Environmental variables serve as predictors of the invasive Asian longhorned tick (Haemaphysalis longicornis Neumann): An approach for targeted tick surveillance.

Since the 2017 discovery of established populations of the Asian longhorned tick, (Haemaphysalis longicornis Neumann) in the United States, populations continue to be detected in new areas. For this exotic and invasive species, capable of transmitting a diverse repertoire of pathogens and blood feeding on a variety of host species, there remains a lack of targeted information on how to best prepare for this tick and understand when and where it occurs. To fill this gap, we conducted two years of weekly tick surveillance at four farms in Tennessee (three H. longicornis-infested and one without) to identify environmental factors associated with each questing life stage, to investigate predictors of abundance, and to determine the likelihood of not collecting ticks at different life stages. A total of 46,770 ticks were collected, of which 12,607 H. longicornis and five other tick species were identified. Overall, abundance of H. longicornis were associated with spring and summer seasons, forested environments, relative humidity and barometric pressure, sunny conditions, and in relation with other tick species. The likelihood of not collecting H. longicornis was associated with day length and barometric pressure. Additional associations for different life stages were also identified and included other tick species, climatic variables, and environmental conditions. Here, we demonstrated that environmental variables can be useful to predict the presence of questing H. longicornis and provide ideas on how to use this information to develop a surveillance plan for different southeastern areas with and without infestations.

Forest-associated habitat variables influence human-tick encounters in the southeastern United States.

Due to the increased frequency of human-tick encounters and expanding ranges of ticks in the United States, there is a critical need to identify environmental conditions associated with tick populations and their likelihood to contact human hosts. In a passive tick surveillance partnership with the US Department of Agriculture Forest Inventory and Analysis (FIA) program, we identified environmental variables associated with tick encounters by forestry personnel. Ticks were identified by species and life stage, and site-specific variables were associated with each tick using FIA forest inventory datasets and generalized linear models with negative binomial distributions. Of the 55 FIA variables available, we identified biotic and abiotic environmental variables associated with Amblyomma americanum L. (carbon in litter material and standing dead tree aboveground dry biomass), Dermacentor variabilis Say (seedling species unevenness and elevation), and Ixodes scapularis L. (carbon in dead woody material and seedling species unevenness). We propose conducting future treatment-control studies using these forestry-related environmental variables to test their ability to alter tick abundance at sites. Land management decisions not only affect common flora and fauna, but changes to these habitats can also alter the way ticks parasitize hosts and use vegetation to find those hosts. These results can be used with land management decisions to prevent future human-tick encounters and highlight risk areas.

Management of Haemaphysalis longicornis (Acari: Ixodidae) on a cow-calf farm in East Tennessee, USA.

Haemaphysalis longicornis Neumann is an exotic and invasive tick species rapidly expanding across the United States. Large infestations of these ticks on cattle can cause anemia, and in eastern regions of the country, they are transmitting Theileria orientalis Ikeda within herds. Methods for managing H. longicornis in the environment are rarely successful and rely on chemicals. To document population effects from producer management decisions, we investigated the change in H. longicornis populations to different tick management practices chosen by producers at 3 different H. longicornis-infested farms. Farm 1 kept a closed herd, chose to cut brush monthly, used on-animal acaricides, and allowed us to drag weekly. Farm 2 kept an open herd, chose to cut brush yearly, did not use on-animal acaricides, and allowed us to drag for ticks weekly/monthly. Farm 3 kept an open herd, chose to cut brush yearly, used on-animal acaracides, and allowed us to drag for ticks monthly. We assessed H. longicornis populations responding to those methods over time using active surveillance methods at each farm. Management decisions on Farms 1 and 3 significantly reduced H. longicornis on farms. Importantly, Farm 1 management decisions reduced the chance of a tick being present by 90%; the number of questing ticks collected fell from 5,000 to 12 H. longicornis in 2 years. Therefore, combined management strategies such as keeping a closed herd, use of on-animal chemical control, mechanical control, and reducing the amount of vegetation on farms were effective ways for producers to manage Haemaphysalis longicornis Neuman (Ixodidae).

