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Acanthamoeba spp., amoebae that live in water and soil, can hitch a ride on a contact lens, then invade a vulnerable eye and destroy the cornea.
What is Acanthamoeba?
Acanthamoeba (pronounced ah-canth-ah-me-baa) literally means spiny amoeba, and that’s exactly what Acanthamoeba spp. are—single celled amoebae that produce spiny pseudopodia as they move slowly along. About five times the size of a human red blood cell, acanthamoebae are large as microbes go, but still much too small to be seen with the naked eye. The most common amoebae in fresh water and soil, Acanthamoeba spp. sometimes cause human infections.
In water, moist soil, mud, and decaying organic material, acanthamoebae feed on bacteria and other microscopic organisms. In water supply systems, these amoebae live in the biofilm of organisms that proliferate on the inside surfaces of pipes, grazing on the other organisms in the biofilm. When the environment gets dry, they wrap themselves up inside a tough cyst wall and wait for the moisture and the food to return. They’re resistant to drying, chlorine, and many antiseptics. They are tough and ubiquitous.
Why is acanthamoeba important?
Though the natural environment for Acanthamoeba spp. is moist decaying organic material, at least six different species are capable of feeding on living tissue. Given the chance, these amoebae will invade human tissues and cause disease—the most common way that they do this is through the cornea of an eye from a contact lens. The destruction of the cornea, acanthamoeba keratitis, can result in the need for corneal transplant, and sometimes even surgical removal of the eye.
A rare cause of eye infections before the days of contact lenses, Acanthamoeba spp. were given a new opportunity when people started regularly putting lenses in their eyes. Tap water is usually the vehicle for the amoeba:
- Washing lenses and lens cases with tap water, and homemade saline made with tap water, allows Acanthamoeba spp. to adhere to contact lenses.
- Improper lens care, particularly conditions in which bacteria proliferate on lenses and in cases and solutions, provides the amoebae with a food supply. They multiply.
- Amoebae adhere to contact lenses—they are able to adhere to some lens materials more readily than others.
- Amoebae are transferred into the eye on the contact lens.
- Even the tiniest scratch or abrasion on the surface of the cornea allows the amoebae to get inside the eye, where they multiply and destroy tissue. A painful and vision destroying infection ensues.
Avoid acanthamoeba eye infection
Even though acanthamoeba keratitis is much more common than it used to be, it is still rare even among contact lens wearers. To avoid this devastating infection:
- Never allow lenses or cases to come in contact with tap water.
- Never swim with contact lenses in, even in a chlorinated swimming pool.
- Don’t shower with contact lenses in your eyes.
- Never wear contact lenses when your eyes are irritated or if you suspect you have even a tiny scratch.
- Do not keep lenses or solutions past their expiry date.
- Do not wear lenses for longer periods than your eye professional recommends.
- Always carefully follow your eye professional’s instructions for cleaning contact lenses.
- A lens cleaning routine that requires rubbing is preferable to one that only requires soaking.
Contact lenses and lens care disinfectants are improving; however, contact lens wearers still have to be careful. Taking the precautions listed above should keep this opportunistic amoeba where it belongs—in the environment.
Related content:
Contact Care
Read about other protozoan parasites of humans:
A Parasite in the Blood Supply
Toxoplasma gondii
Sources:
Drisdelle, Rosemary. “Preventing Infections with Proper Lens Care.” Optical Prism. Mar (2007): 32-36.
Drisdelle, Rosemary. “The Amoeba that Loves Eyes.” Optical Prism. March (2004): 24-26.
Roberts, Larry S. and John Janovy Jr. Foundations of Parasitology 6th ed. Boston: McGraw Hill, 2000.
The copyright of the article Acanthamoeba – Eye Parasite in Human Infections is owned by Rosemary Drisdelle. Permission to republish Acanthamoeba – Eye Parasite in print or online must be granted by the author in writing.
Comments
Nov 12, 2008 2:37 PM
Guest :
I enjoyed your information on human eye parasites but you do not tell us
how to get rid of them through natural means without having to have it or
them surgically removed.
Nov 12, 2008 4:24 PM
Rosemary Drisdelle :
If you think you have an eye infection caused by acanthamoeba, see an eye
specialist immediately. The infection is difficult to treat and a delay
only increases the probability of permanent vision loss.
Nov 24, 2008 4:03 PM
Guest :
I found your web site very informative. My neice has this acanthamoeba
infection. The doctor thinks her contacts are the cause. The doctor was
able to clear up the infection for several months but it came back in both
eyes several weeks ago. Thank you for the information. It's scary knowing
she could loose her eye sight.
Dec 16, 2008 12:32 PM
Guest :
I think there is more eye parasites than this article lets on. I live in
Lake Havasu City, Az on the Colorado River and I think there are a number
of people affected every year. However, most goes unreported because most
of the recreational users of the River are from Cailfornia and when they
return home to Southern California is when and where they get treated.
There are a growing number of locals who are affected every year and local
health authorities down play the numbers involved. The River has become
increasingly contaminated the last few years and I more and more friends
that have had parasitic reactions to their eyes and the strain becomes
increasingly tougher each year. In 2007 a 14 year old boy died from
Naegleria Fowleri swimming at Rotary Beach, Lake Havasu City, Az in the
Colorado River. His death was covered up by local health officials. The
parasites are also covered up. Where's the CDC?
Jun 5, 2009 9:45 PM
Guest :
I too was infected by acanthamoeba back in Aug of 2006. It took couple of
weeks before my doctors could figure out what was wrong with my right eye.
I then had to go out of state, Univ of Iowa, to have my eye worked on.
Lucky for me that it was caught in time with out much damage to my eye. I
do have some scaring on my cornea which has affect my eye sight but I can
still see with corrective lenses.
Aug 11, 2009 10:58 AM
Guest :
My nephew is currently diagnosed with parasite in his right eye. He has
had the infection for over a month. He is on four different drops for his
eye. The drops go ever 20 minutes. I would like some information from
people who have got treatment for there eye and were successful. I would
like to find more from the guest on this site who seeked treatment outside
of state and was cured with mild scaring to the cornea. Please send your
comments on this site or email mahalbk1@telus.net. Thank you for your
help. I am so desperate to find any help for my nephew. karm
Sep 6, 2009 9:03 AM
Guest :
I don't know what it is I have. At first I thought they were floaters, but
I have gone to 3 eye doctors and they don't see them. They always tell me
that the floaters should disappear, but I have had these same
"floaters" for a little over a year now. They are like worm
shaped clear things that I see when I move my eye. The have increased in
length since last year. Also I have noticed little balls, sometimes
grouped together. They look like cells. Could they be eggs? Is it
possible that I am seeing the amoeba's or one of their close relatives?
Sep 7, 2009 4:09 AM
Rosemary Drisdelle :
Cysts and trophozoites of acanthamoeba are only a few thousandths of a
millimeter wide - much too small to be seen without a microscope.
8 Comments
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