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Robert S. Lane - One of the best experts on this subject based on the ideXlab platform.
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ORIGINAL ARTICLES Impacts of an Introduced Forest Pathogen on the Risk of Lyme Disease in California
2016Co-Authors: Andrea Swei, Robert S. Lane, Cheryl J. Briggs, Richard S. OstfeldAbstract:Global changes such as deforestation, climate change, and invasive species have the potential to greatly alter zoonotic disease systems through impacts on biodiversity. This study examined the impact of the invasive pathogen that causes sudden oak death (SOD) on the ecology of Lyme disease in California. The Lyme disease bacterium, Borrelia burgdorferi, is maintained in the far Western United States by a suite of animal reservoirs including the dusky-footed woodrat (Neotoma fuscipes) and deer mouse (Peromyscus maniculatus), and is trans-mitted by the Western black-legged tick (Ixodes pacificus). Other vertebrates, such as the Western Fence Lizard (Sceloporus occidentalis), are important tick hosts but are not reservoirs of the pathogen. Previous work found that higher levels of SOD are correlated with greater abundance of P. maniculatus and S. occidentalis and lower N. fuscipes abundance. Here we model the contribution of these tick hosts to Lyme disease risk and also evaluate the potential impact of SOD on infection prevalence of the tick vector. By empirically parameterizing a static model with field and laboratory data on tick hosts, we predict that SOD reduces an important index of disease risk, nymphal infection prevalence, leading to a reduction in Lyme disease risk in certain coastal woodlands. Direct observational analysis of the impact of SOD on nymphal infection prevalence supports these model results. This study underscores the important direct and indirect impacts of invasive plant pathogens on bio-diversity, the transmission cycles of zoonotic diseases, and ultimately human health. Key Words: Borrelia burgdorferi—Disease ecology—Indirect effects—Nymphal infection prevalence—Phytophthora ramorum—Tick
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Effects of an invasive forest pathogen on abundance of ticks and their vertebrate hosts in a California Lyme disease focus
Oecologia, 2011Co-Authors: Andrea Swei, Robert S. Lane, Richard S. Ostfeld, Cheryl J. BriggsAbstract:Invasive species, including pathogens, can have important effects on local ecosystems, including indirect consequences on native species. This study focuses on the effects of an invasive plant pathogen on a vertebrate community and Ixodes pacificus , the vector of the Lyme disease pathogen ( Borrelia burgdorferi ) in California. Phytophthora ramorum , the causative agent of sudden oak death, is a non-native pathogen killing trees in California and Oregon. We conducted a multi-year study using a gradient of SOD-caused disturbance to assess the impact on the dusky-footed woodrat ( Neotoma fuscipes ) and the deer mouse ( Peromyscus maniculatus ), two reservoir hosts of B. burgdorferi , as well as the impact on the Columbian black-tailed deer ( Odocoileus hemionus columbianus ) and the Western Fence Lizard ( Sceloporus occidentalis ), both of which are important hosts for I. pacificus but are not pathogen reservoirs. Abundances of P. maniculatus and S. occidentalis were positively correlated with greater SOD disturbance, whereas N. fuscipes abundance was negatively correlated. We did not find a change in space use by O. hemionus . Our data show that SOD has a positive impact on the density of nymphal ticks, which is expected to increase the risk of human exposure to Lyme disease all else being equal. A positive correlation between SOD disturbance and the density of nymphal ticks was expected given increased abundances of two important hosts: deer mice and Western Fence Lizards. However, further research is needed to integrate the direct effects of SOD on ticks, for example via altered abiotic conditions with host-mediated indirect effects.
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feeding preferences of the immature stages of three Western north american ixodid ticks acari for avian reptilian or rodent hosts
Journal of Medical Entomology, 2009Co-Authors: Ted J Slowik, Robert S. LaneAbstract:ABSTRACT Larval and nymphal Ixodes pacificus Cooley and Kohls, I. (Ixodes) jellisoni Cooley and Kohls, and Dermacentor occidentalis Marx were tested for host preference when simultaneously presented with a deer mouse (Peromyscus maniculatus Wagner), California kangaroo rat (Dipodomys californicus Merriam), Western Fence Lizard (Sceloporus occidentalis Baird and Girard), and California towhee (Pipilo crissalis Vigors) in an experimental apparatus. Differences were observed in the preferences among the three species and between life stages. More larvae of all species approached and contacted hosts than did nymphs. Subadult I. pacificus entered all host-containing chambers in the highest numbers and remained on Lizards most often after contact. Subadult I. jellisoni entered and remained in the chambers containing kangaroo rats, while rejecting mice, Lizards, and birds as hosts. Subadult D. occidentalis most frequently entered rodent-containing chambers and contacted these hosts. After overnight exposure to a...
