Free-living amoebae, a diverse group of unicellular protists, are notorious for their dual nature—flourishing in environmental reservoirs such as lakes, rivers, and tap water, yet sporadically turning pathogenic when they invade human hosts. These amoebae, including genera like Acanthamoeba, Naegleria, and Balamuthia, are capable of causing severe and often fatal infections, particularly in immunocompromised individuals. The study delves deeply into the extent to which these microorganisms contaminate Iranian water sources, offering a rigorous synthesis of decades of research.

The analysis harnesses data from multiple regional studies, spanning urban tap water supplies, natural freshwater bodies, and recreational water environments. Remarkably, the results indicate a pervasive presence of FLA, with significant variations based on geographical location, seasonality, and water type. This heterogeneity underscores the complex ecological niches that support amoebic life cycles, as well as the differential risks they pose to human populations.

Water infrastructure and environmental management practices emerge as critical factors influencing FLA prevalence. The study reveals that conventional water treatment methods may not always effectively eliminate these resilient organisms. Their cystic forms, in particular, exhibit remarkable resistance to chlorination and other disinfection procedures, raising pressing questions about current public health safeguards. This resilience necessitates a reevaluation of water purification standards in regions vulnerable to FLA contamination.

One striking feature of the meta-analysis is its methodical approach to identifying gaps in surveillance and reporting. By collating data from various provinces in Iran, the researchers illuminate the uneven distribution of research efforts and monitoring initiatives. Some areas, especially rural and underserved regions reliant on untreated surface water, show alarmingly high FLA detection rates. This unevenness signals an urgent need for coordinated nationwide monitoring protocols.

Notably, the study draws attention to the prevalence of Acanthamoeba species, which are implicated in keratitis, a painful and vision-threatening eye infection often associated with contact lens use. This epidemiological data emphasizes the direct risk that contaminated water supplies pose to ocular health, an often overlooked dimension of FLA infections. Furthermore, the evidence suggesting the presence of Naegleria fowleri, the infamous “brain-eating amoeba,” in recreational waters highlights the necessity for public awareness campaigns about safe water practices.

Beyond just enumeration, the research delves into molecular identification techniques that have revolutionized FLA detection. Polymerase chain reaction (PCR) and sequencing methodologies have provided more accurate and rapid identification of amoebic species in water samples. This technological progress has enabled the study to disentangle ambiguous historical data, paving the way for standardized diagnostic protocols applicable not only in Iran but internationally.

The public health ramifications of widespread FLA presence in water are profound. These organisms can bypass traditional bacterial and viral filtration systems, making immunocompromised and pediatric populations particularly vulnerable. The study calls for integrated approaches combining environmental science, microbiology, and clinical surveillance to mitigate these risks effectively. It also advocates for ongoing research into new disinfection technologies capable of targeting resilient amoebic cysts and trophozoites.

Understanding the environmental ecology of FLA also helps explain their persistence and geographic distribution. The meta-analysis synthesizes data correlating temperature, water pH, nutrient levels, and microbial flora with amoebic populations, revealing environmental parameters conducive to their proliferation. Such ecological insights provide a predictive framework for identifying potential hotspots and timing preventive interventions to coincide with peak amoebic activity.

In light of climate change and evolving water use patterns, the relevance of this research cannot be overstated. Increasing temperatures and fluctuating rainfall patterns potentially expand the ecological niches inhabitable by thermophilic species like Naegleria fowleri. Consequently, water sources previously considered low risk may become reservoirs for dangerous pathogens. This emerging threat necessitates adaptive water safety management and surveillance systems that can respond dynamically to environmental changes.

The study also enhances our understanding of amoebae as vectors for other pathogens. FLAs can harbor bacteria such as Legionella pneumophila and Mycobacterium species intracellularly, acting as “Trojan horses” that shield these pathogens from treatment and facilitate transmission. By characterizing FLA prevalence, this research indirectly contributes to broader infection control strategies targeting not just amoebae but associated microbial communities.

