Ensino e pesquisa em saúde coletiva na Inglaterra: algumas observação de dois participantes

A oportunidade dos autores realizarem curso de doutoramento na Inglaterra permitiu um melhor conhecimento sobre o ensino e a pesquisa em saúde coletiva naquele país. Neste artigo são apresentados alguns destes aspectos, bem como sugestões que podem ser úteis no repensar o desenvolvimento desta área do conhecimento no Brasil.

[Cause vs. prediction: history of bathing in rivers as a risk factor and predictor of infection by Schistosoma mansoni]

Através da análise das relações existentes entre as medidas de risco e as medidas de eficiência de testes de diagnóstico ou triagem, são discutidos os problemas e limitações concernentes ao uso de fatores de risco na predição da distribuição de efeitos (infecção, doença, cura) em uma população. Para ilustrar o tema, foi utilizada a associação, em crianças, entre a questão "você já tomou banhos em rios?", muito utilizada em anamneses clínicas ensinadas em diversas escolas médicas do Brasil, e a infecção pelo Schistosoma mansoni. A história de banhos em rios, enquanto um importante fator de risco, mostrou-se mau preditor da ocorrência da infecção esquistossomótica. A análise demonstrou que este achado é, em grande parte, devido a baixa freqüência de história negativa de banhos em rios. Porém, a possibilidade da utilização de fatores de risco isoladamente ou agrupados, com o objetivo de predição de efeitos, é possível e desejável. Apesar de pouco explorado nos seus aspectos práticos ou conceituais, esta área de conhecimento representa um importante ponto de convergência entre a epidemiologia das causas e a epidemiologia das intervenções.

Three-year prospective study of the evolution of Manson's schistosomiasis in north-east Brazil

A cross-sectional study of morbidity associated with Schistosoma mansoni infection in an area in North-East Brazil where the disease is endemic was carried out in 1974. The survey was repeated in 1977, before mass treatment with oxamniquine, providing a cohort of 210 individuals who had both examinations. The high prevalence of hepatomegaly (over 80%) and of splenomegaly (over 15%) contrasted with rates of 10% and 1%, respectively, in a non-endemic area. Over the 3-year period hepatomegaly spontaneously regressed in 13% of patients, and splenomegaly regressed in 56%, a phenomenon most common in older individuals with light infections. Those with heavy infections--ie, 500 or more eggs per g faeces, had an excess risk of splenomegaly of 19.6% and, of its persistence, of 61.5%. Thus, intensity of infection was a critical factor in liver and spleen involvement, and programmes of chemotherapy that reduce infection should mitigate the risk of schistosomal morbidity.

The effect of Schistosoma mansoni infection on child morbidity in the State of Bahia, Brazil. II--Analysis at the individual level

The present investigation was carried out on a sample of 840 children (5 to 16 years old) from ten small towns of the State of Bahia in northeastern Brazil. The objetive was to study, by using a cross sectional methodology, the evolution of schistosomiasis morbidity (hepatic and splenic enlargement) in children, and the role of the intensity of S. mansoni infection in this process. The children were analised in three age groups (5 to 8, to 12 and 13 to 16 years old) and classified as uninfected, mildly infected, moderately infected and heavily infected according to the number of eggs in the stool. In children aged 5 to 8 years, increasing egg counts were not associated with increasing frequencies of hepatic or splenic enlargement. In the 9 to 12 years old group and association was observed with the prevalence of hepatic enlargement, but not with the prevalence of spleen enlargement. In the oldest group, 13 to 16 years old, an association was observed with the prevalence of enlargement of both organs. It was evident that in this population schistosomiasis morbidity develops in the early period of life as a gradual process starting with liver enlargement and followed by spleen enlargement some years later. It was found that the intensity of infection has a fundamental role in this process, although there is a latent period of some years before clinical splenomegaly appears in moderate-heavily infected children. The Authors suggest that the prevalence of splenomegaly in the 13 to 16 years old group is a good measure of the community level of schistosomiasis morbidity and could be used to measure the impact of control programs.

