Community composition of Ixodid ticks parasitizing American black bears in Missouri, USA

Tick abundance and life-stage segregation on the American black bear (Ursus americanus)

Tick abundance and diagnosed cases of tick-borne diseases have been increasing in the United States. American black bear (Ursus americanus) populations have also been increasing in the eastern United States. As a competent host of several species of ticks and a mammal capable of traveling long distances, the role of black bears as hosts for ticks requires further evaluation. Ectoparasite surveys were conducted on black bears in Pennsylvania to evaluate tick presence, abundance, spatial distribution, and association with Sarcoptes scabiei, the etiological agent of sarcoptic mange, on bears to better understand their role in tick ecology and to improve on-host surveillance techniques. Tick burden was evaluated using standard area sampling (10.16 × 10.16 cm squares) on pre-designated body regions on black bears from June 2018–December 2019. In total, 278 unique individual black bears were evaluated, with all ticks identified as Ixodes scapularis (n = 1976; 76.7% adults, 23.3% immatures). Tick presence differed by body region on bears, with the highest percentage of tick observations located on bear ears and muzzle. Ticks also partitioned on black bears by life-stage, with immature ticks primarily recorded on the lower extremities of bears and adult ticks primarily recorded on the front-quarters of bears. This includes the first known record of I. scapularis larvae parasitizing black bears, and observations of all three mobile life-stages concurrently parasitizing bears. Tick abundance was also statistically significant dependent on season, with the highest abundance of ticks recorded in spring and lowest abundance in fall. Adult ticks were less likely to be present on bears with mange. These data reveal the important role black bears may serve in tick ecology and dispersal as all three mobile life-stages of I. scapularis were found parasitizing a mammal capable of traveling far distances in a region with high numbers of Lyme disease cases.

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First record of Ixodes scapularis larvae parasitizing black bears.

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All three I. scapularis mobile life-stages concurrently parasitizing black bears.

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I. scapularis life-stage segregation on black bears.

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Standardized tick survey findings can be used to improve on-host surveillance.

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Bears with sarcoptic mange less likely to have adult ticks present.

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

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.

PREVALENCE OF BABESIA SPP., EHRLICHIA SPP., AND TICK INFESTATIONS IN OKLAHOMA BLACK BEARS (URSUS AMERICANUS)

American black bears (Ursus americanus) are commonly infested with ticks throughout their range, but there are few surveys for tick-borne disease agents in bears. To characterize tick infestations and determine the prevalence of current infection with Babesia spp. and past or current infection with Ehrlichia spp. in newly re-established populations of black bears in east central and southeastern Oklahoma, US, we identified adult (n=1,048) and immature (n=107) ticks recovered from bears (n=62). We evaluated serum and whole blood samples from a subset (n=49) for antibodies reactive to, and characteristic DNA fragments of, Ehrlichia spp., as well as characteristic DNA fragments of Babesia spp. Amblyomma americanum, the most common tick identified, was found on a majority (56/62; 90%) of bears and accounted for 697/1,048 (66.5%) of all ticks recovered. Other ticks included Dermacentor variabilis (338/1,048; 32.3%) from 36 bears, Amblyomma maculatum (9/1,048; 0.9%) from three bears, and Ixodes scapularis (4/1,048; 0.4%) from three bears. Antibodies reactive to Ehrlichia spp. were detected in every bear tested (49/49; 100%); maximum inverse titers to Ehrlichia chaffeensis ranged from 64-4,096 (geometric mean titer 1,525). However, PCR failed to identify active infection with E. chaffeensis, Ehrlichia ewingii, or an Ehrlichia ruminantium-like agent. Infection with Babesia spp. was detected by PCR in 3/49 (6%) bears. Together these data confirm that tick infestations and infection with tick-borne disease agents are common in bears in the southern US. The significance of these infestations and infections to the health of bears, if any, and the identity of the Ehrlichia spp. responsible for the antibody reactivity seen, warrant further evaluation.