Ocular Parasitosis: The Danger of Consuming Raw Food

     “Ocular Parasitosis” is a dangerous condition where parasites escape the digestive system into the bloodstream and cerebrospinal fluid, eventually migrating into various parts of the eye. This condition is closer than you think and can lead to permanent vision loss or even death if it spreads to the brain.

Causes

     The primary cause is consuming raw or undercooked food, especially freshwater and amphibious animals carrying infective larvae. It can also occur from eating unwashed vegetables or drinking water from natural sources contaminated with larvae.

Common Types of Parasites

Three main types are commonly found in Thailand:

• Angiostrongylus (Rat Lungworm): Found in apple snails, cherry snails, shrimp, crabs, frogs, and monitor lizards.
• Gnathostoma: Commonly found in freshwater fish, frogs, snakes, ducks, and poultry.
• Pork Tapeworm: Present as cysts (Cysticercosis) in various tissues.

Migration Paths

After entering the body, parasites penetrate the stomach or intestinal wall into the bloodstream and travel to various areas:

• Inside the Eyes: They can reside beneath the retina (Subretinal), float in the Vitreous humor, inhabit eye muscles, conjunctiva, or even the Optic nerve.
• Nervous System: They often travel via cerebrospinal fluid to the brain, causing meningitis or encephalitis.
• Skin: Particularly Gnathostoma, which moves through subcutaneous tissue causing migratory swelling.

Do Deworming Pills Help?

     Taking anthelmintics (deworming pills) cannot fully prevent ocular parasitosis. Studies show that some patients who take these pills annually still develop the condition. Taking medication only reduces a portion of the risk. If abnormal symptoms occur, do not self-medicate, as it may lead to incorrect treatment and worsening conditions.

Symptoms

Symptoms depend on the parasite's location, but common signs include:

• Ocular Symptoms: Blurred vision (found in up to 90% of cases), double vision, strabismus, eye swelling, bulging eyes, or seeing shadows of parasites moving in the eye.
• Neurological Symptoms: Severe headache, stiff neck/back, seizures, facial or limb paralysis, or loss of consciousness.
• Skin Symptoms: Redness, swelling, stinging pain, and migratory swelling at various points on the body.

Diagnosis and Treatment

• Diagnosis: Requires a thorough examination by an ophthalmologist using specialized equipment to locate the parasite.
• Treatment:
  • Surgery: If a parasite is found in the eye, urgent surgery is often required to remove it before it causes blindness.
  • Medication: Albendazole may be prescribed for Gnathostoma, while Angiostrongylus treatment focuses on supportive care and steroids to reduce brain inflammation.

Prevention

The best prevention is “Changing consumption habits.”

• Eat only cooked and clean food: High-heat cooking is the only way to kill larvae (fish sauce or lime juice cannot kill them). Avoid high-risk raw dishes like "dancing shrimp," raw beef salad, or raw shellfish.
• Hygiene: Wash hands before eating, wash vegetables thoroughly under running water, and drink only boiled water (if sourced from nature).

Ocular parasitosis is closer than you think; a single meal of raw food can lead to lifelong vision loss.