Social insects cooperate in curbing the spread of pathogens. Their systems of behavior could help human societies battling pandemics of our own.
Governments worldwide are encouraging people to maintain space between one another to prevent the spread of the virus; it's easy to draw parallels with scientists' insect subjects. Insect research shows what some scientists say could help humans imagine a more pandemic-resilient society. As with humans, fending off disease can be a tall order for social insects—a category that includes termites, ants, and many species of bees and wasps. Insect workers swap fluids and share close quarters. In most species, there is heavy traffic into and out of the nest. Some ant colonies are as populous as New York City.
Over the past three decades, researchers have explored how that might occur, mapping the myriad ways colonies avoid succumbing to disease. Some of those methods can seem alien. Others, including simple immunization-like behavior and forms of insect social distancing, can seem eerily familiar. They form a kind of parallel epidemiology that might provide insights for human societies battling pathogens of their own–even if, so far, human epidemiologists don’t pay much attention to the field.
While Social Insects have been the subject of intense scientific scrutiny for more than a century, the threat of pathogens and other parasites, researchers say, was long overlooked.
Observers of social insects have long known that the animals keep their homes meticulously clean. Workers deposit waste and dead bodies outside the nests. Social insects groom each other, and often themselves, frequently. But recent research has documented other adaptations that also fight infection. Some ants, for example, harvest antimicrobial tree resins and spread them around their nests, a process researchers have described as “collective medication.” Social insect species also secrete a pharmacopeia of microbe-killing compounds, which they apply to their bodies and surfaces.
Grooming, too, has unexpected benefits. As some ants clean each other, they transfer small amounts of pathogens to their nestmates.
Individuals may get sick. But they can also offer the care, food, and knowledge that saves our lives.
For social insect researchers, one elusive question is whether, like human public health departments that impose coronavirus quarantines on households and restaurant occupancy limits, social insect societies change their interactions to make it harder for diseases to spread—a phenomenon sometimes called organizational immunity. Most social insect colonies have complex systems for dividing up tasks. Some workers may care for the queen, feed larvae, stand on guard duty, or forage. Decades of research have analyzed the division of labor regarding task efficiency. But starting in the early 2000s, mathematical models suggested that those social divisions might also slow down infections. By interacting only with a few designated workers, a queen may be less likely to get sick.
Testing some of those theories on actual colonies, researchers say, has been difficult. But the advent of automated insect tracking systems has opened up new possibilities, allowing researchers to construct detailed pictures of who interacts with whom inside an ant colony, for example.
To map an ant's social network, researchers glue tiny Q.R. code tags, some smaller than a square millimeter, to ants’ thoraxes.
Modular networks alone could slow the spread of infection in the colony. A human virus, after all, spreads more quickly through a lively party of 100 people than it does among 20 isolated clusters of five friends, who mostly hang out with each other.
But the more significant breakthrough came after the team exposed individuals in 11 colonies to the deadly ant-infecting fungus Metarhizium brunneum, with the other 11 serving as controls. Once the ants sensed the pathogens, those networks changed: their modularity increased, and different task groups in the colony interacted less than before. Foragers exposed to the fungus demonstrated fewer contacts. Even unexposed ants started interacting differently, keeping a higher proportion of their connections to smaller circles of nestmates.
Human societies are unlikely to adopt cannibalism as a public health strategy. But the basic principle may be relevant during the coronavirus pandemic. The lesson from the termites could be separate the kids. The kids are going to be a massive puddle of transmission that’s going to infect everybody. Don’t do that.
This thinking has led scientists to build models to find the most effective way to distribute medicines amid a flu epidemic.