Animal Science

Lessons from the insect world: How do ant colonies fight disease?

A trail of sugar ants (Camponotus fulvopilosus) in the Karoo National Park. Ants are thought to have evolved around 168 million years ago and became ecologically dominant about 60 million years ago. Image: Brigitte Braschler, Iimbovane Outreach Project

By Dr David Phair

As the Covid-19 pandemic makes its impact known throughout the world, we are being forced to come to terms with how our modern way of living contributes to the spread of pathogens. We live in densely packed cities full of interacting individuals, each going about their own business as part of the greater economy.

When you consider humankind in this light, it is hard not to draw parallels with the highly social insects such as bees and ants in particular. They, like us, live in densely populated cities and towns, nests packed with hundreds to millions of individuals all working to support the colony. They too must communicate and provide services. Some are food producers, some manage resources and others sweep the proverbial streets.

Like humankind, they too are at high levels of risk when it comes to dealing with the threat of disease and epidemics. Ants, however, have been dealing with this problem for the last 100 million years. This has given them ample time to develop mechanisms for fighting diseases, such as acidic secretions that are antimicrobial, much like the hand sanitisers we are now using every day.

Researchers have found that ants and other social insects use a collection of social behaviours to fight disease in the colony. Called “social immunity”, it is a rapidly growing area of research worldwide. Some of these behaviours can be costly, like a doctor working on the frontlines of a Covid-19 outbreak, putting the individual at risk while providing the colony with protection against disease.

My research into social immunity looked at how three South African ant species respond to the threat of disease: the well-known large pugnacious ants (Anoplolepis custodiens), yellow-haired sugar ants (Camponotus fulvopilosus), and the common fierce ants (Tetramorium sericeiventre). While they all responded differently to disease exposure, none of them implemented a full lockdown.

From quarantine to doctor’s visits

The large pugnacious ants (A. custodiens) used a wide range of social immunity mechanisms to prevent infections and relied heavily on social-based interventions. For example, they implement a form of quarantine where ants that were exposed to the infection did not enter the chambers where the queen and the young stayed; they also generally remained in the nest chamber closest to the colony exit. This species also implemented more frequent and intense allogrooming, their form of a doctor’s visits, where nestmates clean and disinfect the potentially exposed individuals. The parallel I see here is with those countries with very high population densities, where it is important to work together to prevent the spread of disease. In a similar fashion to how some countries have implemented strict lockdowns, these ants prevent risky individuals from interacting with colony members who are essential to the functioning of the colony.

A lab colony of yellow-haired sugar ants. Photo: Dr David Phair

Social distancing and communal disinfection

The yellow-haired sugar ants (C. fulvopilosus) did not show any form of quarantine. They did, however, make use of social distancing. Out of the three species we assessed, these ants engaged with each other the least, relying instead on a self-care approach to prevent the spread of a pathogen. But this was not their only defence against disease. Sugar ants are well known for their liberal use of formic acid, a potent antimicrobial substance, to defend the nest and we expect that they use this substance to manage exposure to pathogens. In one instance, we observed a novel behaviour where an individual applying formic acid would cause surrounding ants to also apply their own formic acid, possibly a form of communal disinfectant.

Innate immunity coupled with grooming

The common fierce ants (T. sericeiventre) appeared to use a measured approach relying on both individual responses to infection and group responses like allogrooming. Out of our three species, they appeared to have the best innate immunity against the infection. We think this may be a result of previous experience with disease, as they live in the wettest areas of the studied species, and for soil dwelling ants, wetter environments harbour more microbial organisms, some of which can be pathogenic. This species response can be paralleled with countries that have experienced previous epidemics and so could react quickly and effectively to minimise the spread of the Covid-19 infection.

What do ant colonies do differently?

While there are many parallels between ants and humans, there are also distinct differences. Many humans can be described as altruistic, willing to put their life on the line to protect others. However, compared to ants we have much to learn. Most ants will do their utmost to protect the colony and there is little to no room for selfish ambition in the functioning of a colony. Those that try to forge their own path are heavily policed. This enables ant colonies to remain relatively unaffected by large scale epidemics, despite their potentially high level of risk.

Another distinct difference is the fact that communication between colonies of ants is rare and epidemics, to my knowledge, do not develop into pandemics. Considering how interconnected humankind is, however, the risks of pandemics are much greater. What can we, therefore, learn from how ants and social insects fight disease? And could we incorporate this knowledge into strategies to combat Covid-19 and any future pandemics? 

Ant wisdom offers hope

Our research does provide some hope, as all three ant species, working together as a colony, were able to mitigate and overcome the effect of exposure to the disease. Taking a lesson from our ants, we should put our own interests aside, cooperate and do what is necessary to mitigate the spread and impact of the Covid-19 pandemic. Ant wisdom suggests that is the right thing to do.

*        Dr David Phair is a postdoctoral fellow in the research group of Prof Theresa Wossler in the Department of Botany and Zoology at Stellenbosch University. His research was funded by the South African Centre for Epidemiological Modelling and Analysis (SACEMA) and a grant from the National Research Foundation (NRF).

Stellenbosch University myrmecologist David Phair. Photo: Nikki Phair

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