The effect of Schistosoma mansoni infection on child morbidity in the state of Bahia, Brazil. I--Analysis at the ecological level

Esta investigação foi levada a efeito em 10 pequenas cidades do Estado da Bahia (Nordeste do Brasil), escolhidas através de um processo amostrai. O objetivo foi estudar as correlações entre as prevalências de hepatomegalia e esplenomegalia, em diferentes áreas, com a prevalência e a intensidade da infecção pelo S. mansoni nas mesmas áreas. Nossas conclusões são: a) a morbidade esquistossomótica (prevalências de hepatomegalia e esplenomegalia) foi diretamente correlacionada com a prevalência e a intensidade da infecção; b) a intensidade da infecção (medida pelo número de ovos nas fezes) mostrou ser um bom indicador do grau de morbidade, explicando a variação da morbidade entre as áreas melhor que a prevalência da infecção; c) a prevalência de esplenomegalia e o tamanho médio do fígado abaixo do rebordo costal na linha me dio-esternal são bom indicadores da prevalência e da intensidade da infecção pelo S. mansoni na comunidade. Nossas conclusões trazem a possibilidade da construção de equações de regressão definitivas entre indicadores de morbidade e indicadores de infecção, de tal forma que o valor de um possa ser usado para predizer o valor do outro.

Multiple causes of anaemia amongst children living near a lead smelter in Brazil

A prevalence study of anaemia was carried out amongst children, aged one to nine years, living near a lead smelter in Santo Amaro City, Northeast Brazil. It was found that the variation in haemoglobin levels was significantly associated with malnutrition and with the interaction between malnutrition and iron deficiency, but not with lead poisoning, iron deficiency, or hookworm infection, having allowed for the effects of age, area of residence, family per capita income and race. The effect of the interaction between malnutrition and iron deficiency on haemoglobin levels was most prominent amongst children aged one year and amongst those living in the most deprived area. The lack of demonstrable interaction between lead poisoning and iron deficiency in the causation of anaemia amongst these children is discussed.

Lead poisoning and hookworm infection as multiple factors in anaemia

A retrospective study was carried out in a rural area of north-eastern Brazil, to search for interactions between biological and chemical agents present in the environment as causes of anaemia. A lead smelter situated in a hookworm endemic area provided the opportunity to look at the effect of this double exposure in relation to laboratory defined anaemia, by comparing the odds ratios in different subgroups of 109 "cases" and 107 "controls". The subgroup with both hookworm infection and chronic lead poisoning--measured by the concentration of delta-ALA excreted in urine--had an odds ratio of developing anaemia five times greater than individuals with neither. Although a synergistic effect could not be demonstrated, the additive effect of the two conditions placed this group in a higher risk category.

A three year follow-up of chemotherapy with oxamniquine in a Brazilian community with endemic schistosomiasis mansoni

Oral oxamniquine was tested as a control strategy for endemic schistosomiasis in a rural area of Bahia, Brazil. Adults were treated with a single dose (12.5 to 15 mg per kg) and children (less than 12 years old) with a total of 20 mg per kg in two doses. The 191 (infected) persons treated represented 69% of the infected population in the study area. Follow-up stool examinations (Kato-Katz method) at one, 3, 6, 13, 25 and 33 months showed the cure rate declining from 80% at three months to 46% at 33 months. Over one half of those not cured showed a decrease in egg counts throughout the follow-up which, after 33 months, remained 66% below the pre-treatment levels. Stool examinations conducted on all study area residents during three years before chemotherapy showed the prevalence and intensity of Schistosoma mansoni infection to be high and stable. 33 months after the chemotherapy the prevalence was 41% and for infected individuals the geometric mean egg count was 121 epg, a decline of respectively 35% and 40% from pre-treatment levels for each index. Chemotherapy of infected persons with oxamniquine protected the community as a whole from high worm burdens for almost three years, although at this point the prevalence began to rise towards pretreatment levels.

Stability of faecal egg excretion in Schistosoma mansoni infection

Stability of Schistosoma mansoni egg excretion was studied in 23 residents of a rural endemic area in North-east Brazil where the over-all prevalence rate was 87% and the peak geometric mean egg excretion was 308 eggs/ml (Bell method) in the 10 to 14-year-old age group. Stool examinations by the Kato method were performed for three to four consecutive days each month for three consecutive months. Both raw and transformed data showed significant stability of S. mansoni egg excretion from day to day and month to month in this population. A single Kato examination detected 68% of individuals who were excreting more than 400 eggs per gramme. Although S. mansoni egg excretion is stable over time, identifying individuals with high egg excretion in endemic populations requires sensitive quantitative methods.