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Chronic Chagas' disease represents the result of the interaction between the host and the parasite, producing different clinical features: from a mild disease to a severe heart failure. In the present investigation, we analyzed whether Trypanosoma cruzi strain and/or reinfections in the acute stage, determine changes in the chronic phase (135 days postinfection, d.p.i) that could explain the diverse evolution of cardiac lesions. After infection of albino Swiss mice (n = 170) with 50 blood trypomastigote of the T. cruzi, strain Tulahuen (n = 80) and the isolate SGO-Z12 (n = 90), respectively, and reinfections at 10 and 20 d.p.i. Parasitemia, survival, electrocardiography, affinity and density of cardiac beta-receptors and histopathology of the heart were studied. Parasitemias in reinfected mice were significantly higher than those in single-infected mice. Survival of SGO-Z12-infected group was significantly higher than the other groups (p < 0.01). All Tulahuen-reinfected mice and 55-67% of the infected and SGO-Z12-reinfected groups presented some electrocardiographic abnormality (p < 0.01). Hearts from single-infected mice presented fibber disorganization and necrosis; reinfected groups also exhibited fibber fragmentation and a diminished affinity and a higher beta-adrenergic receptors' density than the other groups (p < 0.05). Therefore, parasite strain and reinfections determine different cardiac damage, and either (or both) of these factors are involved in the severity of the clinical picture and the prognosis of the chronic cardiac disease.

Objectives:This study utilizes a [US] national sample of emergency medical services (EMS) professionals to explore the hypothesis that demographic and work-related characteristics are associated with involvement in ambulance crashes.Methods:In 2004, a cohort of nationally registered EMS professionals was surveyed to determine ambulance crash involvement during a 12-month period. Involvement in an ambulance crash was the outcome variable of interest. Demographics such as age, community size, service type, call volume, time spent in an ambulance, and current sleep problems were analyzed as independent variables. A multivariate logistic regression model identified variables associated with involvement in an ambulance crash within the past year.Results:Surveys were received from 1,775/5,565 (32.0%) participants; 1,297 (73.1%) met the inclusion criteria. A total of 111 (8.6%) of participants reported being involved in an ambulance crash within the past 12 months. When controlling for call volume and time in an ambulance, the odds of involvement in an ambulance crash within the past year were significantly higher for younger EMS professionals and those reporting sleep problems.Conclusions:Results from this analysis suggest age and sleep problems are associated with involvement in an ambulance crash. Future studies should investigate interventions to minimize the effects of these associations.

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