Viral pathogens and social immunity in ants

Viruses are important infectious pathogens that regularly cause epidemics, especially in dense, large societies, e.g., periodic flu outbreaks in humans, the recent Ebola outbreak in Africa or the bird flu, killing hundreds of thousand birds in Asia. To understand epidemics it is important to put the disease dynamics in a social context. In large, dense societies viruses can spread rapidly from one host to another. Social insects, like ants, termites and some wasps and bees life in huge, complex societies with sometimes millions of closely related individuals. Nestmates within a colony engage in frequent intimate interactions for food and information exchange. All these factors contribute to an optimal environment for viruses spread and persist and frequent epidemics would be expected. However, in reality, recurrent disease outbreaks appear to be very rare events. What are the causes for the unusual resistance of insect societies to viral epidemics? The project Viral disease and social immunity in ants will shed light on this question. To elucidate this question we will establish a model system in the laboratory, using ant societies for our investigations. For a first impression we will determine the viruses infecting our ant model species. We will further infect ants with the newly discovered viruses and track the spread of virus within an individual ant using cutting edge molecular and imaging techniques. However the main focus of the project will be on the spread among colony members, where modern video recording techniques paired with software based tracking systems will give an in-depth insight into the interactions of infected ants with their healthy nestmates. This will help us to understand behaviours performed by the colony members to prevent the spread of a viral disease throughout the colony. Infected ants may isolate themselves from the rest of the colony to prevent the transmission of virus to other colony members. Alternatively the infected ants might produce and spread agents, which might protect other ants from a viral infection. This would be comparable to a vaccination in humans; interacting ants would vaccinate nestmates by interacting with them and therefore protect the whole colony from a fatal epidemic outbreak. Our results will not only give an exciting insight into the social component of the immune defences of insects, but might also help to get a better understanding of their exceptional ecological success.

Viruses are important infectious pathogens that regularly cause epidemics, especially in dense, large societies, e.g., periodic flu outbreaks in humans, the recent Ebola outbreak in Africa or the bird flu, killing hundreds of thousand birds in Asia. To understand epidemics it is important to put the disease dynamics in a social context. In large, dense societies viruses can spread rapidly from one host to another. Social insects, like ants, termites and some wasps and bees life in huge, complex societies with sometimes millions of closely related individuals. Nestmates within a colony engage in frequent intimate interactions for food and information exchange. All these factors contribute to an optimal environment for viruses to spread and to persist and frequent epidemics would be expected. However, in reality, recurrent disease outbreaks appear to be very rare events. What are the causes for the unusual resistance of insect societies to viral epidemics? The project Viral disease and social immunity in ants was tackling these questions by establishing a model system in the laboratory, using ant societies for our investigations. We determined the viruses infecting our ant model species and were able to detect infective, formerly unknown viruses. We established a model with a well-studied virus of solitary insects in our social insects to study the spread among colony members through interactions of infected ants with their healthy nestmates. We have now evidence that healthy ants avoid food contaminated with virus. This may be a first and efficient layer of disease prevention. If we nonetheless infect an ant with the virus we are able to detect small particles in the food ants share amongst each other which are typically involved in an anti-viral immune response of an individual ant. What remains to be seen is the specificity of those particles. In case they are specific, antiviral and can be shared amongst colony members this would be the first account of passive immunization in insects.