Figure 4. Forest plot of the worldwide prevalence of free-living amoebae
in swimming pools and recreational waters.
The global prevalence of FLA in swimming pools and recreational waters
considering studies published up to 2010 (1977-2010) was considerably
higher 51.54% (95% CI = 36.65 – 66.29) than in studies published
after 2010 (>2010-2021) 37.95% (95% CI = 30.34 – 45.86).
Considering the continents covered by the selected studies, the highest
prevalence 59.52% (95% CI = 31.12 – 84.81) was reported in America
and the lowest 34.65% (95% CI = 26.08 – 43.75) in Asia. Among the
countries from which more than one study was included, Malaysia had the
highest prevalence of FLA in swimming pools and recreational waters
89.33% (95% CI = 70.71 – 99.12), and the lowest prevalence 27.91%
(95% CI = 18.73 – 38.13) was recorded in Taiwan. Considering the
different sampling sources, the highest prevalence of FLA 52.27% (95%
CI = 14.55– 88.50) was obtained in indoor heated pools, and the lowest
prevalence 34.75% (95% CI = 20.85– 50.14) was obtained in other
recreational waters. The analysis of studies that used only
morphological methods to identify free-living amoebae showed the highest
prevalence 56.41% (95% CI = 30.09 – 80.92), the lowest prevalence
22.32% (95% CI = 12.28 – 34.33) was obtained from studies based only
on molecular methods (PCR), an intermediate prevalence value 39.94%
(95% CI = 33.64 – 46.41) was obtained by analyzing studies that
simultaneously used morphological and molecular methods (Table 2).
The subgroup analysis revealed that there were statistically significant
differences between the overall prevalence of FLA in water sources and
year (X 2 = 223.0, P < 0.001),
continent (X 2= 71.9, P = 0.002), country
(X 2= 46.4, P < 0.001), sample source
(X 2 = 21.8, P = 0.003) and diagnostic method
(X 2 = 274.0, P < 0.001) (Table 2).
Table 2. Subgroup analysis of FLA in water sources