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Feeding preferences of the immature stages of three Western north American ixodid ticks (Acari) for avian, reptilian, or rodent hosts.
Journal of medical entomology, 2009Co-Authors: Ted J Slowik, Robert S. LaneAbstract:Larval and nymphal Ixodes pacificus Cooley and Kohls, I. (Ixodes) jellisoni Cooley and Kohls, and Dermacentor occidentalis Marx were tested for host preference when simultaneously presented with a deer mouse (Peromyscus maniculatus Wagner), California kangaroo rat (Dipodomys californicus Merriam), Western Fence Lizard (Sceloporus occidentalis Baird and Girard), and California towhee (Pipilo crissalis Vigors) in an experimental apparatus. Differences were observed in the preferences among the three species and between life stages. More larvae of all species approached and contacted hosts than did nymphs. Subadult I. pacificus entered all host-containing chambers in the highest numbers and remained on Lizards most often after contact. Subadult I. jellisoni entered and remained in the chambers containing kangaroo rats, while rejecting mice, Lizards, and birds as hosts. Subadult D. occidentalis most frequently entered rodent-containing chambers and contacted these hosts. After overnight exposure to all nonavian hosts, only I. pacificus parasitized and fed successfully on all three animals. I. jellisoni fed only on kangaroo rats and D. occidentalis fed only on rodents. Molting success ranged from approximately 66 to 95% among tick species and stages. We concluded that, under laboratory conditions, I. pacificus larvae and nymphs prefer Western Fence Lizards, but also will parasitize rodents. Dermacentor occidentalis immatures use deer mice and kangaroo rats similarly, whereas I. jellisoni subadults exclusively parasitize kangaroo rats. California towhees are considerably less attractive as hosts for these three ticks. These host preferences are consistent with what is known about the natural feeding habits of all three ticks.
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Refractoriness of the Western Fence Lizard (Sceloporus occidentalis) to the Lyme disease group spirochete Borrelia bissettii.
The Journal of parasitology, 2006Co-Authors: Robert S. Lane, J. Mun, Lars Eisen, Rebecca J. EisenAbstract:The Western Fence Lizard, Sceloporus occidentalis, is refractory to experimental infection with Borrelia burgdorferi sensu stricto, one of several Lyme disease spirochetes pathogenic for humans. Another member of the Lyme disease spirochete complex, Borrelia bissettii, is distributed widely throughout North America and a similar, if not identical, spirochete has been implicated as a human pathogen in southern Europe. To determine the susceptibility of S. occidentalis to B. bissettii, 6 naive Lizards were exposed to the feeding activities of Ixodes pacificus nymphs experimentally infected with this spirochete. None of the Lizards developed spirochetemias detectable by polymerase chain reaction for up to 8 wk post-tick feeding, infected nymphs apparently lost their B. bissettii infections within 1–2 wk after engorgement, and xenodiagnostic I. pacificus larvae that co-fed alongside infected nymphs did not acquire and maintain spirochetes. In contrast, 3 of 4 naive deer mice (Peromyscus maniculatus) exposed s...
Larry G. Talent - One of the best experts on this subject based on the ideXlab platform.
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Multiple environmental stressors induce complex transcriptomic responses indicative of phenotypic outcomes in Western Fence Lizard.
