An Overview of the Radiation Oncology Alternative Payment Model and Impact on Practices Serving Vulnerable Populations.

Radiation oncology reimbursement methodology has been largely unchanged over the past 30 years, and new approaches are of great interest to practicing radiation oncologists and other health care stakeholders. Traditional radiation oncology reimbursement is based on a series of individual codes for evaluation and management (professional) and technical services, yielding a complex reimbursement system. In an attempt to move toward a simpler, episodic payment model, bundling all of the codes into a single payment, an alternative payment model for radiation oncology was developed. The radiation oncology alternative payment model is a revolutionary change in how radiation oncologic services will be reimbursed and has potential to affect all aspects of radiation oncologic care. Here, the authors review the origin of the currently proposed radiation oncology model and discuss potential implications of this model on the provision of care, especially as it relates to rural practices and other underserved and vulnerable patient populations.

Cosmetic Outcomes of a Phase 1 Dose Escalation Study of 5-Fraction Stereotactic Partial Breast Irradiation for Early Stage Breast Cancer.

PURPOSE: Our purpose was to evaluate cosmetic changes after 5-fraction adjuvant stereotactic partial breast irradiation (S-PBI). METHODS AND MATERIALS: Seventy-five women with in situ or invasive breast cancer stage 0, I, or II, with tumor size ≤3 cm, were enrolled after lumpectomy in a phase 1 dose escalation trial of S-PBI into cohorts receiving 30, 32.5, 35, 37.5, or 40 Gy in 5 fractions. Before S-PBI, 3 to 4 gold fiducial markers were placed in the lumpectomy cavity for tracking with the Synchrony respiratory tracking system. S-PBI was delivered with a CyberKnife robotic radiosurgery system. Patients and physicians evaluated global cosmesis using the Harvard Breast Cosmesis Scale. Eight independent panelists evaluated digital photography for global cosmesis and 10 subdomains at baseline and follow-up. McNemar tests were used to evaluate change in cosmesis, graded as excellent/good or fair/poor, from baseline to year 3. Wilcoxon signed rank tests were used to evaluate change in subdomains. Cohen's kappa (κ) statistic was used to estimate interobserver agreement (IOA) between raters, and Fleiss' κ was used to estimate IOA between panelists. RESULTS: Median cosmetic follow-up was 5, 5, 5, 4, and 3 years for the 30, 32.5, 35, 37.5, and 40 Gy cohorts. Most patients reported excellent/good cosmesis at both baseline (86.3%) and year 3 (89.8%). No dose cohort had significantly worsened cosmesis by year 3 on McNemar analysis. No cosmetic subdomain had significant worsening by year 3. IOA was fair for patient-physician (κ = 0.300, P < .001), patient-panel (κ = 0.295, P < .001), physician-panel (κ = 0.256, P < .001), and individual panelists (Fleiss κ = 0.327, P < .001). CONCLUSIONS: Dose escalation of S-PBI from 30 to 40 Gy in 5 fractions for early stage breast cancer was not associated with a detectable change in cosmesis by year 3. S-PBI is a promising modality for treatment of early stage breast cancer.

Merit-Based Incentive Payment System (MIPS) Participation in Radiation Oncology Practices - A Simple Survey.

PURPOSE: Our purpose was to survey nationwide radiation oncology practices on their participation in, burden of, and satisfaction with the Medicare Access and Children's Health Insurance Program Reauthorization Act of 2015 (MACRA) payment programs. METHODS AND MATERIALS: All radiation oncology practices accredited by a national specialty organization were invited to participate in a voluntary online survey from December 2018 to January 2019. Questions focused on participation in the Merit-based Incentive Payment System (MIPS) in 2017 and 2018, as by the time of this survey, radiation oncology did not yet have a specialty-specific advanced Alternative Payment Model. RESULTS: Of n = 705 solicited practices, n = 199 completed the survey for an overall response rate of 28.2%. Practices varied significantly in their duration of participation in MACRA programs, means of data submission, and reported improvement activities under MIPS. Forty-nine percent of respondents described being either somewhat or extremely dissatisfied with the ease of submitting measures and data in 2018. The estimated cost to the practices of compliance with MACRA was queried in bins; of users able to estimate the cost of compliance for 2018, the median reported bin was $10,001 to $20,000 (range, less than $1000-100,000 or more). CONCLUSIONS: The participation style in MACRA among radiation oncology practices varied substantially in the years 2017 and 2018. The Center for Medicare & Medicaid Services gave no precise estimates on the cost of compliance for MIPS, but estimated a $3019.47 cost of compliance with the mandated Radiation Oncology Alternative Payment Model in the 2020 Final Rule for selected practices. In this survey, respondents commonly reported the cost of compliance with MACRA significantly exceeded this estimate.

