Global warming has caused higher temperatures which can accelerate the spread of antibiotic resistance. — PIXABAY/Pexels
On the African continent, there is currently a man-made phenomenon that is already causing more deaths than malaria, tuberculosis, and AIDS combined. The horror story is antimicrobial resistance (AMR) and it is getting increasingly scarier as it spreads around the world.
The causes of AMR are well-known and indisputable. The roots of AMR can be traced back to the misuse and overuse of antibiotics in human medicine and agriculture. Every time an antibiotic is used, there is a risk that bacteria surviving the treatment will develop resistance. This phenomenon is exacerbated by the frequent and often unnecessary prescription of antibiotics for viral infections against which they are ineffective.
Making matters infinitely more disastrous is the agricultural sector, which contributes very significantly to this problem by using antibiotics not only to treat sick animals but also to promote growth and prevent disease in healthy ones. This practice is particularly prevalent in high-density farming operations, where antibiotics are used to prevent diseases that could easily spread in crowded conditions.
But most people would probably know all this already, and some would also know about a Lancet study that estimated that in 2019, AMR directly killed at least 1.27 million people, and contributed to a further 4.95 million human deaths around the world due to weakened health effects caused by drug-resistant pathogens.
Some people are also aware that by 2050, the number of human deaths directly due to AMR is estimated to be around 10 million per year, dwarfing the total number of Covid-19 deaths of around seven million in the four years since 2020.
Climate change makes AMR worse, much worse
What is much less known is how global climate warming actively and dangerously exacerbates the spread and development of resistant pathogens. Here are some of the climate change factors directly linked to the expansion of AMR:
Higher ambient temperatures around the world are associated with increased bacterial growth rates, which can accelerate the development and spread of antibiotic resistance. Warmer temperatures can enhance the rate at which bacteria replicate and mutate, potentially leading to more frequent occurrences of resistance.
For instance, studies have shown that an increase in temperature is correlated with higher antibiotic resistance rates in pathogens such as Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus. The last-mentioned bacteria is more commonly known as MRSA (methicillin-resistant Staphylococcus aureus), and that was what killed my father.
Regions with warmer climates have higher antibiotic use in both humans and livestock. — PIXABAY/Pexels
Climate change leads to various environmental changes, such as altered rainfall patterns, increased frequency of extreme weather events, and also huge shifts in established ecosystems. These changes affect the quality and quantity of critical resources such as water and arable land, resulting in vast floods and huge searing droughts. And these in turn have huge impacts on food security, and the distribution of disease vectors.
The incidence of waterborne, foodborne, and other vector-borne diseases such as from insects and other people and livestock rises exponentially. The higher occurrence of these diseases often results in increased use of antibiotics, which can further drive the development of resistance.
Higher temperatures have been linked to an increase in healthcare-associated infections. Warmer climates can create conditions that favor the survival and transmission of resistant bacteria within healthcare settings, leading to more frequent and severe outbreaks of infections that are difficult to treat. Healthcare settings include hospitals, indoor and outdoor clinics, community centres, and even homes.
Regions with warmer climates tend to have higher rates of antibiotic use in both humans and livestock. This is partly because warmer temperatures often lead to more infections, which can also be more aggressive, prompting the more frequent use of antibiotics. The increased use of antibiotics in these regions contributes to the natural selection and evolutionary factors that drive the development of AMR, sometimes at rates impossible to achieve without global warming and related human pressures.
Climate change exacerbates pollution, including the presence of contaminants like microplastics in natural water bodies. These contaminants can harbour and spread antibiotic-resistant bacteria. Additionally, the increased use of personal protective equipment and biocides during events like the Covid-19 pandemic has led to higher concentrations of these substances in the environment, further promoting the spread of AMR.
In a warmer climate, yields from livestock farms would often tend to drop, possibly from less or poorer-quality feed. This results in more use of antibiotics to maintain the health and growth of livestock. In short, antibiotics are not used to treat sick animals, but to promote weight gain and bulk, especially in concentration farms with a high density of livestock.
The droppings from such livestock can contain as much as 80% of the antibiotics applied and such waste is often allowed to run off into the land or waterways. This means AMR is spread into other wildlife with unknown chaotic consequences; for example, insects feeding on such wildlife and then biting humans can transmit diseases with no known means of treatment.
Global warming is already creating huge swathes of what is termed Non-Habitable Zones (NHZ) for humans. These NHZs are either too wet, too dry, or too unstable (e.g. due to extreme weather events such as hurricanes, floods, etc) to support human settlements or farms.
Closer contact between humans and animals can cause an increase in zoonotic diseases. — RACHAEL CLAIRE/Pexels
This has the impact of forcing humans and livestock to live in closer proximity in the remaining areas of the planet which are still considered habitable and productive. This closer contact between humans and animals increases significantly the risk of zoonotic and common vector-borne diseases, such as those transmitted by insects.
This closer proximity between humans and animals can lead to more frequent use of antibiotics in both human and veterinary medicine, contributing to the spread of AMR.
Summary
The relationship between AMR and climate change can now be seen as complex and multifaceted. Higher temperatures, environmental changes, increased antibiotic use, and pollution all evidentially contribute to the acceleration of antimicrobial resistance.
The irony is that the use of antibiotics in livestock and humans will very likely increase in the foreseeable future, even as their effectiveness at preventing diseases fade, and often fade quite rapidly. People simply have very few tools to defend against AMR.
Compounding this problem is the lack of new antibiotics available to treat microbial diseases. One of the last-resort classes of antibiotics is called carbapenems, but already pathogens such as Klebsiella pneumoniae and Acinetobacter baumannii are already resistant to carbapenems.
Clearly, addressing this issue is beyond the capabilities of most ordinary people, apart from consumers refusing to buy and eat food that harbour AMR. Overall, this issue requires a comprehensive global approach that includes better management of the use of antibiotics, better environmental protection, more intensive medical research into newer antibiotics, and inter-governmental cooperation to mitigate the impacts of climate change on public health.
And doing nothing about AMR is really not an option. If current trends for AMR continue, some estimates suggest that by 2050, AMR could directly cause 10 million or more deaths each year globally.
There may be a further extrapolated 39 million deaths arising from severe health issues due to exposures to drug-resistant pathogens, and this figure would surpass the global mortality rates of cancer, diabetes, tuberculosis, malaria, etc, combined. The economic cost may spiral to $100 trillion, and it can happen at a time when the world may be struggling with huge economic losses and social disruptions due to extreme weather events.
The views expressed here are entirely the writer’s own.
