Ocular Toxoplasmosis

By Sophia Lazar

Toxoplasmosis is an infection caused by the Toxoplasma gondii parasite, which can be contracted through undercooked meat or indirect or direct contact with cat feces, as cats are the only definitive hosts of the parasite. Even if neither of these situations occurs, the parasite can still be transmitted genetically, most commonly from mother to child. Most cases are asymptomatic, but when symptoms appear, they include headaches, fevers, and swollen lymph nodes. Although toxoplasmosis can have many effects on particular groups, including newborns and those undergoing chemotherapy, Mission Sight wants to highlight its impact on the eyes.

The infection is often left untreated, and although it can resolve on its own within months, in other cases it leads to blindness. This is something to be aware of because 25% of the world’s population will contract it at some point from food. If the parasite goes to the eyes, it becomes ocular toxoplasmosis, and symptoms of this form of infection are eye pain (particularly when in bright light), blurred vision, and specks in vision. Ocular toxoplasmosis can only be diagnosed by clinical observation and, often, antibody tests. Side-effect complications can also occur, such as retinal detachment, which requires immediate medical attention. It can also cause necrotizing retinitis, which is the destruction of the retinal tissue, leading to retinal scars.

One of the most notable aspects of toxoplasmosis is its tendency to recur, which can happen in ocular toxoplasmosis and other types of toxoplasmosis. Around 80% of people who contract toxoplasmosis experience recurrence, making it difficult to treat even if it is detected in its early stages. Recurrence happens because the initial infection forms small cysts, which, in the case of ocular toxoplasmosis, are usually in or near the retinal scars the parasite has caused. The parasite can live in these cysts, and they often lie inactive for long periods. However, they can unexpectedly burst, leading to reinfection. Common treatments include anti-parasitic and anti-inflammatory medicines, but there have been serious side effects to these in some cases. Eye injections are also a common form of treatment, but if patients have recurring toxoplasmosis, they will likely receive longer-term treatments, significantly decreasing the recurrence rate. Ocular toxoplasmosis is also the most common cause of uveitis, which Mission Sight will discuss in a future blog post.

If you experience any abnormalities with your eyes, your vision, or any type of pain, please seek medical attention immediately. Many blindness-causing diseases and infections can be treated if detected early enough!

Bibliography

Khandwala, Nikhila, and Cagri Besirli. "Ocular Toxoplasmosis: A Refresher." American Academy of Opthamology, www.aao.org/eyenet/article/ocular-toxoplasmosis-a-refresher. Accessed 1 July 2024.

"Toxoplasmosis - Symptoms and Causes." Mayoclinic, Mayo Foundation for Medical Education and Research, 3 Nov. 2022, www.mayoclinic.org/diseases-conditions/toxoplasmosis/symptoms-causes/syc-20356249. Accessed 1 July 2024.