In order to protect the unique fauna of the Galapagos Islands, it is critical that we understand how and when parasites spread throughout the archipelago. There are several key components of host-parasite dynamics that influence parasite spread, including the basic reproductive rate of the parasite, host density, transmission mode, and host movement, among other factors. Host movement could be especially important in determining parasite spread in island systems like the Galapagos, because parasites are not always able to move larger distances unaided. Because some hosts (and vectors) show population genetic structure within the Galapagos Islands, we can make inferences about potential parasite spread from knowledge of host population connectivity. In this chapter, we review patterns of population connectivity in Galapagos vertebrates (hosts), arthropod vectors, and parasites, focusing on population genetic studies. Hosts with little to no population genetic structure and high rates of inferred movement (e.g., Galapagos fur seal, Galapagos penguin, great frigatebird, Galapagos dove, small ground finch, small tree finch, large tree finch) are the most likely to spread parasites. More research is needed on parasite spread, particularly studies that simultaneously estimate population connectivity of both host (or multiple hosts, including vectors) and parasite.