BMC genomics, 2018Co-Authors: Kurt A. Gust, Mitchell S. Wilbanks, Vijender Chaitankar, Preetam Ghosh, Xianfeng Chen, Natalie D. Barker, Don Pham, Leona D. Scanlan, Arun Rawat, Larry G. TalentAbstract:The health and resilience of species in natural environments is increasingly challenged by complex anthropogenic stressor combinations including climate change, habitat encroachment, and chemical contamination. To better understand impacts of these stressors we examined the individual- and combined-stressor impacts of malaria infection, food limitation, and 2,4,6-trinitrotoluene (TNT) exposures on gene expression in livers of Western Fence Lizards (WFL, Sceloporus occidentalis) using custom WFL transcriptome-based microarrays. Computational analysis including annotation enrichment and correlation analysis identified putative functional mechanisms linking transcript expression and toxicological phenotypes. TNT exposure increased transcript expression for genes involved in erythropoiesis, potentially in response to TNT-induced anemia and/or methemoglobinemia and caused dose-specific effects on genes involved in lipid and overall energy metabolism consistent with a hormesis response of growth stimulation at low doses and adverse decreases in Lizard growth at high doses. Functional enrichment results were indicative of inhibited potential for lipid mobilization and catabolism in TNT exposures which corresponded with increased inguinal fat weights and was suggestive of a decreased overall energy budget. Malaria infection elicited enriched expression of multiple immune-related functions likely corresponding to increased white blood cell (WBC) counts. Food limitation alone enriched functions related to cellular energy production and decreased expression of immune responses consistent with a decrease in WBC levels. Despite these findings, the Lizards demonstrated immune resilience to malaria infection under food limitation with transcriptional results indicating a fully competent immune response to malaria, even under bio-energetic constraints. Interestingly, both TNT and malaria individually increased transcriptional expression of immune-related genes and increased overall WBC concentrations in blood; responses that were retained in the TNT x malaria combined exposure. The results demonstrate complex and sometimes unexpected responses to multiple stressors where the Lizards displayed remarkable resiliency to the stressor combinations investigated.
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Multiple environmental stressors induce complex transcriptomic responses indicative of phenotypic outcomes in Western Fence Lizard
BMC, 2018Co-Authors: Kurt A. Gust, Mitchell S. Wilbanks, Vijender Chaitankar, Preetam Ghosh, Xianfeng Chen, Natalie D. Barker, Don Pham, Leona D. Scanlan, Arun Rawat, Larry G. TalentAbstract:Abstract Background The health and resilience of species in natural environments is increasingly challenged by complex anthropogenic stressor combinations including climate change, habitat encroachment, and chemical contamination. To better understand impacts of these stressors we examined the individual- and combined-stressor impacts of malaria infection, food limitation, and 2,4,6-trinitrotoluene (TNT) exposures on gene expression in livers of Western Fence Lizards (WFL, Sceloporus occidentalis) using custom WFL transcriptome-based microarrays. Results Computational analysis including annotation enrichment and correlation analysis identified putative functional mechanisms linking transcript expression and toxicological phenotypes. TNT exposure increased transcript expression for genes involved in erythropoiesis, potentially in response to TNT-induced anemia and/or methemoglobinemia and caused dose-specific effects on genes involved in lipid and overall energy metabolism consistent with a hormesis response of growth stimulation at low doses and adverse decreases in Lizard growth at high doses. Functional enrichment results were indicative of inhibited potential for lipid mobilization and catabolism in TNT exposures which corresponded with increased inguinal fat weights and was suggestive of a decreased overall energy budget. Malaria infection elicited enriched expression of multiple immune-related functions likely corresponding to increased white blood cell (WBC) counts. Food limitation alone enriched functions related to cellular energy production and decreased expression of immune responses consistent with a decrease in WBC levels. Conclusions Despite these findings, the Lizards demonstrated immune resilience to malaria infection under food limitation with transcriptional results indicating a fully competent immune response to malaria, even under bio-energetic constraints. Interestingly, both TNT and malaria individually increased transcriptional expression of immune-related genes and increased overall WBC concentrations in blood; responses that were retained in the TNT x malaria combined exposure. The results demonstrate complex and sometimes unexpected responses to multiple stressors where the Lizards displayed remarkable resiliency to the stressor combinations investigated
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Direct and indirect effects of petroleum production activities on the Western Fence Lizard (Sceloporus occidentalis) as a surrogate for the dunes sagebrush Lizard (Sceloporus arenicolus).