Importantly, this meta-analysis exemplifies the critical role of systematic reviews in consolidating fragmented data to inform evidence-based policy. Through stringent inclusion criteria and quantitative methods, the researchers provide a robust estimate of FLA prevalence that can drive regulatory updates concerning water quality standards. Their findings serve as a clarion call for intensified investment in water infrastructure improvements and public health education in Iran and similar contexts worldwide.

Moreover, the insights offered by this study deepen the global dialogue on environmental pathogens rarely captured in routine risk assessments. By spotlighting the silent but significant threat posed by free-living amoebae, the research invites interdisciplinary collaboration spanning parasitology, environmental science, and public health policy. The confluence of these fields promises innovative solutions for early detection, prevention, and treatment of amoebic infections.

The implications for clinical practitioners are equally vital. The meta-analysis reinforces the necessity of heightened vigilance and improved diagnostic acumen for amoebic infections, which often masquerade as nonspecific neurological or ocular conditions. Enhanced awareness and diagnostic capacity can facilitate timely intervention, improving patient outcomes in a domain where morbidity and mortality rates remain unacceptably high.

In conclusion, Shamsi and colleagues’ systematic review and meta-analysis mark an essential milestone in deciphering free-living amoebae’s shadowy presence in Iran’s water reservoirs. Their work not only reveals a silent environmental menace but also lays foundational knowledge imperative for protecting public health. As our global water systems face mounting biological threats, such comprehensive scientific endeavors are crucial to anticipating and neutralizing emerging infectious risks.

Subject of Research: Prevalence and distribution of free-living amoebae (FLA) in various water sources in Iran

Article Title: Prevalence of Free-Living Amoebae in Various Water Sources in Iran: A Systematic Review and Meta-Analysis

Article References:
Shamsi, L., Mamizadeh, M., Mohammadi, M.R. et al. Prevalence of Free-Living Amoebae in Various Water Sources in Iran: A Systematic Review and Meta-Analysis. Acta Parasit. 70, 220 (2025). https://doi.org/10.1007/s11686-025-01154-4

Image Credits: AI Generated

DOI: https://doi.org/10.1007/s11686-025-01154-4

A recent comprehensive bibliometric study, analyzing 1,281 peer-reviewed publications indexed in the Web of Science from 2003 to 2023, has illuminated the trajectory and evolution of PFAS research in drinking water. This study goes beyond isolated investigations by integrating pollution pathways, monitoring techniques, and treatment strategies into a unified conceptual framework. Such an approach identifies critical knowledge gaps and technological bottlenecks that hamper effective PFAS management, including the challenges associated with detecting and removing short-chain and ether-based PFAS compounds, as well as the complex issue of safely handling concentrated treatment residuals.

Research activity on PFAS in drinking water can be segmented into three distinctive phases. The initial phase from 2003 to 2008 was characterized by low publication output, averaging four papers annually. During this period, foundational theoretical concepts were established, laying the groundwork for subsequent studies but leaving many practical aspects unexplored. The gradual development phase, spanning 2009 to 2016, saw a steady increase in research momentum with an average of 31 articles per year. While this period expanded understanding of PFAS properties and environmental distribution, Hhealth correlations remained ambiguous, limiting comprehensive risk assessment frameworks.

A seismic shift in PFAS research occurred from 2017 onward, marked by rapid growth accounting for over 79% of the total publications in this field. This surge was largely in response to heightened regulatory scrutiny, exemplified by the 2017 U.S. Environmental Protection Agency (EPA) health advisories, which intensified the urgency for concrete solutions. This phase underscored the escalating scientific and regulatory efforts to understand not only PFAS occurrence but also their fate, transport, and toxicity in aquatic systems. The rapid escalation of research culminated in an era of innovative analytical methodologies optimized for sensitivity and specificity.

Looking ahead, logistic modeling predicts a continuation of this exponential growth trend in PFAS research, with projections estimating nearly 7,700 cumulative publications by 2030 accompanied by over 240,000 citations. The environmental sciences and engineering domains dominate the research landscape, with notable contributions from the United States, China, and Sweden, reflecting these countries’ commitment to addressing PFAS challenges through advanced scientific inquiry and technological innovation.

