Climate Crisis And Disease: Warmer Temperatures Exacerbate Threat From N. fowleri

Climate Crisis And Disease: Warmer Temperatures Exacerbate Threat From N. fowleri
The impact of heat waves on disease-causing agents, encompassing a diverse array of microbes, cannot be understated. Climate change, specifically elevated temperatures, play a pivotal role in facilitating the dissemination of diseases that afflict the human population, with bacteria, parasites, viruses, and fungi being chief culprits. Bacterial infections exemplify the repercussions of this phenomenon, as pathogenic strains exploit the conducive environment engendered by rising temperatures. Furthermore, the proliferation of parasitic diseases like Naegleria fowleri is exacerbated under such conditions.

The onset of heat waves brings about an environment conducive to the proliferation and transmission of disease-causing agents, underscoring the significance of comprehending and addressing the associated health risks in the face of escalating temperatures. Recent reports of three fatalities in Karachi have once again thrust the spotlight on Naegleria fowleri, an uncommon yet perilous organism colloquially known as the brain-eating amoeba. Naegleria is an ameba commonly found in warm freshwater and only one species of Naegleria infects people, called Naegleria fowleri. Flourishing in warm freshwater ecosystems, this amoeba possesses the capability to infiltrate the human body through the nasal passage. Upon entry, it traverses to the brain, instigating the deterioration of cerebral tissue. Importantly, this organism enters the body through the nasal passage, and contrary to popular belief, drinking contaminated water does not result in infection.  The city of Karachi has witnessed an alarming upsurge in casualties attributed to Naegleria fowleri, accentuating the urgency of delving into the medical facets of this amoeba and comprehending its propensity to thrive amidst sweltering weather conditions.

Hot climatic conditions are directly associated with the prevalence of Naegleria fowleri infections. Rising temperatures and extended hot spells cause water temperatures to rise and water levels to drop, providing the ideal conditions for the amoeba's growth. Given that it prefers warm water, the summertime, when temperatures are greater, becomes especially favorable for its growth and spread.

The impact of rising temperatures on the proliferation of Naegleria fowleri is evident and supported by scientific research. The temperature of the water plays a crucial role in creating a favorable environment for this heat-loving organism. Naegleria fowleri flourishes in warm waters, with optimal growth occurring at temperatures above 30°C, and the ability to tolerate temperatures as high as 46°C. This thermophilic characteristic makes it highly adaptable and capable of spreading in a warming climate. The warmer waters provide an ideal habitat for the amoeba to reproduce and thrive, particularly in Karachi where temperatures are rising. Several studies have demonstrated a clear correlation between the increase in cases and casualties associated with Naegleria fowleri and the rise in temperature. This evidence emphasizes the need to understand and address the implications of rising temperatures on the spread of this dangerous organism.

The first case of N. fowleri was reported in Pakistan in 2008, with a total of 114 deaths reported between 2008 and 2023, as depicted in the graph.

N. fowleri death
Graphical representation of deaths caused by N. fowleri since 2008-2023 in Pakistan. Source: media reports

Climate change, characterized by rising temperatures, and changes in seasonal precipitation rates will impact lakes, rivers and streams. Reduced water quantities result from evaporation and less precipitation during heatwaves and dry weather conditions. As a result, the concentration of the harmful Naegleria fowleri rises in the remaining water, increasing the risk to people. Warm freshwater, within the optimal temperature range for Naegleria fowleri, provides an ideal environment for the amoeba to multiply.

Real-world examples from Karachi corroborate the argument that rising temperatures contribute to the increased presence of Naegleria fowleri. Research shows that, the city experiences prolonged periods of high temperatures, causing its freshwater bodies to become hotter. These elevated temperatures create the perfect breeding ground for N. fowleri, elevating the risk of infection.

Climate change is affecting people's health – a clear argument is the link between rising temperatures and the spread of Naegleria fowleri. The risk of Naegleria infection cannot be eliminated, but preventive measures are necessary to reduce it. For example, recreational activities such as swimming in warm freshwater should be avoided during high temperatures. Apart from this, care should also be taken while using water for ablution rituals.

The author is an urban planner and geographer who is also Associate Director of the Karachi Urban Lab at IBA.