Toxoplasmosis: What Causes It, Who Is at Risk, and How It Is Treated

4 days ago

11 min read

Updated: 2 days ago

Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: September 2026

Editorial note: This article is for educational purposes only and is not a substitute for professional medical advice. Content reflects current clinical guidance and was compiled from dated, authoritative sources listed in the References section.

TL;DR

Toxoplasmosis is an infection with the parasite *Toxoplasma gondii*, most often from undercooked meat or cat feces. More than 40 million people in the United States have been infected, but most never notice — their immune systems keep the parasite dormant for life. Serious disease concentrates in three groups: unborn babies, people with weakened immune systems, and the eye. Most infections need no treatment; drug therapy is reserved for pregnant people, newborns, people with serious illness, and people with weakened immunity.

Quick Answer

What is toxoplasmosis? An infection caused by the parasite *Toxoplasma gondii*, usually spread through undercooked meat, unwashed produce, or contact with cat feces [1]. Over 40 million Americans carry the infection, and roughly 1.1 million new cases occur each year [3], yet most healthy people never develop symptoms [1]. Serious disease affects unborn babies, people with weakened immune systems, and the eye. Most infections need no treatment, while drug therapy — typically pyrimethamine combined with sulfadiazine — is used for pregnant people, newborns, and more-serious cases [2].

What Is Toxoplasmosis?

Toxoplasmosis (tok-so-plaz-MOE-sis) is an infection with a parasite called *Toxoplasma gondii*. People often get the infection from eating undercooked meat. You can also get it from contact with cat feces. The parasite can pass to a baby during pregnancy [1].

The scale of this parasite is large, but its danger to most people is small. More than 40 million people are infected with the parasite in the United States, and about 11 percent of the U.S. population age 6 and older show evidence of past infection [3][4]. An estimated 1.1 million people are newly infected each year [5].

Most people infected with the parasite do not have symptoms. Some people get flu-like symptoms. Serious disease most often affects infants and people with weakened immune systems. Toxoplasmosis during pregnancy may cause miscarriage and birth defects [1].

Quick fact	Detail
What it is	An infection with the parasite Toxoplasma gondii
How it spreads	Undercooked meat, cat feces, unwashed produce, contaminated water and utensils
U.S. exposure	Over 40 million infected; ~1.1 million new infections per year
Symptoms	Usually none; flu-like symptoms in some; severe forms in three groups
Who is at risk	Unborn babies, people with weakened immune systems, people with eye infection
Typical treatment	None for most; drug therapy for pregnant people, newborns, and serious cases

What Does Toxoplasmosis Feel Like?

Most people infected with toxoplasmosis do not have any symptoms. They often do not know they are infected [1].

Some people develop flu-like symptoms, which may include the signs below.

Symptom	What to expect
Fever	Common in symptomatic infection
Swollen lymph nodes	May last for weeks
Headache	Often accompanies other flu-like symptoms
Muscle aches	Typical of the flu-like presentation
Skin rash	Occurs in some symptomatic cases

Can Toxoplasmosis Affect the Eyes?

Yes. The toxoplasma parasites may infect tissues of the inner eye. This can occur in people with healthy immune systems. But the disease is more serious in people with weakened immunity. An infection in the eye is called ocular toxoplasmosis [1].

Symptoms may include eye pain, poor vision, and floaters, which are specks that seem to swim in your vision. Untreated eye disease can cause blindness [1].

Ocular toxoplasmosis warning signs — eye pain, poor vision, and floaters that require prompt ophthalmology care, with the reminder that untreated eye disease can cause blindness

Who Faces Serious Disease from Toxoplasmosis?

Three groups carry most of the risk. Understanding them is the key to understanding this infection.

People with weakened immune systems

People with weakened immune systems are likely to have more-serious disease from toxoplasmosis. A toxoplasmosis infection from earlier in life may become active again [1]. People at risk include those living with HIV/AIDS, people receiving cancer treatment, and people with a transplanted organ.

In addition to serious eye disease, toxoplasmosis can cause severe lung or brain disease for a person with weakened immunity. Rarely, the infection can show up in other tissues throughout the body [1].

