The importance of dog population contact network structures in rabies transmission

This is the final version of the article. Available from Public Library of Science via the DOI in this record.Data Availability: All relevant data are within the paper and its Supporting Information files.Canine rabies transmission was interrupted in N'Djaména, Chad, following two mass vaccination campaigns. However, after nine months cases resurged with re-establishment of endemic rabies transmission to pre-intervention levels. Previous analyses investigated district level spatial heterogeneity of vaccination coverage, and dog density; and importation, identifying the latter as the primary factor for rabies resurgence. Here we assess the impact of individual level heterogeneity on outbreak probability, effectiveness of vaccination campaigns and likely time to resurgence after a campaign. Geo-located contact sensors recorded the location and contacts of 237 domestic dogs in N'Djaména over a period of 3.5 days. The contact network data showed that urban dogs are socially related to larger communities and constrained by the urban architecture. We developed a network generation algorithm that extrapolates this empirical contact network to networks of large dog populations and applied it to simulate rabies transmission in N'Djaména. The model predictions aligned well with the rabies incidence data. Using the model we demonstrated, that major outbreaks are prevented when at least 70% of dogs are vaccinated. The probability of a minor outbreak also decreased with increasing vaccination coverage, but reached zero only when coverage was near total. Our results suggest that endemic rabies in N'Djaména may be explained by a series of importations with subsequent minor outbreaks. We show that highly connected dogs hold a critical role in transmission and that targeted vaccination of such dogs would lead to more efficient vaccination campaigns.This work was supported by the Swiss National Science Foundation under grant number 310030 160067 and the UK National Institute for Health Research (NIHR) Health Protection Research Unit (HPRU) in Modelling Methodology (HPRU-2012-10080) at Imperial College London, in partnership with Public Health England. The Freiwillige Akademische Gesellschaft (http://www.fag-basel.ch/) and the Albert Heim Stiftung (http://www.albert-heim-stiftung.ch/cms/) have contributed to the development of the geo-located sensors