The Medicare Access and CHIP Reauthorization Act of 2015 (MACRA) Made Simple for Medical and Radiation Oncologists: A Narrative Review.

IMPORTANCE: The Medicare Access and CHIP (Children's Health Insurance Program) Reauthorization Act of 2015 (MACRA) instituted significant changes in payment methods for many Medicare Part B billing providers (eg, clinicians and health care facilities). Fulfilling its measures satisfactorily and adhering to its reporting requirements will significantly affect reimbursement, yet previous surveys suggest that clinicians' understanding of MACRA is poor. This review provides fundamental background on MACRA for medical and radiation oncologists. OBSERVATIONS: The Congress.gov database, PubMed, and the Center for Medicare & Medicaid Services website were searched for legislature and publications relevant to the history, structure, and predicted future for MACRA. MACRA originated from concerns of poor-quality care and from the failure of the traditional fee-for-service model and the Medicare Sustainable Growth Rate method to control rising health care costs. The Quality Payment Program of MACRA started the Merit-based Incentive Payment System (MIPS) and the Alternative Payment Model (APM) system to move from the traditional fee-for-service model to value-based payment. The most recent legislation extended the transitional period for MIPS and removed drugs and biologics covered by Medicare Part B. Currently, the primary APM for medical oncology is the Oncology Care Model, and an APM for radiation oncology is awaiting approval. Despite recent calls from the Medicare Payment Advisory Commission to end MIPS, there is no indication that either MIPS or APMs will be repealed in the near future. CONCLUSIONS AND RELEVANCE: MACRA affects the methods of payment for many Medicare Part B billing providers; the included summary equips medical and radiation oncologists with an understanding of its structure and requirements.

Dosimetric comparison of rectal-sparing capabilities of rectal balloon vs injectable spacer gel in stereotactic body radiation therapy for prostate cancer: lessons learned from prospective trials.

This study aimed to compare the rectal-sparing capabilities of rectal balloons vs absorbable injectable spacer gel in stereotactic body radiation therapy (SBRT) for prostate cancer. Patient samples included in this analysis were obtained from 2 multi-institutional prospective trials of SBRT for prostate cancer using a rectal balloon (n = 36 patients) and injectable spacer gel (n = 36). Treatment prescription dose was 45 Gy in 5 fractions in 42 patients; for equal comparison, the remaining 30 patients were rescaled to 45 Gy from 47.5 Gy prescription (n = 6) and 50 Gy prescription (n = 24). The median prostate volumes and body mass index in the 2 patient samples were not statistically significantly different (p= 0.67 and 0.45, respectively), supporting anatomic similarity between cohorts. The injectable spacer gel achieved dosimetric superiority over the rectal balloon with respect to the maximum dose to the rectum (42.3 vs 46.2 Gy, p < 0.001), dose delivered to 33% of the rectal circumference (28 vs 35.1 Gy, p < 0.001), and absolute volume of rectum receiving 45 Gy (V45Gy), V40Gy, and V30Gy (0.3 vs 1.7 cc, 1 vs 5.4 cc, and 4.1 vs 9.6 cc, respectively; p < 0.001 in all cases). There was no difference between the 2 groups with respect to the V50Gy of the rectum or the dose to 50% of the rectal circumference (p= 0.29 and 0.06, respectively). The V18.3Gy of the bladder was significantly larger with the rectal balloon (19.9 vs 14.5 cc, p= 0.003). In this analysis of patients enrolled on 2 consecutive multi-institutional prospective trials of SBRT for prostate cancer, the injectable spacer gel outperformed the rectal balloon in the majority of the examined and relevant dosimetric rectal-sparing parameters. The rectal balloon did not outperform the injectable spacer gel in any measured rectal dose parameter.

α2δ-3 Is Required for Rapid Transsynaptic Homeostatic Signaling.

