Introduction
Chagas disease currently affects some 6 million people around the world. At the chronic stage, cardiomyopathy occurs in about 20–30% of infested people. Most prevalence studies have focused on young to adult people due to the drastic consequences of acquiring the pathogen and the possibility to cure the disease at this age; the prevalence of this disease, the effect of patients' sex and the consequences to senescent people have been largely neglected. This study looks to characterize the seroprevalence of Chagas disease and its relation with occurrence of electrocardiographic anomalies associated with sex and age, and to compare rural and urban populations in Bolivia.
Methodology
Seroprevalence of Chagas disease was determined in blood samples and electrocardiograms were performed on seropositive individuals.
Results
The rural population showed higher seroprevalence than the urban population (92% and 40%, respectively). The proportion of Chagasic cardiac anomalies in seropositive persons was highest in patients of the 50–59 age group (36%) as compared with the 40–49 (8%) and the ≥60 (17%) age groups.
Conclusions
Higher seroprevalence in rural population was attributable to a higher probability to encounter the vector in rural areas. Increased exposure to infection and to development of the disease symptoms together with increased lethality of the disease as patients age explains the age-related Chagasic electrocardiographic anomalies. Since rural and urban populations showed different reactions under Chagas disease and the rural population was mainly of guaraní stock, the genetic and environmental determinants of the results should be further explored.
Adaptation to the most effective pollinator is often conceived as the primary explanation of widespread convergence in flower phenotypes. However, specialization does not exclude the presence of other floral visitors, which may contribute to plant reproduction. Here we combined observations about pollinators visitation rates and effectiveness with nectar secretion dynamics and sugar composition in four Andean Salvia species from Bolivia. The study revealed a wider diversity than expected both in pollination systems and in nectar strategies. While S. haenkei and S. stachydifolia were almost exclusively pollinated by either hummingbirds or bees, respectively, mixed pollination was found in S. orbignaei, a species previously described as hummingbird-pollinated. Salvia personata was exclusively pollinated by syrphid flies. Differences in nectar volume and sugar concentration were found between insect-pollinated species and mixed- or hummingbird-pollinated species. However, the four Salvia species displayed different strategies regarding nectar sugar composition, with sucrose-rich nectar in S. orbignaei, glucose-rich nectar in S. haenkei and S. stachydifolia, and glucose-rich nectar lacking fructose in S. personata, suggesting an adaptation to syrphid fly pollination. Our results provide a clearer picture of floral trait evolution in Salvia and highlight the contribution of some pollinators different from those expected according to the floral syndromes.
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