Environmental toxicology and chemistry, 2016Co-Authors: Scott M. Weir, Larry G. Talent, Ami Knox, Todd A. Anderson, Christopher J. SaliceAbstract:The dunes sagebrush Lizard (Sceloporus arenicolus) is a habitat specialist of conservation concern limited to shin oak sand dune systems of New Mexico and Texas. Because much of the dunes sagebrush Lizard's habitat occurs in areas of high oil and gas production, there may be direct and indirect effects of these activities. We used the congeneric Western Fence Lizard (Sceloporus occidentalis) as a surrogate species to determine direct effects of 2 contaminants associated with oil and gas drilling activities in the Permian Basin: herbicide formulations (Krovar and Quest) and hydrogen sulfide gas (H2S). We exposed Lizards to 2 concentrations of H2S (30 or 90 ppm) and herbicide formulations (1x or 2x label application rate) representing high-end exposure scenarios. We evaluated sublethal behavioral endpoints including sprint speed and time to prey detection and capture. Neither H2S nor herbicide formulations caused significant behavioral effects compared to controls. In order to understand potential indirect effects of oil and gas drilling on the prey base, we quantified terrestrial invertebrate biomass and order diversity at impacted sites to compare to non-impacted sites. We found a significant decrease in biomass at impacted sites, but no significant effects on diversity. Our results suggest little risk from direct toxic effects, but the potential for indirect effects should be further explored. This article is protected by copyright. All rights reserved
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Unraveling the Relative Importance of Oral and Dermal Contaminant Exposure in Reptiles: Insights from Studies Using the Western Fence Lizard (Sceloporus occidentalis)
PloS one, 2014Co-Authors: Scott M. Weir, Larry G. Talent, Todd A. Anderson, Christopher J. SaliceAbstract:Despite widespread recognition of significant data deficiencies, reptiles remain a relatively understudied taxon in ecotoxicology. To conduct ecological risk assessments on reptiles frequently requires using surrogate taxa such as birds, but recent research suggests that reptiles have significantly different exposure profiles and toxicant sensitivity. We exposed Western Fence Lizards, Sceloporus occidentalis, to the same quantities of three model chemicals via oral (gavage) and dermal (ventral skin application) exposure for either 24 or 48 hours. Three phthalate esters (di-methyl phthalate [DMP], di-iso-butyl phthalate [DIBP], and di-n-octyl phthalate [DNOP]) were chosen as model chemicals because they represent a gradient of lipophilicity but are otherwise structurally similar. Overall, the more lipophilic phthalates (DIBP and DNOP) were found to have higher concentrations in tissues than the less lipophilic DMP. Significant differences in tissue concentrations between DIBP and DNOP were tissue-dependent, suggesting that delivery to a site of action following exposure is not only a simple function of lipophilicity. In dermal treatments, DMP usually had fewer detections (except in ventral skin samples), suggesting that lipophilicity (log Kow>2) is a requirement for uptake across the skin. In general, tissue residues were greater in oral treatments than dermal treatments (significant in adipose and liver tissue), but differences were driven strongly by differences in DMP which did not appear to be absorbed well across skin. When differences in tissue residue concentrations between oral and dermal exposure did occur, the difference was not drastic. Taken together these results suggest that dermal exposure should be considered in risk assessments for reptilian receptors. Dermal exposure may be an especially important route for reptiles as their ectothermic physiology translates to lower energetic demands and dietary exposure compared to birds and mammals.
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Multiple environmental stressors elicit complex interactive effects in the Western Fence Lizard ( Sceloporus occidentalis )
Ecotoxicology (London England), 2012Co-Authors: Craig A. Mcfarland, Michael J. Quinn, Matthew A. Bazar, Larry G. Talent, Mark S. Johnson, Mitchell S. Wilbanks, Mandana Nisanian, Robert M. Gogal, Edward J. Perkins, Kurt A. GustAbstract:Evaluation of multiple-stressor effects stemming from habitat degradation, climate change, and exposure to chemical contaminants is crucial for addressing challenges to ecological and environmental health. To assess the effects of multiple stressors in an understudied taxon, the Western Fence Lizard (Sceloporus occidentalis) was used to characterize the individual and combined effects of food limitation, exposure to the munitions constituent 2,4,6-trinitrotoluene (TNT), and Plasmodium mexicanum (Lizard malaria) infection. Three experimental assays were conducted including: Experiment I—TNT × Food Limitation, Experiment II—Food Limitation × Malaria Infection, and Experiment III—TNT × Malaria Infection. All experiments had a 30 day duration, the malaria treatment included infected and non infected control Lizards, food limitation treatments included an ad libitum control and at least one reduced food ration and TNT exposures consisting of daily oral doses of corn oil control or a corn oil-TNT suspension at 5, 10, 20, 40 mg/kg/day. The individual stressors caused a variety of effects including: reduced feeding, reduced testes mass, anemia, increased white blood cell (WBC) concentrations and increased mass of liver, kidney and spleen in TNT exposures; reduced cholesterol, WBC concentrations and whole body, testes and inguinal fat weights given food limitation; and increased WBC concentrations and spleen weights as well as decreased cholesterol and testes mass in malaria infected Lizards. Additive and interactive effects were found among certain stressor combinations including elimination of TNT-induced hormesis for growth under food limitation. Ultimately, our study indicates the potential for effects modulation when environmental stressors are combined.
Jos. J. Schall - One of the best experts on this subject based on the ideXlab platform.
