Age-targeted chemotherapy for control of urinary schistosomiais in endemic populations

Severity of urinary tract morbidity increases with intensity and duration of Schistosoma haematobium infection. We assessed the ability of yearly drug therapy to control infection intensity and reduce S. haematobium-associated disease in children 5-21 years old in an endemic area of Kenya. In year I, therapy resulted in reduced prevalence (66% to 22%, P < 0.001) and intensity of S. haematobium infection (20 to 2 eggs/10 mL, urine), with corresponding reductions in the prevalence of hematuria (52% to 19%, P < 0.001). There was not, however, a significant first-year effect on prevalence of urinary tract abnormalities detected by ultrasound. Repeat therapy in years 2 and 3 resulted in significant regression of hydronephrosis and bladder abnormalities (41% to 6% prevalence, P< 0.001), and further reductions in proteinuria. Repeat age-targeted therapy was associated with decreased prevalence of infection among young children (< 5yr) entering into the target age group. Two years after discontinuation of therapy, intensity of S. haematobium infection and ultrasound abnormalities remained suppressed, but hematuria prevalence began to increase (to 33% in 1989). Reinstitution of annual therapy in 1989 and 1990 reversed this trends. We conclude that annual oral therapy provides an effective strategy for control of morbidity due to S. haematobium on population basis, both through regression of disease in treated individuals, and prevention of infection in untreated subjects.

Alternative approaches in schistosomiasis control

Measures for for the control of schistosomiasis were implemented in Egypt begining 1922. This shows that developing endemic countries are facing this problem for near 70 years. However, results in the control of this infection have not been satisfactorily obtained in spite of the technologies and strategies recently developed. The idea that the social and economic components are relevant in the control of schistosomiasis is not new although its extension and profundity have not usually been well understood. More recently; most of the workers have recognized that the distribution of the prevalence rates of schistosomiasis should not be neglected in the control of the infection. At present field work projects on the control of schistosomiasis are being developed in rural areas of two Brazilian states (Espirito Santo and Pernanbuco). The adopted strategy aims to interfere in the complex relationships between amn and his bio-social-cultural environment, without forgeting tha the unequal distribution of the space is a consequence of the political and economic organization of the Society.

Some personal views on the control of schistosomiasis mansoni

Our views are based, on a recent study of a district of Uniao dos Palmares (Alagoas). Although being a very compact community (32 city blocks holding two thousand families), transmission is very uneven, the geometric mean egg counts in the various blocks ranging between extremes of 96 and 1920. (Results do not correlate with the availability of domestic water supply). We thus are led to conclude that: (a) transmission is primarily peridomestic, resulting from pollution of open ditches and other collections of water; (b) control of transmission can be done on a selective basis, requiring quite medest investments. Given the inefficacy of population-based chemotherapy, when used alone, the author insists that this alternative cannot any longer be overlooked. He also regrets the emphasis placed upon vaccine development; allegations that this would, at any rate, prevent severe morbidity can be dismissed, since-whatever the cause-morbidity due to schistosomiasis has been rapidly declining in Northeast Brazil.

New approaches for the control and eradication of schistosomiasis in Venezuela

Schistosomiasis in Americawith the exception of Brazil, behaves as a chronic mild disease with few clinical manifestations due to low parasite burden. These features restrict the clinical and parasitological diagnosis. The most commonly used stool examination method, Kato-Katz, becomes intensitive when the majority of individuals excrete less than 100 eggs/g of feces. In view that antigen-detecting techniques have not been able to reveal light infections, the antibody detecting assays remain as a very valuable diagnostic tool for epidemiological surveillance. The Venezuelan Schistosomiasis Research group (CECOICE) has designed a mass chemotherapy strategy based on sero-diagnosis. Since blood sampling is one of the important limitating factors for large seroepidemiological trials we developed a simple capillary technique that sucessfully overcomed most of the limitations of blood drawing. In this sense, ELISA seems to be the most adecuate test for epidemiological studies. Soluble egg Schistosoma mansoni antigen (SEA) has been largely used in Venezuela. The sensitivity ELISA-SEA in our hands is 90% moreover its specific reach 92% when populations from non-endemic areas but heavily infected with other intestinal parasites are analyzed. The Schistosomiasis Control Program is currently carrying out the surveillance of endemic areas using ELISA-SEA as the first screening method, followed by the Circumoval Precipitin test for validation assay. The results with these two serological techniques allowed us to defined the criteria of chemotherapy in populations of the endemic areas. On the search of better diagnostic technique, Alkaline Phosphatase Immunoenzyme Assay (APIA) is being evaluated in field surveys.

Epidemiological features and control of schistosomiasis japonica in China

Achievements and successes have been obtained in schistosomiasis control in China. An epidemic survey was carried out and its results analyzed.

