What Is Toxoplasmosis? Causes, Symptoms, and Treatments
Key takeaways:
Toxoplasma gondii is a parasite that can cause toxoplasmosis, which is an infection in humans and animals. But most people do not develop symptoms and are not harmed by the infection.
The infection can be more serious for those with weaker immune systems or when the infection is passed from a pregnant mother to the fetus.
Because the infection is orally transmitted, it can be prevented with washing hands, cooking meat thoroughly, and avoiding cat litter.
Toxoplasmosis is an infection caused by the parasite Toxoplasma gondii. As many as 40 million people carry this parasite in the U.S. But for most people, it does not cause any significant health problems because the parasite can actually exist in an active and inactive form in the body. And most people have the inactive form, which does not pose a significant health risk.
However, when the parasite is in the active form, it can cause an infection that can be serious for people with a weakened immune system. Or when a mother passes it to their developing fetus.
We will explain a little more about the different forms of toxoplasmosis, how it’s spread, and what happens when an active infection becomes more serious.
What are the different forms of toxoplasmosis?
The lifecycle of a parasite is more complicated than you might imagine for such a small organism. But the different phases of that cycle mean that at any given time Toxoplasma can either be active in the body and cause infection, or inactive and harmless.
Active in the body: Also known as active infection, this happens when someone is first exposed to the parasite. Most people don’t have symptoms, and their immune system quickly takes care of the problem. But people with a weakened immune system may have symptoms.
Inactive in the body: Sometimes referred to as latent infection, this occurs after the immune system takes care of the problem by containing the parasite in inactive cysts. Think of these like seeds buried in the soil that never sprout or grow. These cysts can remain dormant in the body for someone’s entire life and never cause any symptoms or harm. Most people who have the parasite have the latent form.
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But in rare cases, the parasite can break free from the cysts and lead to a reactivated infection. This typically occurs when someone becomes immunocompromised after they developed a latent infection.
How do people contract Toxoplasma infection?
People get infected with Toxoplasma most commonly by ingesting it, which is also called oral transmission. This can happen when someone eats or drinks contaminated food or water. Or when they come into contact with cat feces, because cats are the primary carriers of this parasite.
The ways in which Toxoplasma is orally transmitted include:
Touching your mouth with unwashed hands after handling something contaminated by cat feces (such as garden soil, sand, or cat litter)
Drinking contaminated water, which can happen as a result of rain runoff
Eating unwashed produce that was in contact with contaminated soil
Eating raw or undercooked meat from an animal that was infected with the parasite
Eating raw or undercooked shellfish that came from contaminated water
While oral transmission is most common, there are two other ways someone can get toxoplasmosis:
Congenital transmission: This occurs when a mother is actively infected, and the parasite is transmitted to the fetus. This does not occur with the latent form.
Bloodborne transmission: This can occur when contaminated blood gets into someone’s bloodstream, but this is very rare.
Who’s at risk for serious toxoplasmosis infection?
Most people with toxoplasmosis are protected by their immune system, and they transition into the latent form without ever knowing it. But two groups of people are at risk for more serious, potentially life-threatening infection:
1) People with immunocompromising conditions: Examples include HIV, autoimmune
disease, history of organ transplant, and those receiving chemotherapy or other
immunosuppressive medications.
2) Babies who are infected in the womb: A developing fetus is at risk for serious
complications from infection — even if the pregnant mother does not have
any symptoms.
What are the signs and symptoms of toxoplasmosis?
Most people with normal immune function have no symptoms with infection. If they do, the symptoms are often mild and can include:
Muscle aches
Swollen lymph nodes
Flu-like symptoms
People who are immunocompromised can experience more serious symptoms with active or reactivated toxoplasmosis, such as:
Confusion
Headaches
Fever
Nausea
Balance problems
Eye symptoms, like blurred vision, eye discharge, sensitivity to light, and eye pain
Congenital toxoplasmosis can cause miscarriage, stillbirth, or serious illness in the unborn baby. Infection can lead to brain damage or eye problems, and sometimes the child will not have noticeable symptoms until years after birth. Congenital toxoplasmosis has been linked to blindness and mental illness later in life.
How is toxoplasmosis diagnosed?
There are a few different ways to test for toxoplasmosis. Most commonly, this is done by testing for antibodies in the blood. These are proteins created by the immune system when someone has been infected in the past.
It’s surprisingly much easier to test for past infections than to test for an active infection. When someone’s immune system has not yet made antibodies, laboratory tests have to isolate the actual parasite. And this is much more difficult. It is done by collecting a sample of someone's body fluid (such as blood or cerebrospinal fluid) and directly looking for the parasite.
How is toxoplasmosis treated?
Most people don’t need treatment because their immune system contains the parasite. But people who are at risk for severe infections or complications should be treated. This includes:
People with weakened immune systems
People with severe symptoms
Pregnant people with recent (active) infection
Treatment typically includes a combination of medications that fight the infection, including pyrimethamine, sulfadiazine, and folinic acid.
How can I prevent getting infected?
There are steps you can take to help prevent infection with Toxoplasma. This is especially important if you are at risk for severe infection or if you are pregnant or trying to conceive. Most of these are simple hygiene practices, including:
Washing your hands thoroughly with soap and warm water after handling unwashed produce, sand or soil, or cat litter
Washing your hands before eating
Washing all produce under running water before eating it
Ensuring meat is cooked at an appropriate temperature to kill the parasite
Avoiding eating raw shellfish
Drinking filtered water or boiling unfiltered or untreated water before drinking
And if you have a cat at home, you can take certain steps to avoid infection, like:
Have someone else change the cat litter, or use gloves
Make sure the cat litter is changed daily
Avoid stray cats and kittens, because they are more likely to be infected
Keep your cat indoors if possible, as cats generally get infected by eating mice or birds who carry the parasite
The bottom line
Toxoplasmosis is a relatively common parasitic infection. Most people never know they are infected, and it doesn’t cause any problems. But if you have a weakened immune system or if you are pregnant, toxoplasmosis can cause serious illness to you or your baby. Luckily, there are simple steps you can take to decrease your risk of coming into contact with the parasite. This includes staying away from cat litter, handwashing, and avoiding foods that are more likely to be contaminated.
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References
Centers for Disease Control and Prevention. (2018). Parasites - Toxoplasmosis (toxoplasma infection).
Dunay, I. R., et al. (2018). Treatment of toxoplasmosis: Historical perspective, animal models, and current clinical practice. Clinical Microbiology Reviews.