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clonal diversity of a Lizard malaria parasite plasmodium mexicanum in its vertebrate host the Western Fence Lizard role of variation in transmission intensity over time and space
Molecular Ecology, 2007Co-Authors: A M Vardo, Jos. J. SchallAbstract:Within the vertebrate host, infections of a malaria parasite (Plasmodium) could include a single genotype of cells (single-clone infections) or two to several genotypes (multiclone infections). Clonal diversity of infection plays an important role in the biology of the parasite, including its life history, virulence, and transmission. We determined the clonal diversity of Plasmodium mexicanum, a Lizard malaria parasite at a study region in northern California, using variable microsatellite markers, the first such study for any malaria parasite of Lizards or birds (the most common hosts for Plasmodium species). Multiclonal infections are common (50-88% of infections among samples), and measures of genetic diversity for the metapopulation (expected heterozygosity, number of alleles per locus, allele length variation, and effective population size) all indicated a substantial overall genetic diversity. Comparing years with high prevalence (1996-1998 = 25-32% Lizards infected), and years with low prevalence (2001-2005 = 6-12%) found fewer alleles in samples taken from the low-prevalence years, but no reduction in overall diversity (H = 0.64-0.90 among loci). In most cases, rare alleles appeared to be lost as prevalence declined. For sites chronically experiencing low transmission intensity (prevalence approximately 1%), overall diversity was also high (H = 0.79-0.91), but there were fewer multiclonal infections. Theory predicts an apparent excess in expected heterozygosity follows a genetic bottleneck. Evidence for such a distortion in genetic diversity was observed after the drop in parasite prevalence under the infinite alleles mutation model but not for the stepwise mutation model. The results are similar to those reported for the human malaria parasite, Plasmodium falciparum, worldwide, and support the conclusion that malaria parasites maintain high genetic diversity in host populations despite the potential for loss in alleles during the transmission cycle or during periods/locations when transmission intensity is low.
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Manipulation of the vertebrate host's testosterone does not affect gametocyte sex ratio of a malaria parasite.
The Journal of parasitology, 2003Co-Authors: Sarah M. Osgood, Rebecca J. Eisen, Andrew R. Wargo, Jos. J. SchallAbstract:Gametocyte sex ratio of the malaria parasite Plasmodium mexicanum is variable in its host, the Western Fence Lizard (Sceloporus occidentalis), both among infections and within infections over time. We sought to determine the effect of host physiological quality on the gametocyte sex ratio in experimentally induced infections of P. mexicanum. Adult male Lizards were assigned to 4 treatment groups: castrated, castrated + testosterone implant, sham implant, and unmanipulated control. No significant difference in gametocyte sex ratio was found among the 4 treatment groups. Two other analyses were performed. A surgery stress analysis compared infection sex ratio of castrated, castrated + testosterone implant, and sham implant groups with the unmanipulated control group. A testosterone alteration analysis compared infection sex ratio of the castrated and castrated + testosterone implant groups with the sham implant and unmanipulated control groups. Again, no significant difference was observed for these 2 compa...
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Prevalence of a malarial parasite over time and space: Plasmodium mexicanum in its vertebrate host, the Western Fence Lizard Sceloporus occidentalis
The Journal of Animal Ecology, 1995Co-Authors: Jos. J. Schall, Azra B. MarghoobAbstract:1. We studied patterns of abundance of the malarial parasite Plasmodium mexicanum in its vertebrate host, the Western Fence Lizard Sceloporus occidentalis, over a 13-year period at 51 study sites in northern California, USA. Abundance of the vectors, sandflies in the genus Lutzomyia, was also studied among sites during a single warm season, and among nights at one site during two seasons. 2. The parasite differed in prevalence (per cent of Lizards infected) in males and females; males were more often infected. Prevalence increased with body size (= older Lizards were more often infected). 3. Malaria prevalence varied among sites: 0-50% of Lizards were infected. Topography explains part of this variation because malaria was rare or absent at sites. > 500 m elevation. However, sites at lower elevations, even when within short distances of one another, varied in malaria prevalence. 4. Abundance of vectors was not related to prevalence of malaria at a site; sandflies were found at some sites where malaria was rare or absent, including those at high elevations. Wind speed, relative humidity and sky brightness did not affect numbers of sandflies active, but vectors were active only when air temperature was > 16°C. 5. Parasite prevalence varied among years. Environmental conditions (temperature, rainfall and plant biomass produced at the study region) were not correlated with parasite prevalence. The changes in prevalence over time resembled a cycle of long duration (10 years). 6. Classical models developed for study of malaria in humans suggest explanations for variation in prevalence of P. mexicanum among sites, and a more recent theory suggests an explanation for the possible long-duration cycle observed in this study
Ted J Slowik - One of the best experts on this subject based on the ideXlab platform.
