Parasitic Infection: Types, Symptoms, and Prevention Strategies
Updated: 2 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Parasitic infections are illnesses caused by parasites living and reproducing in your body. Parasites are organisms that need another living thing (a host) to get the nutrients they need to survive [1]. Parasitic infections can cause fever, fatigue, intestinal symptoms, skin rashes or neurological symptoms, and most are treated with medication [1].
Quick Answer: What is a parasitic infection?
A parasitic infection is any illness caused by a parasite living and reproducing in the body, whether protozoa, helminths or ectoparasites. People get them from contaminated food or water, undercooked meat, insect bites, soil or unprotected sex. Symptoms vary and may include fever, fatigue and diarrhea. Most parasites only go away with medication, and handwashing helps prevent them. [1]
What the research says
Protozoal infections such as malaria still carry a huge burden. A Lancet review reports that insecticide-treated bednets and artemisinin-based combination therapies have more than halved the global burden of malaria, yet it remained high, with 445,000 deaths and more than 200 million cases in 2016 (Ashley et al., Lancet, 2018).
Ectoparasite infections are very common. A 2024 review estimates that more than 200 million people worldwide have scabies at any one time, with an annual prevalence of 455 million, and notes that at least two consecutive treatments are needed because drugs don't kill all developmental stages of the mite (Fernando et al., Nat Rev Dis Primers, 2024).
Helminth infections can reach the brain. A 2025 review describes neurocysticercosis, in which Taenia solium cysts infest the central nervous system, as a significant cause of neurological disorders and epilepsy in endemic regions, with sub-Saharan Africa emerging as a newly recognized hotspot, and points to antigen-based assays and combination antiparasitic treatment as recent advances (Singh et al., Curr Opin Neurol, 2025).
Research summaries are based on article abstracts retrieved from PubMed.
What Is a Parasitic Infection?
Parasitic infections are any illnesses or conditions caused by parasites living and reproducing in your body. Parasitic infections often cause intestinal illness, with symptoms such as diarrhea and vomiting, but they can also cause itchy skin rashes or infect other parts of your body, like your brain or lungs [1].
Types of parasites that infect humans
Type | What they are | Where they can infect |
Protozoa | Single-celled parasites. | Your blood, intestinal tract (gut), brain, skin, eyes and other parts of your body. |
Helminths | Parasitic worms, including flukes (trematodes), tapeworms (cestodes), roundworms (nematodes) and thorny-headed worms (acanthocephalans). Both adults and immature (larval) helminths can infect you. | Usually your intestinal tract, but also your skin, brain and other tissues. |
Ectoparasites | Insects and arachnids (spider-like bugs) that burrow into your skin and live there, including ticks, mites, lice and fleas. | They usually don't infect other parts of your body. |
Source: Cleveland Clinic [1].
Illustration of the three main types of human parasites: protozoa, helminths, and ectoparasites.
What are the common parasitic infections?
The most common parasitic infections include malaria, toxoplasmosis, head lice, giardiasis and pinworms. Other examples include trichomoniasis, cryptosporidiosis, cyclosporiasis, cysticercosis, strongyloidiasis, tapeworm infections, Chagas disease, leishmaniasis and schistosomiasis [1].
What are the symptoms of a parasitic infection?
Parasitic infection symptoms depend on where in the body the infection is located. Common symptoms include fever, muscle aches, fatigue, nausea, vomiting and diarrhea [1]. Depending on the location of the infection, you might also have:
Neurological symptoms, such as seizures, severe headache or disorientation.
Skin symptoms, such as redness, itching, rash or sores.
Sometimes parasitic infections don't cause any symptoms [1].
How do parasitic infections spread?
You can get parasitic infections from [1]:
Drinking contaminated water or getting it in your mouth.
Eating undercooked meat.
Eating contaminated food, such as food washed with contaminated water.
Mosquito, tick, fly or other insect bites from insects that carry parasites.
Contaminated surfaces.
Unprotected sex.
Contaminated dirt (soil).
If you're pregnant, some parasitic infections can pass from you to the fetus [1].
Who is at higher risk?
Some parasitic infections, like pinworms, are common all over the world. Many others are more common in rural areas without developed sanitation systems. People at higher risk include young children and their parents or caregivers, and people with compromised immune systems, such as people with HIV/AIDS or cancer or those on immunosuppressive medications [1].
How are parasitic infections diagnosed?
Providers diagnose parasitic infections by looking for parasites, or signs of parasites such as eggs, in body fluids or tissues. To test for parasites, a provider might take samples of your stool, blood, skin or other affected tissue, phlegm (sputum), or the fluid around your brain and spinal cord. Depending on your symptoms, a provider may also use X-rays, MRI or CT scans [1].
Symptoms can be similar to many other infectious diseases, so the only way to know for sure whether you have a parasitic infection is to have a provider evaluate you [1].
Visual guide to the diagnostic process for parasitic infections, from initial assessment to testing and a treatment plan.
How are parasitic infections treated?
