Figure 1.

Theoretical framework describing the spread of a tick population and its infection with a pathogen in a system of amplification, dilution and reproduction hosts. Solid red lines indicate the transmission cycle of the pathogen circulating in the tick and host populations. Solid grey and blue lines show the death and birth processes, respectively, in the tick and host populations. Solid green lines correspond to the transport of ticks by migratory birds or terrestrial hosts. Reproduction hosts are not competent hosts for transmitting the pathogen to ticks. See electronic supplementary material, appendix S2, for details on the Allee effect.