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Eye Parasite Floaters (Toxoplasmosis): Causes, Prevention & Treatment

Toxoplasmosis is a parasitic disease that reproduces within cats, but the disease can also harm vulnerable human populations. The disease is treated with medications that reduce the severity of the infection.

Eye floaters are sometimes a symptom of the parasitic infection.

What Is Toxoplasmosis? 

Toxoplasmosis is a disease caused by the Toxoplasma gondii (T gondii) parasite. 

T gondii is an Apicomplexa. Apicomplexans are a group of intracellular parasites called protists, which are similar to single-celled organisms. Apicomplexans are responsible for other diseases like malaria and neosporosis as well as toxoplasmosis. 

Toxoplasma gondii is one of the most resourceful and successful parasites in existence. As a parasitic organism, it requires a host. Although it can use any animal as its host, cat owners should be especially careful since felines are its primary host.

It’s estimated that over 40 million people in the U.S. may have the Toxoplasma parasite. Most people who are infected don’t have symptoms.

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How Toxoplasmosis Spreads

On rare occasions, infected blood is a vector for toxoplasmosis

Babies can become infected by their mothers during pregnancy, but the disease is not regularly spread through humans in most circumstances. 

Although toxoplasmosis requires feline hosts to truly flourish and reproduce, they can use virtually any animal as an intermediate host. However, cats remain their main host and the most important to their life cycle. 

It is only within cats that toxoplasma gondii is capable of sexual reproduction. Cats usually become infected by toxoplasma via eating an infected intermediate host like a mouse. 

When infected cats defecate, their feces contain zygotic structures called oocysts. These oocysts have spores that if inhaled by humans may cause a T. gondii infection. 

These are ways that toxoplasmosis is commonly spread:

  • Consuming water that has the parasite in it
  • Congenital transmission
  • Unintentionally ingesting cat feces with the parasite, such as eating after changing a cat litter box
  • Consuming undercooked shellfish, lamb, pork, or venison that is infected

Symptoms of Toxoplasmosis

Again, many people who have the parasite have no symptoms. Pregnant women, elderly individuals, and people with compromised immunity are most at risk for symptoms, and these can become severe.

If symptoms occur, they may be flu-like, including achiness and swollen lymph nodes. Eye floaters may be present. 

Severe cases can result in ocular toxoplasmosis and damage to the brain and other organs.

Even though toxoplasmosis usually presents no symptoms, this does not make it harmless. Asymptomatic carriers of the disease can develop cysts that populate in places like the retina. 

Most infants born with toxoplasmosis show no symptoms, but it can be a severe illness in the very young. 

Toxoplasmosis & Eyesight

Toxoplasmosis can lead to blindness if left untreated through an eye condition called ocular toxoplasmosis

Ocular toxoplasmosis damages the retina, resulting in blurry vision in the early stages. The condition may initially resolve on its own. However, when the parasites reemerge, severe eye damage can take place. 

Congenital toxoplasmosis, a condition that occurs in infants when a pregnant woman contracts the infection, can lead to ocular toxoplasmosis. Children born with a toxoplasmosis infection may have retinal damage due to a condition called necrotizing retinochoroiditis

Retinochoroiditis will result in decreasing ocular health over time. Depending on the location of the infection, the damage can be quite sudden. 

Treatment of Toxoplasmosis

Asymptomatic infections typically will not require much medical intervention. People with severe cases of toxoplasmosis will require treatment. 

During the initial examination, a blood test can reveal whether or not the patient came into contact with T gondii. 

If toxoplasmosis is in an acute stage, medications can be provided. Usually, these medications will be antifungal and/or antiparasitic in nature, and they can reduce the severity of the infection. 

In children with congenital toxoplasmosis, these medications are commonly prescribed:  

  •  Pyrimethamine
  •  Sulfadiazine
  •  Leucovorin

Preventing the Transmission of Eye Parasites

The easiest way to avoid toxoplasmosis and other eye parasites is to stay away from potential contaminants. That means taking measures to properly maintain your food and environment.

Food should be cooked to a safe temperature. Use a food thermometer to ensure your meat and shellfish are properly cooked. 

Thoroughly wash your hands, especially after being outside, handling raw meats, or cleaning cat litter boxes. If possible, pregnant women should have someone else clean up kitty litter to avoid contact with cat feces.


  1. Parasites – Toxoplasmosis (Toxoplasma infection). Centers for Disease Control and Prevention.

  2. Introduction to the Apicomplexa. University of California, Berkeley.

  3. Annual Burden of Ocular Toxoplasmosis In The United States. (March 2010). The American Journal Of Tropical Medicine And Hygiene.

  4. Association Between Toxoplasma Gondii Infection and History of Blood Transfusion: A Case-Control Seroprevalence Study. (April 2018). Journal of International Medical Research.

  5. The Cat Is Out of the Bag: How Parasites Know Their Hosts. (September 2019). PLOS BIOLOGY.

  6. Ocular Toxoplasmosis. (January 1973). The British Journal of Ophthalmology.

  7. Ocular Involvement In Toxoplasmosis. (June 1993). The British Journal of Ophthalmology.

  8. Ocular Toxoplasmosis II: Clinical Features, Pathology and Management. (September 2012). Clinical & Experimental Ophthalmology.

  9. Parasites – Toxoplasmosis (Toxoplasma Infection) Resources for Health Professionals. (July 2022). Centers for Disease Control and Prevention.

Last Updated November 1, 2022

Note: This page should not serve as a substitute for professional medical advice from a doctor or specialist. Please review our about page for more information.

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