Disease or drought: environmental fluctuations release zebra from a potential pathogen-triggered ecological trap.

When a transmission hotspot for an environmentally persistent pathogen establishes in otherwise high-quality habitat, the disease may exert a strong impact on a host population. However, fluctuating environmental conditions lead to heterogeneity in habitat quality and animal habitat preference, which may interrupt the overlap between selected and risky habitats. We evaluated spatio-temporal patterns in anthrax mortalities in a plains zebra (Equus quagga) population in Etosha National Park, Namibia, incorporating remote-sensing and host telemetry data. A higher proportion of anthrax mortalities of herbivores was detected in open habitats than in other habitat types. Resource selection functions showed that the zebra population shifted habitat selection in response to changes in rainfall and vegetation productivity. Average to high rainfall years supported larger anthrax outbreaks, with animals congregating in preferred open habitats, while a severe drought forced animals into otherwise less preferred habitats, leading to few anthrax mortalities. Thus, the timing of anthrax outbreaks was congruent with preference for open plains habitats and a corresponding increase in pathogen exposure. Given shifts in habitat preference, the overlap in high-quality habitat and high-risk habitat is intermittent, reducing the adverse consequences for the population.

Immunological Evidence of Variation in Exposure and Immune Response to Bacillus anthracis in Herbivores of Kruger and Etosha National Parks.

Exposure and immunity to generalist pathogens differ among host species and vary across spatial scales. Anthrax, caused by a multi-host bacterial pathogen, Bacillus anthracis, is enzootic in Kruger National Park (KNP), South Africa and Etosha National Park (ENP), Namibia. These parks share many of the same potential host species, yet the main anthrax host in one (greater kudu (Tragelaphus strepsiceros) in KNP and plains zebra (Equus quagga) in ENP) is only a minor host in the other. We investigated species and spatial patterns in anthrax mortalities, B. anthracis exposure, and the ability to neutralize the anthrax lethal toxin to determine if observed host mortality differences between locations could be attributed to population-level variation in pathogen exposure and/or immune response. Using serum collected from zebra and kudu in high and low incidence areas of each park (18- 20 samples/species/area), we estimated pathogen exposure from anti-protective antigen (PA) antibody response using enzyme-linked immunosorbent assay (ELISA) and lethal toxin neutralization with a toxin neutralization assay (TNA). Serological evidence of pathogen exposure followed mortality patterns within each system (kudus: 95% positive in KNP versus 40% in ENP; zebras: 83% positive in ENP versus 63% in KNP). Animals in the high-incidence area of KNP had higher anti-PA responses than those in the low-incidence area, but there were no significant differences in exposure by area within ENP. Toxin neutralizing ability was higher for host populations with lower exposure prevalence, i.e., higher in ENP kudus and KNP zebras than their conspecifics in the other park. These results indicate that host species differ in their exposure to and adaptive immunity against B. anthracis in the two parks. These patterns may be due to environmental differences such as vegetation, rainfall patterns, landscape or forage availability between these systems and their interplay with host behavior (foraging or other risky behaviors), resulting in differences in exposure frequency and dose, and hence immune response.

Radiotherapy in age-related macula degeneration.

PURPOSE: To ascertain the benefit from radiotherapy in age-related macula degeneration in a single-arm longitudinal study. METHODS AND MATERIALS: From 1997 to 1998, 39 patients with occult and 33 patients with classic choroidal neovascularization (CNV) were irradiated with 16 Gy. Fluorescein angiography and measurements of visual acuity were performed before and 3, 6, and 12 months after irradiation. RESULTS: Complete follow-up data for 1 year were available from 69 patients. The mean patient age was 72 years (range 49-92). Vision decreased in 43, was stable in 18, and improved in 8 cases. The mean vision deteriorated significantly (p = 0.02, Wilcoxon test), particularly within the first 3 months. Patients with occult CNV did significantly better than did those with classic CNV (p = 0.03). The proportion of patients retaining vision > or = 0.2 fell from 65% to 42% (p <0.01), for classic and occult CNV from 50% to 23%, and for occult CNV from 77% to 56% (p < 0.02), respectively. CNV size increased in 30 patients and was stable in 38. Neither age (p = 0.17) nor gender (p = 0.21, chi-square test) influenced prognosis. Four patients reported transitional complaints. CONCLUSION: Low-dose fractionated radiotherapy with 16 Gy is well tolerated. However, vision and reading ability were not preserved in most patients.

A multipractice clinical evaluation of an ORMOCER restorative--2-year results.

