Common Parasitic Eye Infections — Types and Treatments

Parasitic eye infections are defined as severe infections affecting the eye and the structures adjacent to the eye, by parasites, either protozoan or metazoan.

Types of Parasitic Eye Infections:

The most common eye infections caused by parasites, in humans are as follows:

• Acanthamoeba Keratitis
• Ocular Onchocerciasis
• Ocular Toxoplasmosis

Acanthamoeba Keratitis:

Acanthamoeba are amoeba found in water sources. Here, infection occurs due to contaminated water.

Symptoms of this infection include itchy, red eyes, swelling and pain in the eyes. It also causes blurred vision accompanied by watering of the eyes.

Ocular Onchocerciasis:

It is an infection caused by a water-borne nematode called Onchocerca volvulus. The disease is transmitted due to bites caused by black flies, that are found near fast-flowing rivers. Thus, this condition is also known as river blindness.

Symptoms include itchy, red eyes and sensitivity to light (photophobia). If undetected, over years, a scarring can form and progress to visual loss, ultimately leading to blindness.

Ocular Toxoplasmosis:

It is the most common parasitic infections of the eyes, worldwide. It is caused by the protzoan parasite namely, Toxoplasma gondii. The parasite is transmitted to humans through cats. The two forms of the organism that cause disease symptoms are bradyzoites and tachyzoites.

Symptoms here vary, but when the disease becomes active, floaters in the images and blurred vision occur. But inactive disease does not cause visual symptoms. Usually the infection goes unnoticed until inflammation is observed in the central retina.

Treatments – Drugs and Medication:

• Keratitis: It is treated using an aggressive combination of surgery and drugs. Ketaconazoles are the prescribed drugs and the surgery involves keratoplasty.
• Onchocerciasis: Ivermectin is the anti-parasitic of choice for treating this condition. The aim of this therapy is to eliminate completely, the microfilarial stage of this disease.
• Toxoplasmosis: The classic treatment for ocular toxoplasmosis is a combination of sulfadiazine, folinic acid and pyramethamine, for six weeks. Frequent blood tests to monitor drug toxicity have to be performed to control side effects of these drugs.