Resource selection by New York City deer reveals the effective interface between wildlife, zoonotic hazards and humans.

Although the role of host movement in shaping infectious disease dynamics is widely acknowledged, methodological separation between animal movement and disease ecology has prevented researchers from leveraging empirical insights from movement data to advance landscape scale understanding of infectious disease risk. To address this knowledge gap, we examine how movement behaviour and resource utilization by white-tailed deer (Odocoileus virginianus) determines blacklegged tick (Ixodes scapularis) distribution, which depend on deer for dispersal in a highly fragmented New York City borough. Multi-scale hierarchical resource selection analysis and movement modelling provide insight into how deer's movements contribute to the risk landscape for human exposure to the Lyme disease vector-I. scapularis. We find deer select highly vegetated and accessible residential properties which support blacklegged tick survival. We conclude the distribution of tick-borne disease risk results from the individual resource selection by deer across spatial scales in response to habitat fragmentation and anthropogenic disturbances.

Experimental oral delivery of the systemic acaricide moxidectin to free-ranging white-tailed deer (Artiodactyla: Cervidae) parasitized by Amblyomma americanum (Ixodida: Ixodidae).

Orally delivered, host-targeted, systemic acaricide treatment has potential to be an effective areawide tick abatement strategy. Past efforts using ivermectin for livestock were reported effective at controlling both Amblyomma americanum (L.) and Ixodes scapularis Say on Odocoileus virginianus (Zimmermann). However, the labeled 48-day withdrawal period for human consumption largely prevented utilization of this strategy targeting I. scapularis in autumn, when peak adult host-seeking activity coincides with regulated white-tailed deer hunting seasons. The modern-day compound moxidectin is the active ingredient in the pour-on formulation Cydectin (5 mg moxidectin/ml; Bayer Healthcare LLC), with a labeled 0-day withdrawal period for human consumption of treated cattle. We sought to re-examine the systemic acaricide approach for tick management by determining if we could successfully deliver Cydectin to free-ranging white-tailed deer. Over 2 yr in late spring/early summer, coinciding with adult and nymphal A. americanum activity, we fed Cydectin-coated corn to free-ranging white-tailed deer in coastal Connecticut. Through serum analysis, we documented moxidectin levels at or above those previously reported effective for control of ectoparasites (5-8 ppb for moxidectin and ivermectin) in 24 of 29 white-tailed deer captured (83%) while exposed to treated corn. While we did not document differences in burdens of parasitizing A. americanum based on moxidectin sera levels, we did document fewer engorged specimens on deer with increased sera levels. The systemic use of moxidectin for tick management in critical reproductive hosts has the potential to be effective in an areawide capacity while also permitting human consumption of treated venison.

Assessment of humaneness using gunshot targeting the brain and cervical spine for cervid depopulation under field conditions.

Population reduction or eradication of domestic or non-domestic species may be required to address their impacts on the environment, other species, or human interests. Firearms are often used to accomplish these practical management objectives, and there is increased concern that the methods used may compromise animal welfare. We document the accuracy and humaneness of gunshot placement to the brain and cervical vertebrae of Philippine deer (Rusa marianna) on Guam during depopulation activities as a model for meeting AVMA standards of euthanasia under field conditions (e.g., animal is not in hand). Deer were shot with a .223 caliber rifle from 10-125 m and approached immediately (<20 s) for assessment. A subset of adult deer was further evaluated for physiological responses including cessation of heart rate, respiration, ocular reflexes, and post-mortem spasms. All deer shot in the brain (n = 132) and upper cervical spine (C1-C3; n = 18) died immediately due to the destruction of the brain or spinal tissue. Shot placements were all within 1.9 cm of the point of aim (i.e., the center of the target region). The accuracy and immediate insensibility resulting from targeting of C1-C3 demonstrates that this is an alternative target site when animal positioning is not optimal for targeting the brain, or there is a need to preserve brain tissue (e.g., Chronic Wasting Disease testing). While targeting of C4 -C7 vertebrae (n = 6) was accurate and resulted in immediate incapacitation, the failure to produce immediate insensibility does not support the use of this shot placement when upper cervical or brain shot placement is an option. It is reasonable to achieve sufficient accuracy to target the brain or upper cervical vertebrae of deer under field conditions and meet standards of euthanasia while accomplishing management objectives.