Table of ContentsView AllTable of ContentsTypesSymptomsTestingRisksTreatmentLimiting Exposure
Table of ContentsView All
View All
Table of Contents
Types
Symptoms
Testing
Risks
Treatment
Limiting Exposure
There are various types and subtypes of parasites. The three main classes of parasites are protozoa, helminths, and ectoparasites, which can cause disease.
If you contract a parasite, you may live with it for years without noticing any symptoms develop. When symptoms do occur, they can typically affect the gastrointestinal tract and lead to symptoms such as nausea and vomiting, diarrhea, or stomach pain.
This article discusses the various types of parasites that live in humans, their symptoms, and how to tell if you have one.
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Parasites That Live in Humans
Ectoparasites
Ectoparasites burrow into the skin or attach themselves to their host and stay put for an extended period of time. In some cases, these parasites can live on the body for weeks or months. These types tend to live off a person’s blood while they are attached.
Parasite Examples: EctoparasitesSeveral types of ectoparasites can cause human disease, including:TicksFleasMitesLice
Parasite Examples: Ectoparasites
Several types of ectoparasites can cause human disease, including:TicksFleasMitesLice
Several types of ectoparasites can cause human disease, including:
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Helminths
Helminths are larger multicellular organisms that you can see with the naked eye when they are in the adult stages. Not all helminths act parasitic, as some can survive without a host, making them free-living. When a helminth has reached adulthood, it can produce larva and eggs.
Helminths often take the shape of a worm and typically live in the gastrointestinal (GI) tract, causing issues. In some cases, these parasites can also enter the blood,lymphatic system, or tissue under the skin.
Parasite Examples: HelminthsVarious types of helminths can lead to disease in human hosts, such as:FlatwormsThorny-headed wormsRoundworms
Parasite Examples: Helminths
Various types of helminths can lead to disease in human hosts, such as:FlatwormsThorny-headed wormsRoundworms
Various types of helminths can lead to disease in human hosts, such as:
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Protozoa
Protozoa are one-celled microorganisms that, like helminths, can require a host to live but can also be free-living. Once they have infiltrated a human body, they can multiply, causing them to grow in numbers and drive the onset of serious infections.
Parasite Examples: ProtozoaProtozoa that can cause human disease include:Sarcodina (amoeba,Entamoeba)Mastigophora (flagellates,Giardia and Leishmania)Ciliophora (ciliates,Balantidium)Sporozoa (Plasmodium, Cryptosporidium)
Parasite Examples: Protozoa
Protozoa that can cause human disease include:Sarcodina (amoeba,Entamoeba)Mastigophora (flagellates,Giardia and Leishmania)Ciliophora (ciliates,Balantidium)Sporozoa (Plasmodium, Cryptosporidium)
Protozoa that can cause human disease include:
Protozoa and the Illnesses They Cause
Symptoms Parasites Cause
The symptoms a person develops after contracting a parasite will differ, depending on the type.
Ectoparasite symptoms can include:
Helminths typically fail to cause symptoms in human hosts. If they do, the symptoms can include:
Protozoa often affect the gastrointestinal tract and can lead to symptoms such as:
Parasites and the Onset of Bowel DisordersA protozoa infection is often associated with the onset of irritable bowel syndrome because of the way it affects the gastrointestinal tract.
Parasites and the Onset of Bowel Disorders
A protozoa infection is often associated with the onset of irritable bowel syndrome because of the way it affects the gastrointestinal tract.
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Testing for Parasites
If you believe you have a parasitic infection, seeing a healthcare provider is essential. They’ll be able to help you with where to go for the proper testing. Typically, tests are done at specific testing centers or labs nationwide.
Various tests will be conducted, including:
Once the results are ready, a healthcare provider will review them with you to determine the next steps regarding treatment.
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Risks of Untreated Symptoms From Parasites
Parasitic infections can be severe if they are left untreated. Over time, the parasites continue to damage the host.
If they are left untreated for a more extended period, people can start to experience serious health consequences, including:
Who Is Most at Risk for Untreated Parasitic Infections?Untreated parasitic infections are becoming more common in the United States. According to data, those living in impoverished communities are the most at risk of contracting and developing an untreated parasitic infection.
Who Is Most at Risk for Untreated Parasitic Infections?
Untreated parasitic infections are becoming more common in the United States. According to data, those living in impoverished communities are the most at risk of contracting and developing an untreated parasitic infection.
Treating Parasites
Treatments are recommended for most parasites. However, ectoparasites could be as easy as removing the organism from your skin, washing yourself and your clothes and bedding, and cleaning the home from any infestation that may cause the parasites to burrow into you again.
For other types of parasites, medical treatment is needed and often entails using antiparasitic drugs. They can include:
These medications are designed to kill parasites within the body while helping you excrete them from your system. When taking the drugs, you will be given a set schedule, dosage, and treatment duration that must be adhered to ensure that the parasites are dead and gone from your body.
Some alternative and complementary therapies that may be suggested to you alongside a primary treatment can help speed up the process of getting rid of a parasite. Some options include:
Severe Parasitic Infection TreatmentIf parasites cause a severe infection, other therapies may have to be explored to help rid the body of the infestation. These include surgery and more potent drugs.
