A parasite is an organism which lives inside another living organism, and depends on other creatures in order to stay alive. They often harm their host in the process.
Many different parasites affect humans and they can transmit deadly diseases such as malaria and trichomoniasis, which can be passed on during sex.
Around three quarters of parasites are so small they’re not visible to the human eye. Some, such as worms, may grow much larger.
Examples of parasites which may live in humans include tapeworms and roundworm, which both live in the digestive tract.
Possible symptoms of parasite infection include skin bumps or rashes, weight loss or increased appetite, abdominal pain, vomiting or diarrhoea, and fever.
Parasitic eye infections can cause symptoms such as pain, inflammation, watery eyes, blurred vision, sensitivity to light, itching and even blindness.
Acanthamoeba keratitis is one of the main infections of they eye, caused by the parasite acanthamoeba. The organism is found within freshwater and marine environments worldwide.
It’s transmitted through direct contact with the parasite and the cornea of your eye. Those with poor contact lens care are at a higher risk.
Some parasites enter the body through the mouth or skin, and then travel to the eye.
For example, toxocariasis is a rare infection caused by roundworm parasites caught from handling soil or sand contaminated with infected animal faeces.
When it infects the eyes, it’s referred to as ocular toxoplasmosis. It can cause blurred vision and eye pain. But cases are very rare.