Use of Postacute Care by Nursing Home Residents Hospitalized for Stroke or Hip Fracture: How Prevalent and to What End?

OBJECTIVES: To examine nursing home (NH) residents' use of Medicare‐paid skilled nursing facility (SNF) services and the outcomes of that care and to identify clinical and non‐clinical factors associated with that care. DESIGN: Retrospective cohort. SETTING: United States. PARTICIPANTS: NH residents aged 65 and older with Medicare claims for a hospitalization for hip fracture or stroke during 2001 to 2003. MEASUREMENTS: Resident diagnoses and use of SNF postacute care were measured using Medicare hospital claims. Market and provider characteristics were drawn from the Provider of Services file. Baseline characteristics, institutionalization, and mortality outcomes were drawn from the Minimum Data Set and Medicare Denominator File. RESULTS: Of the NH population hospitalized for hip fracture (49,903) or stroke (23,084), 79.7% and 64.1%, respectively, used the SNF benefit. Residents not using the SNF benefit had poorer baseline health status; their mortality rates and rates of resuming long‐term care were similar to the rates of residents who used the SNF benefit. CONCLUSION: NH residents used postacute SNF benefits at high rates yet had similar mortality and institutionalization outcomes as those without SNF care.     

Parasite diversity and coinfection determine pathogen infection success and host fitness

While the importance of changes in host biodiversity for disease risk continues to gain empirical support, the influence of natural variation in parasite diversity on epidemiological outcomes remains largely overlooked. Here, we combined field infection data from 2,191 amphibian hosts representing 158 parasite assemblages with mechanistic experiments to evaluate the influence of parasite richness on both parasite transmission and host fitness. Using a guild of larval trematode parasites (six species) and an amphibian host, our experiments contrasted the effects of parasite richness vs. composition, observed vs. randomized assemblages, and additive vs. replacement designs. Consistent with the dilution effect hypothesis extended to intrahost diversity, increases in parasite richness reduced overall infection success, including infections by the most virulent parasite. However, the effects of parasite richness on host growth and survival were context dependent; pathology increased when parasites were administered additively, even when the presence of the most pathogenic species was held constant, but decreased when added species replaced or reduced virulent species, emphasizing the importance of community composition and assembly. These results were similar or stronger when community structures were weighted by their observed frequencies in nature. The field data also revealed the highly nested structure of parasite assemblages, with virulent species generally occupying basal positions, suggesting that increases in parasite richness and antagonism in nature will decrease virulent infections. Our findings emphasize the importance of parasite biodiversity and coinfection in affecting epidemiological responses and highlight the value of integrating research on biodiversity and community ecology for understanding infectious diseases.     

From the Cover: Host and parasite diversity jointly control disease risk in complex communities

