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Models used to investigate the relationship between biodiversity change and vector-borne disease risk often do not explicitly include the vector; they instead rely on a frequency-dependent transmission function to represent vector dynamics. However, differences between classes of vector (e.g., ticks and insects) can cause discrepancies in epidemiological responses to environmental change. Using a pair of disease models (mosquito- and tick-borne), we simulated substitutive and additive biodiversity change (where noncompetent hosts replaced or were added to competent hosts, respectively), while considering different relationships between vector and host densities. We found important differences between classes of vector, including an increased likelihood of amplified disease risk under additive biodiversity change in mosquito models, driven by higher vector biting rates. We also draw attention to more general phenomena, such as a negative relationship between initial infection prevalence in vectors and likelihood of dilution, and the potential for a rise in density of infected vectors to occur simultaneously with a decline in proportion of infected hosts. This has important implications; the density of infected vectors is the most valid metric for primarily zoonotic infections, while the proportion of infected hosts is more relevant for infections where humans are a primary host. [ABSTRACT FROM AUTHOR]

Pathogens that can infect multiple host species will have different dynamics than pathogens that are restricted to a single species of host. This article examines the conditions for establishment and long-term population dynamic behavior of pathogens that infect multiple species of hosts. The article attempts to address three major questions in this area: First, under which conditions will increases in the diversity of host species buffer infectious disease outbreaks, and under which conditions will host diversity amplify disease outbreaks? Second, under what conditions is it possible to control an infectious agent by focusing control against only one host species? Third, what role does host species diversity play in maintaining pathogen persistence? The answers to these questions supply some important general insights into the role that biodiversity plays in buffering humans and other species against new and emerging pathogens. [ABSTRACT FROM AUTHOR]