The smell of infection - detecting infectious disease and determining mechanisms underlying the spread of disease in social networks

Social organization facilitates contacts between individuals altering the probability of parasite transmission. Consequently, social animals have evolved mechanisms to mitigate the risks of infection. One mechanism by which parasites may alter contact patterns could be through avoidance of infected individuals by uninfected based on changes in 'smell'. Both non-infectious and infectious diseases can cause a change in volatile organic compounds (VOCs) in many species, including, livestock, wildlife and humans. Studies on female mice demonstrate odour-based discrimination between infected and uninfected males for a range of parasites, including, influenza virus, the protozoan, Eimeria vermiformis, and the nematode, Heligomosomoides polygyrus. Proof of concept in our parasite-cockroach colony system has shown that we can detect distinct scents associated with infection in whole animals. However, parasites may also have evolved to exploit and/or manipulate host behaviour - contact patterns - to improve transmission. As such, epidemics may themselves drive contact network patterns. Apiculture worldwide has been threatened by the emergence of infectious diseases, and associated with effects ranging from reduction in honey productivity to full colony collapse. Using honey bees as a model system we aim to investigate the effect of pathogen load, virulence, mode of transmission on contact networks and the role of 'smell' as a mechanism that alters how epidemics progress in social networks. By combining VOC analysis with detailed behavioural observations, we aim to determine if the odour of infection is a mechanism driving infectious disease dynamics and to tease apart the directional effects of contacts between infected and uninfected individuals - are infected individuals avoided by uninfected individuals thereby reducing parasite transmission. Alternatively, does the parasite manipulate host odour to attract uninfected individuals, so increasing parasite transmission?