Robert J. Warren

Infectious prions in pre-clinical deer and transmission of chronic wasting disease solely by environmental exposure.

Key to understanding the epidemiology and pathogenesis of prion diseases, including chronic wasting disease (CWD) of cervids, is determining the mode of transmission from one individual to another. We have previously reported that saliva and blood from CWD-infected deer contain sufficient infectious prions to transmit disease upon passage into naïve deer. Here we again use bioassays in deer to show that blood and saliva of pre-symptomatic deer contain infectious prions capable of infecting naïve deer and that naïve deer exposed only to environmental fomites from the suites of CWD-infected deer acquired CWD infection after a period of 15 months post initial exposure. These results help to further explain the basis for the facile transmission of CWD, highlight the complexities associated with CWD transmission among cervids in their natural environment, emphasize the potential utility of blood-based testing to detect pre-clinical CWD infection, and could augur similar transmission dynamics in other prion infections.

Ecosystem Processes and Human Influences Regulate Streamflow Response to Climate Change at Long-Term Ecological Research Sites

Analyses of long-term records at 35 headwater basins in the United States and Canada indicate that climate change effects on streamflow are not as clear as might be expected, perhaps because of ecosystem processes and human influences. Evapotranspiration was higher than was predicted by temperature in water-surplus ecosystems and lower than was predicted in water-deficit ecosystems. Streamflow was correlated with climate variability indices (e.g., the El Niño—Southern Oscillation, the Pacific Decadal Oscillation, the North Atlantic Oscillation), especially in seasons when vegetation influences are limited. Air temperature increased significantly at 17 of the 19 sites with 20- to 60-year records, but streamflow trends were directly related to climate trends (through changes in ice and snow) at only 7 sites. Past and present human and natural disturbance, vegetation succession, and human water use can mimic, exacerbate, counteract, or mask the effects of climate change on streamflow, even in reference basins. Long-term ecological research sites are ideal places to disentangle these processes.

Comparisons of lethal and nonlethal techniques to reduce raccoon depredation of sea turtle nests

Depredation of sea turtle nests by raccoons (Procyon lotor) can hinder management attempts to increase recruitment of turtle hatchlings. We tested 3 techniques for their effectiveness in reducing raccoon predation on turtle nests. During 1993-94, direct comparisons of lethal removal, nonlethal conditioned taste aversion (CTA), and nest screening were conducted at Canaveral National Seashore (CNS), Florida. Lethal removal of 215 raccoons, at a level of about 50% of the population using the barrier beach, was not effective at reducing nest depredation. Nonlethal use of estrogen-laced eggs to induce conditioned taste aversion had no significant effect on nest depredation rate. Nest screening was the only treatment that significantly reduced nest depredation. Nest screening was labor-intensive and more expensive than lethal removal and CTA, but maintained raccoons as part of the coastal ecosystem while affording protection to sea turtle nests.

B Cells and Platelets Harbor Prion Infectivity in the Blood of Deer Infected with Chronic Wasting Disease

ABSTRACT Substantial evidence for prion transmission via blood transfusion exists for many transmissible spongiform encephalopathy (TSE) diseases. Determining which cell phenotype(s) is responsible for trafficking infectivity has important implications for our understanding of the dissemination of prions, as well as their detection and elimination from blood products. We used bioassay studies of native white-tailed deer and transgenic cervidized mice to determine (i) if chronic wasting disease (CWD) blood infectivity is associated with the cellular versus the cell-free/plasma fraction of blood and (ii) in particular if B-cell (MAb 2-104+), platelet (CD41/61+), or CD14+ monocyte blood cell phenotypes harbor infectious prions. All four deer transfused with the blood mononuclear cell fraction from CWD+ donor deer became PrPCWD positive by 19 months postinoculation, whereas none of the four deer inoculated with cell-free plasma from the same source developed prion infection. All four of the deer injected with B cells and three of four deer receiving platelets from CWD+ donor deer became PrPCWD positive in as little as 6 months postinoculation, whereas none of the four deer receiving blood CD14+ monocytes developed evidence of CWD infection (immunohistochemistry and Western blot analysis) after 19 months of observation. Results of the Tg(CerPrP) mouse bioassays mirrored those of the native cervid host. These results indicate that CWD blood infectivity is cell associated and suggest a significant role for B cells and platelets in trafficking CWD infectivity in vivo and support earlier tissue-based studies associating putative follicular B cells with PrPCWD. Localization of CWD infectivity with leukocyte subpopulations may aid in enhancing the sensitivity of blood-based diagnostic assays for CWD and other TSEs.