An ecological and epidemiological single-season survey of Anaplasma and Ehrlichia positive ticks in Victoria Falls National Park, Zimbabwe.

There is an urgent need for continued research on the ecology of tick-borne diseases in Africa. Our objective was to provide a preliminary description of the ecology and epidemiology of tick species, tick-borne pathogens, and animal hosts in Zimbabwe, focusing efforts at Victoria Falls National Park, for a single season. We tested the hypothesis that tick surveillance and pathogen screening data can be used to model associations among ticks, hosts, and pathogens. We collected ticks from domesticated animals and wildlife in Zimbabwe and screened the ticks for the presence of Anaplasma and Ehrlichia bacteria. Nearly 30% of the screened ticks were PCR-positive; 89% of tick species were PCR-positive, and 88% of animal species carried at least one PCR-positive tick. We sequenced a subset of amplicons that were similar to three Anaplasma species and three Ehrlichia species. The odds of a tick being PCR-positive increased when many ticks were collected from the host or the tick was collected from a cow (domesticated animal). Tick species shared host species more often than expected. We demonstrate that ticks in northwestern Zimbabwe present a One Health problem for nearby wildlife and humans.

Supplemental feeding of deer reduces tick abundance in Mississippi, U.S.A.

Prior research on baiting and feeding of wildlife found changes in habitat and the concentration of wildlife on a local scale (e.g., hundreds of meters). Since changes in habitat and host density affect ticks, feeding wildlife may lead to changes in tick and tick-borne disease ecology. We quantified the effect of feeding deer on ticks and tick-borne diseases at 79 pairs of sites with and without deer feeders during May-August of 2019 and 2020. We captured 0.4 fewer adult (p<0.05) and 1.2 fewer nymphal ticks (p=0.01) at feeder sites. This effect intensified over time with one fewer tick trapped at old feeders (≥5 years) compared to new feeders (<5 years, p<0.05). Greater daily wildlife visitation rates (p<0.001) may have allowed questing ticks to encounter hosts more readily. Most collected ticks were Amblyomma americanum (92.8%), a vector of Ehrlichia and Rickettsia pathogens, though prevalence of these pathogens did not differ (p>0.13) at a local scale. Supplemental deer feeding appears to influence ticks, possibly due to decreased tick habitat and increased wildlife use around feeders. Our findings indicate feeding does not lead to increased prevalence of Ehrlichia or Rickettsia bacteria within A. americanum locally.

Spray and Pour-On Acaricides Killed Tennessee (United States) Field-Collected Haemaphysalis longicornis Nymphs (Acari: Ixodidae) in Laboratory Bioassays.

Haemaphysalis longicornis Neumann (Asian longhorned tick) is an exotic and invasive tick species presenting a health and economic threat to the United States (U.S.) cattle industry due to its ability to transmit pathogens and infest hosts in large numbers. The objective of this study was to evaluate available products at causing H. longicornis mortality in a laboratory bioassay. The efficacy of products was evaluated at label rates using H. longicornis nymphs collected from a cattle farm in eastern Tennessee in two different bioassays (spray or dip) against untreated controls. After exposure, ticks were transferred to clean petri dishes and checked for mortality at 0, 1, 2, 3, 4, 21, 24, and 48 h post exposure. No mortality occurred in the untreated controls, whereas all treated ticks were dead within 24 h of exposure (P < 0.0001). These findings support the hypothesis that currently available spray and pour-on products are effective at causing H. longicornis mortality. We conclude that these acaricides can be used as a component to prevent H. longicornis dispersal and for control in the U.S.

No Evidence of Competition Between the Blacklegged Tick (Acari: Ixodidae) and American Dog Tick on the Rodent Host White-Footed Deermouse (Rodentia: Cricetidae) in Southwestern Tennessee.

