A meta-analysis suggesting that the relationship between biodiversity and risk of zoonotic pathogen transmission is idiosyncratic

Abstract

Zoonotic pathogens are significant burdens on global public health. Because they are transmitted to humans from non-human animals, the transmission dynamics of zoonoses are necessarily influenced by the ecology of their animal hosts and vectors. The 'dilution effect' proposes that increased species diversity reduces disease risk, suggesting that conservation and public health initiatives can work synergistically to improve human health and wildlife biodiversity. However, the meta-analysis that we present here indicates a weak and highly heterogeneous relationship between host biodiversity and disease. Our results suggest that disease risk is more likely a local phenomenon that relies on the specific composition of reservoir hosts and vectors, and their ecology, rather than patterns of species biodiversity.

Figure 1

Distribution of Fisher's Z‐values (with 95% CI) for studies describing relationships between biodiversity and disease risk. Dotted line represents mean Fisher's Z‐value from random effect model for all studies combined, and dashed line represents mean Fisher's Z‐value from fixed‐effect model for all studies combined.

Figure 2

Distribution of P‐values for studies describing relationships between biodiversity and disease risk. The size of the point is proportional to the sample size, and the vertical line indicates the conventional level of statistical significance, P = 0.05.

Figure 3

Relationship between effect size (Fisher's Z) and standard error for studies describing relationships between biodiversity and disease risk (dotted line shows mean Fisher's Z from random effect model). Points should be in the shape of an inverted funnel if there is no publishing bias. Gray shades (from darker to lighter) represent the confidence intervals around zero corresponding to 0.1 > P > 0.05, 0.05 > P > 0.01, and P < 0.01. Circles = hantavirus, triangles =  WNV, squares = tick‐borne, diamond = plague. Open plotting symbols indicate the three unpublished studies.