PFAS contamination arises primarily through surface runoff, soil leaching, and atmospheric deposition. Each pathway contributes to the dispersal of these chemicals into groundwater and surface water sources, complicating source-tracking and remediation efforts. Surface runoff often transfers PFAS from industrial or firefighting sites into adjacent water bodies, soil leaching facilitates contamination of aquifers, and atmospheric deposition spreads volatile PFAS compounds over wide geographic regions.

Analytical detection of PFAS has traditionally depended on sophisticated laboratory-based techniques such as liquid chromatography–tandem mass spectrometry (LC-MS/MS). This method remains the gold standard for quantifying PFAS at trace levels due to its sensitivity and molecular specificity. Nevertheless, recent advancements have introduced portable high-selectivity sensors capable of in situ monitoring, offering the potential for real-time field deployment. These emerging technologies promise to dramatically enhance spatial and temporal resolution of PFAS monitoring, which is critical for risk identification and effective mitigation.

The removal of PFAS from drinking water streams continues to present formidable challenges. Current treatment methodologies, including activated carbon adsorption, ion-exchange resins, membrane filtration technologies, and advanced oxidation processes, each come with inherent limitations and trade-offs relating to cost, efficacy, and operational complexity. Activated carbon, while widely used, struggles with short-chain PFAS. Ion-exchange methods demonstrate improved selectivity but are costly and generate concentrated waste brines. Membrane technologies provide physical separation yet require energy-intensive operations. Advanced oxidation is effective for organic contaminants but less so for highly stable PFAS molecules.

This multifaceted problem demands a paradigm shift from fragmented scientific inquiries to integrated, system-level approaches. The coupling of laboratory-based LC-MS/MS analytical platforms with field-deployable sensor networks, supported by standardized data protocols, is essential to close existing monitoring gaps. Such integration would improve detection of recalcitrant short-chain and ether-based PFAS, whose risk profiles are not yet fully understood. Additionally, addressing the treatment bottleneck necessitates development of multistage “intercept-and-destroy” treatment trains that synergistically combine adsorption, degradation, and residuals management steps under cost-performance metrics that facilitate technology scaling and regulatory acceptance.

Moreover, the safe management of concentrated treatment residuals involves environmental and engineering challenges to prevent secondary contamination. Residual concentrations of PFAS in spent media from adsorption or ion-exchange units demand innovative disposal or destruction technologies capable of breaking the strong carbon-fluorine bonds characteristic of these substances. Thermal destruction methods, plasma treatments, and advanced catalytic processes are under investigation but require optimization for economic and environmental sustainability.

This comprehensive bibliometric synthesis ultimately calls for enhanced global collaboration and policy coordination to bridge scientific advancements with practical implementation. Only by aligning efforts across analytical chemistry, environmental engineering, regulatory policy, and public health can the pervading threat of PFAS contamination in drinking water be effectively mitigated. The pressing need for tiered regulatory standards, robust data sharing networks, and economically viable technologies underscores the critical nexus of science, technology, and governance in safeguarding water quality against these persistent contaminants.

In essence, the ongoing and projected explosion of research reflects an urgent collective response to a complex environmental health challenge. Future progress hinges on multidisciplinary integration that marries detection, treatment, and management strategies within an overarching, systematized framework. By accelerating these convergent pathways, the scientific community aims to translate burgeoning knowledge into tangible outcomes—empowering stakeholders with practical tools to achieve safer drinking water and protect public health from the insidious legacy of PFAS pollution.

Subject of Research: Not applicable

Article Title: Insights into the fate of per- and polyfluoroalkyl substances (PFASs) in drinking water based on bibliometric analysis: research hot spots, challenges, and trends

Web References: http://dx.doi.org/10.1016/j.wateco.2025.100017

Image Credits: Chong Liu, et al

Keywords: Technology, Engineering, Computer science, Biomedical engineering, Environmental engineering, Chemical engineering