RESUMO
Negative density dependence (NDD) in biotic interactions of interference such as plant-plant competition, granivory and herbivory are well-documented mechanisms that promote species' coexistence in diverse plant communities worldwide. Here, we investigated the generality of a novel type of NDD mechanism that operates through the mutualistic interactions of frugivory and seed dispersal among fruit-eating birds and plants. By sampling community-wide frugivory interactions at high spatial and temporal resolution in Pennsylvania, Puerto Rico, Peru, Brazil and Argentina, we evaluated whether interaction frequencies between birds and fruit resources occurred more often (selection), as expected, or below expectations (under-utilization) set by the relative fruit abundance of the fruit resources of each plant species. Our models considered the influence of temporal scales of fruit availability and bird phylogeny and diets, revealing that NDD characterizes frugivory across communities. Irrespective of taxa or dietary guild, birds tended to select fruits of plant species that were proportionally rare in their communities, or that became rare following phenological fluctuations, while they mostly under-utilized abundant fruit resources. Our results demonstrate that negative density-dependence in frugivore-plant interactions provides a strong equalizing mechanism for the dispersal processes of fleshy-fruited plant species in temperate and tropical communities, likely contributing to building and sustaining plant diversity. This article is part of the theme issue 'Diversitydependence of dispersal: interspecific interactions determine spatial dynamics'.
Assuntos
Aves , Frutas , Simbiose , Animais , Aves/fisiologia , Frutas/fisiologia , Dispersão de Sementes , Comportamento Alimentar , Densidade Demográfica , Herbivoria , Argentina , Pennsylvania , Brasil , Porto RicoRESUMO
OBJECTIVES: The present study was carried out in seven maternity hospitals to determine the prevalence of maternal syphilis at the time of delivery and the associated risk factors, to conduct a pilot project of rapid syphilis testing in hospital laboratories, to assure the quality of syphilis testing, and to determine the rate of congenital syphilis in infants born to women with syphilis at the time of delivery--all of which would provide baseline data for a national prevention programme in Bolivia. METHODS: All women delivering either live-born or stillborn infants in the seven participating hospitals in and around La Paz, El Alto, and Cochabamba between June and November 1996 were eligible for enrolment in the study. FINDINGS: A total of 61 out of 1428 mothers (4.3%) of live-born infants and 11 out of 43 mothers (26%) of stillborn infants were found to have syphilis at delivery. Multivariate analysis showed that women with live-born infants who had less than secondary-level education, who did not watch television during the week before delivery (this was used as an indicator of socioeconomic status), who had a previous history of syphilis, or who had more than one partner during the pregnancy were at increased risk of syphilis. While 76% of the study population had received prenatal care, only 17% had syphilis testing carried out during the pregnancy; 91% of serum samples that were reactive to rapid plasma reagin (RPR) tests were also reactive to fluorescent treponemal antibody-absorption (FTA-ABS) testing. There was 96% agreement between the results from local hospital laboratories and national reference laboratories in their testing of RPR reactivity of serum samples. Congenital syphilis infection was confirmed by laboratory tests in 15% of 66 infants born to women with positive RPR and FTA-ABS testing. CONCLUSION: These results indicate that a congenital syphilis prevention programme in Bolivia could substantially reduce adverse infant outcomes due to this disease.
Assuntos
Garantia da Qualidade dos Cuidados de Saúde , Sorodiagnóstico da Sífilis/métodos , Sífilis Congênita/prevenção & controle , Sífilis/prevenção & controle , Análise de Variância , Bolívia/epidemiologia , Feminino , Maternidades/normas , Humanos , Recém-Nascido , Laboratórios Hospitalares/normas , Modelos Logísticos , Projetos Piloto , Gravidez , Prevalência , Fatores de Risco , Sífilis/diagnóstico , Sífilis/epidemiologia , Sífilis Congênita/diagnóstico , Sífilis Congênita/epidemiologiaRESUMO
PIP: To evaluate the epidemiologic significance of breastfeeding to the transmission of human immunodeficiency virus (HIV) in a country with a high prevalence of HIV infection, the 1720 seronegative women who delivered at the University Teaching Hospital in Lusaka, Zambia, in a 3- month period in 1987 were enrolled in a longitudinal study. Only 634 (37%) of these women returned for testing at the 1-year follow-up point. Of these, 19 (3%) had become seropositive. The infection was asymptomatic in all 19 women at the time of the 1-year follow-up; however, 5 of these women soon developed generalized persistent adenopathy and 3 had spontaneous abortions during the year in which seroconversion occurred. 30 of the spouses of the women in the study sample were HIV-positive; the relative risk of seroconversion was 3.84 in women with HIV-infected spouses compared to those with HIV-negative spouses. Other significant risk factors for HIV seroconversion included: history of genital ulceration after delivery (relative risk, 15.51), use of a cloth to remove vaginal secretions during intercourse (dry sex) (relative risk, 37.95), and blood transfusion (relative risk, 10.89). 3 infants born to these 19 women also seroconverted; 2 years after seroconversion, only 1 of the 3 infected children was symptomatic (persistent, generalized lymphadenopathy). Other sources of HIV infection 9e.g., scarification, blood transfusions, use of contaminated needles during immunization) aside from breastfeeding were not recorded in these 3 infants. Although there is a high prevalence of HIV infection in Zambia, the health benefits of breastfeeding (in terms of the prevention of mortality from diarrheal disease) still outweigh the small risk of HIV transmission.^ieng