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feeding preferences of the immature stages of three Western north american ixodid ticks acari for avian reptilian or rodent hosts
Journal of Medical Entomology, 2009Co-Authors: Ted J Slowik, Robert S. LaneAbstract:ABSTRACT Larval and nymphal Ixodes pacificus Cooley and Kohls, I. (Ixodes) jellisoni Cooley and Kohls, and Dermacentor occidentalis Marx were tested for host preference when simultaneously presented with a deer mouse (Peromyscus maniculatus Wagner), California kangaroo rat (Dipodomys californicus Merriam), Western Fence Lizard (Sceloporus occidentalis Baird and Girard), and California towhee (Pipilo crissalis Vigors) in an experimental apparatus. Differences were observed in the preferences among the three species and between life stages. More larvae of all species approached and contacted hosts than did nymphs. Subadult I. pacificus entered all host-containing chambers in the highest numbers and remained on Lizards most often after contact. Subadult I. jellisoni entered and remained in the chambers containing kangaroo rats, while rejecting mice, Lizards, and birds as hosts. Subadult D. occidentalis most frequently entered rodent-containing chambers and contacted these hosts. After overnight exposure to a...
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Feeding preferences of the immature stages of three Western north American ixodid ticks (Acari) for avian, reptilian, or rodent hosts.
Journal of medical entomology, 2009Co-Authors: Ted J Slowik, Robert S. LaneAbstract:Larval and nymphal Ixodes pacificus Cooley and Kohls, I. (Ixodes) jellisoni Cooley and Kohls, and Dermacentor occidentalis Marx were tested for host preference when simultaneously presented with a deer mouse (Peromyscus maniculatus Wagner), California kangaroo rat (Dipodomys californicus Merriam), Western Fence Lizard (Sceloporus occidentalis Baird and Girard), and California towhee (Pipilo crissalis Vigors) in an experimental apparatus. Differences were observed in the preferences among the three species and between life stages. More larvae of all species approached and contacted hosts than did nymphs. Subadult I. pacificus entered all host-containing chambers in the highest numbers and remained on Lizards most often after contact. Subadult I. jellisoni entered and remained in the chambers containing kangaroo rats, while rejecting mice, Lizards, and birds as hosts. Subadult D. occidentalis most frequently entered rodent-containing chambers and contacted these hosts. After overnight exposure to all nonavian hosts, only I. pacificus parasitized and fed successfully on all three animals. I. jellisoni fed only on kangaroo rats and D. occidentalis fed only on rodents. Molting success ranged from approximately 66 to 95% among tick species and stages. We concluded that, under laboratory conditions, I. pacificus larvae and nymphs prefer Western Fence Lizards, but also will parasitize rodents. Dermacentor occidentalis immatures use deer mice and kangaroo rats similarly, whereas I. jellisoni subadults exclusively parasitize kangaroo rats. California towhees are considerably less attractive as hosts for these three ticks. These host preferences are consistent with what is known about the natural feeding habits of all three ticks.
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Nymphs of the Western black-legged tick (Ixodes pacificus) collected from tree trunks in woodland-grass habitat.
Journal of vector ecology : journal of the Society for Vector Ecology, 2001Co-Authors: Ted J Slowik, Robert S. LaneAbstract:Nymphs of the Western black-legged tick, Ixodes pacificus, were found on the trunks of trees during spring and summer in northWestern California. In a woodland-grass habitat, large- and medium-sized (>130 cm and 80 - 130 cm in circumference, respectively), moss-covered oak ( Quercus spp.) trees supported ticks significantly more often than trees without these characteristics. Additionally, trees with basal leaf-litter and lacking shade (at time of sampling) were significantly associated with the presence of ticks. Mean tick- burdens were >1 for all oaks (1.06), all trees with basal leaf-litter (1.05), and all trees of large-circumference (1.19); 0.79 ticks per tree were collected over the entire study. Moss reduced the surface temperature of trees by a mean of 1.9°C (range of 1.6 - 5.0°C) and increased relative humidity by up to 2.5% from the ambient. These microclimatic changes, along with the presence of refugia in bark and Western Fence Lizard ( Sceloporus occidentalis) hosts on the lower-most surface of trees, likely accounted for ticks questing on the trunks. Although of undetermined epidemiological significance, the presence of host-seeking I. pacificus nymphs on tree trunks may shed light on the relation of abiotic and biotic factors to the life history of this important vector of disease.
