Amoeba Found in Soil Turns Part of Gardener's Brain Into Liquid

A man has died after being infected with an amoeba that turned part of his brain to liquid, doctors in the U.S. have reported. It is thought he may have contracted the amoeba after being exposed to contaminated soil while potting plants.

The 82-year-old died after just over a week in hospital, with an autopsy showing the cause of death to be granulomatous amebic encephalitis—a rare infection of the brain and spinal cord normally caused by the species acanthamoeba.

Matt Schimmel and Ishan Mehta, from Emory University in Atlanta, have published a report in the NEJM detailing the case.

The man arrived at an emergency department having felt weak for the last two weeks. He had previously suffered from a type of blood cancer, but had been in remission for over a decade. After being admitted, he became weaker on the right side and developed an "altered mental status." An MRI scan showed an abnormality in the left frontal lobe of his brain.

He was treated for bacterial, fungal and viral meningitis. However, his condition worsened and he became drowsy and started to have seizures. An MRI two days later showed a large lesion in the temporal lobe. He died nine days after first arriving in hospital.

An autopsy showed "liquefactive necrosis" in part of his brain. According to ScienceDirect, this is where injured tissue gets softer to the point where it "transforms into a pastelike mush or watery debris." The autopsy also showed the acanthamoeba species, allowing them to confirm granulomatous amebic encephalitis.

According to the U.S. Centers for Disease Control and Prevention, most people will be exposed to acanthamoeba at some point in their lives without becoming ill. Granulomatous amebic encephalitis tends to develop in people with weakened immune systems. A more common disease to develop from acanthamoeba infection is acanthamoeba keratitis. This is an infection of the eye that can result in permanent damage to vision and blindness.

Infection with acanthamoeba differs from the more commonly known Naegleria fowleri. This is a brain-eating amoeba found in freshwater sources that attacks the central nervous system, causing inflammation and destruction of the brain and lining.

People who develop granulomatous amebic encephalitis from acanthamoeba infection tend to be diagnosed either in the advanced stages of the disease or after death via autopsy.

"This rare central nervous system infection caused by free-living amoebas, particularly acanthamoeba species, is usually fatal," Schimmel and Mehta wrote in the NEJM report. "The amoeba is transmitted through contact with soil or freshwater. Discussion with the patient's wife revealed only an exposure to soil from potted-plant maintenance."