Using network modeling to investigate rabies spread through a raccoon population

Background/Question/Methods

The number and duration of contacts made between individuals in wildlife populations can be highly heterogeneous. These differences can be at the individual level, with some individuals tending to make more contacts than others.  Also, there can be dramatic changes in contacts throughout the whole population, for example during different seasons. This heterogeneity in contact patterns is important when considering the spread of an infectious disease through a population.

Contact networks are a powerful tool for understanding the transmission of diseases through populations where contact structure is variable. Network modeling provides a means of capturing the complexity of interaction patterns, which other types of models can fail to do.

We used raccoon social interaction data, collected using proximity logging collars in suburban Illinois, to construct adjacency matrices specifying the connections made between raccoons over one year. These matrices formed the basis of our network model, which we used to simulate the spread of rabies through the raccoon population. Raccoons act as a reservoir for rabies, with raccoon rabies epidemic across the eastern United States.

Results/Conclusions

Raccoon interaction patterns were highly seasonal, so we created separate networks for the breeding and non-breeding seasons. In addition, we observed two types of contacts made by the raccoons: a) long-term, stable interactions that occurred regularly throughout a season, and b) short-term, random contacts. Both types of interactions were found to have a significant impact on disease dynamics, and more specifically, on the incidence and spread of rabies throughout a raccoon population. These results have important implications for potential rabies control measures.