Investigations that analyze interspecific associations of vectors on their hosts are important for understanding community structure and implementing ways to comprehend mechanisms of pathogen transmission. We assessed the interspecific association of two tick species (Ixodes scapularis Say (Ixodida: Ixodidae) and Dermacentor variabilis Say (Ixodida: Ixodidae)) on the rodent host Peromyscus leucopus Rafinesque (Rodentia: Cricetidae) at the Hobart Ames Research and Education Center in southwestern Tennessee. Of the rodents captured, 95 (63%) had neither species of tick, 6 (4%) had both tick species, 25 (16%) had I. scapularis only, and 26 (17%) had D. variabilis only. A coefficient of association (C7 = -0.08) was calculated, which suggested there was competition between the two species of ectoparasites, but this value was not significant, indicating that there was a neutral relationship between the tick species on P. leucopus. The co-occurrence of both tick species on their host at the same time suggested that the two tick species can occupy the same host and use the same resources without competing.

Small-mammal characteristics affect tick communities in southwestern Tennessee (USA).

Life histories can influence the degree of parasite infestations on a host. Pressures exerted on hosts based on age and sex convey varying degrees of parasite prevalence due to differences in host lifestyles, but it is not known how interactions between different host traits affect tick numbers. The objective of this study was to determine if host characteristics (e.g., age, sex, weight, and their interactions) affect the mean number of ticks found on small mammals regardless of host species or habitat. Sherman live traps were placed in forest and grass/forb habitats representative of the southeastern United States. After capture, host characteristics were recorded, and hosts were then searched for ticks. A total of 281 small mammals (148 Peromyscus leucopus, 34 P. maniculatus, 76 Sigmodon hispidus, 16 Microtus pinetorum, and 7 Ochrotomys nuttalli) and 610 ticks (488 Dermacentor variabilis, 114 Ixodes scapularis, 1 Amblyomma americanum, and 7 A. maculatum) were collected in this study. Host's age, sex, and weight affected the number of ticks collected from small mammals and significant interaction effects between host traits occurred (weight by sex, weight by age, and sex by age). For instance, female subadult rodents had significantly more ticks compared to female adults, male subadults had significantly fewer ticks compared to male adults, and the number of ticks on a host increased as host body mass increased. These results support the hypothesis that the number of ticks vary on rodent hosts based on life histories and trait interactions. Therefore, understanding the behavioral mechanisms of a host can aid in the management of parasites in the environment.

Evidence Types and Trends in Tropical Forest Conservation Literature.

To improve the likelihood of conservation success, donors, policy makers, nongovernmental organizations (NGOs), and researchers are increasingly interested in making conservation decisions based on scientific evidence. A major challenge in doing so has been the wide variability in the methodological rigor of existing studies. We present a simple framework to classify different types of conservation evidence, which can be used to understand the strengths, weaknesses, and biases in the conservation effectiveness literature. We then apply this framework to evaluate the evidence for the efficacy of four important strategies in tropical forest conservation. Even though there has been an increase in methodologically rigorous studies over time, countries that are globally important in terms of their biodiversity are still heavily under-represented by any type of conservation effectiveness evidence.

Impacts of stage-specific acute pesticide exposure on predicted population structure of the soft-shell clam, Mya arenaria.