The homeostatic modulation of neurotransmitter release, termed presynaptic homeostatic potentiation (PHP), is a fundamental type of neuromodulation, conserved from Drosophila to humans, that stabilizes information transfer at synaptic connections throughout the nervous system. Here, we demonstrate that α2δ-3, an auxiliary subunit of the presynaptic calcium channel, is required for PHP. The α2δ gene family has been linked to chronic pain, epilepsy, autism, and the action of two psychiatric drugs: gabapentin and pregabalin. We demonstrate that loss of α2δ-3 blocks both the rapid induction and sustained expression of PHP due to a failure to potentiate presynaptic calcium influx and the RIM-dependent readily releasable vesicle pool. These deficits are independent of α2δ-3-mediated regulation of baseline calcium influx and presynaptic action potential waveform. α2δ proteins reside at the extracellular face of presynaptic release sites throughout the nervous system, a site ideal for mediating rapid, transsynaptic homeostatic signaling in health and disease.

What Are Medical Students in the United States Learning About Radiation Oncology? Results of a Multi-Institutional Survey.

PURPOSE: The purposes of this study were to assess the exposure that medical students (MSs) have to radiation oncology (RO) during the course of their medical school career, as evidenced by 2 time points in current medical training (ie, first vs fourth year; MS1s and MS4s, respectively) and to assess the knowledge of MS1s, MS4s, and primary care physicians (PCPs) about the appropriateness of RT in cancer management in comparison with RO attendings. METHODS: We developed and beta tested an electronic survey divided into 3 parts: RO job descriptions, appropriateness of RT, and toxicities of RT. The surveys were distributed to 7 medical schools in the United States. A concordance of >90% (either yes or no) among RO attendings in an answer was necessary to determine the correct answer and to compare with other subgroups using a χ(2) test (P<.05 was significant). RESULTS: The overall response rate for ROs, MS1s, MS4s, and PCPs was 26%; n (22 + 315 + 404 + 43)/3004. RT misconceptions decreased with increasing level of training. More than 1 of 10 MSs did not believe that RT alone could cure cancer. Emergent oncologic conditions for RT (eg, spinal cord compression, superior vena cava syndrome) could not be identified by >1 of 5 respondents. Multiple nontoxicities of RT (eg, emitting low-level radiation from the treatment site) were incorrectly identified as toxicities by >1 of 5 respondents. MS4s/PCPs with an RO rotation in medical school had improved scores in all prompts. CONCLUSIONS: Although MS knowledge of general RT principles improves from the first to the fourth year, a large knowledge gap still exists between MSs, current PCPs, and ROs. Some basic misconceptions of RT persist among a minority of MSs and PCPs. We recommend implementing formal education in RO fundamentals during the core curriculum of medical school.

Rare Red Rashes: A Case Report of Levetiracetam-Induced Cutaneous Reaction and Review of the Literature.

Cutaneous reactions secondary to medications are rare but can be serious events resulting in morbidity and mortality and can be caused by anticonvulsant medications. Levetiracetam has been considered relatively safe compared with other antiepileptics with regard to skin eruptions. We report a case of a cutaneous reaction secondary to levetiracetam. A 64-year-old man presented to the hospital with an altered mental status and aphasia. Imaging revealed a left basal ganglia mass. A biopsy of the lesion was obtained, and levetiracetam was started at 500 mg intravenously twice a day for seizure prophylaxis. After 13 doses, the patient developed a diffuse, erythematous, warm, blanching, morbilliform rash. Levetiracetam was discontinued, and methylprednisolone was started. After 4 days, the rash dissipated. Levetiracetam is an antiepileptic medication that has an unknown mechanism of action. To date, there are only 4 cases reported involving skin reactions from levetiracetam. Two of the cases were classified as Stevens-Johnson Syndrome: 1 as toxic epidermal necrolysis and 1 as erythema multiforme. Our case was classified as a morbilliform rash. A Naranjo score of 7 suggested a probable cause for a levetiracetam-induced skin reaction. Antiepileptic medications are used in certain cases to prevent seizures in patients with central nervous system tumors. Although levetiracetam seems to have fewer side effects than the traditional antiepileptic medications, it is important for the healthcare provider to continuously evaluate the need for all medications and discontinue unneeded ones to help avoid potential medication adverse effects.

Evolution of temporal and spectral dynamics of pathologic high-frequency oscillations (pHFOs) during epileptogenesis.