Organ system	Symptoms
Lung infection	Breathing problems, fever, cough
Brain inflammation (encephalitis)	Confusion, poor coordination, muscle weakness, seizures, changes in alertness

The national picture underscores the stakes: roughly 225,000 cases of toxoplasmosis are reported each year in the United States, resulting in about 5,000 hospitalizations and 750 deaths, largely concentrated in people with compromised immunity [6].

Unborn babies and infants

Toxoplasmosis can pass from the mother to the fetus during a pregnancy. This is called congenital toxoplasmosis [1].

Infection during the first trimester often causes more-severe disease. It also may result in miscarriage. For some babies with toxoplasmosis, serious disease may be present at birth or appear early in infancy [1].

Medical problems at or near birth	Description
Hydrocephalus	Too much fluid in or around the brain
Severe eye infection	Can threaten vision
Irregularities in brain tissues	Detected on imaging
Enlarged liver or spleen	Signs of systemic infection

Symptoms of severe disease vary and may include problems with mental or motor skills, blindness or other vision problems, hearing problems, seizures, heart disorders, jaundice (yellowing of the skin and whites of the eyes), and rash [1].

Most babies with toxoplasmosis do not show symptoms. But problems may show up later in childhood or teenage years. These include return of eye infections, problems with motor skill development, problems with thinking and learning, hearing loss, slowed growth, and early puberty [1].

An estimated 400 to 4,000 cases of congenital toxoplasmosis occur each year in the United States [7].

Congenital toxoplasmosis risks — how infection reaches the baby during pregnancy, possible problems at birth and later in childhood, and the two prevention pillars: prenatal testing when indicated and food-hygiene practices

What Causes Toxoplasmosis?

Toxoplasma gondii is a parasite that can infect most animals and birds. It can only go through the entire cycle of reproduction in domestic and wild cats. These are the main hosts for the parasite [1].

Immature eggs, a middle stage of reproduction, can be in the feces of cats. This immature egg allows the parasite to make its way through the food chain. It can pass from soil and water to plants, animals, and humans. Once the parasite has a new host, the reproduction cycle goes on and causes an infection [1].

If you are in typical health, your immune system keeps the parasites in check. They stay in your body but are not active. This often gives you lifelong immunity. If you are exposed to the parasite again, your immune system would clear it out. If your immune system is weakened later in life, parasite reproduction can start again. This causes a new active infection that can lead to serious disease and complications [1].

How Do People Catch the Parasite?

People often get a toxoplasma infection through one of the following routes.

Exposure route	How it happens
Cat feces with the parasite	Cats that hunt or are fed raw meat are more likely to carry the parasite; infection occurs if you touch your mouth after touching anything in contact with cat feces, such as gardening or cleaning a litter box
Contaminated food or water	Undercooked beef, lamb, pork, venison, chicken, and shellfish are known carriers; unpasteurized goat milk and untreated drinking water also may be carriers
Unwashed fruits and vegetables	The surface of produce may carry the parasite
Contaminated kitchen tools	Cutting boards, knives, and other utensils that contact raw meat or unwashed produce
Organ transplant or transfused blood	Rarely, parasites are passed through a transplant or transfusion

Food safety temperatures

Cooking is one of the most reliable defenses. The recommended internal temperatures are [1][8]:

Food	Minimum safe internal temperature
Whole meats and fish	145°F (63°C), with at least 3 minutes of rest
Ground meat	160°F (71°C)
Whole and ground poultry	165°F (74°C)

What Increases the Risk of Serious Disease?

The parasite is found throughout the world. Anyone can become infected [1].

Risks of serious disease from toxoplasmosis include things that prevent the immune system from fighting infections, such as infection with HIV/AIDS, chemotherapy treatment for cancer, high-dose steroids, and drugs that prevent the rejection of transplanted organs [1].

People who are pregnant face a distinct risk: not for themselves, but for the baby. Pregnant people without immunity who acquire the infection during pregnancy can pass it to the fetus [1][9].

How Is Toxoplasmosis Diagnosed?