A combined laboratory and modeling approach was used to assess the impact of selected pesticides on early life stages of the soft-shell clam, Mya arenaria. Clams were exposed for 24h as veligers or pediveligers to the broad-spectrum herbicide hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1h,3h)-dione; Velpar], the phenoxyacetic acid herbicide, 2,4-D (2,4-dichlorophenoxyacetic acid; Agway Super BK 32), or phosmet (Imidan). In addition, juvenile clams were exposed for 24h to 2,4-D and their growth monitored for 21 months. Laboratory experiments indicated veligers were more sensitive to acute pesticide exposure than pediveligers, with 2,4-D exposed veligers exhibiting the lowest survival among all treatments. Relative to controls, juvenile clams exposed to 0.5 ppm 2,4-D had enhanced survival following the initial 3 months of grow out. Juveniles exposed to 0.5, 5 and 10 ppm 2,4-D showed an initial growth delay relative to control clams, but at 21 months post-exposure these clams were significantly larger than control clams. Data from the larval and juvenile exposures were used to generate a stage-specific matrix model to predict the effect of pesticide exposure on clam populations. Impacts on simulated clam populations varied with the pesticide and stage exposed. For example, 2,4-D exposure of veligers and pediveligers significantly reduced predicted recruitment as well as population growth rate compared to controls, but juvenile exposure to 2,4-D did not significantly reduce population growth rate. With the exception of veligers exposed to 10 ppm, hexazinone exposure at the both veliger and pediveliger stages significantly reduced predicted recruitment success compared to 0 ppm controls. Hexazinone exposure also reduced modeled population growth rates, but these reductions were only slight in the pediveliger exposure simulations. Veliger and pediveliger exposure to phosmet reduced modeled population growth rate in a dose-dependent fashion. Changes in modeled population stable stage distributions were also observed when veligers were exposed to any pesticide. These results suggest that both the stage of exposure and the specific toxicant are important in predicting effects of pesticide exposure on soft-shell clam populations, with earlier life stages showing greater sensitivity to the pesticides tested.

Extensor mechanism allograft reconstruction in TKA at a mean of 56 months.

Extensor mechanism disruption in total knee arthroplasty (TKA) occurs infrequently but often requires surgical intervention. We compared two cohorts undergoing extensor mechanism allograft reconstruction and presumed both types of extensor mechanism allograft reconstruction will be successful but for different indications and forms of extensor failure. Nineteen consecutive patients with extensor mechanism disruption after TKA were treated. Two different types of extensor mechanism allografts were used: quadriceps tendon-patella-patella tendon-tibial tubercle, and Achilles tendon allograft. Demographic factors, diagnosis at extensor failure, Knee Society clinical rating scores, radiographs, and patient satisfaction were recorded. The average time from extensor mechanism disruption to surgery was 6.6 months (range, 1-24 months). At a mean followup of 56 months (range, 24-96 months), all patients were community ambulators. The mean Knee Society score improved from 27 points preoperatively to 76 points postoperatively. There was no loss of knee flexion postoperatively. The mean postoperative lag was 14 degrees. Fifteen patients had an extensor lag of less than 10 degrees. All patients thought their functional status had improved, and 89% were satisfied with the results of the allograft reconstruction. The total extensor mechanism allograft and Achilles tendon allograft both were successful in the treatment of the failed extensor mechanism.

A predictive tool for the self-management of diabetes (Librae): evaluation using a continuous glucose monitoring system.

AIMS: Diabetes self-management involves a difficult balancing act between insulin, food and exercise. The challenge is to develop innovative, validated algorithms to aid patient decision-making and optimize glycaemic control. 'Librae' is a computerized diabetes simulator in diary format, developed as an educational predictive tool for patients, reducing 'trial and error' by allowing patients to simulate and experiment with dietary or insulin adjustments on a 'body double'. We have evaluated the predictive ability of Librae using continuous blood glucose monitoring (CGMS). METHODS: Patients with Type 1 Diabetes attending the Paediatric Clinic were invited to use 'Librae' for 1 week and were then fitted with a CGMS for 72 h. The predictive ability of 'Librae' was compared with concurrent data obtained from the CGMS. RESULTS: Seven thousand nine hundred and sixty paired blood glucose values were obtained from the 11 patients who completed the study. 'Librae' underestimated the measured CGMS values, the error having a positive mean of 0.35 mmol/l (95% confidence interval 0.22-0.48 mmol/l). However, Librae tended to overestimate at low levels of blood glucose readings, and underestimate at high levels of blood glucose readings. CONCLUSION: The modelled values of 'Librae' correlated well with the CGMS data, but clinically unacceptable errors occurred at extremes of blood glucose levels. Concurrent CGMS recordings have provided a large data set to modify and improve the existing Librae model and patient feedback has led to improvements in its usability. Librae may provide a useful tool to improve diabetes self-management education and optimize glycaemic control.

