Ecological interactions between hosts and parasites: Salmonella slyly slinks among sixty social sleepies
Bull, M., Godfrey, S. and Gordon, D. (2012) Ecological interactions between hosts and parasites: Salmonella slyly slinks among sixty social sleepies. In: Ecological Society of Australia, Annual Conference, 3 - 7 December, Melbourne, Australia.
Background/question/methods: Conventional models of host-parasite dynamics suggest equal exposure to infection by all members of a population. In reality, the exposure of individual hosts will depend on the mechanism of transmission, and for many parasites social networks in host populations could determine host-parasite dynamics. However, empirical support for social networks as pathways for disease transmission, particularly for indirectly transmitted parasites, is lacking for many wildlife populations. We constructed the social network in a population of Australian sleepy lizards (Tiliqua rugosa). Data loggers on each of 60 lizards recorded GPS locations every 10 minutes of every day through the 120 day lizard activity season. We deduced social contact from the proximity of pairs of lizards in synchronised location records, and used the frequency of contacts to derive weighted network edges between pairs of lizards. We found multiple genetic strains of the enteric bacterium Salmonella enterica within the population.
Results/conclusions: Pairs of lizards that hosted the same bacterial genotypes were more strongly connected in the social network than were pairs of lizards that did not. In contrast, there was no significant association between spatial proximity of lizard pairs and shared bacterial genotype infections. These results provide strong correlative evidence that bacterial infections are passed around the social network, rather than that adjacent lizards are picking up the same infection from some common source. They provide a foundation for new understanding of host-parasite dynamics and for the control of exotic pathogens that threaten wildlife populations.
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