Toxoplasmosis is a widespread infection caused by a microscopic parasite, Toxoplasma gondii . While the parasite is found all over the world, it rarely causes significant illness in people with healthy immune systems, as the body can typically keep the infection under control. After an initial infection, the parasite enters a dormant state, forming inactive cysts in tissues like the brain, muscles, and eyes, where it can remain for life. The symptoms a person experiences depend heavily on whether their immune system is strong, has been weakened by other conditions, or if the infection is passed from a mother to her unborn child during pregnancy.
For most healthy, immunocompetent people, a new toxoplasmosis infection is either completely asymptomatic or causes mild, flu-like symptoms that can be easily mistaken for other common illnesses. If symptoms do appear, they often include fever, headache, muscle aches, fatigue, and swollen lymph nodes, particularly painless lumps in the neck. A sore throat or a rash may also occur. In a small number of cases, an immunocompetent person might develop more specific complications, such as ocular toxoplasmosis, an eye infection that typically causes inflammation in the back of the eye (posterior uveitis) and can lead to blurred vision or floaters. In contrast, individuals with weakened immune systems face a much greater risk of severe, life-threatening disease. This group includes people with HIV/AIDS (especially when their CD4 count is low), those undergoing chemotherapy, or recent organ transplant recipients. For these individuals, a new infection or, more commonly, the reactivation of a dormant one can cause serious illness. The most frequent presentation is toxoplasmic encephalitis, an infection of the brain that can cause persistent headaches, confusion, seizures, fever, poor coordination, changes in mental state, and focal neurological issues like weakness on one side of the body. The parasite can also cause severe disease outside of the brain, leading to pneumonitis (inflammation of the lungs with cough and shortness of breath) or chorioretinitis (a severe eye infection causing pain and vision loss).
When a woman acquires a primary toxoplasmosis infection during pregnancy, she can pass the parasite to her fetus, a condition known as congenital toxoplasmosis. The consequences for the baby are often more severe if the infection occurs early in the pregnancy and can result in miscarriage, stillbirth, or serious health problems at birth. Newborns with congenital toxoplasmosis may have an enlarged liver and spleen, seizures, blindness, or significant developmental and intellectual disabilities. However, many infants, especially those infected later in pregnancy, may show no signs of illness at birth. These children can develop symptoms months or even years later, which may include:
- Severe eye infections that can impair vision or lead to blindness
- Hearing loss
- Learning disabilities or developmental delays
How do I know if I've ever had toxoplasmosis?
The most reliable way to determine if you have ever had toxoplasmosis is through a blood test ordered by your healthcare provider. This test checks for specific antibodies that your immune system creates to fight the T. gondii parasite. The presence of a particular type of antibody, known as IgG, indicates that you have been infected at some point in your life, even if you never experienced symptoms. Because these antibodies typically remain in your system for life, a positive IgG result usually signifies a past, inactive infection. Your doctor can perform this simple test and interpret the results to confirm whether you have previously been exposed to the parasite.
Are you infected with toxoplasmosis for life?
Yes, once a person is infected with Toxoplasma gondii , the parasite remains in the body for life. Following the initial, or acute, phase of infection, the host’s immune system forces the parasite into a dormant state where it forms tissue cysts, primarily in the brain and muscles. These cysts, which contain a slowly multiplying form of the parasite called bradyzoites, persist throughout the host's lifespan. In most healthy people, the immune system keeps these cysts in check, preventing any further illness. However, the infection can reactivate and cause severe disease if a person becomes immunocompromised later in life.
What does toxoplasmosis look like on skin?
While skin-related symptoms of toxoplasmosis are uncommon, they can present in a few different ways. In the acquired form of the disease, skin lesions might appear as roseola-like or erythema multiforme-like eruptions, itchy nodules (prurigo-like nodules), hives (urticaria), or maculopapular lesions, which are flat, red areas of skin with small bumps. In rare cases of congenital toxoplasmosis, newborns may show signs like a general skin rash, yellowing of the skin (jaundice), or tiny purple or red dots called petechiae due to a low platelet count. Some infants may also develop distinctive purplish-blue spots known as "blueberry muffin" lesions.
What are the worst symptoms of toxoplasmosis?
While most people with toxoplasmosis experience mild, flu-like symptoms or none at all, the infection can cause severe and life-threatening issues in certain individuals. The worst symptoms typically occur in people with weakened immune systems, who may develop serious neurological problems like confusion, seizures, trouble with balance, and meningoencephalitis (inflammation of the brain and its surrounding membranes). For an unborn child infected during pregnancy, the consequences can be devastating. Congenital toxoplasmosis can lead to spontaneous abortion, fetal death, or severe, long-term damage, including hydrocephalus (fluid on the brain), significant brain and eye damage, and neurological disorders.
How do people with toxoplasmosis see?
Toxoplasmosis can significantly impact a person's vision through a condition known as ocular toxoplasmosis. This occurs when the Toxoplasma gondii parasite becomes active in the retina of one or both eyes, causing inflammation, eye pain, and sensitivity to light. People with this condition often experience blurred vision, as the infection can create inflammatory lesions and scars on the retina. These vision problems may arise from an initial infection, the reactivation of a dormant infection, or as a complication of congenital toxoplasmosis, where an infant is born with the infection. In severe or untreated cases, this damage can lead to permanent vision loss or even blindness.
What are the mental symptoms of toxoplasmosis?
Toxoplasmosis infection is associated with a variety of mental symptoms and an increased risk for several psychiatric disorders. One large-scale study identified anxiety as the most characteristic symptom linked to the infection, with other evidence suggesting a strong association with conditions such as schizophrenia, obsessive-compulsive disorder (OCD), and attention deficit hyperactivity disorder (ADHD). Beyond specific disorders, the infection can also impair cognitive functions, leading to issues like prolonged reaction times, reduced memory, and difficulty with long-term concentration. Some research also points to subtle personality shifts, including decreased novelty-seeking and changes in traits like jealousy or rule-following.
Does toxoplasmosis affect your behavior?
Yes, a growing body of evidence suggests that a chronic Toxoplasma gondii infection can affect human behavior. Numerous studies have found a correlation between latent toxoplasmosis and an increased risk for certain psychiatric conditions, including schizophrenia, as well as more subtle shifts in personality, such as increased risk-taking, introversion, or suspicion. However, it's important to note that these findings show a strong association rather than definitive proof that the parasite directly causes these behavioral changes. In fact, some researchers now believe these effects may be driven by the host's own immune response, where long-term, low-level neuroinflammation triggered by the infection alters brain function.
