What are the other Names for this Condition? (Also known as/Synonyms)

• Acanthamoeba Infection, NOS

What is Acanthamoeba Infection? (Definition/Background Information)

• Acanthamoeba Infection is caused by a single-celled organism that generally does not harm humans. However, when infection does occur, it can cause severe damage in various parts of the body
• The organism is found in natural environments all around the world and is highly-prevalent in water sources such as lakes, rivers, swimming pools, drinking water systems, and air-conditioning systems. It is also found in soil and dust
• The amoeba enters the human body through a single-entry point (such as the skin) and may disperse throughout the body, causing disseminated (widespread) infection. This can eventually lead to the following conditions:
  • Acanthamoeba keratitis, a painful infection of the cornea (the transparent layer forming the front of the eye), caused by the amoeba entering the eye, through contact lens. Lifelong visual impairment or blindness may result from this infection
  • Granulomatous amoebic encephalitis (GAE), which is a lethal infection of the brain and spinal cord 
• The diagnosis of this infection is made via clinical eye examinations using optical imaging techniques and/or culturing corneal scrapings to check for the presence of amoeba. Brain scans and spinal taps may become necessary, if the infection spreads to other parts of the body
• Presently, Acanthamoeba Infection is treated using anti-bacterial and anti-fungal agents. The prognosis for the infection is good, if it is diagnosed early and treated promptly
• The infection can be prevented by maintaining proper hygiene, such as while using contact lenses

Who gets Acanthamoeba Infection? (Age and Sex Distribution)

• Acanthamoeba Infection is a very rare condition that predominantly affects contact lens users
• In advanced countries, the infection occurs at a frequency of 33:1 million contact lens users
• Individuals of all ages, races, ethnic groups, and both genders are susceptible to this infection, at any time during the year
• Elderly adults are more susceptible to infection of the eyes (Acanthamoeba keratitis)

What are the Risk Factors for Acanthamoeba Infection? (Predisposing Factors)

The following are the risk factors for Acanthamoeba Infection:

• Improper use, storage, and disinfection of contact lenses, which may include:
  • Cleaning lenses with tap water
  • Wearing lenses in the shower, swimming pool, or hot tub
  • Contact between contaminated water and the eye
• History of injury to the cornea
• A compromised immune system, with more frequent cases of disseminated infection and GAE

The following are some conditions that can cause immunosuppression:

• AIDS
• Organ transplantation
• Steroids or abuse of antibiotics
• Diabetes mellitus
• Cancer
• Lupus (SLE)
• Liver cirrhosis

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Acanthamoeba Infection? (Etiology)

The cause of Acanthamoeba Infection is an amoeba, Acanthamoeba, which gains entry to the body through the eyes and nose, or an opening in the skin (such as a cut).

• When the organism enters the body through the eyes, it can lead to acanthamoeba keratitis
• Acanthamoeba entering the body through the nostrils or skin wound may lead to disseminated infection and granulomatous amoebic encephalitis (GAE), by traveling to the lungs, brain, and spinal cord
• Skin infections do not necessarily lead to a disseminated infection

Acanthamoeba Infection has never been reported to spread from one individual to another through contact.

What are the Signs and Symptoms of Acanthamoeba Infection?

The signs and symptoms of Acanthamoeba Infection may vary between affected individuals. The commonly reported symptoms include:

• Eye pain, redness, and excessive tearing
• Blurred vision
• Sensitivity to light
• Sensation of something in the eye

Granulomatous amebic encephalitis symptoms typically progress over multiple weeks. Once the brain and spinal cord are affected, the symptoms may include:

• Headaches and fever
• Stiff neck
• Nausea and vomiting
• Tiredness, confusion, and lack of attention and focus
• Loss of balance and body coordination
• Seizures
• Hallucinations

How is Acanthamoeba Infection Diagnosed?

The diagnosis of Acanthamoeba Infection may be difficult, as corneal infections caused by other microbes may present with similar symptoms. The diagnosis of the infection is generally made by:

• A thorough physical examination and an assessment of symptoms
• An evaluation of the affected individual’s medical history
• An eye examination by a specialist, who may:
  • Observe Acanthamoeba cysts through confocal microscopy, which is a non-invasive optical imaging technique
  • Request culture of corneal scrapings to determine presence of the amoeba 

Granulomatous amebic encephalitis and disseminated infection are harder to diagnose, and they are often only discovered at advanced stages. Tests used for these diagnoses include:

• Brain scans
• Biopsies of the skin and sinuses
• Spinal taps

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Acanthamoeba Infection?

The potential complications from Acanthamoeba Infection include the following:

• Progression into more severe diseases of the eye, resulting in severe scarring of the eye, if left untreated or if treatment fails
• Treatment for Acanthamoeba keratitis can result in the following complications:
  • Fixed dialed pupil
  • Damage to the iris
  • Vascularization of the cornea
  • Secondary bacterial infections
• If Acanthamoeba Infection of the skin is left untreated, infection can travel to the brain and spinal cord, which can be fatal

How is Acanthamoeba Infection Treated?

The treatment for Acanthamoeba Infection may be difficult, if the amoeba is in the cyst form. The regimens for treatment are not well established for this infection. The following are some general treatment methods:

• For pain, over-the-counter painkillers
• For skin, following cleaning of sores (if required), optical antiseptic agents, such as polyhexamethylene biguanide (0.02%) and chlorhexidine (0.02%), may be recommended
• A healthcare provider may make a recommendation for the topical applications with or without the anti-protozoal drug diamidine such as propamidine (0.1%) or hexamidine (0.1%)
• Acanthamoeba keratitis can be treated with antiseptic eye drops. Some reports have suggested that treatments, such as collagen cross-linking and anti-fungal drugs, have resulted in successful treatment, but more research needs to be performed on these possibilities. Treatment can last anywhere from 3 months to more than a year
• Acanthamoeba keratitis can also be treated with a corneal transplant, if there is corneal perforation. However, surgery is usually postponed until the eye is free of infection
• For granulomatous amoebic encephalitis, a combination of miltefosine (obtained from US Centers for Disease Control) and an antiprotozoal (pentamidine), antibiotic (sulfonamide or trimethoprim), or antifungal agent (flucytosine or Fluconazole) is generally used for treatment

How can Acanthamoeba Infection be Prevented?

The following are some guidelines for possible prevention of Acanthamoeba Infection:

• Clean and replace lenses according to the instructions of the eye care provider
• Remove lenses before any activity involving contact with water
• Store reusable lenses in the proper storage container
• Replace storage cases in a timely manner
• Wash hands with soap and water before touching one’s eyes
• Have regular eye examinations
• Seek treatment for underlying medical conditions that may reduce immunity
• In general, follow good hygiene practices

What is the Prognosis for Acanthamoeba Infection? (Outcomes/Resolutions)

• The prognosis for Acanthamoeba Infection of the eyes and skin is good, since the condition is treatable with an early diagnosis and prompt treatment
• Individuals with Acanthamoeba Infection of the brain and spinal cord (GAE) often succumb to the condition

Additional and Relevant Useful Information for Acanthamoeba Infection:

• According to the US CDC, most individuals will likely get exposed to Acanthamoeba; however, not everyone are infected
• The eye infections are more likely to occur in healthy individuals, whereas GAE is more common in individuals with a compromised immunity