OBJECTIVE: In temporal lobe epilepsy (TLE), pathologic high frequency oscillations (pHFOs, 200-600 Hz) are present in the hippocampus, especially the dentate gyrus (DG). The pHFOs emerge during a latent period prior to the onset of spontaneous generalized seizures. We used a unilateral suprahippocampal injection of kainic acid (KA) mouse model of TLE to characterize the properties of hippocampal pHFOs during epileptogenesis. METHODS: In awake head-fixed mice, 4-14 days after KA-induced status epilepticus (SE), we recorded local field potentials (LFPs) with 64-channel silicon probes spanning from CA1 alveus to the DG hilus, or with glass pipettes in the DC mode in the CA1 str radiatum. RESULTS: The pHFOs, are observed simultaneously in the CA1 and the DG, or in the DG alone, as early as 4 days post-SE. The pHFOs ride on top of DC deflections, occur during motionless periods, persist through the onset of TLE, and are generated in bursts. Burst parameters remain remarkably constant during epileptogenesis, with a random number of pHFOs generated per burst. In contrast, pHFO duration and spectral dynamics evolve from short events at 4 days post-SE to prolonged discharges with complex spectral characteristics by 14 days post-SE. Simultaneous dural EEG recordings were exceedingly unreliable for detecting hippocampal pHFOs; therefore, such recordings may deceptively indicate a "silent" period even when massive hippocampal activity is present. SIGNIFICANCE: Our results demonstrate that hippocampal pHFOs exhibit a dynamic evolution during the epileptogenic period following SE, consistent with their role in transitioning to the chronic stage of TLE.

Landscape position influences microbial composition and function via redistribution of soil water across a watershed.

Subalpine forest ecosystems influence global carbon cycling. However, little is known about the compositions of their soil microbial communities and how these may vary with soil environmental conditions. The goal of this study was to characterize the soil microbial communities in a subalpine forest watershed in central Montana (Stringer Creek Watershed within the Tenderfoot Creek Experimental Forest) and to investigate their relationships with environmental conditions and soil carbonaceous gases. As assessed by tagged Illumina sequencing of the 16S rRNA gene, community composition and structure differed significantly among three landscape positions: high upland zones (HUZ), low upland zones (LUZ), and riparian zones (RZ). Soil depth effects on phylogenetic diversity and ß-diversity varied across landscape positions, being more evident in RZ than in HUZ. Mantel tests revealed significant correlations between microbial community assembly patterns and the soil environmental factors tested (water content, temperature, oxygen, and pH) and soil carbonaceous gases (carbon dioxide concentration and efflux and methane concentration). With one exception, methanogens were detected only in RZ soils. In contrast, methanotrophs were detected in all three landscape positions. Type I methanotrophs dominated RZ soils, while type II methanotrophs dominated LUZ and HUZ soils. The relative abundances of methanotroph populations correlated positively with soil water content (R = 0.72, P < 0.001) and negatively with soil oxygen (R = -0.53, P = 0.008). Our results suggest the coherence of soil microbial communities within and differences in communities between landscape positions in a subalpine forested watershed that reflect historical and contemporary environmental conditions.

Selectins in Liver Ischemia and Reperfusion Injury.

Liver ischemia reperfusion injury is mediated by a complex system of signaling cascades and inflammatory response resulting in organ damage. Selectins are a group of cell adhesion glycoproteins that play a key role in the initial immunological response. L-selectins, found on leukocytes, initiate the original adhesion and rolling phase of leukocyte extravasation upon liver sinusoidal endothelial cells (LSECs). P-selectins, found on platelets and tissue-specific endothelial cells, further increases leukocyte-endothelial adhesion and rolling. P-selectin-ligand binding also initiates intracellular signals that produce adhesion molecules to start firm adhesion and increase local chemokine production. L-selectin-ligand binding on the leukocytes increases adhesion molecule expression and chemokines, but also initiate changes in intracellular structural actin. E-selectin expression occurs with the presence of TNF-α and/or IL-1ß. E-selectin-ligand binding decreases leukocyte rolling velocity and increases adhesion molecules. Together, these glycoproteins transition the leukocyte response from original margination and rolling to firm adhesion and eventually migration.

Safety and feasibility of STAT RAD: Improvement of a novel rapid tomotherapy-based radiation therapy workflow by failure mode and effects analysis.