A diagnosis of toxoplasmosis is based on blood tests. Laboratory tests can detect two types of antibodies. One antibody is an immune system agent that is present during a new and active infection with the parasite. The other antibody is present if you had an infection at any time in the past. Depending on the results, your healthcare professional may repeat a test after two weeks [2].

More diagnostic tests are used depending on other symptoms, your health, and other factors [2].

Situation	Diagnostic approach
Eye symptoms	Exam by an ophthalmologist using special lenses or cameras to see tissues inside the eye
Brain and nervous system symptoms	Brain imaging (MRI or CT), cerebral spinal fluid (CSF) test, rarely brain tissue sampling
Pregnancy (suspected active infection)	Diagnostic blood test when symptoms suggest active infection or ultrasound shows irregular features; amniotic fluid test (amniocentesis) to confirm fetal infection
Newborn (suspected infection)	Blood tests, then brain ultrasound or CT, CSF tests, eye tests, hearing tests, and EEG

One detail matters for readers in the United States: pregnant people here are not routinely screened for toxoplasmosis. Recommendations for screening vary in other countries. Your healthcare professional may order a diagnostic blood test if your symptoms might be from an active toxoplasma infection, or if ultrasound images of your baby show irregular features linked to toxoplasmosis [2].

How toxoplasmosis is diagnosed — from antibody blood tests to situation-specific exams for the eye, brain, pregnancy, and newborns

How Is Toxoplasmosis Treated?

Medicine is used to treat active infections. How much and how long you take medicine depends on different factors. These include how seriously ill you are, your immune system health, where the infection is located, and your stage of pregnancy [2].

Most infections do not need treatment [1]. Treatment decisions look like this:

Group	Typical approach
Healthy person, no symptoms	No treatment
Pregnant person with active infection	Drug treatment to reduce transmission to the baby [1][2]
Newborn with congenital infection	Drug treatment may last 1 to 2 years, with frequent follow-up [2]
Person with weakened immunity (HIV/AIDS, transplant, chemotherapy)	Drug treatment, often longer or preventive [2]
Serious eye disease	Drug treatment plus anti-inflammatory glucocorticosteroids [2]

Your healthcare professional may give you a combination of prescription drugs [2]:

Drug	What it does	Notable cautions
Pyrimethamine (Daraprim)	Fights infections caused by microscopic organisms; can block the body's use of folic acid	Long-term use may cause bone marrow suppression and liver toxicity
Leucovorin calcium	Helps correct the effects of pyrimethamine on folic acid activity	Given alongside pyrimethamine
Sulfadiazine	Antibiotic often prescribed with pyrimethamine	Alternatives include clindamycin (Cleocin) and azithromycin (Zithromax)

Treatment for infants may last 1 to 2 years. Regular and frequent follow-up appointments are needed to watch for side effects, vision problems, and physical, intellectual, and overall development [2].

In addition to the regular drug treatment, eye disease also may be treated with anti-inflammatory steroids called glucocorticosteroids [2].

How Can You Prevent Toxoplasmosis?

Certain precautions can help prevent toxoplasmosis. The prevention list below comes from current clinical guidance [1].

Prevention step	Detail
Garden with gloves	Wear gloves when working outdoors; wash your hands with soap and water afterward
Cook meat thoroughly	Use a meat thermometer; follow the temperature table above
Avoid raw shellfish	Do not eat raw clams, mussels, or oysters, particularly during pregnancy
Wash kitchen utensils thoroughly	Soapy water after contact with raw meats or unwashed fruits and vegetables; wash hands before and after food preparation
Wash all fruits and vegetables	Before eating, peeling, or cooking
Avoid unpasteurized goat milk	Skip it and products made from the milk
Avoid untreated water	Particularly during pregnancy
Cover children's sandboxes	Prevents outdoor cats from using them as litter boxes

For cat lovers

If you are pregnant or otherwise at risk of toxoplasmosis, take these steps to protect yourself [1]:

Step	Recommendation
Help your cat stay healthy	Keep your cat indoors; feed it dry or canned cat food, not raw or undercooked meat
Avoid stray cats or kittens	Avoid stray cats, especially kittens; do not get a new cat when you are pregnant
Manage the litter box safely	Have someone else clean the box daily if possible; if someone else cannot clean it, wear gloves and a face mask to change the litter, then wash your hands well

When Should You See a Doctor?

