Ixodes scapularis (Acari: Ixodidae) Reservoir Host Diversity and Abundance Impacts on Dilution of Borrelia burgdorferi (Spirochaetales: Spirochaetaceae) in Residential and Woodland Habitats in Connecticut, United States

Abstract

The dilution effect in the zoonotic disease transmission cycle theorizes that an increased diversity of host species will alter transmission dynamics, result in a decrease in pathogen prevalence, and potentially lower human disease incidence. The interrelationship of Borrelia burgdorferi (Johnson, Schmid, Hyde, Steigerwalt, and Brenner) (Spirochaetales: Spirochaetaceae), the etiological agent of Lyme disease (LD), and its primary vector, blacklegged ticks (Ixodes scapularis Say) (Acari: Ixodidae), is a commonly used example of the dilution effect, suggesting that an increased diversity of host species will be found in large, undisturbed forested tracts and lower diversity in fragmented forests. Given that Connecticut woodlands are mature with heavy upper canopies and generally poor habitat quality, we hypothesized there would be higher diversity of host species resulting in lower prevalence of B. burgdorferi in white-footed mice (Peromyscus leucopus Rafinesque) (Rodentia: Cricetidae) in forested residential areas. Using camera and live small mammal trapping techniques, we determined there was a greater richness of reservoir host species, significantly higher encounters with hosts, and significantly lower B. burgdorferi host-infection in residential areas as compared to large, intact forested stands. Furthermore, we determined that the driving factor of pathogen dilution was not host species diversity, but rather overall encounter abundance with alternative hosts, regardless of habitat type. Our study challenges major concepts of the dilution effect within the Connecticut landscape and calls for new managerial actions to address the current state of our woodlands and abundance of host species in the interest of both forest and public health.

Towards common ground in the biodiversity–disease debate

“…Deforestation and urbanization can affect disease risk both directly and indirectly, via impacts on biodiversity, temperature, sanitation, access to health care, human population density, area of impervious surfaces, contact with biodiversity or other factors 28,53 . These multivariate relationships can make it difficult to disentangle the effects of biodiversity per se (see ref.…”

The Ecology and Phylogeny of Hosts Drive the Enzootic Infection Cycles of Hantaviruses

“…These environmental alterations can increase the risk of human interaction with infected rodents [9,92,93,94]. Patch networks have been shown to artificially increase the number of different potential hosts, thereby creating an artificial localized increase in species richness [95,96,97] while decreasing species diversity [39,40,72,79,80,98].…”

Reconciling the Entomological Hazard and Disease Risk in the Lyme Disease System

“…Alternate camps either question the effect’s existence or adhere to the hypothesis that degraded landscapes confer greater zoonosis risk because they support larger populations of generalist, pathogen-competent species, independent of biodiversity [ 22 ]. The potential decoupling of these various effects is supported by a recent study finding greater diversity of reservoir host species, similar white-footed mouse (i.e., competent host) populations, and reduced B. burgdorferi exposure in mice in mixed forest-suburban habitats, as opposed to large, intact forested stands [ 41 ].…”