PURPOSE: The clinical challenge of radiation therapy (RT) for painful bone metastases requires clinicians to consider both treatment efficacy and patient prognosis when selecting a radiation therapy regimen. The traditional RT workflow requires several weeks for common palliative RT schedules of 30 Gy in 10 fractions or 20 Gy in 5 fractions. At our institution, we have created a new RT workflow termed "STAT RAD" that allows clinicians to perform computed tomographic (CT) simulation, planning, and highly conformal single fraction treatment delivery within 2 hours. In this study, we evaluate the safety and feasibility of the STAT RAD workflow. METHODS AND MATERIALS: A failure mode and effects analysis (FMEA) was performed on the STAT RAD workflow, including development of a process map, identification of potential failure modes, description of the cause and effect, temporal occurrence, and team member involvement in each failure mode, and examination of existing safety controls. A risk probability number (RPN) was calculated for each failure mode. As necessary, workflow adjustments were then made to safeguard failure modes of significant RPN values. After workflow alterations, RPN numbers were again recomputed. RESULTS: A total of 72 potential failure modes were identified in the pre-FMEA STAT RAD workflow, of which 22 met the RPN threshold for clinical significance. Workflow adjustments included the addition of a team member checklist, changing simulation from megavoltage CT to kilovoltage CT, alteration of patient-specific quality assurance testing, and allocating increased time for critical workflow steps. After these modifications, only 1 failure mode maintained RPN significance; patient motion after alignment or during treatment. CONCLUSIONS: Performing the FMEA for the STAT RAD workflow before clinical implementation has significantly strengthened the safety and feasibility of STAT RAD. The FMEA proved a valuable evaluation tool, identifying potential problem areas so that we could create a safer workflow.

Intracellular bicarbonate regulates action potential generation via KCNQ channel modulation.

Bicarbonate (HCO3(-)) is an abundant anion that regulates extracellular and intracellular pH. Here, we use patch-clamp techniques to assess regulation of hippocampal CA3 pyramidal cell excitability by HCO3(-) in acute brain slices from C57BL/6 mice. We found that increasing HCO3(-) levels enhances action potential (AP) generation in both the soma and axon initial segment (AIS) by reducing Kv7/KCNQ channel activity, independent of pH (i.e., at a constant pH of 7.3). Conversely, decreasing intracellular HCO3(-) leads to attenuation of AP firing. We show that HCO3(-) interferes with Kv7/KCNQ channel activation by phosphatidylinositol-4,5-biphosphate. Consequently, we propose that, even in the presence of a local depolarizing Cl(-) gradient, HCO3(-) efflux through GABAA receptors may ensure the inhibitory effect of axoaxonic cells at the AIS due to activation of Kv7/KCNQ channels.

Short report: Exposing laboratory-reared fleas to soil and wild flea feces increases transmission of Yersinia pestis.

Laboratory-reared Oropsylla montana were exposed to soil and wild-caught Oropsylla montana feces for 1 week. Fleas from these two treatments and a control group of laboratory-reared fleas were infected with Yersinia pestis, the etiological agent of plague. Fleas exposed to soil transmitted Y. pestis to mice at a significantly greater rate (50.0% of mice were infected) than control fleas (23.3% of mice were infected). Although the concentration of Y. pestis in fleas did not differ among treatments, the minimum transmission efficiency of fleas from the soil and wild flea feces treatments (6.9% and 7.6%, respectively) were more than three times higher than in control fleas (2.2%). Our results suggest that exposing laboratory-reared fleas to diverse microbes alters transmission of Y. pestis.

Why only some plants emit isoprene.

Isoprene (2-methyl-1,3-butadiene) is emitted from many plants and it appears to have an adaptive role in protecting leaves from abiotic stress. However, only some species emit isoprene. Isoprene emission has appeared and been lost many times independently during the evolution of plants. As an example, our phylogenetic analysis shows that isoprene emission is likely ancestral within the family Fabaceae (= Leguminosae), but that it has been lost at least 16 times and secondarily gained at least 10 times through independent evolutionary events. Within the division Pteridophyta (ferns), we conservatively estimate that isoprene emissions have been gained five times and lost two times through independent evolutionary events. Within the genus Quercus (oaks), isoprene emissions have been lost from one clade, but replaced by a novel type of light-dependent monoterpene emissions that uses the same metabolic pathways and substrates as isoprene emissions. This novel type of monoterpene emissions has appeared at least twice independently within Quercus, and has been lost from 9% of the individuals within a single population of Quercus suber. Gain and loss of gene function for isoprene synthase is possible through relatively few mutations. Thus, this trait appears frequently in lineages; but, once it appears, the time available for evolutionary radiation into environments that select for the trait is short relative to the time required for mutations capable of producing a non-functional isoprene synthase gene. The high frequency of gains and losses of the trait and its heterogeneous taxonomic distribution in plants may be explained by the relatively few mutations necessary to produce or lose the isoprene synthase gene combined with the assumption that isoprene emission is advantageous in a narrow range of environments and phenotypes.

