Tuesday, December 02, 2025

Ants signal deadly infection in altruistic self-sacrifice

Early disease detection in the colony: Ants signal incurable sickness to save others

Institute of Science and Technology Austria

Unpacking of a fatally-infected pupa from its cocoon — image:
When an ant pupa signals its imminent death caused by an incurable infection, worker ants unpack it from its cocoon and disinfect it, leading to its demise.
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Credit: © Christopher D. Pull / ISTA

Ant colonies operate as tightly coordinated “superorganisms” with individual ants working together, much like the cells of a body, to ensure their collective health. Researchers at the Institute of Science and Technology Austria (ISTA) have now discovered that terminally ill ant brood, like infected cells, release an odor signaling their impending death and the risk they pose. This sophisticated early warning system facilitates rapid detection and removal of pathogenic infections. The study was published in Nature Communications.

In many social animals, group members try to conceal their sickness to prevent social exclusion. Ant brood, however, take the opposite approach. When facing an incurable infection, ant pupae actively emit an alarm signal that warns the colony of the contagion risk they are about to pose.

Upon receiving the signal, worker ants respond swiftly by unpacking the terminally ill pupae from their cocoon, creating small openings in their body surface and applying their antimicrobial poison, formic acid, which functions as a self-produced disinfectant. While this treatment immediately kills the pathogens multiplying inside the pupa, it also results in the pupa’s own demise.

“What appears to be self-sacrifice at first glance is, in fact, also beneficial to the signaler: it safeguards its nestmates, with whom it shares many genes. By warning the colony of their deadly infection, terminally ill ants help the colony remain healthy and produce daughter colonies, which indirectly pass on the signaler’s genes to the next generation,” explains Erika Dawson, first author of the study and former postdoc in the Social Immunity’ research group headed by Sylvia Cremer at ISTA.

Their collaborative study with chemical ecologist Thomas Schmitt from the University of Würzburg in Germany describes this altruistic disease signaling in social insects for the first time. If a fatally ill ant were to conceal its symptoms and die undetected, it could become highly infectious, endangering not only itself but the entire colony. Active signaling of the incurably infected instead allows effective disease detection and pathogen removal by the colony.

Altruistic self-sacrifice

At the colony level, ants function as a “superorganism,” effectively forming a single living entity. While one or more queens are responsible for producing offspring, the non-fertile workers take on all tasks related to colony maintenance and health. This mirrors cell specialization in the human body, where germline cells in the reproductive organs are dedicated to offspring production while somatic cells carry out all other essential functions.

In both organisms and superorganisms, reproductive and non-reproductive components are fully interdependent, with each essential for the survival of the whole. Cooperation is therefore crucial. Much like cells in our body, individual ants collaborate closely, even engaging in altruistic self-sacrifice for the benefit of the colony.

Find-me and eat-me signal

Why would a complex early warning system evolve if sick animals can simply isolate themselves from the colony? “Adult ants that approach death leave the nest to die outside the colony. Similarly, workers that have been exposed to fungal spores practice social distancing,” explains Cremer. “Yet, this is only possible for mobile individuals. Ant brood within the colony, like infected cells in tissue, are largely immobile and lack this option.”

Body cells and ant brood, such as developing pupae, both rely on external assistance to safeguard the colony. Intriguingly, both address this challenge in similar ways: they emit a chemical signal that attracts either the body’s immune cells or the colony’s workers, allowing these helpers to detect and eliminate them as potential sources of infection. Immunologists call this the “find-me and eat-me signal.”

“The signal must be both sensitive and specific,” explains Cremer. “It should help to identify all terminally-sick ant pupae but be precise enough to avoid triggering the unpacking of healthy pupae or those capable of overcoming the infection with their own immune system.” What properties must such a signal have to achieve this level of precision?

Changes in pupal scent profile

Schmitt, whose research focus is on chemical communication in social insects, explains that workers specifically target individual pupae out of the brood pile. “This means the scent cannot simply diffuse through the nest chamber but must be directly associated with the diseased pupa. Accordingly, the signal does not consist of volatile compounds but instead is made up of non-volatile compounds on the pupal body surface.”

In particular, the intensity of two odor components from the ants’ natural scent profile increases when a pupa is terminally ill. To test whether this odor change alone could trigger the workers’ disinfection behavior, the researchers transferred the signal odor to healthy pupae and observed the workers’ reaction.

“We extracted the smell from the signaling pupae and applied it to healthy brood,” Cremer says in describing the experimental approach. The results were conclusive: Transfer of the signal scent alone was sufficient to induce unpacking by the ants, revealing that the altered body odor of fatally-infected pupae serves the same function as the ‘find-me and eat-me’ signal of infected body cells.

Signaling only in uncontrollable cases

According to Dawson, the fascinating aspect is that ants do not signal infection indiscriminately. “Queen pupae, which have stronger immune defenses than worker pupae and can limit the infection on their own, were not observed to emit this warning signal to the colony,” she explains. “Worker brood, on the other hand, were unable to control the infection and signaled to alert the colony.”

By signaling only when an infection becomes uncontrollable, the sick brood enable the colony to respond proactively to real threats. At the same time, this approach ensures that individuals capable of recovery are not sacrificed unnecessarily. “This precise coordination between the individual and colony level is what makes this altruistic disease signaling so effective,” Cremer concludes.

Information on animal studies

To better understand fundamental processes, for example in the fields of behavioral biology, immunology or genetics, the use of animals in research is indispensable. No other methods, such as in silico models, can serve as an alternative. The animals are collected, reared, and used in the experiments in accordance with strict legal regulations.

