Acanthamoeba is a germ commonly found in soil, dust, fresh water sources
Acanthamoeba is a germ commonly found in soil, dust, fresh water sources

Acanthamoeba is a germ commonly found in soil, dust, fresh water sources (such as lakes, rivers, and hot springs), swimming pools, brackish water, and seawater. It can also be found in hot tubs, heating and air conditioning units, humidifiers, and drinking water systems (such as taps or water pipes). Acanthamoeba infection generally does not spread from one person to another. Most people exposed to Acanthamoeba do not get sick from it.

There are two species of Acanthamoeba: A castellanii, and A polyphaga. They are responsible for most infections. Acanthamoeba can enter the body through:

  • Skin: Through a cut, wound, or broken skin while swimming in contaminated water.
  • Nasal passages: Inhaled into the lower respiratory tract and enters the lungs.
  • Eye: It can enter eyes through contact lenses or a contaminated lens solution. It can cause severe inflammation called keratitis.

Once it enters the body, the amoeba travels through the bloodstream to other parts of the body, especially the lungs, brain, and spinal cord and causes serious, rare, fatal infections and inflammation.

Acanthamoeba infection of eyes (Acanthamoeba keratitis) is quite common and has been linked to:

  • Contact lens use.
  • Poor contact lens hygiene.
  • Swimming or showering in contaminated water.
  • Eye injury or trauma.
  • Weak immunity.
  • Trauma to the eye.
  • Low levels of anti-Acanthamoeba immunoglobulins-A (immune system proteins) in tears.

A study says 75% of patients with Acanthamoeba keratitis contracted the infection from contact lenses. It was found 22% of patients used hard contact lenses, 40% used daily-wear soft lenses, and 38% wore extended wear or other types of lenses. In 2007, United States Food and Drug Administration (US FDA) announced an outbreak of Acanthamoeba keratitis, which was associated with the manufacturing of Complete Moisture Plus Multi-Purpose Solution.

What are the symptoms of Acanthamoeba infections?

The life cycle of Acanthamoeba has two stages: it forms fluid-filled sacs (cysts) and grows parasites (trophozoites) in the tissue. These parasites can invade the body causing symptoms.

  • Central nervous system (CNS): When Acanthamoeba enters through the respiratory system or ulcerated skin, it can affect the CNS and cause granulomatous amoebic encephalitis (GAE) or brain swelling in people with weak immunity. It is characterized by:
  • Eye infection can cause Acanthamoeba keratitis. The symptoms of Acanthamoeba keratitis can resemble symptoms of other more common eye infections. The symptoms, which can last from several weeks to months, are not the same for everyone and may include:
  • Other organs: Infections may spread throughout the entire body including sinuses, lungs, and other organs. This also occurs more commonly in those with a weaker immune system known as disseminated infection.

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What are the complications of Acanthamoeba infection?

Acanthamoeba infection may cause various illnesses in the body, such as:

  • Acanthamoeba keratitis may lead to:
    • Inflammation of the lacrimal gland.
    • Scarring of the cornea (clear outer layer of the eye).
    • Damage to the eye (optic) nerve.
    • Clouding of the clear lens of the eye (cataract).
    • Reduction of blood supply to the back of the eyeball (rare).
    • Blindness.
  • Skin lesions
  • Infections in those with weaker immunity
  • Serious fatal infection and inflammation of the brain and spinal cord (granulomatous amoebic encephalitis or GAE)
  • Death

Is there any treatment for Acanthamoeba keratitis?

Acanthamoeba eye infection (Acanthamoeba keratitis) is usually treatable. They are:

  • Medication: Medical treatment of full-blown Acanthamoeba keratitis is still in the developmental stage.
    • Pain-relieving drops will be prescribed.
    • Consequently, a combination of topical Biguanide and Diamidine therapy is used to treat Acanthamoeba keratitis. Topical dual therapy with Chlorhexidine 0.02% and Propamidine 0.1% hourly for 2-3 days is most followed. The frequency of the therapy may be lowered to four times a day. For disease limited to the epithelium, therapy may be discontinued after 2-4 weeks. For more intense infection, long-standing therapy is preferred.
    • Recurrence is quite common and Acanthamoeba cysts are treatment-resistant; therefore, the frequency of medical treatment will be reduced very slowly. Sometimes, treatment may continue for many months.
  • Surgical intervention: In case of tear or scarring in the cornea (clear outer layer of the eye), the eye doctor may suggest corneal transplantation called keratoplasty. Also, after keratoplasty surgery, active medical therapy using antibiotics, antivirals, or antiparasitics will be given in the case of any active infection to avoid recurrent infection in the graft.

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Medically Reviewed on 2/3/2021
References
Centers for Disease Control and Prevention. Parasites — Acanthamoeba — Granulomatous Amebic Encephalitis (GAE); Keratitis. https://www.cdc.gov/parasites/Acanthamoeba/index.html

Bernfeld E. Acanthamoeba Keratitis. American Academy of Ophthalmology https://eyewiki.aao.org/Acanthamoeba_Keratitis