Effect of estrogen deficiency on skeletal and alveolar bone density in sheep.

BACKGROUND: This study provides a longitudinal assessment of changes in alveolar and skeletal bone mineral density (BMD) in ovariectomized animals. METHODS: Following ovariectomy (OVX) (n = 6) or sham-operation (n = 6) intraoral radiographs were made at 4-month intervals and serum 17-beta-estradiol, osteocalcin, and interleukin (IL)-6, urinary deoxypyridinium, and salivary IL-6, deoxypyridinium, and osteocalcin concentrations were evaluated. Twelve months after surgery, animals were sacrificed and the mandible and radius/ulna removed. Bones were sectioned and radiographed. Mean BMD and cortical thicknesses were calculated from each region. RESULTS: OVX animals had a progressive decrease in serum 17-beta-estradiol, increased serum osteocalcin and IL-6, urinary deoxypyridinium and salivary IL-6, osteocalcin and deoxypyridinium (P < 0.001), suggesting that they were becoming osteoporotic. The BMD of the radius/ulna and mandibular alveolar bone was significantly reduced in OVX animals (P < 0.05 and P < 0.001, respectively). Reduced alveolar bone BMD became evident in OVX animals 6 months after surgery and became more severe during the subsequent 6 months. Alveolar crestal height was also significantly reduced in OVX animals (P < 0.001). These biochemical and density changes preceded a significant reduction in serum 17-beta-estradiol, which occurred between 4 and 8 months following surgery. CONCLUSIONS: Serial measurements of alveolar BMD predicts loss of skeletal BMD in OVX sheep. Changes in alveolar BMD precede estrogen deficiency, suggesting that early signs of reduced BMD may be detected in peri-menopausal women. The presence of biomarkers of bone metabolism within saliva and their correlation with reduced BMD suggests that saliva could be used as an adjunct screening method for assessment of skeletal bone density.

Stem design and dislocation after revision total hip arthroplasty: clinical results and computer modeling.

The effect of the size and shape of the neck and the taper of the femoral stem on dislocation rate after revision total hip arthroplasty was examined. Design I had a large (14/16), long taper with a circular neck cross-section; a fixed 42-mm offset; and a neck that was anteverted relative to the stem. Design II was characterized by a smaller (12/14), shorter taper; a trapezoidal neck cross-section; a progressive (40-50 mm) offset; and no neck anteversion relative to the stem. The stems were digitized and placed through a range of motion using virtual reality software, and the cross-sectional area of the neck, length of the taper, and total arc of motion before impingement between the neck and liner were compared. The dislocation rate at a minimum of 2 years' follow-up was 15.4% (8 of 52) for design I compared with 4.3% (2 of 46) for design II. This finding was consistent with the results of computer modeling, which showed that design I had a cross-sectional area that was 32% greater and a total arc of motion that was 76% less compared with design II. The results suggest that neck and taper design may be an important factor in dislocation after revision total hip arthroplasty.

An aryl hydrocarbon receptor (AHR) homologue from the soft-shell clam, Mya arenaria: evidence that invertebrate AHR homologues lack 2,3,7,8-tetrachlorodibenzo-p-dioxin and beta-naphthoflavone binding.

