A parasitic infection can cause various symptoms, depending on the organism. These can include flu-like or gastrointestinal symptoms, among others. Treatment may include medications.

Parasites are organisms that live off other organisms, or hosts, to survive. Some parasites don’t noticeably affect their hosts. Others grow, reproduce, or invade organ systems that make their hosts sick, resulting in a parasitic infection.

Parasitic infections are a big problem in tropical and subtropical regions of the world. Malaria is one of the deadliest parasitic diseases. Parasitic infections can also occur in the United States. Common parasitic infections found in the United States include:

The symptoms of parasitic infections vary depending on the organism. For example:

  • Trichomoniasis is a sexually transmitted infection caused by a parasite that often produces no symptoms. In some cases, it may cause itching, redness, irritation, and an unusual discharge in your genital area.
  • Giardiasis may cause diarrhea, gas, upset stomach, greasy stools, and dehydration.
  • Cryptosporidiosis may cause stomach cramps, stomach pain, nausea, vomiting, dehydration, weight loss, and fever.
  • Toxoplasmosis may cause flu-like symptoms, including swollen lymph nodes and muscle aches or pains that can last for over a month.

Parasitic infections can be caused by three types of organisms:

  • protozoa
  • helminths
  • ectoparasites

Protozoa are single-celled organisms that can live and multiply inside your body. Some infections caused by protozoa include giardiasis. This is a serious infection that you can contract from drinking water infected with Giardia protozoa.

Helminths are multi-celled organisms that can live in or outside of your body. They’re more commonly known as worms. They include flatworms, tapeworms, thorny-headed worms,and roundworms.

Ectoparasites are multicelled organisms that live on or feed off your skin. They include some insects and arachnids, such as mosquitos, fleas, ticks, and mites.

Parasitic infections can be spread in a number of ways. For example, protozoa and helminths can be spread through contaminated water, food, waste, soil, and blood. Some can be passed through sexual contact. Some parasites are spread by insects that act as a vector, or carrier, of the disease. For example, malaria is caused by parasitic protozoa that are transmitted by mosquitos when they feed on humans.

Anyone can get a parasitic infection. But some people are at greater risk than others. You’re more likely to contract a parasitic infection if you:

  • have a compromised immune system or are already sick with another illness
  • live or travel in tropical or subtropical regions of the world
  • lack a clean supply of drinking water
  • swim in lakes, rivers, or ponds where Giardia or other parasites are common
  • work in childcare, work with soil regularly, or work in other contexts where you come into contact with feces on a consistent basis

Outdoor cats can come into contact with infected rodents and birds. This makes their owners more likely to contract toxoplasmosis, a type of protozoa. Toxoplasmosis can be very harmful for pregnant women and their developing babies. The infection is spread through cat feces. If you’re pregnant, it’s important to have someone else clean the litter box daily.

Parasitic infections can be diagnosed in a number of ways. For example, your doctor might perform or order:

  • A blood test
  • A fecal exam: In such an exam, a sample of your stool will be collected and checked for parasites and their eggs.
  • An endoscopy or colonoscopy: These tests may be ordered if the results of a stool exam are inconclusive. While you are sedated, your doctor will pass a thin flexible tube through your mouth or rectum and into your digestive system to examine your intestinal tract.
  • X-rays, magnetic resonance imaging (MRI), or computerized axial tomography (CAT): These scans are used to check for signs of lesions or injury to your organs caused by parasites.

Your doctor may also order tests to check for bacteria or other things that can cause infections.

Your treatment plan will depend on your specific diagnosis. Typically, your doctor will prescribe medications. For example, they may prescribe medications to treat trichomoniasis, giardiasis, or cryptosporidiosis. They probably won’t prescribe medications for toxoplasmosis if you’re not pregnant and otherwise healthy, unless you have a severe and prolonged infection.

Your doctor may also recommend other treatments to relieve your symptoms. For example, many parasitic infections can cause diarrhea, which often leads to dehydration. Your doctor will likely encourage you to drink plenty of fluids to replenish those you lose.

There are several steps you can take to lower your risk of contracting a parasitic infection:

  • Practice safe sex, using a condom.
  • Wash your hands regularly, especially after handling uncooked food or feces.
  • Cook food to its recommended internal temperature.
  • Drink clean water, including bottled water when you’re traveling.
  • Avoid swallowing water from lakes, streams, or ponds.
  • Avoid cat litter and feces when you’re pregnant.

If you suspect you have a parasitic infection, make an appointment with your doctor. They can help diagnose the cause of your symptoms and recommend a treatment plan. By getting early treatment, you can help stop the spread of infection to other people.