Yersinia pestis infection and laboratory conditions alter flea-associated bacterial communities.

We collected Oropsylla montana from rock squirrels, Spermophilus varigatus, and infected a subset of collected fleas with Yersinia pestis, the etiological agent of plague. We used bar-tagged DNA pyrosequencing to characterize bacterial communities of wild, uninfected controls and infected fleas. Bacterial communities within Y. pestis-infected fleas were substantially more similar to one another than communities within wild or control fleas, suggesting that infection alters the bacterial community in a directed manner such that specific bacterial lineages are severely reduced in abundance or entirely eliminated from the community. Laboratory conditions also significantly altered flea-associated bacterial communities relative to wild communities, but much less so than Y. pestis infection. The abundance of Firmicutes decreased considerably in infected fleas, and Bacteroidetes were almost completely eliminated from both the control and infected fleas. Bartonella and Wolbachia were unaffected or responded positively to Y. pestis infection.

Interactions among symbionts of Oropsylla spp. (Siphonoptera: Ceratophyllidae).

We used high-throughput DNA sequencing to explore bacterial communities of three species of Oropyslla fleas [Oropsylla hirsuta (Baker), Oropsylla montana (Baker), and Oropsylla tuberculata cynomuris (Jellison)] and detected seven bacterial lineages related to known insect symbionts. No significant co-occurrence patterns were detected among bacterial lineages, but relative abundance data suggest that the two most common lineages (Bartonella and Rickettsiales) interact negatively. Furthermore, presence of these two lineages significantly reduced bacterial diversity within fleas.

Bacterial communities of two parthenogenetic aphid species cocolonizing two host plants across the Hawaiian Islands.

Aphids (Hemiptera: Aphididae) have been the focus of several studies with respect to their interactions with inherited symbionts, but bacterial communities of most aphid species are still poorly characterized. In this research, we used bar-coded pyrosequencing to characterize bacterial communities in aphids. Specifically, we examined the diversity of bacteria in two obligately parthenogenetic aphid species (the melon aphid, Aphis gossypii, and the cardamom aphid, Pentalonia caladii) cocolonizing two plant species (taro, Colocasia esculenta, and ginger, Alpinia purpurata) across four Hawaiian Islands (Hawaii, Kauai, Maui, and Oahu). Results from this study revealed that heritable symbionts dominated the bacterial communities for both aphid species. The bacterial communities differed significantly between the two species, and A. gossypii harbored a more diverse bacterial community than P. caladii. The bacterial communities also differed across aphid populations sampled from the different islands; however, communities did not differ between aphids collected from the two host plants.

Population genetic structure of the prairie dog flea and plague vector, Oropsylla hirsuta.

Oropsylla hirsuta is the primary flea of the black-tailed prairie dog and is a vector of the plague bacterium, Yersinia pestis. We examined the population genetic structure of O. hirsuta fleas collected from 11 prairie dog colonies, 7 of which had experienced a plague-associated die-off in 1994. In a sample of 332 O. hirsuta collected from 226 host individuals, we detected 24 unique haplotype sequences in a 480 nucleotide segment of the cytochrome oxidase II gene. We found significant overall population structure but we did not detect a signal of isolation by distance, suggesting that O. hirsuta may be able to disperse relatively quickly at the scale of this study. All 7 colonies that were recently decimated by plague showed signs of recent population expansion, whereas 3 of the 4 plague-negative colonies showed haplotype patterns consistent with stable populations. These results suggest that O. hirsuta populations are affected by plague-induced prairie dog die-offs and that flea dispersal among prairie dog colonies may not be dependent exclusively on dispersal of prairie dogs. Re-colonization following plague events from plague-free refugia may allow for rapid flea population expansion following plague epizootics.