Toxoplasma gondii, a parasite, causes an infection referred to as toxoplasmosis. It is the most popular cause of eye inflammation in the world. The parasite lives in cat feces and raw and undercooked meat particularly in venison, pork and lamb. It can also found in contaminated water.

Cats are the only known host of Toxoplasma gondii, although the parasite is found in most animals. The parasite only reproduces in cats and the eggs exit the host’s body through feces. Cats don’t display symptoms of the parasitic infection even though they are hosts.

There are more than 60 million people in the US infected with the parasite. Those at a higher risk for severe toxoplasmosis are infants whose mothers have an active infection during pregnancy and people with compromised immune systems.

Also Known As

  • Congenital toxoplasmosis
  • Acquired toxoplasmosis



Causes and Risk Factors

In the case of acquired toxoplasmosis, infections happen only through ingesting the parasite. It can’t be transmitted through contact with an infected person. Ingestion can occur through:

  • Drinking contaminated water 
  • Cross-contamination with unwashed cutting boards and  knives
  • Eating contaminated food like unwashed fruits and vegetables, uncooked meat and unpasteurized or raw dairy products
  • Gardening can expose people to contaminated manure and cat feces
  • Not washing hands after cleaning a cat’s litter box
  • Touching the mouth with contaminated hands can lead to an infection
  • In rare cases, an infection can occur through blood transfusion or organ transplant

Congenital toxoplasmosis is transmitted to an infant from an infected mother during pregnancy. A mother can pass the disease to her child if she gets an infection right before or during the pregnancy.

Signs & Symptoms

In most cases, people with toxoplasmosis have no signs or symptoms. Toxoplasmosis symptoms may include: 


  • Fatigue
  • Eye pain
  • Headache
  • Eye redness
  • Blurred vision
  • Excess tearing
  • Reduced vision
  • Sensitivity to light 
  • Body aches and pains
  • Swollen lymph nodes 
  • Seeing floaters in the eyes

Often, the symptoms last for weeks or months and may go away on their own.
In babies symptoms include:

  • Low birth-weight
  • Ocular toxoplasmosis
  • Enlarged liver or spleen
  • Yellowing of the skin and eyes (jaundice)


The eye care professional may conduct a comprehensive eye exam. The tests may include:

  • OCT
  • Slit lamp exam
  • B-Scan ultrasound
  • Dilated fundus exam
  • Fluorescein angiography
  • Blood test to look for antibodies to the Toxoplasma gondii parasite. If the patient tests positive for the antibodies, he/she may conduct further tests to establish when the infection occurred


Treatment is aimed at controlling the symptoms.

Medical Treatment

In most cases, there is no need for treatment because the patients are healthy with robust immune systems that can fight off the disease. 

In severe cases of toxoplasmosis where vision is affected, the eye doctor may prescribe anti-parasitic medications, steroids and antibiotics to control the symptoms. 

Infected pregnant women are referred to a specialist for professional guidance and treatment.

Surgical Treatment

The eye surgeon may use a vitrectomy to treat severe cases of the inflammation of the retina and to remove macula scar tissue.

Prognosis/Long-term outlook

For people with weakened immune systems, toxoplasmosis can cause serious problems including damage to the optic nerve and the macula (the part of the eye that gives full vision abilities). It may even lead to severe vision loss.
Babies born with the disease may later develop problems such as:

  • Eye infections
  • Hearing loss
  • Vision loss
  • Learning disabilities

Toxoplasmosis has no cure. Drugs don’t eliminate the parasite from the body; they can only control the symptoms. 

Prevention/Follow Up

Tips to help prevent toxoplasmosis include:

  • Ensuring all meat is well cooked
  • Washing all fresh produce well before eating  it
  • Never drink unpasteurized or consume raw dairy products
  • Washing all cutting boards and utensils that are used to handle raw meat
  • Washing hands after scooping or cleaning cat litter 
  • Kids and pregnant women shouldn’t handle the cat litter
  • Wearing gloves and washing hands after handling soil or working in the garden
  • Individuals with a weakened immune system, pregnant women and those planning on becoming pregnant, should go for a toxoplasmosis test