Christopher J. Salice - One of the best experts on this subject based on the ideXlab platform.
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Direct and indirect effects of petroleum production activities on the Western Fence Lizard (Sceloporus occidentalis) as a surrogate for the dunes sagebrush Lizard (Sceloporus arenicolus).
Environmental toxicology and chemistry, 2016Co-Authors: Scott M. Weir, Larry G. Talent, Ami Knox, Todd A. Anderson, Christopher J. SaliceAbstract:The dunes sagebrush Lizard (Sceloporus arenicolus) is a habitat specialist of conservation concern limited to shin oak sand dune systems of New Mexico and Texas. Because much of the dunes sagebrush Lizard's habitat occurs in areas of high oil and gas production, there may be direct and indirect effects of these activities. We used the congeneric Western Fence Lizard (Sceloporus occidentalis) as a surrogate species to determine direct effects of 2 contaminants associated with oil and gas drilling activities in the Permian Basin: herbicide formulations (Krovar and Quest) and hydrogen sulfide gas (H2S). We exposed Lizards to 2 concentrations of H2S (30 or 90 ppm) and herbicide formulations (1x or 2x label application rate) representing high-end exposure scenarios. We evaluated sublethal behavioral endpoints including sprint speed and time to prey detection and capture. Neither H2S nor herbicide formulations caused significant behavioral effects compared to controls. In order to understand potential indirect effects of oil and gas drilling on the prey base, we quantified terrestrial invertebrate biomass and order diversity at impacted sites to compare to non-impacted sites. We found a significant decrease in biomass at impacted sites, but no significant effects on diversity. Our results suggest little risk from direct toxic effects, but the potential for indirect effects should be further explored. This article is protected by copyright. All rights reserved
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Unraveling the Relative Importance of Oral and Dermal Contaminant Exposure in Reptiles: Insights from Studies Using the Western Fence Lizard (Sceloporus occidentalis)
PloS one, 2014Co-Authors: Scott M. Weir, Larry G. Talent, Todd A. Anderson, Christopher J. SaliceAbstract:Despite widespread recognition of significant data deficiencies, reptiles remain a relatively understudied taxon in ecotoxicology. To conduct ecological risk assessments on reptiles frequently requires using surrogate taxa such as birds, but recent research suggests that reptiles have significantly different exposure profiles and toxicant sensitivity. We exposed Western Fence Lizards, Sceloporus occidentalis, to the same quantities of three model chemicals via oral (gavage) and dermal (ventral skin application) exposure for either 24 or 48 hours. Three phthalate esters (di-methyl phthalate [DMP], di-iso-butyl phthalate [DIBP], and di-n-octyl phthalate [DNOP]) were chosen as model chemicals because they represent a gradient of lipophilicity but are otherwise structurally similar. Overall, the more lipophilic phthalates (DIBP and DNOP) were found to have higher concentrations in tissues than the less lipophilic DMP. Significant differences in tissue concentrations between DIBP and DNOP were tissue-dependent, suggesting that delivery to a site of action following exposure is not only a simple function of lipophilicity. In dermal treatments, DMP usually had fewer detections (except in ventral skin samples), suggesting that lipophilicity (log Kow>2) is a requirement for uptake across the skin. In general, tissue residues were greater in oral treatments than dermal treatments (significant in adipose and liver tissue), but differences were driven strongly by differences in DMP which did not appear to be absorbed well across skin. When differences in tissue residue concentrations between oral and dermal exposure did occur, the difference was not drastic. Taken together these results suggest that dermal exposure should be considered in risk assessments for reptilian receptors. Dermal exposure may be an especially important route for reptiles as their ectothermic physiology translates to lower energetic demands and dietary exposure compared to birds and mammals.