Host–parasite interactions are embedded within complex communities composed of multiple host species and a cryptic assemblage of other parasites. To date, however, surprisingly few studies have explored the joint effects of host and parasite richness on disease risk, despite growing interest in the diversity–disease relationship. Here, we combined field surveys and mechanistic experiments to test how transmission of the virulent trematode Ribeiroia ondatrae was affected by the diversity of both amphibian hosts and coinfecting parasites. Within natural wetlands, host and parasite species richness correlated positively, consistent with theoretical predictions. Among sites that supported Ribeiroia, however, host and parasite richness interacted to negatively affect Ribeiroia transmission between its snail and amphibian hosts, particularly in species-poor assemblages. In laboratory and outdoor experiments designed to decouple the relative contributions of host and parasite diversity, increases in host richness decreased Ribeiroia infection by 11–65%. Host richness also tended to decrease total infections by other parasite species (four of six instances), such that more diverse host assemblages exhibited ∼40% fewer infections overall. Importantly, parasite richness further reduced both per capita and total Ribeiroia infection by 15–20%, possibly owing to intrahost competition among coinfecting species. These findings provide evidence that parasitic and free-living diversity jointly regulate disease risk, help to resolve apparent contradictions in the diversity–disease relationship, and emphasize the challenges of integrating research on coinfection and host heterogeneity to develop a community ecology-based approach to infectious diseases.One of the most fundamental challenges facing contemporary disease ecology involves understanding host–parasite interactions within complex communities (1, 2). Whereas epidemiological research has historically focused on interactions between individual host and parasite species, growing evidence indicates that incorporating more realistic levels of diversity is essential for managing infectious diseases. Because most emerging parasites use or depend on multiple host species (3, 4), understanding transmission dynamics often demands detailed information on the host community (e.g., refs. 5 and 6). Concurrently, interactions among parasites are increasingly recognized in affecting disease outcomes (7, 8). Virtually all hosts in nature support a diverse assemblage of pathogenic and nonpathogenic microorganisms (9), which can interact both directly (e.g., competition for space or resources) or indirectly through host immunity (10, 11). Thus far, however, there have been few empirical efforts to unite these disparate lines of research and understand disease dynamics within multihost, multiparasite communities, in part owing to the challenges involved in understanding complex interactions operating across different scales (e.g., within and between hosts) (12, 13).A central question, therefore, concerns how host and parasite assemblages interact to determine transmission and disease severity within ecological communities. Thus far, two divergent perspectives have emerged regarding the relationship between biodiversity and parasitism. On one hand, recent interest has focused on the dilution effect hypothesis, which posits that increases in host diversity will reduce transmission or disease risk when accompanied by declines in the overall competence of the community (e.g., refs. 14 and 15). On the other hand, increases in host diversity are also hypothesized to promote parasite diversity by enhancing colonization opportunities and supporting a wider suite of parasite life cycles (host diversity begets parasite diversity hypothesis; ref. 16), such that host diversity and parasite diversity correlate positively (17, 18). Rather than contradicting each other, these seemingly divergent perspectives on the diversity–disease relationship emphasize differences in both terminology and ecological process. Parasite diversity is not equivalent to disease risk; given that many parasitic species cause relatively little harm to the host under normal conditions, disease risk is better equated to the abundance or prevalence of the most virulent parasites, rather than the overall richness of parasites per se (5, 19). Increases in parasite diversity may even function to reduce transmission if parasites are antagonistic with one another within hosts (19–22).Static patterns of parasite richness or species composition may also offer relatively little insight into transmission, or the capacity of a parasite to move locally between hosts (15, 23). Thus, even if more species-rich communities support higher parasite diversity owing to greater colonization opportunities, this provides limited information about how diversity per se affects parasite transmission within the community. Indeed, if parasite diversity alters transmission of the most virulent infections, it could function to amplify or mask any host-driven dilution effects, emphasizing the importance of field and experimental studies that explicitly measure transmission dynamics. These observations raise an intriguing question: If parasite diversity increases with host diversity and higher parasite richness can function to reduce disease risk, what are the individual and combined contributions of free-living and parasitic diversity to the diversity–disease relationship? Given the ubiquity of coinfection in natural host communities and the predominant tendency of diversity–disease research to focus on field-based correlations, studies that can disentangle the magnitude and relative contributions of differing components of community diversity—both free-living and parasitic—are increasingly essential.Here, we integrated field surveys and experimental manipulations of a multihost, multiparasite system to concurrently test the effects of host and parasite richness on transmission of a virulent parasite. By linking previously collected field data on host richness from 345 wetlands in California with new information on the full macroparasite communities of 1,686 hosts, we tested the influence of amphibian host and parasite richness on realized transmission of the pathogenic trematode Ribeiroia ondatrae, which causes mortality and malformations in amphibians (24–26). However, because we expected host diversity, parasite diversity, and parasite load to correlate in the field owing to links between colonization and diversity, we used an experimental approach first in the laboratory and then in seminatural outdoor mesocosms to decouple the unique effects of each form of diversity on infection by Ribeiroia and the total parasite community. While building upon previous efforts examining the individual effects of host and parasite richness in isolation (15, 19, 27–30), this study combines cross-sectional coinfection data, field-based measurements of transmission, and new experiments to explicitly examine the effects of host species richness on infection by an entire parasite assemblage, thereby mechanistically evaluating the joint effects of host and parasite diversity on disease risk.     