Mechanisms driving understory evergreen herb distributions across slope aspects: as derived from landscape position

In the Northern Hemisphere, the surface of south-facing slopes orients toward the sun and thus receives a greater duration and intensity of solar irradiation, resulting in a relatively warmer, drier microclimate and seasonal environmental extremes. This creates potentially detrimental conditions for evergreen plants which must endure the full gamut of conditions. I hypothesize that (1) increased southerly aspect will correlate negatively with evergreen understory plant distributions; (2) derived environmental variables (summer and winter light and heat load) will predict variance in evergreen distributions as well as topographic position (aspect, slope, and elevation) and (3) winter light will best predict evergreen understory plant distributions. In order to test these hypotheses, survey data were collected characterizing 10 evergreen understory herb distributions (presence, abundance, and reproduction) as well as the corresponding topographical information across north- and south-facing slopes in the North Carolina mountains and Georgia piedmont. The best predictive models were selected using AIC, and Bayesian hierarchical generalized linear models were used to estimate the strength of the retained coefficients. As predicted, evergreen understory herbs occurred and reproduced less on south-facing than north-facing slopes, though slope and elevation also had robust predictive power, and both discriminated well between evergreen species. While the landscape variables explained where the plants occurred, winter light and heat load provided the best explanation why they were there. Evergreen plants likely are limited on south-facing slopes by low soil moisture combined with high temperatures in summer and high irradiance combined with lower temperatures in winter. The robust negative response of the understory evergreen herbs to increased winter light also suggested that the winter rather than the summer (or growing season) environment provided the best predictive power for understory evergreen distributions, which has substantive implications for predicting responses to global climate change.

A test of the scent-station survey technique for bobcats

Scent-station surveys have been widely used to monitor bobcat (Felis rufus) populations, but relationships between bobcat abundance and the index derived from scent-station surveys have not been validated. In autumn 1988 and 1989 we reintroduced bobcats (n = 31) to Cumberland Island, Georgia. We conducted 15 scent-station surveys during September-February 1988, 1989, and 1990 to obtain scent-station indices (SSI) as we increased bobcat density. We found a positive relationship (r 2 = 0.45, P = 0.0066) between population size and SSI. However, because SSI variance also was correlated positively with SSI, we transformed data to meet the assumption of homoscedasticity for the regression model (r 2 = 0.73, P < 0.001)

Energy, Protein, and Seasonal Influences on White-Tailed Deer Fawn Nutritional Indices

Shortand long-term influences of dietary energy and protein on physiological indices of nutritional status were determined in a factorial experiment with 12 male and 12 female captive whitetailed deer (Odocoileus virginianus) fawns. Blood and urine samples were collected after 1, 2, 4, 8, 16, and 32 weeks on experimental diets. Body weights throughout the experiment were greater (P < 0.001) for male than for female fawns. Concentrations of blood urea nitrogen (BUN) and urinary urea/creatinine (U/C) ratios throughout the experiment were greater (P < 0.001) in fawns on high protein diets than in fawns on low protein diets. Blood urea nitrogen concentrations and urinary U/C ratios also were greater (P < 0.01) in fawns on low energy diets than in fawns on high energy diets over the duration of the experiment. A substantial reduction in BUN concentrations was observed after 8 months in those fawns which initially exhibited elevated BUN concentrations. Significant differences were observed among sample periods during the 8-month experiment for hemoglobin, packed cell volume, mean corpuscular hemoglobin content, albumin, BUN, cholesterol, nonesterified fatty acids, total ketone bodies, and urinary U/C ratios. J. WILDL. MANAGE. 46(2):302-312 Physiological indices for assessing nutritional status of populations of wild animals, most notably cervids, have long been the subject of research in wildlife science. Biochemical analyses of blood and urine hold promise as being reliable nutritional indices. However, assessing nutritional status with these methods must necessarily depend on controlled experiments to evaluate their efficiency and accuracy. Several investigators have examined nutritional indices of whitetailed deer under controlled conditions (Kirkpatrick et al. 1975, Seal et al. 1978a, Bahnak et al. 1979). No reports have been found in which differences in nutritional indices according to energy, protein, sex, and duration of dietary exposure were examined in a single experiment. The objective of the present study was to determine the shortand long-term effects of dietary energy and protein on nutritional indices of male and female white-

