Evolution of holometabola insect digestive systems: physiological and biochemical aspects

This review takes into account primarily the work done in our laboratory with insects from the major Holometabola orders. Only the most significant data for each insect will be presented and a proposal on the evolution of Holometabola insect digstive systems will be advanced.

Evaluation of different Cypermethrin formulations and concentrations in the control of Musca domestica

Cypermethrin (4 g/l, 5 g/l wettable powder and 7 ml/l, 10 ml/l emulsifiable concentrate) was tested, under laboratory conditions, against the adult Musca domestica. As a standard for comparison, a 6 ml/l concentrate suspension formulation of deltamethrin was used. One and twenty-four hours after application, mortality counts showed that the substances under test killed, respectively, more than 80% and 85% of the exposed insects. Under the conditions of the test, cypermethrin was considered effective in the control of the house fly.

Epidemiological distribution of Plasmodium falciparum drug resistance in Brazil and its relevance to the treatment and control of malaria

With the use of a simple formulary, field by health agents was ewstablished a monitoring programme for responses of P. falciparum to the antimalarial drugs. This monitoring programme is emphasized for knowledge of the epidemiology of the drug resistance and the control of malaria falciparum in Amazonan Basin where occurs more than 95% of Brazilian malaria cases every year. It was demonstrated that still now 4-aminoquinolines have a great importance for the mortality control in areas where just SUCAM (National Health Foundation - Health Ministry) agenst are present without any medical assistance. The results obtained permitted the simplification of malaria treatment in Brazil Important conclusions were established in the field of malaria drug resistance.

Harmonization of research and control in schistosomiasis

I have been employed by several different organizations during over 30 years working on schistosomiasis, the majority spent in endemic areas of Caribean, South America, Africa and the Western Pacific. Much of the work is best classified as applied research but sometimes it strayed to the extremes of either public health control programmes or pure research. Over this period, there have been several significant research developments that have altered our whole approach to control. Ideally, research and control should complement each other but, in reality, they sometimes have conflicting objectives. Public health workers understandably wish to provide immediate, shot-term protection to the communities in their care, but research workers may, within ethical limits, reasonably want to observe untreated communities for extended periods in order to understand the underluing process of transmission, disease pathogenesis and immunity to help develop more effective control measures. An example of this situation has occured recently in Senegal where water development projects seem to have favoured the introduction and spreed of Schistosoma mansoni in the Senegal River Basin. I have been asked to be the scientific consultant to the newly formed ESPOIR programme, linking European research organizations and the Senegal Ministry of Health, to reconcile the conflictiong aims of public health workers, wishing to use whatever funds can be obtained for an immediate chemotherapy to try to eliminate the focus, at present confined to the vicinity of a relatively small, commercially run sugar irrigation scheme; and research workers who see a rare chance to study the development of immune mechanisms in a adults in a community not previously exposed to the infection. This information could prove invaluable in understanding the development of immunity and the pathogenesis of disease, leading eventually to the development of vaccines to revolutionise the future approach to schistosomiasis...

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.

Determination and control of schistosomiasis

The subject of this conference reflects the scientific community's interest in seeking to understand the complex causal web whose various social, economic, and biological components interact in the production and reproduction of schistosomiasis and its control in relation to community participation. From the onset, the author stresses the impossibility of dealing separately with community participation, as if social components were just one more "weapon" in the arsenal for schistosomiasis control. This study begins with a brief historical review of the 71 years of control activities with this endemic disease, stressing the enormous efforts and huge expenditures in this field vis-à-vis the limited results, despite the extraordinary technological development of specific, classical control inputs such as new treatment drugs and molluscicides. The article then discusses the various strategies used in control programs, emphasizing ideological consistencies and contradictions. Interactions at the macro and micro levels are discussed, as are the determinants and risk factors involved in producing the disease's endemicity. Unequal occupation of space leaves the segregated portion of the population exposed to extremely favorable conditions for transmission of the disease. This raises the issue of how to control an endemic disease which is so closely linked to the way of life imposed on the population. The study challenges the classical control model and suggests an alternative model now undergoing medium-term investigation in the States of Espirito Santo, and Pernambuco, Brazil. The author concludes that we do not need new strategies, but a new control model, contrary to the prevailing classical model in both concept and practice. From the conceptual point of view, the new model mentioned above is different from others in that schistosomiasis control is seen from a social perspective stressing the population's accumulated knowledge in addition to the building of shared knowledge. The model's praxis has the following characteristics: (1) it is integrated with and financed by research agencies and health services; (2) it operates at the local health services level; (3) use of molluscicides has been eliminated; (4) emphasis is given to individual medical treatment and improvement of sanitary conditions.