Talk to your healthcare professional about a test if you are worried about exposure to the parasite, or if you are planning a pregnancy or are pregnant [1].

The symptoms of severe toxoplasmosis include blurred vision, confusion, and loss of coordination. These need immediate medical care, particularly if you have a weakened immune system [1].

How Can You Prepare for Your Appointment?

You are likely to start by seeing your healthcare professional. If you are pregnant, you will likely see your obstetrician. You also may see a perinatologist, a specialist in fetal health. In some cases, you will see an infectious disease specialist [2].

Question you will likely be asked	How to prepare
What are your symptoms?	Note each symptom and its severity
When did they start?	Note the approximate date
Have you been diagnosed with toxoplasmosis in the past?	Bring prior lab results if available
Do you have a cat? Is it indoor or outdoor? Do you change the litter?	Be ready to describe your cat and litter habits
Have you recently eaten raw or undercooked meat or fish?	Recall recent meals honestly
Have you had unpasteurized goat's milk products?	Recall recent foods and drinks
Do you garden or work outdoors? Do you wear gloves?	Describe your exposure habits
What medicine, vitamins, or supplements do you take?	Bring a written list

Conclusion: What to Do About Toxoplasmosis

Two anchor truths frame toxoplasmosis. First, most infections never announce themselves — over 40 million Americans carry the parasite, and most stay healthy for life because their immune systems keep it dormant [1][3]. Second, the risk is not evenly distributed — unborn babies, people with weakened immune systems, and the eye bear the serious consequences [1].

Practice food hygiene now. Cook meat to safe internal temperatures, wash produce, and keep raw meat away from other foods. These habits are the single most effective defense [1].
If you are pregnant or planning pregnancy, ask your healthcare professional about testing, and follow the cat-care and food-safety steps above [1][2].
Seek immediate care for blurred vision, confusion, or loss of coordination — especially with a weakened immune system [1].
If diagnosed, follow the treatment and follow-up plan completely; infant treatment can extend one to two years, and the follow-up protects vision and development [2].

Frequently Asked Questions

Can you get toxoplasmosis from your cat? Yes, but only through contact with infected cat feces — touching your mouth after handling a litter box or contaminated soil. Cats that hunt or eat raw meat are more likely to carry the parasite. Indoor cats fed commercial food pose very low risk, especially since litter is cleaned daily before the parasite becomes infectious [1].

Can toxoplasmosis go away on its own? In healthy people, the immune system usually controls the parasite without any treatment, and most infections cause no symptoms at all. The parasite often remains dormant for life, and the immune system clears repeat exposures [1].

Is toxoplasmosis dangerous during pregnancy? It can be. The parasite can pass from the mother to the fetus during pregnancy, and infection during the first trimester often causes more-severe disease and may result in miscarriage. Because the U.S. does not routinely screen pregnant people, ask your doctor about testing if you may have been exposed [1][2].

Do you need antibiotics for toxoplasmosis? Not usually. Most infections need no treatment. Drug treatment — typically pyrimethamine with sulfadiazine, plus leucovorin — is used for pregnant people, newborns, people with serious illness, and people with weakened immune systems [1][2].

Can toxoplasmosis cause blindness? Untreated eye disease (ocular toxoplasmosis) can cause blindness. It can occur even in people with healthy immune systems and may involve eye pain, poor vision, and floaters [1].

How long does treatment last for a baby? Drug treatment for infants may last 1 to 2 years, with regular follow-up appointments to monitor for side effects, vision problems, and physical, intellectual, and overall development [2].

Can toxoplasmosis come back years later? Yes, in people whose immune systems weaken later in life. An infection from earlier in life may become active again, potentially causing serious lung or brain disease [1].

How common is toxoplasmosis? Very common. Over 40 million people in the United States have been infected, about 11 percent of Americans age 6 and older show evidence of past infection, and an estimated 1.1 million new infections occur each year [3][4][5].