Ecological studies on the intermediate host snails and the relevance to schistosomiasis control

A detailed knoledge of distribution patterns schistosome intermediate hsts and their populations dynamics and factors affecting these patterns will provide useful information about the possibilities and desirability of conducting snail control measures in various transmission situations. On the basis of various case studies the association between the occurence of human water contacts and the presence of schistosome intermediate hosts or infections in the intermediate hosts is illustrated. Other parameters affecting snail distribution patterns and density fluctuations are discussed. It is concluded that ecological studies on the intermediate host are extremely relevant, either to optimally apply existing control measures or to develop alternative measures of snail control, such as ecological or biological control.

Toxoplasmosis and mental retardation: report of a case-control study

A case-control study evaluating the association between mental retardation and toxoplasmosis was conducted among 845 school children in Belo Horizonte, MG, Brazil. Cases (450) were mentally retarded children attending a public school for special education. Controls (395) were children from the regular public school system. Clinical and anthropometric examinations and interviews were carried out to determine risk factors for toxoplasmosis and mental retardation. Diagnosis of Toxoplasma gondii infection was based upon an indirect immunofluorescent test (IFA); 55% of cases and 29% of controls were positive. The Relative Odds of mental retardation in children with positive serology was 3.0 (95% CI 2.2-4.0). Maternal exposure to cats and contact with soil were associated with an increased risk of mental retardation. Retinochoroiditis was fourfold more prevalent among cases than controls and was only diagnosed in T. gondii IFA positive participants. Congenital toxoplasmosis, in its subclinical form, appears to be an important component in the etiology of mental retardation, especially in high risk (lower socio-economic) groups. The population attributable risk was estimated as 6.0 - 9.0%, suggesting the amount of mental retardation associated with this infection.

Dengue in Brazil - situation, transmission and control: a proposal for ecological control

This article discusses dengue in terms of its conceptual and historical aspects, epidemiological and clinical/pathological nature, and evolution up to the present situation in Brazil. The author discusses the ecological relationship in both the production of dengue and its control. Comparison is made between traditional dengue-control programs and a proposed socially-controlled program of an ecological nature without the use of insecticides. Stress is placed on interdisciplinary technical and scientific activity, broadbased participation by communities in discussing methodological aspects involving them, and prospective evaluation comparing the communities selected for intervention and control communities with regard to clinical and subclinical dengue cases and vector infestation rates in relation to climatic, socio-economic, and behavioural factors.

Thevetia peruviana (Family: Apocynaceae) in the control of slug and snail pests

An aqueous extract prepared from Kernels of the fruit of Thevetia peruviana (Pers.) Schumann (Family : Apocynaceae) was found under experimental conditions, to be toxic ti the slug Laevicaulis alte (Férussac) and the snail Achatina fulica Bowdich, the important agrihorticultural pests of Indo-Pacific countries. Concentrations as low as 1% (w/v) killed all the slugs exposed in less than 981.00 (± SD 22.76) min, and 2% of the extract killed 100% of the slugs L. alte and 50%, 50% and 30% of the snail A. fulica in between 92.34 (± SD 6.63) - 321.33 (± SD 4.14) and 271.20 (± SD 17.54) - 298.26 (± SD 16.69) min respectively. The most effective concentration of the extract was 20%; it killed 100% of exposed slugs and snails within a short time (40-50 and 90-1440 min respectively) when the extract was exposed on the soil in experimental trays or when it was applied to potato slices offered as food to the gastropods.

Vectors control importance on leishmaniasis transmission

We reviewed the control of transmission of leishmaniasis regarding chemotherapy, reservoirs elimination, vaccination and insect control through the use of chemical insecticides. We also discussed complementary measures like monitoring traps, impregnated bednets and curtains, repelents, pheromones, biological control, etc. A cost comparison of insecticide interventions through the use of products belonging to the four main chemical groups was also alone, comparing together conventional formulations versus a slow-release insecticide developed by the Núcleo de Pesquisas de Produtos Naturais, Universidade Federal do Rio de Janeiro. We finally did recommendations on the situation that would justify an insecticide intervention to control sandflies.

The brazilian leishmaniasis control program

The control methods used in Brazil for both cutaneous and visceral leishmaniasis by the Ministry of Health's National Health Foundation (Fundação Nacional de Saúde) are presented. Data referring to the programme between 1980 and 1991 is presented. There was an increase in the total number of notified cases of cutaneous leishmaniasis until 1987 and from this date onwards the number has remained between 23,000 and 26,000 per year. There were significantly fewer cases of visceral leishmaniasis during the same period and until 1991 the greatest number of cases reported in one year was 2,511 in 1985. The overall picture is that it is difficult to evaluate to what extent the control methods employed have reduced the number of cases of either form of the disease. It is suggested that there is an urgent need for a closer approximation of research and health workers to review the actual control strategies and to define procedures capable of assessing accurately their impact.