Severe Parasitic Infection Treatment
If parasites cause a severe infection, other therapies may have to be explored to help rid the body of the infestation. These include surgery and more potent drugs.
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How to Limit Parasite Exposure
To reduce your risk of contracting a parasite, you can:
How Contagious Are Parasites?Parasites are contagious and are typically spread in the following ways:Fecal-oral transmissionThe consumption of contaminated food or waterClose person-to-person contact
How Contagious Are Parasites?
Parasites are contagious and are typically spread in the following ways:Fecal-oral transmissionThe consumption of contaminated food or waterClose person-to-person contact
Parasites are contagious and are typically spread in the following ways:
During International Travel
If you are traveling to a location where the risk of contracting a parasite is higher, there are some things you will want to do to ensure you don’t accidentally get a parasitic infection. They include:
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Summary
Although parasitic infections are not as common as other types, such as viral or bacterial, they can still be prevalent in the United States. The three main parasites that cause human disease are transmitted in similar ways, with the exception of ectoparasites.
18 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Gizaw Z, Engdaw GT, Nigusie A, Gebrehiwot M, Destaw B.Human ectoparasites are highly prevalent in the rural communities of northwest ethiopia: A community-based cross-sectional study.Environ Health Insights.2021 Jul 21;15:11786302211034463. doi:10.1177/11786302211034463National Library of Medicine Medical Microbiology 4th Edition.Helminths: Structure, classification, growth, and development.Centers for Disease Control and Prevention.About parasites.Centers for Disease Control and Prevention.Lyme disease: Transmission.Safe Drinking Water Foundation.Protozoan parasites.Centers for Disease Control and Prevention.Food worker handwashing and restaurant factors.Capela R, Moreira R, Lopes F.An overview of drug resistance in protozoal disease.Int J Mol Sci. 2019 Nov;20(22):5748. doi:10.3390/ijms20225748Gunning K, Kiraly B, Pippitt K.Lice and scabies: Treatment update.Am Fam Physician.2019 May 15;99(10):635-642.Centers for Disease Control and Prevention.About soil-transmitted helminths. February 23, 2024.Osman M, El Safadi D, Cian A, Benamrouz S et al.Prevalence and risk factors for intestinal protozoan infections with cryptosporidium, giardia, blastocystis and dientamoeba among schoolchildren in Tripoli, Lebanon.PLoS Negl Trop Dis.2016 Mar 14;10(3):e0004496. doi:10.1371/journal.pntd.0004496Mount Sinai.Intestinal parasites.Centers for Disease Control and Prevention.Diagnosis of parasitic diseases.Sepsis Alliance.Parasitic infections.Hotez PJ.Neglected parasitic infections and poverty in the United States.PLoS Negl Trop Dis.2014 Sep 4;8(9):e3012. doi:10.1371/journal.pntd.0003012Huang H, He Q, Guo B, Xu X, Wu Y, Li X.Progress in redirecting antiparasitic drugs for cancer treatment.Drug Des Devel Ther.2021 Jun 22;15:2747-2767. doi:10.2147/DDDT.S308973Centers for Disease Control and Prevention.What causes parasitic diseases.Memorial Sloan Kettering Library.What are parasites?Canadian Medical.How can you protect yourself from parasites from exotic destinations?February 7, 2014.
18 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Gizaw Z, Engdaw GT, Nigusie A, Gebrehiwot M, Destaw B.Human ectoparasites are highly prevalent in the rural communities of northwest ethiopia: A community-based cross-sectional study.Environ Health Insights.2021 Jul 21;15:11786302211034463. doi:10.1177/11786302211034463National Library of Medicine Medical Microbiology 4th Edition.Helminths: Structure, classification, growth, and development.Centers for Disease Control and Prevention.About parasites.Centers for Disease Control and Prevention.Lyme disease: Transmission.Safe Drinking Water Foundation.Protozoan parasites.Centers for Disease Control and Prevention.Food worker handwashing and restaurant factors.Capela R, Moreira R, Lopes F.An overview of drug resistance in protozoal disease.Int J Mol Sci. 2019 Nov;20(22):5748. doi:10.3390/ijms20225748Gunning K, Kiraly B, Pippitt K.Lice and scabies: Treatment update.Am Fam Physician.2019 May 15;99(10):635-642.Centers for Disease Control and Prevention.About soil-transmitted helminths. February 23, 2024.Osman M, El Safadi D, Cian A, Benamrouz S et al.Prevalence and risk factors for intestinal protozoan infections with cryptosporidium, giardia, blastocystis and dientamoeba among schoolchildren in Tripoli, Lebanon.PLoS Negl Trop Dis.2016 Mar 14;10(3):e0004496. doi:10.1371/journal.pntd.0004496Mount Sinai.Intestinal parasites.Centers for Disease Control and Prevention.Diagnosis of parasitic diseases.Sepsis Alliance.Parasitic infections.Hotez PJ.Neglected parasitic infections and poverty in the United States.PLoS Negl Trop Dis.2014 Sep 4;8(9):e3012. doi:10.1371/journal.pntd.0003012Huang H, He Q, Guo B, Xu X, Wu Y, Li X.Progress in redirecting antiparasitic drugs for cancer treatment.Drug Des Devel Ther.2021 Jun 22;15:2747-2767. doi:10.2147/DDDT.S308973Centers for Disease Control and Prevention.What causes parasitic diseases.Memorial Sloan Kettering Library.What are parasites?Canadian Medical.How can you protect yourself from parasites from exotic destinations?February 7, 2014.