What causes toxoplasmosis?
Toxoplasmosis is caused by an infection by the parasite T. gondii. Humans get toxoplasmosis after accidentally eating (ingesting) something contaminated with the parasite.
Because of the way the parasite hides in your body, you can have symptoms of toxoplasmosis when you’re initially infected or at a later time. When the parasite initially enters your body, some people get flu-like symptoms. But in most cases, your immune system can get rid of the initial infection without causing any symptoms.
While your immune cells are fighting it off, T. gondii makes small sacs (cysts) in your body. It can live in these cysts, inactive (dormant), for long periods of time. Research suggests that the cysts break open periodically and your body fights off the infection. Like the initial infection, this usually causes no symptoms.
If your immune system is weakened, though, these ruptured cysts can cause a new case of toxoplasmosis (reactivation).
How do you get toxoplasmosis?
You typically get toxoplasmosis from ingesting something contaminated with the parasite T. gondii.
T. gondii reproduces in a cat’s intestines and ends up in their poop. Cat poop can contaminate soil, water, plant material and the food we eat.
You can accidentally ingest T. gondii after coming in contact with something that’s contaminated, such as:
- Cleaning a cat’s litter box.
- Gardening in soil where cats live.
- Drinking water that hasn’t been boiled or treated.
- Eating unwashed fruits or vegetables.
- Eating undercooked or improperly refrigerated meat.
Toxoplasmosis isn’t contagious, but a pregnant person can pass the parasite that causes it to a fetus. You can also get toxoplasmosis after receiving an infected organ transplant or blood transfusion, though this is rare.
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What are the symptoms of toxoplasmosis in humans?
The symptoms of toxoplasmosis depend on where the parasite is active. This tends to be different depending on whether it’s a new (acute) infection, a reactivation or present at birth (congenital).
Ocular toxoplasmosis (toxoplasmosis of the eye) symptoms
Ocular toxoplasmosis is an infection of T. gondii in one or both eyes. It’s most common in teens or young adults who were born with a T. gondii infection. Rarely, ocular toxoplasmosis happens when you’re first infected with T. gondii. Symptoms of ocular toxoplasmosis include:
- Eye pain.
- Blurred vision
- Blindness.
Acute toxoplasmosis symptoms
Acute toxoplasmosis is your body’s response to an initial infection with T. gondii. Most people don’t feel sick, but you might have flu-like symptoms, including:
- Fever.
- Fatigue.
- Muscle aches.
- Painless, swollen lymph nodes in your neck or armpits.
- Sore throat.
- Enlarged liver and spleen (hepatosplenomegaly).
- Ocular toxoplasmosis (rare).
Reactivated toxoplasmosis symptoms
If you have a weakened immune system (immunocompromised), you might have had a previous T. gondii infection that reactivates when your body is no longer able to fight off infections easily. This includes people living with AIDS or cancer, or those on medications that suppress the immune system. Reactivated toxoplasmosis usually causes symptoms related your brain and spinal cord (central nervous system or CNS). CNS symptoms can include:
- Headaches.
- Confusion.
- Seizures.
- Fever.
- Facial paralysis.
- Vision changes.
- Numbness.
- Weakness or loss of motor skills.
- Toxoplasmic encephalitis.
- Coma.
Congenital toxoplasmosis symptoms
Congenital (present at birth) toxoplasmosis is passed from a pregnant person to the fetus. Some babies won’t have any symptoms at birth, but are at high risk for developing them later on. These symptoms may include:
- Yellowish skin and eyes (jaundice).
- Rash.
- Enlarged liver and spleen (hepatosplenomegaly).
- Vision loss, eye pain or sensitivity to light (retinochoroiditis).
- Calcium deposits in their brain.
- Fluid on the brain (hydrocephalus).
- Small head size (microcephaly).
- Seizures.
- Delays in motor skill development.
- Learning delays or differences.
- Ocular toxoplasmosis.
