Many factors influence Ixodes scapularis tick populations, including the presence of the hosts. This tick requires blood meals from vertebrate hosts to complete its lifecycle and has been found on 125 vertebrate species. Hosts, in turn, vary in their permissiveness (i.e. the ability for ticks to successfully feed). This results in heterogeneity in tick infestation and adds further complexity in understanding the mechanisms that influence I. scapularis abundance throughout the North America. We aimed to understand tick population dynamics by examining the prevalence and intensity of tick infestation in relation to species diversity via meta-analysis. To accomplish this, we conducted a literature search with the search terms: Ixodes dammini and Ixodes scapularis. Prior to 1996, I. scapularis and I. dammini was considered as two distinct species. We extracted raw data on the prevalence and intensity of infestation and used general linear regression to determine the relationships between measures of species diversity and host specific I. scapularisprevalence and intensity. More specifically, we look at how increases in species diversity influenced tick burdens on vertebrate hosts that are both highly permissive for the tick and highly competent for zoonotic pathogens such as Lyme disease.
Results/Conclusions
We found 22 articles, in which researchers examined the I. scapularis prevalence and intensity. This dataset includes 62 total host species with community species richness ranging from 2 to 33 species. As species diversity increases, the prevalence of I. scapularis on all hosts increases (R2= 0.204, p<0.001), however, there is no relationship between I. scapularis intensity (R2= 0.1, p>0.05). The prevalence of ticks on Peromyscus leucopus (White-footed mouse) increased with species diversity (R2=0.313, p<0.001); and the intensity of infestation decreased (R2=0.034, p<0.05). Furthermore, we found that with increased species diversity, tick prevalence on highly permissive hosts increases (R2=0.22, p<0.001). Increased species richness is associated with decreased tick intensity (R2=0.064, p<0.01). Overall, we found that with more hosts in a community, there is a larger proportion of hosts that have ticks, but fewer ticks per host. These results provide moderate support for the dilution effect mechanism: Encounter Reduction, where added hosts lower the probability that ticks encounter reservoir hosts. With the assumption that increased biodiversity adds less competent hosts for a zoonotic pathogen, these results support the conclusion that increasing vertebrate biodiversity could be an effective strategy for reducing human disease risk.