Toxoplasmosis is one of the most common parasitic infections because it can infect any warm-blooded mammal—including humans. Though typically mild in healthy adults, pregnant women can transmit the infection to their babies, potentially causing serious complications, including hearing loss.

Toxoplasmosis is an infection caused by a single-cell parasite called Toxoplasma gondii (T. gondii).^[1] There are several categories of toxoplasmosis, including acquired and congenital.

Acquired toxoplasmosis: If a person with a healthy immune system comes in contact with a host infected with the T. gondii parasite, they may contract the infection. This is called acquired toxoplasmosis. In healthy adults, acquired toxoplasmosis may cause flu-like symptoms or no symptoms at all.

Congenital toxoplasmosis: If a pregnant woman becomes infected, she can pass the infection to her fetus through the placenta, which can cause serious problems for the growing baby, including:

• Premature birth
• Intracranial calcifications
• Chorioretinitis
• Hydrocephalus
• Hearing loss

There may not be signs of infection at birth, but children who have been infected may develop complications later in life.

Toxoplasmosis is caused by coming into contact with the parasite T. gondii. Cats are “definitive hosts” of T. gondii.^[2] Domestic or wild cats can contract toxoplasmosis by eating infected prey (“intermediate hosts”) and then shed it out in their feces. Other toxoplasmosis causes^[3] include:

• Eating raw or undercooked meat from an infected animal.
• Drinking unpurified water contaminated with the parasite.
• Consuming soil or contaminated materials, such as after gardening or digging in sand.
• Accidentally ingesting traces of cat feces, especially if hands aren’t washed after cleaning the litter box.
• Rare transmission through organ transplants or blood transfusions (only from infected donors).

About 20% of pregnant women^[4] who contract toxoplasmosis pass it to their fetus.

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Studies have shown a connection between toxoplasmosis and hearing loss, but the reasons aren’t fully understood. Toxoplasma infection causes inflammation and damage to the inner ear structures or auditory nerve and may also disrupt neural pathways involved in auditory processing.^[5]

Some research into latent toxoplasmosis^[6]—or an infection that has laid dormant in the host—has shown some correlation between a long-term infection and hearing loss in adults.

Studies suggest that up to 40% of infants born with the infection may eventually suffer some form of hearing loss, but the connection isn’t totally clear.^[7]

Some studies have found varying degrees of sensorineural hearing loss,^[8] meaning the loss is caused by damage to the inner ear structures or the auditory nerve. Others have found infection can disrupt the processing of auditory information^[9] in the brain.

In healthy adults, toxoplasmosis may not present any symptoms. In fact, adults may not even know they’ve been infected. If symptoms do present, they are most often characterized as mild and flu-like.^[10] In adults who are immunocompromised^[11] symptoms may be more severe and include fever, nausea, headaches and seizures.

Congenital toxoplasmosis may present diagnostic markers that healthcare providers look for during ultrasound, including hydrocephalus and intracranial calcifications.^[12]

Some infants born with congenital toxoplasmosis don’t have any symptoms at birth, but some issues may develop soon after birth or years later as a result of infection,^[13] including:

• Jaundice
• Toxoplasmosis rash
• Intellectual disabilities
• Seizures
• Vision issues
• Hearing loss

Testing for toxoplasmosis will vary depending on your age and health. Adults may receive a blood test designed to detect certain antibodies that help doctors differentiate between an acute or chronic infection. The toxoplasmosis diagnosis process may also include brain imaging, testing spinal fluid or an evaluation by an eye specialist, depending on your symptoms.^[14]

If you’re pregnant and your care team suspects you may have toxoplasmosis, they will order a blood test. To determine if the infection has been passed to the fetus, your doctor may recommend testing the amniotic fluid, a process called amniocentesis.^[15]

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Healthy adults with a new toxoplasma infection may not require treatment at all. Your doctor will determine the best course of treatment if symptoms persist or become severe.

For pregnant women diagnosed with toxoplasmosis, the first goal is to prevent fetal infection by administering the antibiotic Spiramycin. If tests determine the fetus is already infected, doctors will treat with a combination of anti-parasitic and antibiotic medications.^[16] The goal is to reduce complications for both mother and baby.  Infected infants are treated with anti-parasitic medication, an antibiotic and folic acid for a year after birth.^[17]

Here are some specific tips for toxoplasmosis prevention ^[18]:

• Do not eat raw or undercooked meat.
• Rinse fruit and vegetables under running water before eating.
• Clean food prep areas with hot, soapy water.
• Wear gloves when gardening in areas that may be contaminated with cat feces.
• Wash your hands with soap and water after gardening, preparing raw meat or cleaning the litter box.
• If you are a cat owner, change the litter box daily.
• If you are pregnant, have someone else change the litter box.

Toxoplasmosis is preventable, and early detection is key to reducing complications. If you’re pregnant, immunocompromised or experiencing symptoms, consult a healthcare provider for testing and treatment options. For concerns about hearing loss related to congenital or latent toxoplasmosis, seek an evaluation from a medical professional.