Lung cancer: a cost and outcome study based on physician practice patterns.

Chemotherapy is now an acceptable treatment for selected patients with non-small-cell lung cancer. With the wide assortment of cytotoxic and supportive-care drugs, there are opportunities for assessing the value of various treatment approaches. This study was undertaken to assess variations in treatment patterns in a large oncology group with emphasis on costs incurred and survival. A total of 1215 patients seen in 1996 by Medical Oncologists (a community-based private practice) were identified as new lung cancer patients by review of billing data. Of these, 858 received chemotherapy and were evaluated for charges. Three hundred were evaluated for charges, hospice care, and survival. Differences in practice patterns for physicians and the causes of those differences were assessed. Differences in survival, charges, and hospice care for those patients who were seen by high-charge and low-charge physicians were measured. Clear differences emerged in practice patterns for these Medical Oncologists. Higher charges were associated with higher average number of chemotherapy cycles given, greater use of second- and third-line chemotherapy and greater use of support drugs, particularly G-CSF and erythropoietin. For stage IV non-small-cell lung cancer, there was no difference in survival or in hospice utilization for the two groups. For all patients combined, there was no significant survival difference. There may be as much as 100% difference in costs incurred for lung cancer chemotherapy based on variations in practice patterns alone without a measurable survival difference. These results suggest approaches for cost-minimization and disease management. These suggestions have been reinforced by recent clinical data and guideline development.     

Effects of Payment Changes on Trends in Post-Acute Care

Objective. To test how the implementation of new Medicare post-acute payment systems affected the use of inpatient rehabilitation facilities (IRFs), skilled nursing facilities (SNFs), and home health agencies.
Data Sources. Medicare acute hospital, IRF, and SNF claims; provider of services file; enrollment file; and Area Resource File data.
Study Design. We used multinomial logit models to measure realized access to post-acute care and to predict how access to alternative sites of care changed in response to prospective payment systems.
Data Extraction Methods. A file was constructed linking data for elderly Medicare patients discharged from acute care facilities between 1996 and 2003 with a diagnosis of hip fracture, stroke, or lower extremity joint replacement.
Principal Findings. Although the effects of the payment systems on the use of post-acute care varied, most reduced the use of the site of care they directly affected and boosted the use of alternative sites of care. Payment system changes do not appear to have differentially affected the severely ill.
Conclusions. Payment system incentives play a significant role in determining where Medicare beneficiaries receive their post-acute care. Changing these incentives results in shifting of patients between post-acute sites.     

Acute aquatic toxicity of two commonly used fungicides to midwestern amphibian larvae

Fungicide usage has increased globally in response to the rise in fungal pathogens, especially in the agricultural sector. However, research examining the toxicity of fungicides is still limited for many aquatic species. In this study, we examined the acute toxicity of two widely used fungicides, chlorothalonil and pyraclostrobin, on six North American larval amphibian species across multiple families using 96-h LC50 tests. We found that pyraclostrobin was approximately 3.5x more toxic than chlorothalonil; estimated LC50 values ranged from 5–18?µg/L for pyraclostrobin and 15–50?µg/L for chlorothalonil. Comparing across amphibian groups, we found that salamanders were 3x more sensitive to pyraclostrobin than anuran species and equally as sensitive to chlorothalonil. Notably, our estimated LC50 values within the range of the expected environmental concentration for these fungicides suggesting environmental exposures could lead to direct mortality in these species. Given the widespread and increasing usage of fungicides, additional work should be conducted to assess the general risk posed by these chemicals to amphibian and their associated aquatic habitats.