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. 2017 Dec 15;58(3):401-412.
doi: 10.1093/ilar/ily001.

Species Identity Supersedes the Dilution Effect Concerning Hantavirus Prevalence at Sites Across Texas and México

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Free PMC article

Species Identity Supersedes the Dilution Effect Concerning Hantavirus Prevalence at Sites Across Texas and México

Matthew T Milholland et al. ILAR J. .
Free PMC article

Abstract

Recent models suggest a relationship exists between community diversity and pathogen prevalence, the proportion of individuals in a population that are infected by a pathogen, with most inferences tied to assemblage structure. Two contrasting outcomes of this relationship have been proposed: the "dilution effect" and the "amplification effect." Small mammal assemblage structure in disturbed habitats often differs from assemblages in sylvan environments, and hantavirus prevalence is often negatively correlated with habitats containing high species diversity via dilution effect dynamics. As species richness increases, prevalence of infection often is decreased. However, anthropogenic changes to sylvan landscapes have been shown to decrease species richness and/or increase phylogenetic similarities within assemblages. Between January 2011 and January 2016, we captured and tested 2406 individual small mammals for hantavirus antibodies at 20 sites across Texas and México and compared differences in hantavirus seroprevalence, species composition, and assemblage structure between sylvan and disturbed habitats. We found 313 small mammals positive for antibodies against hantaviruses, evincing an overall prevalence of 9.7% across all sites. In total, 40 species of small mammals were identified comprising 2 taxonomic orders (Rodentia and Eulipotyphla). By sampling both habitat types concurrently, we were able to make real-world inferences into the efficacy of dilution effect theory in terms of hantavirus ecology. Our hypothesis predicting greater species richness higher in sylvan habitats compared to disturbed areas was not supported, suggesting the characteristics of assemblage structure do not adhere to current conceptions of species richness negatively influencing prevalence via a dilution effect.

Figures

Figure 1
Figure 1
Sites sampled across Texas and México where small mammals were trapped and tested for hantavirus antibodies between January 2011 and January 2016. At each site, sylvan and disturbed habitats were sampled concurrently.
Figure 2
Figure 2
Sites sampled across Texas and México where small mammals were trapped and tested for hantavirus antibodies between January 2011 and January 2016. At each site, sylvan and disturbed habitats were sampled concurrently. Circle size represents abundance (N) of small mammals at each site. Red wedges show the proportion of individuals seropositive for hantavirus antibodies at each site. Sites numbers are listed in white and follow a north-south latitudinal gradient (see Figure 1).
Figure 3
Figure 3
Sites sampled across Texas and México where small mammals were trapped and tested for hantavirus antibodies between January 2011 and January 2016. At each site, sylvan and disturbed habitats were sampled concurrently. Here, circle size is based on species richness (S) of small mammals captured at each site. Red wedges show the proportion of taxonomic genera seropositive for hantavirus antibodies at each site. Sites numbers are listed in white and follow a north-south latitudinal gradient (see Figure 1).
Figure 4
Figure 4
Bar graph showing hantavirus prevalence across sites sampled across Texas and México where small mammals were trapped and tested for hantavirus antibodies between January 2011 and January 2016. At each site, sylvan and disturbed habitats were sampled concurrently. Red bars indicate seroprevalence of small mammal assemblages sampled in disturbed habitats, while sylvan samples are displayed in blue. Black numbers at the top of each bar represent species richness of the assemblage. Orange dashed-line indicates the mean of seroprevalence across all sites.

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