Journal

Nature Communications

DOI

10.1038/s41467-025-66175-z

Method of Research

Experimental study

Subject of Research

Animals

Article Title

Altruistic disease signalling in ant colonies

Article Publication Date

2-Dec-2025

Ant pupae represent the developmental stage between the larval and adult stages. Immobile, they are unable to react to infection by leaving the nest. Instead, when infected and nearing death, they emit an odor signal alerting the worker ants that they will become a highly contagious infection risk that may threaten the health of the entire colony.

Credit

© Line V. Ugelvig & Barbara Leyrer / ISTA

Ant pupae represent the developmental stage between the larval and adult stages. Immobile, they are unable to react to infection by leaving the nest. Instead, when infected and nearing death, they emit an odor signal alerting the worker ants that they will become a highly contagious infection risk that may threaten the health of the entire colony.

Credit

© Line V. Ugelvig & Barbara Leyrer / ISTA

Worker ants organize the colony brood into separate nest chambers. Larvae, which have hatched from eggs and require frequent care, are grouped and fed often. Pupae, in contrast, do not eat and are protected from desiccation by their cocoons, so they only need occasional inspections.

Credit

© ISTA

Ant experiments in the lab. Ant pupae are collected in a dish, and individually infected on glass plates by gently rolling them through a spore suspension using soft forceps. Infected pupae emit chemical signals of their fatal condition when workers are nearby.

Credit

© Sylvia Cremer / ISTA

Worker ants organize the colony brood into separate nest chambers. Larvae, which have hatched from eggs and require frequent care, are grouped and fed often. Pupae, in contrast, do not eat and are protected from desiccation by their cocoons, so they only need occasional inspections.

Credit

© ISTA

Destructive disinfection [VIDEO]

The video shows worker ants inspecting their brood, selecting a pupa, and initiating the destructive disinfection process.

Credit

Rising complexity in pediatric patients is reshaping hospital care

University of Rochester Medical Center

A new national analysis shows that over the past two decades, inpatient care for children with complex chronic conditions (CCCs) has become far more intensive—and is now overwhelmingly concentrated in urban teaching children’s hospitals. The authors argue that these shifts necessitate changes in pediatric training, staffing, and Medicaid policy.

Analyzing U.S. hospital discharge data from 2000 to 2022, the study found that children with at least one CCC now account for more than two-fifths of pediatric bed days and nearly three-fifths of hospital charges. Examples include children with cerebral palsy, congenital heart defects, and genetic disorders, and although these children represent a small share of the overall pediatric population, their hospital stays are longer, more complex, and increasingly involve multiple co-occurring conditions and reliance on medical technologies such as feeding and breathing tubes. Children with multiple CCCs drove most of the growth, and discharges for those with three or more CCCs increased more than threefold over the study period.

“Over the last 20 years, the inpatient pediatric caseload has shifted, the children we see in the hospital are far more complex, and almost all children with complex conditions seek care in specialty children’s hospitals,” said Nathaniel Bayer, MD, associate professor at the University of Rochester’s Golisano Children’s Hospital and lead author of the study which appears in JAMA Network Open. “That concentration of very sick children has real implications for where care happens, who delivers it, and how it is paid for.”

From a small group to a large share of inpatient resources

The study grew out of a national collaboration among pediatric health services researchers from the University of Rochester, Boston Children’s Hospital, Johns Hopkins University, the University of Vermont, Children’s Mercy Hospital in Kansas City, the University of Toronto, and the Children’s Hospital Association. Jay Berry, MD, MPH, with Boston Children’s Hospital and Harvard University, is the senior author of the study. The new research builds on a similar analysis conducted 15 years ago.

Using the Kids’ Inpatient Database series and national weighting, the research team estimated trends in discharge rates, bed days, and hospital charges for children with and without CCCs. Between 2000 and 2022:

The rate of hospital discharges for children with at least one CCC rose by more than 24 percent, while the discharge rate for children without CCCs fell by more than 9 percent.
Children with CCCs increased their share of total pediatric bed days and, despite consisting of 22 percent of all discharges, represent 40 percent of bed days and almost 60 percent of hospital charges.
The number of children with two CCC diagnoses increased by 60 percent, and the number with three or more increased by 340 percent.

“What jumped out was the rise in hospital resource use by children with multiple, interacting chronic conditions. These are kids who require highly coordinated, intensive inpatient care,” said Bayer.

Implications for children’s hospitals

The study’s findings raise operational and policy concerns. The authors note that most of these complex hospitalizations are covered by Medicaid, and current reimbursement levels frequently do not reflect the true costs of the care provided. “Children’s hospitals are providing the majority of this care, but payment rates aren’t keeping up. That mismatch contributes to closures of pediatric units in community and rural hospitals and centralizes care in academic centers with unsustainable financial models,” said Bayer.

The study also highlighted implications for the workforce and training. “Residency and fellowship programs need to adapt so future pediatricians and subspecialists are prepared to care for these medically complex children. The inpatient experience is changing—residents may care for sicker, more complex patients—and training must address that reality.”

Systemic and federal responses are required

The paper calls for a multi-pronged response: hospitals should evaluate team structures and staffing models to ensure safe, coordinated inpatient care; training programs should update curricula and clinical experiences; and policymakers should consider Medicaid policy changes that acknowledge the distinct needs and costs of medically complex children.

“We need pediatric-specific Medicaid policies and payment structures that recognize these children aren’t the same as the average adult Medicaid population,” said Bayer. “If we want to sustain high-quality pediatric inpatient care, reimbursement and workforce investments have to follow from the public and private payers.”

The study contributes to a growing body of evidence documenting the evolution of pediatric inpatient care. The research team hopes their findings will inform hospital planning, training reforms, and policy discussions at the state and federal levels.