The aryl hydrocarbon receptor (AHR) mediates numerous toxic effects following exposure of vertebrate animals to certain aromatic environmental contaminants, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). To investigate possible effects of TCDD on invertebrates, a cDNA encoding an AHR homologue was cloned from the soft-shell clam, Mya arenaria. The predicted amino acid sequence contains regions characteristic of vertebrate AHRs: basic helix-loop-helix (bHLH) and PER-ARNT-SIM (PAS) domains and a glutamine-rich region. Phylogenetic analysis shows that the clam AHR sequence groups within the AHR subfamily of the bHLH-PAS family, in a clade containing AHR homologues from Drosophila melanogaster and Caenorhabditis elegans. AHR mRNA expression was detected in all tissue types tested: adductor muscle, digestive gland, foot, gill, gonad, mantle, and siphon. The in vitro-expressed clam AHR exhibited sequence-specific interactions with a mammalian xenobiotic response element (XRE). Velocity sedimentation analysis using either in vitro-expressed clam AHR or clam cytosolic proteins showed that this AHR homologue binds neither [(3)H]TCDD nor [(3)H]beta-naphthoflavone (BNF). Similarly, in vitro-expressed D. melanogaster and C. elegans AHR homologues lacked specific binding of these compounds. Thus, the absence of specific, high-affinity binding of the prototypical AHR ligands TCDD and BNF, is a property shared by known invertebrate AHR homologues, distinguishing them from vertebrate AHRs. Comparative studies of phylogenetically diverse organisms may help identify an endogenous ligand(s) and the physiological role(s) for this protein.

Quantitative reverse transcription polymerase chain reaction of a molluscan metallothionein mRNA.

A quantitative assay based on competitive reverse transcription polymerase chain reaction (RT-PCR) was developed for metallothionein (MT) mRNA of the mollusc Crassostrea virginica and applied to analysis of MT mRNA of hemocytes. The assay was based on titration of a competitive external standard cRNA derived from the coding region of the oyster MT mRNA. Serial dilutions of the cRNA standard were coamplified with a constant amount of total RNA using biotinylated primers common to both target and standard sequences. Amplified products were bound to streptavidin-coated plates and hybridized to sequence-specific fluorescein-labeled probes. Detection was based on single photon counting of chemiluminescence generated by an alkaline phosphatase-conjugated antifluorescein antibody. For quantification, the target chemiluminescence was normalized to that of the standard, and the amount of target MT mRNA in the sample was derived from the titration. Cadmium-induced MT mRNA equivalent to that in 180 hemocytes was easily detected, and, for routine quantitative analysis, was sufficiently sensitive to quantify basal and induced MT mRNA. Basal hemocyte MT mRNA of 133+/-8 (1 S.E.) amol per microgram total RNA was induced 5-fold to 573+/-14 amol per microgram total RNA by in vitro exposure to 15 microM CdCl(2) for 20 h.

Disruption of metallothionein expression with antisense oligonucleotides abolishes protection against cadmium cytotoxicity in molluscan hemocytes.

The relationship between metallothionein (MT) induction and cytotoxicity was examined in isolated oyster hemocytes exposed in vitro to cadmium, copper, and zinc. In all cases MT induction increased to peak levels with increased metal dose, then declined with continued increases in dose. The effectiveness of these metals as inducers of MT was cadmium > copper > zinc, with cadmium the most effective inducer in magnitude of induction and sensitivity to dose. Cytotoxicity of the metals, based on decreases in lysosomal neutral red retention times, was copper > cadmium > zinc. Zinc was relatively nontoxic and a poor inducer of MT. Cadmium, which was intermediate in toxicity, required concentrations in excess of that causing peak induction of MT to have substantial effects on lysosomal membrane integrity. In contrast, copper was highly cytotoxic at concentrations below that which resulted in peak MT induction. This reversal in the rank order of cadmium and copper suggested that the toxicity of cadmium was tempered by the protective effects of MT. This was verified by disrupting MT expression with antisense phosphorothioate-substituted oligodeoxynucleotides. Administration of 2.5 microM CdCl(2), which induced MT but had no effect on lysosomal membrane stability when administered alone, reduced neutral red retention time to 41% of control levels when administered in the presence of antisense. The resulting toxicity was greater than that caused by a comparable concentration of copper. The findings represented evidence that expression of MT protects against cadmium toxicity in an estuarine mollusc.