The Contribution of Wildlife Hosts to the Rise of Ticks and Tick-Borne Diseases in North America

Abstract

Wildlife vertebrate hosts are integral to enzootic cycles of tick-borne pathogens, and in some cases have played key roles in the recent rise of ticks and tick-borne diseases in North America. In this forum article, we highlight roles that wildlife hosts play in the maintenance and transmission of zoonotic, companion animal, livestock, and wildlife tick-borne pathogens. We begin by illustrating how wildlife contribute directly and indirectly to the increase and geographic expansion of ticks and their associated pathogens. Wildlife provide blood meals for tick growth and reproduction; serve as pathogen reservoirs; and can disperse ticks and pathogens—either through natural movement (e.g., avian migration) or through human-facilitated movement (e.g., wildlife translocations and trade). We then discuss opportunities to manage tick-borne disease through actions directed at wildlife hosts. To conclude, we highlight key gaps in our understanding of the ecology of tick–host interactions, emphasizing that wildlife host communities are themselves a very dynamic component of tick–pathogen–host systems and therefore complicate management of tick-borne diseases, and should be taken into account when considering host-targeted approaches. Effective management of wildlife to reduce tick-borne disease risk further requires consideration of the ‘human dimensions’ of wildlife management. This includes understanding the public’s diverse views and values about wildlife and wildlife impacts—including the perceived role of wildlife in fostering tick-borne diseases. Public health agencies should capitalize on the expertise of wildlife agencies when developing strategies to reduce tick-borne disease risks.

Survey of Ticks and Tick-Borne Rickettsial and Protozoan Pathogens in Eswatini

“…Wildlife areas could act as the source of certain ticks and pathogens to domestic animals in the surrounding areas. Wild animals can amplify tick populations and be the source of pathogen infection in ticks [117]. For example, wild ungulates, some of which are carriers of Theileria species, are the preferred hosts of R. appendiculatus and R. simus, but when given the opportunity these ticks will parasitize cattle and can transmit disease causing Theileria species [62].…”

Molecular Detection of Tick-Borne Pathogens in American Bison (Bison bison) at El Uno Ecological Reserve, Janos, Chihuahua, Mexico

“…Wild vertebrates are associated with several enzootic cycles of tick-borne pathogens contributing to the increase of ticks and TBDs in North America, playing an important role in the maintenance and transmission of zoonoses to livestock, humans, and other wildlife [34]. A more than two-fold increase in TBDs has been observed from 2004 (>22,000 cases) to 2016 (>48,000 cases) in the USA alone [35], and up to 476,000 people per year are infected with Lyme disease [36], with reports in both Mexico and USA [37][38][39][40] involving wild animals [41][42][43][44][45].…”

Context-dependent host dispersal and habitat fragmentation determine heterogeneity in infected tick burdens: an agent-based modelling study

“…It has been recognized that the ecological process of dispersal (i.e. individual movement from a natal habitat patch to a new patch) is essential to understand the expanding distributions of species in response to anthropogenic environmental changes [21][22][23], including ticks and tick-borne pathogens [18]. In many spatial models projecting future trends in tick-borne diseases [24][25][26], host dispersal behaviour is linked to landscape characteristics in simplistic ways (e.g.…”

“…It is likely that tick burden patterns are driven by complex interactions with these host-intrinsic and -extrinsic factors [ 11 , 16 ]. Wildlife hosts are an essential component of the enzootic cycle of tick-borne pathogens [ 18 ] and thus any changes in host populations associated with landscape heterogeneity (i.e. landscape composition and configuration), intra- and interspecific interactions (e.g.…”