The hidden menace: how climate change is amplifying Naegleria fowleri risks

Naegleria fowleri, often called brain-eating amoeba, is a shape-shifting flagellate belonging to the phylum Percolozoa[1]. It has the ability to tolerate temperatures as high as 45°C and feeds on bacteria living in freshwater bodies[2]. Although about 40 species of N. fowleri have been identified, it is one of the only species that has the ability to cause Primary Amoebic Meningoencephalitis (PAM)[3]. Symptoms of PAM resemble that of bacterial or viral meningitis, with headache, fever, stiff neck, seizures, and death occurring within a span of 3–7 days after the onset of symptoms[4]. The acute infection develops when Naegleria-infected water is drawn into the nasal passage during recreational activities, such as swimming or bathing[5]. The infection occurs when N. fowleri adheres to the nasal mucosa, moves along the olfactory nerve, and reaches the olfactory bulb, which allows it to spread to other parts of the central nervous system (CNS)[4]. The virulence of N. fowleri is determined by the ability of the organism to attack brain tissue via its food cup, secondly, it secretes a variety of cytolytic chemicals including phospolipolytic enzyme, neuraminidase, phospholipase and acid hydrolase which damages the nerves in the CNS. Similarly, a strong immune response is generated which further damages the CNS[1]. Diagnosis of PAM involves a PCR test that detects N. fowleri in the cerebrospinal fluid (CSF) and tissues, along with immunohistochemical testing and indirect immunofluorescent staining that can detect the amoeba[6]. Laboratory studies usually reveal increased levels of leukocytes along with glycosuria and hyperglycemia. CSF examination shows a predominance of polymorph nuclear cells with an increase in CSF protein levels or a decrease in glucose levels[4].These findings occur due to the disruption in the blood brain barrier and inflammatory reaction which occurs due to the release of various cytolytic enzymes[7]. N. fowleri cases have been reported among 39 different nations. USA, Pakistan, Mexico, India, Czech Republic are one of the few countries who have been impacted the most by this organism[1]. A steady rise in the number of cases has been seen since 2008 in Pakistan (Table 1[1,9] shows the number of cases from 2008-2024 in Pakistan) with the most recent case being that of a 19 year-old male who was admitted to the hospital on 18 August 2024, the patient reported that he had not participated in any activities that involved water except for using water for ablution at the mosque and at home. Another case that was reported showed a 22 year-old factory worker who passed away after visiting the local swimming pool[9]. Although N. fowleri cases have remained low in the recent years, it may be due to under-reporting of cases, avoidance of water activities due to the covid-19 pandemic and increased public awareness. While case numbers have not spiked, climate change is providing environmental conditions that have become more favorable for the growth of N. fowleri. Table 1 - Reported cases of PAM in Pakistan (2008–2024) Year Number of cases 2008 2 2009 11 2010 20 2011 13 2012 22 2013 3 2014 14 2015 13 2016 5 2017 6 2018 7 2019 11 2020 16 2021 1 2022 5 2023 5 2024 5 With the death toll being raised to 5, this editorial aims to shed light on the rise of N. fowleri cases in Pakistan and the role of climate change coupled with government negligence and the need for strict policy implementation. Climate change is an example of one of the biggest challenges of the 21st century, which is associated with an altered eco-system that impacts human health. One of the concerning outcomes of climate change is the proliferation of N. fowleri[10], with the rising temperature, the condition for the growth of N. fowleri in freshwater is becoming increasingly favorable, presenting a significant public health risk[10]. N. fowleri requires a temperature range from 30°C to 40°C to grow; therefore, it is found in water and soil that is warm, such as geothermal sources and places where human activities result in water bodies being warm over extended period[11]. Climate models have predicted a global rise in average temperature leading to drought in certain areas and precipitation in others. Drought may prompt the utilization of rooftop rainwater collection systems, which can become breeding grounds for the amoeba, while increased rainfall can lead to nutrient-rich runoff, promoting its growth in freshwater systems[11]. With the surge in average temperatures, there is growth of cyanobacteria and eubacteria in warm water bodies, which acts as a nutrient source for N. fowleri, increasing its existence in pools and lakes[12]. Notably, N. fowleri has not been isolated from seawater, suggesting that it is unable to thrive in high NaCl concentrations. Nevertheless, it has been detected in brackish water environments, where salinity levels are lower[13]. In vitro studies indicate that at salinity levels above 1.5%, N. fowleri encysts and eventually loses viability[13]. Experimental results further confirm that salt concentration has a negative effect on N. fowleri growth, as the number of viable cells decreases with increasing salinity in both nutrient-rich and nutrient-poor conditions. As expected, trophozoite growth was significantly higher in the bactocasitone and salt culture medium compared to water and salt-incubated conditions. In water with increased salinity, the cell population was reduced by half within 24 hours, although the initial concentration was 100 cells/mL, and trophozoites remained detectable. These findings align with previous studies, which report that N. fowleri can tolerate up to 5 g/L of salt, with viability decreasing as salt concentrations increase. Moreover, all studies indicate that salt concentrations above 15 g/L completely inhibit the growth of N. fowleri trophozoites[13]. N. fowleri has been frequently detected in Karachi’s water supply due to faulty water distribution and chlorination system which in turn leads to cross-contamination between the domestic supply line and sewage water. Pakistan, being a Muslim country, uses water not only for drinking but also to perform ablution, which has now been increasingly linked to N. fowleri infection as contaminated water is often sucked through the nose[14]. N. fowleri has been found in Karachi’s domestic water supply, this is unexpected because amoebas cannot survive in salt water, which is primarily what Karachi’s water is usually. This finding suggests that the strain of N. fowleri found in Pakistan may be distinct from those found elsewhere in the world or may have developed a tolerance to saline environment[15]. Pakistan has a reputation for being a developing nation, with a high percentage of illiteracy and a sizable population living in poverty. The quality of care provided by the health systems is far from sufficient, and many people still cannot access or find health facilities. Epidemics of waterborne illnesses are made worse by the lack of awareness and inadequate sanitation. It is imperative that authorities recognize the widespread health issues and take decisive action to end the suffering[16]. To prevent N. fowleri infection, it is necessary that the general public follows some necessary steps which include using nose clips if swimming in freshwater area, similarly keeping your head above the water while swimming in hot springs, along with using distilled water to rinse your sinuses[16]. Strict policy implementation and chlorine disinfection should occur regularly along with the installation of biofilm monitors to avoid further outbreaks[1]. In Pakistan, majority of people are still unaware of the risks associated with N. fowleri, therefore to prevent future outbreaks it is important to make sure that the general public is aware about the symptoms, preventative measures like chlorinating water, and the importance of early treatment and diagnosis. In addition to holding educational workshops, public health advertising campaigns should be started on social media, radio, newspaper and television. Coordination between different research centers and public health groups should occur to foster solid relationships which is essential to devise plans that include early detection, surveillance, and quick action to protect the general public from the dangers associated with N. fowleri. This makes it easier to pool resources and data and may improve the burden on the healthcare system. Moreover, this decreases the overall disparities in the healthcare system, guaranteeing that everyone has access to the right resources and services[1]. In conclusion, while short-term solutions such as education and chlorine treatments are necessary, more work needs to be done to address the broader issues at play. The government needs to invest in research to close the knowledge gaps surrounding N. fowleri and its relationship with environmental factors. By fostering cooperation across different sectors and disciplines, we can better understand the challenges posed by this pathogen and develop effective strategies to protect public health in the future.