Antiviral ART in Ants

Social insects live in dense colonies and express many close social interactions, such as food- sharing by mutual regurgitation and exchange of body surface waxes to build a common colony odor. While this physical proximity and close interactions between susceptible hosts should make them prime targets for infectious disease, epidemics occur scarcely in social insect colonies. This is because they cooperate not only in foraging, nest construction and offspring rearing, but also in their disease defence, leading to social immunity. They are therefore not only protected from disease by their individual immune systems, but also by a diversity of sophisticated collective defences, such as joint nest hygiene, sanitary care, infection treatment and social distancing. Whereas honeybees are known to be highly affected by viral disease, ants were long thought to suffer more from fungal and bacterial disease than from viruses. Recent sequencing studies have however shown that many viral diseases are associated with ants, even if they rarely cause disease outbreaks. We currently lack an understanding how ants so efficiently defend themselves against viral disease. Whilst it is known that their individual immune systems show the same (siRNA) response than other insects like fruit flies or mosquitoes, their behavioural responses both at the individual and collective level are little understood. Disease defences can be categorized into Avoidance, Resistance and Tolerance mechanisms, combining to the ART of disease protection. In this project, we will use the ant host viral pathogen system of garden ants and a general insect virus (CrPV) that we recently established in the laboratory, to address all three aspects of disease defence. We will test if ants can prevent infection by avoiding virus-contaminated food uptake, if they can reduce viral load by social interactions, and if living in the social group makes them more tolerant against viral infection. Experimentally, we will observe the ants individual and social behaviour, both when healthy but at risk of contamination, as well as over the course of disease. We will study not only the behavioural repertoire of the infected ants and their nestmates, but will also determine the changes in the whole colony social interaction network upon disease. To do so, we tag each ant individually with a QR code that is read automatedly from videos, providing spatial data and hence proximity information of all colony members over the two weeks of disease progression at a high temporal resolution (2 frames per second). Combined with quantification of the viral load, this will allow us to determine transmission dynamics through the colony. Lastly, we will determine whether nestmates of infected individuals become immunized through exchange of pathogen or immune effector molecules through the colony, and how healthy nestmates may support infected ants to cope with their infection.