Toxoplasmosis is an infection caused by a single-celled parasite most common in tropical areas of the world. Usually, it’s harmless because the human immune system knows how to fight it off.
But toxoplasmosis can damage eyesight and cause other serious health problems in certain situations. Indeed, anybody who gardens, handles uncooked meat or has a house cat faces a risk of toxoplasmosis. And pregnant moms who are newly infected can transmit it to their unborn babies.
Toxoplasmosis poses many questions, such as:
What is toxoplasmosis?
How does toxoplasmosis spread in humans?
What are the top symptoms of toxoplasmosis?
How does toxoplasmosis damage vision?
How do doctors treat toxoplasmosis?
What’s the best way to prevent a toxoplasmosis infection?
Because All About Vision focuses primarily on eye health and vision issues, this article will zoom in on toxoplasmosis threats to human eyesight. See the toxoplasmosis section of the U.S. Centers for Disease Control and Prevention (CDC) website to find out about the risks of this disease throughout the human body. See the Humane Society's pregnancy and toxoplasmosis page to find out more about safely living with house cats during pregnancy.
Now, let’s check out the answers to common questions about toxoplasmosis and eye health:
What exactly is a toxoplasmosis infection?
A one-cell parasite called toxoplasma gondii lives in the bloodstreams and digestive tracts of a wide variety of animals. It’s most common in hot, tropical areas of the world, but it can infect people just about anywhere.
In humans, a healthy immune system usually has all the defenses it needs against toxoplasmosis. But it can threaten the health of people with low immunities and diseases like HIV/AIDS. And there’s a risk of transmission from a pregnant mom to her child.
How do people get infected with toxoplasmosis?
The CDC cautions that toxoplasmosis is one of the most common food-related infections. In the United States, the most common source of infection is contamination from raw meat or eating unwashed produce.
This is a more likely source of infection than handling cat feces. If a person eats contaminated food, toxoplasma might reproduce in their body.
All sorts of species carry the toxoplasma parasite — including humans. The animal most likely to give toxoplasmosis to us is a house cat that goes outdoors and hunts for prey like mice and birds. When cats eat infected prey, toxoplasmosis spreads in their digestive tracts and gets into their feces.
But how does it get into our bodies? It’s easier than you might think. If you’re gardening or cleaning your cat’s litter box, you may touch cat poop and contaminate your hands. Then if you handle food before washing your hands, you can swallow the parasite and infect yourself.
If you do this while you’re pregnant, you may expose your unborn child to serious health risks. Vision damage is one of these threats. We’ll cover that next.
How does toxoplasmosis threaten eyesight?
Once the toxoplasma parasite enters the bloodstream, it finds its way into major organs like the brain and liver. It also can infect the eyes, causing a disease called ocular toxoplasmosis. The disease is a form of retinopathy because it attacks the retina, the layer of light-sensitive nerves that transmit visual signals to the brain.
When the Toxoplasma gondii parasite enters the body’s bloodstream, it can infect the choroid (the layer of blood vessels) in the retina. This results in a condition called toxoplasma retinochoroiditis.
Once in the retina, the parasite can cause scars and extensive tissue damage. About one out of four people with a history of toxoplasma retinochoroiditis issues are legally blind in at least one eye.
Over time, ocular toxoplasmosis can damage or even destroy the retina if left untreated.
Congenital toxoplasmosis and children’s eyesight
Congenital toxoplasmosis happens when a pregnant mother passes the parasite to her unborn child. The infection can damage the eyes, ears, skin and nervous system. Some babies are born with few obvious signs of an infection and problems show up only in their teens.
Keep in mind that most people have no symptoms or problems with toxoplasmosis. When it gets into the body, the immune system usually fights it off.
It’s the exceptions that cause problems. Understanding the symptoms, treatment and prevention of toxoplasmosis infections can help if you become one of those exceptions.
What are the common symptoms of toxoplasmosis?
Catching toxoplasmosis may feel like you’ve got the flu. Symptoms can include:
Body aches and pains
Swollen lymph glands
These symptoms may last a few days to a few months and go away on their own as the body builds up immunities. Symptoms for people with low immunities may include mood swings, brain swelling and muscle spasms.
Ocular plasmosis symptoms
These are common signs that toxoplasmosis has gotten into your vision system:
Floaters in your field of view
Ocular toxoplasmosis can cause inflammation of the retina. Blindness can happen if you don’t see an eye doctor to check it out.
Toxoplasmosis symptoms in babies
Doctors are trained to scan for evidence of toxoplasmosis in newborns and young children. These are the common symptoms:
Birth weight below normal
Liver or spleen larger than normal
Yellowed skin and eyes (jaundice)
Some babies have no symptoms at birth but develop signs of vision loss, hearing loss and learning disabilities as they mature.
How will my doctor treat a toxoplasmosis infection?
The treatment for toxoplasmosis depends on who has it. For instance:
Pregnant women may get antibiotics or other medications to prevent transmission to the baby.
Children born with toxoplasmosis may take anti-parasite medications.
People with low immunities need different medications, which may have strong side effects.
Consulting with an ophthalmologist is highly recommended. These medical doctors specializing in eye diseases and surgery know how to scan the retina for signs of scarring or other injuries caused by toxoplasmosis.
What should I do to prevent a toxoplasmosis infection?
There’s no cure for toxoplasmosis. When it gets into your body, it doesn’t go away completely. Thus, your best approach is to avoid infections. You can do that by:
Taking care with food. Anybody with contaminated hands can infect raw meat. Cooking meat to 152 degrees kills the toxoplasma parasite. Wash fruits and vegetables thoroughly before you eat them. Avoid unpasteurized milk and other raw dairy products.
Keeping your hands clean. If you’re gardening, wear gloves and wash your hands when you’re done.
Cleaning kitchen utensils. Knives, forks, cutting boards and anything else that touches meat must be kept clean to avoid contamination.
Treating cat litter properly. If you have a cat, always wear gloves when changing cat litter and wash your hands when you’re finished. Keeping your cat indoors also reduces the risk of them becoming a carrier. The best way to prevent toxoplasma infection from cat feces is to change the cat litter box daily. This is because the parasite does not become infectious for 1 to 5 days after the cat has eliminated the feces.
Talking to your doctor about pregnancies. You could be carrying the toxoplasma parasite with no risk to yourself but transmit it to your baby and cause problems. Your doctor may want to do a blood test to see if you have any of the parasites in your system.
If you have retinal damage from toxoplasmosis, it should show up when your eye doctor conducts an eye exam. If you have any reason to believe you might’ve been exposed to the parasite, schedule an eye doctor’s appointment right away.
Parasites - Toxoplasmosis (toxoplasma infection). U.S. Centers for Disease Control and Prevention. August 2019.
Pregnancy and toxoplasmosis. The Humane Society of The United States. Accessed May 2021.
Toxoplasmosis in cats. Cornell Feline Health Center. June 2018.
Toxoplasma retinochoroiditis. StatPearls. February 2021.
Toxoplasmosis. EyeWiki, American Academy of Ophthalmology. April 2020.
Congenital toxoplasmosis. MedlinePlus, U.S. National Library of Medicine. April 2019.
What is toxoplasmosis? American Academy of Ophthalmology. April 2020.
Toxoplasmosis symptoms. American Academy of Ophthalmology. April 2020.
Toxoplasmosis treatment. American Academy of Ophthalmology. April 2020.
Page published in May 2021
Page updated in January 2022
Medically reviewed in August 2021