Providers use different medications to treat different types of parasitic infections, including antiparasitics (anthelmintics or antiprotozoals), antibiotics and antifungals. Sometimes you might need a combination of medications, and your provider will choose the treatment that is best for the specific infection you have [1].
Most parasites only go away with medication or a combination of medications. Providers treat some skin infections, lice and mites with medicated lotions or shampoos [1]. Treatment details can differ by parasite. For example, scabies usually needs at least two consecutive treatments [3], and neurocysticercosis may be treated with combination antiparasitic regimens [4].
What to expect
What you can expect depends on the kind of infection you have, how severe it is, whether you have a compromised immune system, and how well you respond to standard treatments. Some parasitic infections respond well to medication, but some can last a long time or keep coming back. Ask your healthcare provider what to expect in your specific situation [1].
How can parasitic infections be prevented?
A few precautions can reduce your risk of parasitic infections [1]:
Wash your hands frequently, especially when preparing food, before eating, after going to the bathroom and after changing diapers.
Don't swim when you have diarrhea. Wait until you haven't had diarrhea for at least two weeks before swimming in a public pool again.
Practice safe food habits: store food properly, heat meat and poultry to a safe temperature, and wash or peel fruits and vegetables before eating.
Use a condom or dental dam during any kind of sex.
Protect yourself from bug bites with protective clothing, bug spray and, if necessary, mosquito netting.
Be an informed traveler. Learn about infectious diseases at your destination. Precautions might include taking preventive medications before you get sick or getting vaccinated.
Infographic of parasitic infection management steps and preventive hygiene measures.
When should you see a doctor about a parasitic infection?
See your healthcare provider if you have symptoms of a parasitic infection. Let them know if you recently traveled, could have been bitten by a tick, mosquito or other bug (even if you don't remember it), swam in water that could have been contaminated, or ate or drank something that could have been contaminated [1].
Go to the emergency room if you have a fever over 103 degrees Fahrenheit (40 degrees Celsius), seizures, confusion or disorientation, yellowing of your skin or eyes (jaundice), or symptoms of dehydration such as extreme thirst, peeing very little, weakness and a high heart rate [1].
What is the bottom line on parasitic infections?
Parasitic infections affect millions of people around the world. Some people show no signs, while others develop life-threatening symptoms. Providers can cure most parasitic infections with medication, and handwashing, safe food and water habits, and protection from bug bites lower your risk. If you have symptoms, talk to a healthcare provider [1].
Frequently Asked Questions
Are parasitic infections contagious?
It depends on the parasite. People can get parasitic infections from contaminated water, food, surfaces or soil, from insect bites, and through unprotected sex. If you are pregnant, some parasitic infections can pass to the fetus.
What are the three main types of parasites that infect humans?
Protozoa (single-celled parasites), helminths (parasitic worms), and ectoparasites (insects and arachnids such as ticks, mites, lice and fleas).
What are the most common parasitic infections?
The most common include malaria, toxoplasmosis, head lice, giardiasis and pinworms.
Who is at higher risk of a parasitic infection?
Young children and their parents or caregivers, and people with compromised immune systems, such as those with HIV/AIDS or cancer or those taking immunosuppressive medications.
Can parasites affect the brain?
Yes. Protozoa and helminths can infect the brain and other parts of the body, which can cause neurological symptoms such as seizures, severe headache or disorientation.
How are parasitic infections diagnosed?
Providers look for parasites or signs of them, such as eggs, in samples of stool, blood, skin or other tissue, phlegm, or fluid around the brain and spinal cord. X-rays, MRI or CT scans may also be used.
How do you get rid of parasites in your body?
Most parasites go away only with medication or a combination of medications. Some skin infections, lice and mites are treated with medicated lotions or shampoos.
Do parasitic infections always cause symptoms?
No. Sometimes parasitic infections don't cause any symptoms.
Is it safe to swim in a public pool after diarrhea?
Wait until you haven't had diarrhea for at least two weeks before swimming in a public pool again.
When is a parasitic infection an emergency?
Go to the emergency room for a fever over 103 degrees Fahrenheit (40 degrees Celsius), seizures, confusion or disorientation, yellowing of the skin or eyes (jaundice), or dehydration symptoms.
Related Resources
External resource for deeper reading:
References
Cleveland Clinic. Parasitic Infection. Cleveland Clinic Health Library. Last updated April 7, 2023. https://my.clevelandclinic.org/health/diseases/24885-parasitic-infection
Ashley EA, Pyae Phyo A, Woodrow CJ. Malaria. Lancet. 2018;391(10130):1608-1621. PMID: 29631781. DOI: 10.1016/S0140-6736(18)30324-6
Fernando DD, Mounsey KE, Bernigaud C, et al. Scabies. Nat Rev Dis Primers. 2024;10(1):74. PMID: 39362885. DOI: 10.1038/s41572-024-00552-8
Singh G, Chomba M, Sander JW. Neurocysticercosis: current diagnostic and treatment paradigms. Curr Opin Neurol. 2025;38(4):380-387. PMID: 40605684. DOI: 10.1097/WCO.0000000000001396
Medical disclaimer
This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have about a medical condition.
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