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D.V. Seal, II, M.E. Shoff, A. Rogerson, K. Kessler, S. Schatz; Prevalence of Acanthamoeba and Other Naked Amoebae in South Florida Tap Water . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2409.
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To identify the prevalence of naked amoebae in tap water in south Florida to ascertain the risk for amoebal infections of the cornea in contact lens wearers. This provides the first baseline survey of US water and allows comparisons with other countries worldwide
Over the course of a 2–year period, water samples were collected from sites throughout Broward County, Florida. Because most American homes have mixer faucets and do not have storage tanks, water was sampled in all cases using sterile swabs from the inside surface film of the cistern reservoir tank serving the lavatory. This was supplied by cold municipal mains water. The presence of amoebae in samples was based on an enrichment cultivation method appropriate for Acanthamoeba (and some other amoebae). Amoebae were identified using diagnostic features discernable by light microscopy.
A total of 283 samples were processed and amoebae were noted in 80 of these. Acanthamoeba were found on 8 occasions (2.8 %). The genera Hartmannella and Vahlkampfia, rarely involved in keratitis cases, were found in 3.5 % and 2.8 % of samples, respectively. A total of 19 different naked amoebae were recorded and amoebae (regardless of genus) were present in 19.4 % of all samples.
Previous surveys in England and Korea have shown that acanthamoebae are found in 15 to 30% of tap water samples in the home and have been associated with corneal infection in contact lens wearers who have exposed their lenses to tap water. The incidence of acanthamoebae infection in the US has been lower than that of the UK and it has been postulated that this is related to the lack of a storage water tank in the loft. The low incidence of Acanthamoeba in the South Florida water supply supports this view although a larger, more comprehensive survey encompassing other states is needed. However, the level of treatment of municipal water is clearly not effective at killing amoebal cysts (or trophozoites) as evidenced by the high occurrence of amoebae (19.4 %) in this study.
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