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Gizaw Z, Engdaw GT, Nigusie A, Gebrehiwot M, Destaw B.Human ectoparasites are highly prevalent in the rural communities of northwest ethiopia: A community-based cross-sectional study.Environ Health Insights.2021 Jul 21;15:11786302211034463. doi:10.1177/11786302211034463National Library of Medicine Medical Microbiology 4th Edition.Helminths: Structure, classification, growth, and development.Centers for Disease Control and Prevention.About parasites.Centers for Disease Control and Prevention.Lyme disease: Transmission.Safe Drinking Water Foundation.Protozoan parasites.Centers for Disease Control and Prevention.Food worker handwashing and restaurant factors.Capela R, Moreira R, Lopes F.An overview of drug resistance in protozoal disease.Int J Mol Sci. 2019 Nov;20(22):5748. doi:10.3390/ijms20225748Gunning K, Kiraly B, Pippitt K.Lice and scabies: Treatment update.Am Fam Physician.2019 May 15;99(10):635-642.Centers for Disease Control and Prevention.About soil-transmitted helminths. February 23, 2024.Osman M, El Safadi D, Cian A, Benamrouz S et al.Prevalence and risk factors for intestinal protozoan infections with cryptosporidium, giardia, blastocystis and dientamoeba among schoolchildren in Tripoli, Lebanon.PLoS Negl Trop Dis.2016 Mar 14;10(3):e0004496. doi:10.1371/journal.pntd.0004496Mount Sinai.Intestinal parasites.Centers for Disease Control and Prevention.Diagnosis of parasitic diseases.Sepsis Alliance.Parasitic infections.Hotez PJ.Neglected parasitic infections and poverty in the United States.PLoS Negl Trop Dis.2014 Sep 4;8(9):e3012. doi:10.1371/journal.pntd.0003012Huang H, He Q, Guo B, Xu X, Wu Y, Li X.Progress in redirecting antiparasitic drugs for cancer treatment.Drug Des Devel Ther.2021 Jun 22;15:2747-2767. doi:10.2147/DDDT.S308973Centers for Disease Control and Prevention.What causes parasitic diseases.Memorial Sloan Kettering Library.What are parasites?Canadian Medical.How can you protect yourself from parasites from exotic destinations?February 7, 2014.
Gizaw Z, Engdaw GT, Nigusie A, Gebrehiwot M, Destaw B.Human ectoparasites are highly prevalent in the rural communities of northwest ethiopia: A community-based cross-sectional study.Environ Health Insights.2021 Jul 21;15:11786302211034463. doi:10.1177/11786302211034463
National Library of Medicine Medical Microbiology 4th Edition.Helminths: Structure, classification, growth, and development.
Centers for Disease Control and Prevention.About parasites.
Safe Drinking Water Foundation.Protozoan parasites.
Centers for Disease Control and Prevention.Food worker handwashing and restaurant factors.
Capela R, Moreira R, Lopes F.An overview of drug resistance in protozoal disease.Int J Mol Sci. 2019 Nov;20(22):5748. doi:10.3390/ijms20225748
Gunning K, Kiraly B, Pippitt K.Lice and scabies: Treatment update.Am Fam Physician.2019 May 15;99(10):635-642.
Centers for Disease Control and Prevention.About soil-transmitted helminths. February 23, 2024.
Osman M, El Safadi D, Cian A, Benamrouz S et al.Prevalence and risk factors for intestinal protozoan infections with cryptosporidium, giardia, blastocystis and dientamoeba among schoolchildren in Tripoli, Lebanon.PLoS Negl Trop Dis.2016 Mar 14;10(3):e0004496. doi:10.1371/journal.pntd.0004496
Mount Sinai.Intestinal parasites.
Centers for Disease Control and Prevention.Diagnosis of parasitic diseases.
Sepsis Alliance.Parasitic infections.
Hotez PJ.Neglected parasitic infections and poverty in the United States.PLoS Negl Trop Dis.2014 Sep 4;8(9):e3012. doi:10.1371/journal.pntd.0003012
Huang H, He Q, Guo B, Xu X, Wu Y, Li X.Progress in redirecting antiparasitic drugs for cancer treatment.Drug Des Devel Ther.2021 Jun 22;15:2747-2767. doi:10.2147/DDDT.S308973
Centers for Disease Control and Prevention.What causes parasitic diseases.
Memorial Sloan Kettering Library.What are parasites?
Canadian Medical.How can you protect yourself from parasites from exotic destinations?February 7, 2014.
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