Eye ailments caused by pests: Classification, remedies, and precautions
Parasites can cause a range of eye problems, each with distinct mechanisms leading to various symptoms and requiring specific treatments. This article explores three types of eye parasites: protozoa, helminths (worms), and ectoparasites (external parasites like mites).
Protozoan Eye Parasites
Protozoa can infect the eye but are more commonly associated with systemic infections affecting the eye indirectly. One example is Toxoplasma gondii causing ocular toxoplasmosis. However, the bacterium Chlamydia trachomatis (a bacterial protozoa-related pathogen) leads to a disease called trachoma, which causes chronic inflammation, resulting in scarring of the inner eyelids and entropion (inward turning), eventually leading to blindness. Symptoms include redness, discharge, and eyelid deformities. Treatment involves antibiotics and maintaining strict hygiene.
Helminths (Parasitic Worms)
Onchocerciasis, also known as African River Blindness, is a helminth infection caused by the nematode Onchocerca volvulus. This parasite affects all ocular tissues, causing early signs such as eyelid nodules, conjunctivitis, and chemosis. Later, microfilariae invade the cornea, causing "snowflake" opacities and chronic sclerosing keratitis that leads to scarring, corneal neovascularization, and blindness. Further involvement of the iris and ciliary body causes iridocyclitis, which may lead to glaucoma and cataracts. Posterior segment infection results in chorioretinitis and optic nerve damage. Other helminth infections like Thelaziasis involve eyeworms transmitted by flies feeding on animal tears, causing irritation, tearing, and conjunctivitis. Treatment involves mechanical removal of worms and antibiotic eye ointments to prevent secondary infections.
Ectoparasites (Mites)
Demodex mites reside in hair follicles and sebaceous glands around the eyes, causing blepharitis (eyelid inflammation), itching, redness, eyelash loss, and sometimes rashes around the eyes. Diagnosis is by microscopic examination of skin scrapings. Treatment typically involves topical agents like metronidazole, tea tree oil, or other acaricides to eradicate mites and reduce inflammation.
The table below summarises the eye parasites, their mechanisms of disease, symptoms, and treatments:
| Parasite Type | Examples | Mechanism of Eye Disease | Symptoms | Treatment | |---------------------|------------------------------|-------------------------------------------------|--------------------------------|----------------------------------| | Protozoa | Chlamydia trachomatis (Trachoma) | Chronic conjunctival infection and scarring | Eyelid scarring, entropion, discharge, redness, blindness | Antibiotics (e.g., azithromycin), hygiene | | Helminths (Nematodes) | Onchocerca volvulus, Thelazia spp. | Microfilarial invasion of ocular tissues (cornea, iris, retina), or larvae in eyelids | Eyelid nodules, conjunctivitis, keratitis, iridocyclitis, glaucoma, tearing, irritation | Antiparasitics (ivermectin for Onchocerciasis), worm extraction, antibiotics for secondary infections | | Ectoparasites (Mites) | Demodex folliculorum, D. brevis | Infestation of hair follicles, sebaceous glands around eyelids | Blepharitis, itching, redness, eyelash loss | Topical acaricides (metronidazole), eyelid hygiene |
This classification clarifies how eye parasites cause disease by either direct tissue invasion and inflammation (helminths), chronic infection and scarring (protozoa-related like trachoma), or surface infestation causing irritation (ectoparasites). Treatments are tailored accordingly to eliminate the parasite and manage inflammation or secondary infections.
Prevention methods for parasitic infections include eating properly cooked food, drinking water from a clean source, using insecticide on skin, covering skin, and practicing good hygiene, especially for contact lens wearers. Ocular toxocariasis, caused by parasitic roundworms called Toxocara, can lead to vision loss if the larvae travel to the host's eyes. The World Health Organization (WHO) notes that over 30 million people with the Onchocerca volvulus infection live in thirty-one countries in sub-Saharan Africa. The Centers for Disease Control and Prevention (CDC) estimate that as many as 60% of people 6 years old and older have the Toxoplasma gondii infection in the US.
Individuals at a higher risk of infection with Toxoplasma gondii are those who are immunocompromised and pregnant people. Symptoms of African eye worm may include itching and swelling, especially in the joints, and if the worms travel to a person's eyes, it can make them itchy, painful, and sensitive to light. The American Academy of Ophthalmology (AAO) recommends speaking to an ophthalmologist if a person has any unusual vision symptoms, including loss of vision, blurred vision, pain in or around the eye, excessive tearing, redness or inflammation around the eye, sensitivity to light, floaters, itchy or crusty eyelids, or the sensation that something is in the eye.
River blindness, or onchocerciasis, is caused by a parasitic worm called the Onchocerca volvulus and can lead to blindness due to lesions in the eyes, especially in tropical areas. Loa loa is a parasitic worm from West and Central Africa that causes loiasis, or African eye worm. Gnathostomiasis is another infection caused by a parasitic worm and occurs due to eating raw or undercooked freshwater fish carrying the larvae. Acanthamoeba keratitis is a rare but serious eye infection caused by a single-celled organism called an amoeba, which can lead to severe pain and loss of vision, especially among contact lens wearers. Demodicosis is caused by tiny mites called Demodex folliculorum that live in human hair follicles and can cause eye problems when their numbers increase on the face.
In conclusion, understanding the different types of eye parasites and their mechanisms of disease is crucial for effective treatment and prevention. It is essential to maintain good hygiene, eat properly cooked food, and seek medical attention if experiencing unusual vision symptoms.
- Parasites can infect the eye and cause distinct diseases, each with unique symptoms and treatments.
- Protozoa, such as Toxoplasma gondii, can cause ocular toxoplasmosis, but Chlamydia trachomatis leads to trachoma, causing chronic inflammation and eventually blindness.
- Trachoma symptoms include redness, discharge, and eyelid deformities.
- Treatment for trachoma involves antibiotics and maintaining strict hygiene.
- Onchocerciasis, or African River Blindness, is a helminth infection caused by Onchocerca volvulus and can lead to blindness.
- Onchocerciasis affects all ocular tissues, causing eyelid nodules, conjunctivitis, and chemosis.
- Later stages involve microfilariae invading the cornea, causing opacities and chronic sclerosing keratitis.
- Posterior segment involvement results in chorioretinitis and optic nerve damage.
- Thelaziasis, caused by eyeworms transmitted by flies feeding on animal tears, causes irritation, tearing, and conjunctivitis.
- Demodex mites living in hair follicles and sebaceous glands around the eyes cause blepharitis, itching, redness, eyelash loss, and rashes.
- Treatment for Demodex mites typically involves topical agents like metronidazole, tea tree oil, or other acaricides.
- Prevention methods for parasitic infections include eating properly cooked food, drinking clean water, using insecticide on skin, covering skin, and practicing good hygiene.
- Ocular toxocariasis, caused by parasitic roundworms called Toxocara, can lead to vision loss.
- Over 30 million people with Onchocerca volvulus infection live in sub-Saharan Africa.
- Individuals at higher risk of Toxoplasma gondii infection are immunocompromised and pregnant people.
- Symptoms of African eye worm may include itching and swelling, especially in the joints, and if the worms travel to a person's eyes, they can cause itchiness, pain, and sensitivity to light.
- River blindness, or onchocerciasis, is caused by a parasitic worm and can lead to blindness in tropical areas.
- Other infections such as loiasis, gnathostomiasis, Acanthamoeba keratitis, and Demodicosis can also affect the eyes and cause adverse effects on vision and eye health.