The putative niche requirements and landscape dynamics of Microstegium vimineum: an invasive Asian grass

The theoretical foundations of population and community ecology stress the importance of identifying crucial niche requirements and life history stages of invasive species and, in doing so, give insight into research and management. We focus on Microstegium vimineum, an invasive grass which is causing marked changes in the structure and function of US forests. We describe M. vimineum’s life history and habitat characteristics, infer its niche requirements and synthesize this information in the context of population dynamics and management. Based on the results synthesized here, M. vimineum’s crucial niche requirements appear to be light (reproductive output), soil moisture (reproductive output, seedling recruitment) and aboveground coverage by leaf-litter and competing species (seedling recruitment and survival). These data suggest a source-sink dynamic might allow M. vimineum to disperse and thrive along sunny, and sometimes wet, edge habitats and, in turn, these populations might act as source populations for adjacent shady forest habitats. By evaluating M. vimineum in the context of its stage-specific requirements, we highlight potential weaknesses in its life history that provide strategies for effective management.

Aerosol Transmission of Chronic Wasting Disease in White-Tailed Deer

ABSTRACT While the facile transmission of chronic wasting disease (CWD) remains incompletely elucidated, studies in rodents suggest that exposure of the respiratory mucosa may be an efficient pathway. The present study was designed to address this question in the native cervid host. Here, we demonstrate aerosol transmission of CWD to deer with a prion dose >20-fold lower than that used in previous oral inoculations. Inhalation of prions may facilitate transmission of CWD and, perhaps, other prion infections.

Upward ant distribution shift corresponds with minimum, not maximum, temperature tolerance

Rapid climate change may prompt species distribution shifts upward and poleward, but species movement in itself is not sufficient to establish climate causation. Other dynamics, such as disturbance history, may prompt species distribution shifts resembling those expected from rapid climate change. Links between species distributions, regional climate trends and physiological mechanism are needed to convincingly establish climate-induced species shifts. We examine a 38-year shift (1974-2012) in an elevation ecotone between two closely related ant species, Aphaenogaster picea and A. rudis. Even though A. picea and A. rudis are closely related with North American distributions that sometimes overlap, they also exhibit local- and regional-scale differences in temperature requirements so that A. rudis is more southerly and inhabits lower elevations whereas A. picea is more northerly and inhabits high elevations. We find considerable movement by the warm-habitat species upward in elevation between 1974 and 2012 with A. rudis, replacing the cold-habitat species, A. picea, along the southern edge of the Appalachian Mountain chain in north Georgia, USA. Concomitant with the distribution shifts, regional mean and maximum temperatures remain steady (1974-2012), but minimum temperatures increase. We collect individuals from the study sites and subject them to thermal tolerance testing in a controlled setting and find that maximum and minimum temperature acclimatization occurs along the elevation gradient in both species, but A. rudis consistently becomes physiologically incapacitated at minimum and maximum temperatures 2 °C higher than A. picea. These results indicate that rising minimum temperatures allow A. rudis to move upward in elevation and displace A. picea. Given that Aphaenogaster ants are the dominant woodland seed dispersers in eastern deciduous forests, and that their thermal tolerances drive distinct differences in temperature-cued synchrony with early blooming plants, these climate responses not only impact ant-ant interactions, but might have wide implications for ant-plant interactions.