Free-living Amoebozoa infection

Free-living Amoebozoa Infections are diseases caused by amoebas belonging to the Amoebozoa group that are not parasitic but can cause illness in humans when they invade the body. These amoebas are typically found in soil, freshwater, and other environmental sources. The most notable infections include those caused by Naegleria fowleri, Acanthamoeba spp., and Balamuthia mandrillaris. These infections, although rare, can be severe and often fatal.

Etiology

Free-living Amoebozoa infections are caused by several species of amoebas that thrive in environmental reservoirs. Naegleria fowleri, often referred to as the "brain-eating amoeba," causes primary amebic meningoencephalitis (PAM), a devastating infection of the brain. Acanthamoeba spp. are known for causing Acanthamoeba keratitis, mainly in contact lens users, and granulomatous amoebic encephalitis (GAE), a chronic and often fatal brain infection. Balamuthia mandrillaris is another causative agent of GAE, primarily affecting individuals with weakened immune systems.

Transmission

The transmission of free-living Amoebozoa to humans is typically through inhalation of contaminated water droplets, contact with contaminated soil, or through the eyes. For instance, Naegleria fowleri infections occur when water containing the amoeba enters the body through the nose, usually during swimming or diving in warm freshwater places. Acanthamoeba and Balamuthia infections can occur through skin wounds or inhalation of dust containing the amoebas.

Symptoms and Diagnosis

Symptoms of free-living Amoebozoa infections vary depending on the causative organism and the site of infection. PAM caused by Naegleria fowleri presents with severe headache, fever, nausea, vomiting, followed by stiff neck, seizures, altered mental status, and coma, often leading to death within a week. Acanthamoeba keratitis manifests as eye pain, redness, blurred vision, and sensitivity to light. GAE symptoms include headache, fever, stiff neck, and neurological deficits that progress over weeks to months.

Diagnosis of these infections involves clinical suspicion combined with laboratory tests, including microscopy, culture, PCR, and imaging techniques like MRI or CT scans for brain infections.

Treatment

Treatment options for free-living Amoebozoa infections are limited and often not well established due to the rarity of these diseases. Amphotericin B, a potent antifungal drug, has been used to treat PAM with some success, especially when administered early. For Acanthamoeba and Balamuthia infections, combinations of antimicrobials including miltefosine, pentamidine, sulfadiazine, and fluconazole have been tried with varying outcomes.

Prevention

Preventive measures for free-living Amoebozoa infections include avoiding contact with potentially contaminated water, especially in warm climates where these amoebas thrive. For contact lens users, proper lens hygiene is crucial to prevent Acanthamoeba keratitis.

Epidemiology

Free-living Amoebozoa infections are rare but have been reported worldwide, with Naegleria fowleri infections predominantly occurring in warm freshwater bodies in the United States, Australia, and other parts of the world. Acanthamoeba and Balamuthia have a wider distribution due to their presence in soil and dust.

Conclusion

Free-living Amoebozoa infections, though rare, pose a significant health risk due to their severe and often fatal outcomes. Increased awareness, early diagnosis, and prompt treatment are essential for improving patient outcomes. Ongoing research into effective treatments and preventive measures is crucial to combat these devastating infections.