Reservoir host community and vector density predict human tick-borne diseases across the United States

Abstract

In the United States, tick-borne disease cases have tripled since the 1990s and cost upwards of 10 billion USD annually. Tick density and densities and diversity of non-human mammalian reservoir hosts are hypothesized to drive tick-borne disease dynamics and are targets for interventions. Here, we relate human prevalence of four tick-borne diseases (Lyme disease, monocytic ehrlichiosis, granulocytic anaplasmosis, and babesiosis) to tick and reservoir host community data collected by the U.S. National Ecological Observatory Network (NEON) across the contiguous U.S. We show that human disease prevalence is correlated positively with tick and reservoir host densities and negatively with mammalian diversity for Lyme disease and ehrlichiosis, but positively for anaplasmosis and babesiosis. Our results suggest that the efficacy of tick-borne disease interventions depends on tick and host densities and host diversity. Thus, policymakers and disease managers should consider these ecological contexts before implementing preventative measures. SignificanceTick-borne disease incidence has increased in the United States over the last three decades. Because life-long symptoms can occur if reactive antibiotics are not administered soon after the tick bite, prevention is imperative. Yet, control of tick-borne zoonoses has been largely unsuccessful, at least partly because of a limited understanding of the ecological complexities of these diseases, especially non-Lyme disease tick-borne zoonoses. We use continental-scale data to quantify the relationships among four tick-borne diseases and tick and reservoir host communities, revealing that disease incidence is driven by a combination of tick densities and reservoir host densities and diversity. Thus, the efficacy of tick-borne disease interventions is likely dependent on these ecological contexts.