Have you ever had an itchy eye? Has your eye ever been red and burning, or have you ever had swelling and discharge from it? These are common symptoms of conjunctivitis. It can be the result of allergies, irritants, bacteria, or viruses. In many cases, the issue will go away on its own, either by flushing the eye, or even taking antihistamines. Sometimes a doctor will prescribe an antibiotic. But what would you do if you suddenly saw something pass through your vision? Checking in the mirror you see it’s a worm? Congratulations, you have just met loa loa, the eye worm.
Loa loa is an arthropod-borne roundworm commonly found in the rain forests in West Africa and has native origins in Ethiopia. Loa loa translates to “worm worm” but is most commonly known as the “eye worm” as it is commonly found in the conjunctiva of the eye.
Eye worms have a simple structure that consists of a head, body, and a blunt tail. The outer body of the worm consists of 3 protective layers made up of collagen and other compounds which aid in protecting it while it while it lives within its hosts digestive system. The worms vary in color and size with male adults ranging from 20-34 mm long and 350-430 um wide. A female adult ranges from 20-70 mm long and is typically 425 um wide.
A human is the definitive host, being infected by the bite of an infected horsefly (deer fly, yellow fly), bearing third-stage filarial larvae in its proboscis. The flies usually bite during the day, and more commonly during the rainy season. They are attracted by smoke from wood fires, and movement. Once in the human host, the larvae mature into adults, living in the subcutaneous tissue, the fat layer, traveling in the peripheral blood during the day, and migrate to the lungs at night.
Once she reaches maturity, a female can produce approximately 250-300 microfilaria (the minute larva of a filaria) which range in size from 250-300 um in length, and 6-8 um in width. She will continue to produce microfilaria for the rest of her life, which can span 10-15 years on average. These larvae tend to live within spinal fluids, urine, and sputum, and also circulate in the blood stream. These microfilariae develop over the course of 5-6 months and can live up to 17 years.
As if being infected with these worms isn’t bad enough, they also cause a disease called loiasis, which also happens to be a “neglected disease.” Neglected diseases are diseases common in low-income populations in regions of Africa, Asia, and the Americas which receive little to no research funding.
Often infected people do not develop any symptoms. When symptoms are present, they are usually several months after infection. Symptoms include itchy, non-painful swellings of the body that come and go. While the swelling can show up anywhere, it is most common near joints. One tell-tale sign is the development of an eye worm that crawls across the surface of your eye. In some cases, you can even see a worm as it crawls under your skin. Other, less common, symptoms include muscle pain, joint pain, and fatigue.
Treatment can be dangerous. The worms can be removed via surgery, but that will not cure the infection, as they will be located throughout the body and it is impossible to surgically remove them all. A medication, DEC, or diethylcarbamazine, can be used to kill the parasite, however that comes with its own risks. It’s safe to say that prevention is the best cure.
You can safeguard yourself from the loa loa by wearing long pants and long-sleeved shirts in areas where there is a risk. Avoid smoke and wood fires. If you are going to be in an area for an extended duration, you can reduce your risk by taking DEC on a weekly basis. This, however, must be done with the consultation of a tropical medicine expert.
Be careful when it comes to flies. They can do more than bite you, in fact, what’s that scratching in your ear?
Leave a Reply