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Ant doctors amputating an infected limb
Beneath the forest floor, where the bustling societies of ants thrive, an extraordinary healthcare system unfolds—one that blends chemical warfare, social organization, and even contagious resilience to fend off disease. With colonies that can house up to half a million workers, species like the thatch ant and the black garden ant have developed intricate methods to protect themselves from the devastating effects of pathogens. Their tactics mirror some of the most sophisticated human strategies, from antiseptics and quarantine to vaccination and social distancing, all scaled down to a miniature yet highly organized world.
Medical Disinfection
Take the thatch ant, Formica paralugubris, for example. Living in densely populated colonies of several hundred thousand workers makes them particularly vulnerable to outbreaks, but they have mastered an advanced form of disinfection. When disease looms, these tiny chemists mix formic acid from their venom glands with antimicrobial tree resins to create a potent antiseptic blend that coats the nest, turning it into a chemically fortified fortress. This concoction not only keeps the nest clean but also burns away harmful microbes on ants returning from outside foraging, ensuring that the whole colony remains safeguarded. The mixture significantly boosts the antifungal properties of the resin, rendering the nest nearly impervious to pathogens like Metarhizium brunneum, a fungus that can wipe out entire insect populations.
Formica paralugubris with resin, by Jonghyun Park
Some species, such as harvester ants, produce natural antibiotics like albomycin, which can effectively combat drug-resistant bacteria such as MRSA. These findings have spurred researchers to explore the potential of ant-derived compounds as a new class of treatments for human superbugs.
Amputations and Surgery
However, even on an individual level, ants have learned to control disease throughout the body. Researchers conducted behavioral and microbiological experiments to understand the response of C. floridanus workers to injured nestmates. They found that when a worker's leg was injured at the femur, other ants quickly amputated the damaged limb by biting through the leg at its base. This swift response drastically improved the injured ant’s chances of survival, compared to those whose wounds were left untreated. However, when injuries were more distal—closer to the foot—nestmates responded differently. Instead of amputating, they focused their attention on wound care at the injury site.
Amputation seemed to only make a difference in survival when it occurred immediately after pathogen exposure. Delaying the procedure left the ants vulnerable to infection. Detailed micro-CT scans revealed that the key to the ants' decision-making might lie in hemolymph (ant blood) circulation. Muscles responsible for hemolymph flow were concentrated in the femur, suggesting that femur injuries may slow the spread of pathogens long enough for nestmates to perform life-saving amputations.
Social Distancing
During disease outbreaks, ants employ an approach perhaps familiar to us: social distancing. Researchers at the University of Bristol found that when these ants detect an infection in the colony, they quickly reconfigure their nest’s layout to limit the spread of disease. After introducing fungus-infected ants to laboratory colonies, scientists observed that healthy ants began segregating foragers, which are more likely to be exposed to disease, and the queen and brood to the more protected core, protected areas. These changes created natural barriers, much like human quarantine measures, to minimize contact between healthy and sick individuals.
Scientists used individual QR codes to track the behaviour of ants in response to the presence of an infectious disease. (Photo: Timothée Brütsch, University of Lausanne)
Immunization
Yet, while the infected ants are distanced to some degree, they aren’t completely isolated or left to fend for themselves. In fact, ants engage in a behavior known as "social immunization," where they deliberately spread a diluted form of the pathogen throughout the colony. When an ant licks an infected nestmate to remove fungal spores, some of those spores transfer to the grooming ant’s body in small, manageable amounts. This low-level exposure acts as a kind of vaccination, priming the immune systems of the healthy ants and preparing them to fight off the pathogen. Sylvia Cremer and her team at the Institute of Science and Technology Austria found that this behavior helps establish a colony-wide immune response, where increased production of antifungal proteins boosts resilience across the entire group. As a result, despite the presence of the fungus, only about 2 percent of the ants in socially immunized colonies succumb to infection—a remarkably low casualty rate for a tightly-knit society.
The Ant Social Immune System
The possibility that solutions to modern medicine’s most pressing challenges might come from the world of ants underscores the untapped pharmacological promise that lies in nature.
This complex interplay between chemical defenses and social behaviors shows that ants are not just individual insects fighting for survival but participants in a highly coordinated "social immune system." In this system, each ant’s actions contribute to the health of the colony as a whole. For instance, when black garden ants reposition the queen and brood away from infected areas, they create a dynamic, living architecture that evolves in response to disease threats. This adaptable environment could inspire new approaches in human architecture and public health, potentially leading to buildings and spaces designed to limit the spread of infectious diseases by changing layout or airflow patterns in real-time.
Ant societies also challenge our assumptions about quarantine and isolation.
While humans typically separate the sick entirely, ants adopt a more balanced approach that combines distancing with low-level, controlled exposure to pathogens. Their habit of redistributing fungal spores across the colony not only helps build immunity but also shares the burden of infection, demonstrating a kind of contagious resilience or "infectious selflessness." By ensuring that each member of the colony has some exposure to the pathogen, the ants collectively strengthen their defense against future outbreaks.
In essence, ants have turned their colonies into fortified strongholds and clinics, where chemical defenses, architectural adjustments, and social behaviors intertwine to create a resilient social immune system. Their ability to adapt and respond to disease threats with such precision offers insights far beyond entomology, hinting at new ways humans could think about managing public health and preventing the spread of infections.
From the chemical-coated tunnels of the thatch ant to the strategic nest designs of the black garden ant, the lessons from these tiny doctors of the natural world might hold the key to keeping even the largest populations healthy. The ants have been perfecting their craft for millions of years, and now, it seems, it’s our turn to learn from their miniature marvels of medicine.
Further Reading
Sebastian Stockmaier et al.,Infectious diseases and social distancing in nature. Science 371, eabc8881(2021).DOI:10.1126/science.abc8881
Frank, Erik.T. et al., Wound-dependent leg amputations to combat infections in an ant society. Current Biology, Volume 34, Issue 14, 3273 - 3278.e3
Pull CD, Cremer S. Co-founding ant queens prevent disease by performing prophylactic undertaking behaviour. BMC Evol Biol. 2017 Oct 13;17(1):219. doi: 10.1186/s12862-017-1062-4. PMID: 29025392; PMCID: PMC5639488
Milutinović, B. et al. (2020) ‘Social immunity modulates competition between coinfecting pathogens’, Ecology Letters, 23(3), pp. 565–574. doi:10.1111/ele.13458.
Brütsch T, Jaffuel G, Vallat A, Turlings TC, Chapuisat M. Wood ants produce a potent antimicrobial agent by applying formic acid on tree-collected resin. Ecol Evol. 2017 Mar 6;7(7):2249-2254. doi: 10.1002/ece3.2834. PMID: 28405288; PMCID: PMC5383563.
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