Integrate Study of a Bolivian Population Infected by Trypanosoma cruzi, the Agent of Chagas Disease

A cross section of a human population (501 individuals) selected at random, and living in a Bolivian community, highly endemic for Chagas disease, was investigated combining together clinical, parasitological and molecular approaches. Conventional serology and polymerase chain reaction (PCR) indicated an active transmission of the infection, a high seroprevalence (43.3%) ranging from around 12% in < 5 years to 94.7% in > 45 years, and a high sensitivity (83.8%) and specificity of PCR. Abnormal ECG tracing was predominant in chagasic patients and was already present among individuals younger than 13 years. SAPA (shed acute phase antigen) recombinant protein and the synthetic peptide R-13 were used as antigens in ELISA tests. The reactivity of SAPA was strongly associated to Trypanosoma cruzi infection and independent of the age of the patients but was not suitable neither for universal serodiagnosis nor for discrimination of specific phases of Chagas infection. Anti-R-13 response was observed in 27.5% only in chagasic patients. Moreover, anti-R13 reactivity was associated with early infection and not to cardiac pathology. This result questioned previous studies, which considered the anti-R-13 response as a marker of chronic Chagas heart disease. The major clonets 20 and 39 (belonging to Trypanosoma cruzi I and T. cruzi II respectively) which circulate in equal proportions in vectors of the studied area, were identified in patients' blood by PCR. Clonet 39 was selected over clonet 20 in the circulation whatever the age of the patient. The only factor related to strain detected in patients' blood, was the anti-R-13 reactivity: 37% of the patients infected by clonet 39 (94 cases) had anti-R13 antibodies contrasting with only 6% of the patients without clonet 39 (16 cases).

Assessment of Efficiency and Adequacy of Retention Terraces

Due to losses caused by water erosion, the development of techniques that increase the efficiency of soil conservation practices is fundamental. Terracing of agricultural lands is an important conservation practice. Bearing in mind that improperly built terraces may negatively affect the landscape, the purpose of this work was to evaluate the efficiency as well as the adequacy of retention terraces. Assessments were performed in four terraces implanted in different states, all located in the mideastern region of the state of Minas Gerais. The water storage efficiency of the terraces was determined by comparing the effective with the required storage capacity, as established in the project. Proposals were also made for the adequacy of the assessed terraces, based on the correction of the characteristics that jeopardized storage efficiency. The storage efficiency of three of the four assessed terraces was below the required levels (0.5-13 %). The main properties influencing storage capacity were: uniformity of ridge crest height, terrace end closure, and the cross section finishing. In two of the three low-efficiency terraces, the correction of these characteristics proved sufficient to raise the storage efficiency to nearly 100 %.

Diagnóstico rápido e dialogado em estudos de desenvolvimento rural sustentável

O principal objetivo deste trabalho foi verificar se a suposição de predominância da agricultura familiar na microbacia do Taquara Branca, Sumaré, SP, poderia ser sustentada com base em informações concretas. Foi possível a utilização de amostragem probabilística, pois estava disponível um mapa com os limites das 106 propriedades da microbacia, sendo sorteadas 33 delas para a aplicação de questionários do tipo cross-section. A técnica multivariada empregada foi a análise de agrupamentos, para a qual foi utilizado o procedimento PROC CLUSTER do SAS. Nessa análise só foram considerados os dados referentes aos 22 respondentes que exerciam atividade agrícola. Após a análise unidimensional, algumas perguntas foram selecionadas com base na variabilidade entre as respostas e, a partir destas, construíram-se as variáveis necessárias para se proceder à análise multidimensional. A análise de agrupamento permitiu identificar claramente três grupos naturais entre as 22 propriedades. De acordo com as características dos componentes de cada grupo, foi possível classificá-los em: grupo 1, doze propriedades de agricultura familiar; grupo 2, seis propriedades de agricultura não familiar em pequenas áreas; e grupo 3, quatro propriedades de agricultura não familiar em grandes áreas. Embora não seja predominante (apenas 36%), a agricultura familiar é o grupo mais freqüente na microbacia do Taquara Branca.