Health Australia (Commonwealth Union) – To prevent the risk of acquiring an Acanthamoeba infection, swimmers are advised by researchers to remove their contact lenses before entering the water.
In a collaborative study involving UNSW Sydney, the University of Technology Sydney (UTS), and the University of the West of Scotland, scientists have detected the presence of Acanthamoeba, a microorganism capable of causing an exceptionally rare yet potentially vision-threatening eye infection, in seawater at four coastal sites in New South Wales (NSW). These findings are detailed in the Science of The Total Environment.
Acanthamoeba keratitis (AK) occurs when Acanthamoeba infiltrates the cornea, the transparent outer layer of the eye. This organism sustains itself by feeding on bacteria and corneal cells, leading to inflammation and damage to the cornea. Eradicating the infection poses challenges as there are currently no drugs effective against both the cyst and trophozoite life stages of Acanthamoeba. Consequently, AK can result in vision loss, with approximately one-quarter of AK patients experiencing less than 25 percent of their vision or even going blind.
Though AK is exceedingly rare, estimated to affect between 10 and 40 Australians each year, it is crucial to remain vigilant, particularly for individuals who wear contact lenses. Acanthamoeba from the environment can become trapped between the contact lens and the eye, paving the way for infection.
Binod Rayamajhee, the first author of the study, who is pursuing a PhD focused on Acanthamoeba at UNSW Medicine & Health, emphasizes that wearing contact lenses is the primary risk factor, especially if individuals come into contact with contaminated water or combine their contact lenses with it.
Previous research by UNSW researchers revealed that approximately one-third of tap water samples from bathroom sinks in greater Sydney contained Acanthamoeba. Washing contact lenses in tap water presents a significant risk for AK, as does showering and swimming while wearing contact lenses.
Mr. Rayamajhee notes that two earlier studies, one in Sydney and another in Melbourne, indicated that nearly 20 percent of patients contracted AK after swimming in seawater or freshwater with their contact lenses. However, this study marks the first investigation into the levels of Acanthamoeba in Australian aquatic environments.
Throughout their investigation, the researchers gathered water samples from four coastal sites in New South Wales (NSW). These specific locations are frequented by individuals engaging in recreational activities such as swimming and kayaking, and they undergo routine water quality assessments to ensure safety. The proximity of these sites to urbanized areas introduces the possibility of water contamination, which, in turn, can create conditions conducive to the proliferation of Acanthamoeba.
“We chose coastal sites to look for the presence of Acanthamoeba species that we knew experienced high levels of seasonal variability in environmental conditions, as well as intermittent impacts from stormwater and sewage contamination. We aimed to identify any links between environmental factors and the presence of the organism,” explained co-author Professor Justin Seymour, the lead of the Ocean Microbiology Group at UTS.
Between August 2019 and July 2020, the research team conducted multiple sampling sessions at each of the designated sites, with the exception of March and April 2020 due to COVID-19 restrictions. During these sessions, they meticulously assessed various water parameters, including temperature, dissolved oxygen concentration, pH, and salinity. Furthermore, the researchers extracted DNA from the water samples, allowing them to quantify the levels of Acanthamoeba and bacterial communities present.
Remarkably, Acanthamoeba was detected in water samples collected from all four coastal sites, with approximately 38 percent of the samples overall yielding positive results.
The prevalence of Acanthamoeba displayed variations across the sites. At the most heavily urbanized site, more than half of the samples exhibited the presence of Acanthamoeba. In contrast, at the least urbanized site, Acanthamoeba was found in approximately 32 percent of the samples.
The study unveiled a noteworthy correlation between the presence of Acanthamoeba and heightened levels of the intl1 gene within the water samples. The intl1 gene serves as an indicator of contamination resulting from human activities in aquatic environments.
