RESUMO

We investigated the influence and relative importance of insecticides and other agricultural stressors in determining variability in invertebrate communities in small streams in intensive soy-production regions of Brazil and Paraguay. In Paraguay we sampled 17 sites on tributaries of the Pirapó River in the state of Itapúa and in Brazil we sampled 18 sites on tributaries of the San Francisco River in the state of Paraná. The riparian buffer zones generally contained native Atlantic forest remnants and/or introduced tree species at various stages of growth. In Brazil the stream buffer width was negatively correlated with sediment insecticide concentrations and buffer width was found to have moderate importance in mitigating effects on some sensitive taxa such as mayflies. However, in both regions insecticides had low relative importance in explaining variability in invertebrate communities, while various habitat parameters were more important. In Brazil, the percent coverage of soft depositional sediment in streams was the most important agriculture-related explanatory variable, and the overall stream-habitat score was the most important variable in Paraguay streams. Paraguay and Brazil both have laws requiring forested riparian buffers. The ample forested riparian buffer zones typical of streams in these regions are likely to have mitigated the effects of pesticides on stream invertebrate communities. This study provides evidence that riparian buffer regulations in the Atlantic Forest region are protecting stream ecosystems from pesticides and other agricultural stressors. Further studies are needed to determine the minimum buffer widths necessary to achieve optimal protection.

Assuntos

RESUMO

We investigated relationships among insecticides and aquatic invertebrate communities in 22 streams of two soy production regions of the Argentine Pampas over three growing seasons. Chlorpyrifos, endosulfan, cypermethrin, and lambda-cyhalothrin were the insecticides most frequently detected in stream sediments. The Species at Risk (SPEAR) pesticide bioassessment index (SPEARpesticides) was adapted and applied to evaluate relationships between sediment insecticide toxic units (TUs) and invertebrate communities associated with both benthic habitats and emergent vegetation habitats. SPEARpesticides was the only response metric that was significantly correlated with total insecticide TU values for all three averaged data sets, consistently showing a trend of decreasing values with increasing TU values (r2=0.35 to 0.42, p-value=0.001 to 0.03). Although pyrethroids were the insecticides that contributed the highest TU values, toxicity calculated based on all insecticides was better at predicting changes in invertebrate communities than toxicity of pyrethroids alone. Crustaceans, particularly the amphipod Hyalella spp., which are relatively sensitive to pesticides, played a large role in the performance of SPEARpesticides, and the relative abundance of all crustaceans also showed a significant decreasing trend with increasing insecticide TUs for two of three data sets (r2=0.30 to 0.57, p-value=0.003 to 0.04) examined. For all data sets, total insecticide TU was the most important variable in explaining variance in the SPEARpesticides index. The present study was the first application of the SPEAR index in South America, and the first one to use it to evaluate effects of pesticides on invertebrate communities associated with aquatic vegetation. Although the SPEAR index was developed in Europe, it performed well in the Argentine Pampas with only minor modifications, and would likely improve in performance as more data are obtained on traits of South American taxa, such as pesticide sensitivity and generation time.

Assuntos

RESUMO

Only limited data are available on the impact of measles outbreak response immunization (ORI) in developing countries. We conducted a community survey in Espindola, a rural border community in northern Peru, following a measles outbreak and subsequent ORI to study the epidemiology and impact of the outbreak and to evaluate the costs and benefits of measles ORI. During the outbreak, 150 of the 553 Espindola residents developed clinical cases of measles. Adults accounted for 44.0% of cases, and were frequently identified as primary cases. The attack rate among all susceptible people was 45.5% and was highest (61.2%) for the 16-20 year age group. Among adults, significant risk factors for developing measles included being aged 16-20 years (relative risk [RR] = 3.06, 95% CI = 2.08, 4.49) and being male (RR = 1.73, 95% CI = 1.11, 2.71). Among serologically confirmed cases, 60.7% developed diarrhoea and 32.1% pneumonia. The overall case-fatality rate was 3.3%, but reached 19.1% in the 0-23-month age group. Failure to reach children through either routine immunization or national campaigns made this community vulnerable to the severe and extensive impact of measles virus importation. The ORI campaign targeted non-measles case children aged 6 months to 15 years, regardless of their previous immunization status, and was effective in terminating this measles outbreak and in preventing morbidity, loss of livelihood and death despite the involvement of large numbers of adults in measles transmission. The last measles case occurred within 3 weeks of completing ORI. The ORI campaign, which would have cost approximately US$ 3000 in 1998, saved as many as 1155 person-days of work among 77 adults, prevented an estimated 87 cases of diarrhoea and 46 cases of pneumonia, and averted 5 deaths.

PIP: A community survey of the epidemiology and impact of measles outbreak response immunization (ORI) in Espindola, Peru. Blood specimens from 29 clinical cases having the onset of symptoms within 5 weeks to collection were tested for the anti-measles virus nucleoprotein antibody. Questionnaires were given to the head of the household and the 29 clinical cases to identify clinical symptoms an disease outcomes and to determine vaccination coverage. Attack rates, vaccine effectiveness, and predictive value positive was also calculated. Findings showed that primary cases were frequent among adults, who accounted for 44% of cases. The attack rate among all susceptible people was 45.5% and was highest among adults aged 16-20 (61.2%). For the serologically confirmed cases, 60.7% developed diarrhea and 32.1% pneumonia. Case fatality rate was 19.1% for children aged 0-23 months and 1.5% for adults aged 16-40 years. The lack of national campaigns or access to routine immunization caused the severe impact of measles virus outbreak. The ORI campaign targeted nonmeasles case children aged 6 months to 15 years regardless of immunization status, which was effective in terminating measles outbreak, morbidity, and mortality. This campaign cost approximately US$3000 and in 1998 saved 1155 person-days of work among 77 adults. It also prevented 87 diarrhea and 46 pneumonia cases and averted 5 deaths.

Assuntos