OBJECTIVES: This ongoing prospective study evaluates the clinical performance of an ORMOCER restorative material (Definite; Degussa) in combination with a self-conditioning adhesive (Etch & Prime 3.0; Degussa). METHOD AND MATERIALS: Three hundred fifty-six restorations (48 Class I, 150 Class II, 63 Class III, 32 Class IV, and 63 Class V) in 117 patients (17 to 65 years) were placed by 5 operators at 5 centers. Fillings were placed with cotton roll isolation using clear matrix bands for Classes III and IV and metal matrix bands for Class II restorations. Follow-ups took place after 6, 12, and 24 months whereby modified Ryge criteria were recorded. With 33 randomly selected Class I and II restorations, measurements of occlusal wear (3-dimensional laser scanner) and marginal analyses (scanning electron microscope) were done using replicas. RESULTS: At 24 months, 307 restorations were available for evaluation. The cumulative number of losses in the 5 cavity classes (I, II, III, IV, and V) and the percentages of scores for the clinical parameters in the 4 categories (Alfa, Beta, Charlie, and Delta) of the retained restorations were loss (1/ 6/ -/ 2/ 7), marginal integrity (93.1/ 6.9/-/-), marginal discoloration (73.5/ 25.5/ 1/ -), anatomic form (82.8/17.2/-/-), and fracture (93.1/ 6.9/-/ -). Marginal analysis showed 48.7% "continuous margin" initially and 13.2% at 24 months (difference statistically significant, a = 0.05). Occlusal wear at 24 months was 12.3 Microm for premolars and 21.4 Microm for molars. CONCLUSIONS: The overall clinical performance of the ORMOCER restorative over 24 months was acceptable with concerns related to marginal quality and to retention of Class V restorations.

Reducing the overall treatment time for radiotherapy of metastatic spinal cord compression (MSCC): 3-year results of a prospective observational multi-center study.

BACKGROUND: This prospective multi-center study investigates a reduction of the overall treatment time for radiotherapy of MSCC, which is important for these mostly disabled patients. PATIENTS AND METHODS: Two standard fractionation schedules, 30 Gy/10 fractions/2 weeks (n = 71) and 40 Gy/20 fractions/4 weeks (n = 65) were compared for functional outcome and ambulatory status. Motor function was graded using an 8-point-scale before RT, at the end and at 6, 12 and 24 weeks after RT. A multi-variate analysis was performed for functional outcome. Included variables were the fractionation schedule and the three relevant prognostic factors. These factors are the type of primary tumor, the time of developing motor deficits before RT and the pre-treatment ambulatory status. RESULTS: The ambulatory rates were 49% in the 30 Gy group and 52% in the 40 Gy group before RT (P = 0.888), and 56% and 60% after RT (P = 0.888). Improvement of motor function occurred in 45% of the 30 Gy group and 40% of the 40 Gy group (P = 0.752). The relevant prognostic factors were comparably distributed in both groups. According to the multivariate analysis, a slower development of motor deficits (P < 0.001), a favorable histology (P = 0.040) and being ambulatory (P = 0.045) were associated with better functional outcome, whereas the fractionation schedule had no significant impact (P = 0.311). CONCLUSIONS: The data suggest both schedules to be comparably effective for functional outcome. Thus, 30 Gy/10 fractions/2 weeks should be applied instead of 40 Gy/20 fractions/4 weeks. The reduction of the overall treatment time from 4 to 2 weeks means less discomfort for the paraparetic or paraplegic patient.

One-year evaluation of an Ormocer restorative-a multipractice clinical trial.

The purpose of this ongoing prospective long-term study was to evaluate the clinical performance of Ormocer restorative material in combination with a self-conditioning adhesive. Five operators at five clinics placed 356 restorations (48 class I, 150 class II, 63 class III, 32 class IV, and 63 class V) in 117 patients aged 17 to 65 years. All fillings were placed with cotton roll isolation and clear matrix bands for class III and IV restorations, and metal matrix bands and an incremental placement technique were used for class II restorations. In follow-up examinations after 6 and 12 months, modified Ryge criteria were recorded on all restorations. With 33 randomly selected class I and II restorations, measurements of occlusal wear (via 3D laser scanner) and qualitative and quantitative marginal analysis (via scanning electron microscope) were performed using a replica technique. After placing the fillings, patients reported postoperative hypersensitivity corresponding to B scores in 19 cases and to C scores in four cases. At 12-month recall, 328 restorations were available for evaluation. Losses in the five cavity classes (I, II, III, IV, V) numbered 0, 2, 0, 1, and 6, respectively. The percentages of retained restorations for clinical parameters in four categories (Alpha, Beta, Charlie, Delta) were: 94.7, 5, 0.3, and 0 (marginal integrity), 81.2, 18.8, 0, and 0 (marginal discoloration), 75.2, 24.8, 0, and 0 (anatomic form), and 95, 4.7, 0.3, and 0 (fracture), respectively. Marginal analysis showed 48.7% "continuous margin" initially and 17.7% at 12 months (difference statistically significant, P=0.05). The occlusal wear at 12 months was 10.0 microm (SD 11.6) for premolars and 22.0 microm (SD 24.1) for molars. Over the 12-month observation period, the Ormocer restorative was clinically effective in combination with a self-conditioning adhesive, and concern persists related to the marginal quality and retention of class V restorations.