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Effects of inorganic lead on Western Fence Lizards (Sceloporus occidentalis)
Environmental pollution (Barking Essex : 1987), 2009Co-Authors: Christopher J. Salice, Matthew A. Bazar, Jamie G. Suski, Larry G. TalentAbstract:Although anthropogenic pollutants are thought to threaten reptilian species, there are few toxicity studies on reptiles. We evaluated the toxicity of Pb as lead acetate to the Western Fence Lizard (Sceloporus occidentalis). The acute lethal dose and sub-acute (14-day) toxicity studies were used to narrow exposure concentrations for a sub-chronic (60-day) study. In the sub-chronic study, adult and juvenile male Lizards were dosed via gavage with 0, 1, 10 and 20 mg Pb/kg-bw/day. Mortality was limited and occurred only at the highest dose (20 mg Pb/kg-bw/d). There were statistically significant sub-lethal effects of 10 and 20 mg Pb/kg-bw/d on body weight, cricket consumption, organ weight, hematological parameters and post-dose behaviors. Of these, Pb-induced changes in body weight are most useful for ecological risk assessment because it is linked to fitness in wild Lizard populations. The Western Fence Lizard is a useful model for reptilian toxicity studies.
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dose related effects following oral exposure of 2 4 dinitrotoluene on the Western Fence Lizard sceloporus occidentalis
Environmental Toxicology and Chemistry, 2008Co-Authors: Jamie G. Suski, Matthew A. Bazar, Christopher J. Salice, John T. Houpt, Larry G. TalentAbstract:2,4-dintitrotoluene (2,4-DNT) is an explosive frequently found in the soil of military installations. Because reptiles can be common on these sites, ecological risk assessments for compounds such as 2,4-DNT could be improved with toxicity data specific to reptiles. Western Fence Lizards, Sceloporus occidentalis, were used to develop a laboratory toxicity model for reptiles. A hierarchical approach was used; acute to subchronic studies were conducted to provide toxicity data relevant to short- and long-term exposures. First, a modified median lethal dose (LD50) study was conducted on male and female Lizards using a stage-wise probit model. The LD50 was 577 mg/kg for female and 380 mg/kg for male Lizards. Subsequently, a subacute experiment was conducted to further assess 2,4-DNT toxicity to male Lizards and to define exposure levels for a longer term, subchronic study. The subchronic study was conducted for 60 consecutive days; male Lizards were exposed to 0, 9, 15, 25, 42, 70 mg/kg/d. Dose-dependent mortality was observed in the three highest dose groups (25, 42, and 70 mg/kg/d); all other animals survived the study duration. Benchmark dose model calculations based on mortality indicated a 5% effect level of 15.8 mg/kg/d. At study termination, a gross necropsy was performed, organ weights were taken, and blood was collected for clinical and hematological analysis. Body weight, kidney weight, food consumption, postdose observations, and blood chemistries all were found to be significantly different from controls at doses above 9 mg/kg/d. Also, preliminary results suggest behavioral observations, and reduced food consumption may be a sensitive indicator of toxicity. The present study indicates Sceloporus occidentalis is suitable for evaluating toxicity of compounds to reptilian species.
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Dose‐related effects following oral exposure of 2,4‐dinitrotoluene on the Western Fence Lizard, Sceloporus occidentalis
Environmental toxicology and chemistry, 2008Co-Authors: Jamie G. Suski, Matthew A. Bazar, Christopher J. Salice, John T. Houpt, Larry G. TalentAbstract:2,4-dintitrotoluene (2,4-DNT) is an explosive frequently found in the soil of military installations. Because reptiles can be common on these sites, ecological risk assessments for compounds such as 2,4-DNT could be improved with toxicity data specific to reptiles. Western Fence Lizards, Sceloporus occidentalis, were used to develop a laboratory toxicity model for reptiles. A hierarchical approach was used; acute to subchronic studies were conducted to provide toxicity data relevant to short- and long-term exposures. First, a modified median lethal dose (LD50) study was conducted on male and female Lizards using a stage-wise probit model. The LD50 was 577 mg/kg for female and 380 mg/kg for male Lizards. Subsequently, a subacute experiment was conducted to further assess 2,4-DNT toxicity to male Lizards and to define exposure levels for a longer term, subchronic study. The subchronic study was conducted for 60 consecutive days; male Lizards were exposed to 0, 9, 15, 25, 42, 70 mg/kg/d. Dose-dependent mortality was observed in the three highest dose groups (25, 42, and 70 mg/kg/d); all other animals survived the study duration. Benchmark dose model calculations based on mortality indicated a 5% effect level of 15.8 mg/kg/d. At study termination, a gross necropsy was performed, organ weights were taken, and blood was collected for clinical and hematological analysis. Body weight, kidney weight, food consumption, postdose observations, and blood chemistries all were found to be significantly different from controls at doses above 9 mg/kg/d. Also, preliminary results suggest behavioral observations, and reduced food consumption may be a sensitive indicator of toxicity. The present study indicates Sceloporus occidentalis is suitable for evaluating toxicity of compounds to reptilian species.
