs, liver, brain, and intestines. Because of this reason, people in North America, usually refrain from keeping raccoons as a pet.ย 

Clonorchiasis: Clonorchiasis or Chinese liver fluke, is passed on to humans when they ingest poorly processed, preserved, or raw freshwater fish.

Guinea Worm

Guinea worms affect subcutaneous muscles and tissues to cause ulcers and blisters. It is possible to see the worms in these blisters. Once the worms are removed or shed, they penetrate the soil or get into water bodies to be passed on from there.ย 


Intestinal diseases can be caused by hookworms. These parasites lay eggs in the soil and their larvae can infect humans by entering through the top layers of their skin. A rash or itches are the early symptoms of the disease caused by hookworms. These worms are commonly found in dark and damp places having poor sanitation.ย 


Human beings can also get parasite infection by consuming food items contaminated by cockroaches, mealworms, rodents, and flour beetles.

Echinococcosis Tapeworm

Cystic echinococcosis causes painful cysts. Alveolar echinococcosis can be sourced to the lungs or liver and is the reason behind the tremors occurring in the liver. Humans are usually affected when they eat contaminated food containing the feces of infected animals, or when they contact the worm directly.ย 

Enterobiasis Pinworm

Enterobius vermicularis can be categorized as a tapeworm or pinworm and resides in the rectum and colon of humans. This worm is known to lay eggs in the anal area of its hosts while they are asleep. The main sign of parasite infection caused by Enterobius vermicularis is itching. This itching can spread via the oral-fecal route.

Way Forward

These are just a few of the many diseases that are attributed to parasites. If youโ€™re grappling with any of the above or other signs and symptoms of parasitic infection then itโ€™s recommended that you show yourself to a doctor or nutritionist to avoid any complications later on.

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