Optos image of old peripheral retina scar and retinal traction from Toxoplasmosis. Toxoplasmosis is an infection caused by a parasite called toxoplasma gondii. Up to 40% of people in the US have been exposed to the toxoplasma parasite, but a normal immune system defends against disease. Those individuals that are HIV+ are at risk. Common sources of infection are undercooked meat (particularly pork, lamb and venison), cats, birds and other animals. The parasite can also be found in soil contaminated by animal feces. Toxoplasmosis most often affects the brain. Less commonly, toxoplasmosis can affect the eyes, lungs and other parts of the body. It can be seen in the eye during ophthalmocopy as a chorio-retinitis.