The WHO Collaborating Centre for Research and Control of Schistosomiasis at Niamey, Niger

The Centre de Recherche sur les Méningites et les Schistosomes (CERMES) is a research institute depending on the Organisation de Coordination et de Coopération pour la lutte contre les Grandes Endémies - a West African Organization for Public Health - devoted to the studies on schistosomiasis and meningitis. The staff includes 32 persons with 11 scientists and one financial officer. The activities of the CERMES involving schistosomiasis concern three research units: (a) ecology of human and animal schistosomiasis transmission; the CERMES defined the different patterns of schistosomiasis transmission in Niger (involving African dry savana); in this field, we have shown, (i) the existence of important variability in conditions of transmission of S. haematobium and, (ii) natural hybridization between parasitic species of the ruminants (S. bovis and S. curassoni) and genetic interaction between human and animal parasites; (b) definition of morbidity indicators usable for rapid assessment methods, for appraisal of the severity of the disease and for the evaluation of the efficiency of control methods; we have established the correlation between ultrasonographic data and some cheap and simple field indicators; (c) immune response and protective immunity induced by recombinant glutathion S-transferase (Sm28, Sb28 and Sh28) in homologous and heterologous animal models including goats, sheep and non human primates (Erythrocebus patas). In Niger, we participate in all control programs against schistosomiasis to define control strategies, to supervise operations and to participate in their evaluation with external experts. International collaborations constitute a frame including four laboratories in Africa and six laboratories in developed countries (Europe and USA)

The identification and characterization of new immunogenic egg components: implications for evaluation and control of the immunopathogenic T cell response in schistosomiasis

In schistosomiasis, granuloma formation to parasite eggs signals the beginning of a chronic and potentially life-threatening disease. Granulomas are strictly mediated by CD4+ T helper (Th) cells specific for egg antigens; however, the number and identity of these T cell-sensitizing molecules are largely unknown. We have used monoclonal T cell reagents derived from egg-sensitized individuals as probes to track down, isolate and positively identify several egg antigens; this approach implicitly assures that the molecules of interest are T cell immunogens and, hence, potentially pathogenic. The best studied and most abundant egg component is the Sm-p40 antigen. Sm-p40 and its peptide 234-246 elicit a strikingly immunodominant Th-1-polarized response in C3H and CBA mice, which are H-2k strains characterized by severe egg-induced immunopathology. Two additional recently described T cell-sensitizing egg antigens are Schistosoma mansoni phosphoenolpyruvate carboxykinase (Sm-PEPCK) and thioredoxin peroxidase-1 (Sm-TPx-1). In contrast to Sm-p40, both of these molecules induce a more balanced Th-1/Th-2 response, and are relatively stronger antigens in C57BL/6 mice, which develop smaller egg granulomas. Importantly, Sm-p40 and Sm-PEPCK have demonstrated immunogenicity in humans. The findings in the murine model introduce the important notion that egg antigens can vary significantly in immunogenicity according to the host's genetic background. A better knowledge of the principal immunogenic egg components is necessary to determine whether the immune responses to certain antigens can serve as indicators or predictors of the form and severity of clinical disease, and to ascertain whether such responses can be manipulated for the purpose of reducing pathology.

Epidemiological and control aspects of schistosomiasis in Brazilian endemic areas

The present work analyzes the epidemiology of schistosomiasis in Brazil, its expansion, the attempts to control the disease, and the overall difficulties. The authors present the distribution of schistosomiasis intermediary hosts in Brazil, the migration routes of the human population, and disease distribution in highly and lowly endemic areas and isolated foci. They also analyze the controlling programs developed from 1977 to 2002, indicating the prevalence evolution and the reduction of disease morbi-mortality. In addition, the authors also evaluate controlling methods and conclude that: (a) no isolated method is able to control schistosomiasis, and every controlling program should consider the need of a multidisciplinary application of existing methods; (b) in long term, basic sanitation, potable water supply, as well as sanitary education, and community effective participation are important for infection control; (c) in short term, specific treatment at endemic areas, associated with control of intermediary hosts at epidemiologically important foci, are extremely relevant for controlling disease morbidity, although not enough for interrupting infection transmission.

Low transmission areas of schistosomiasis in Venezuela: consequences on the diagnosis, treatment, and control

Schistosomiasis low transmission areas as Venezuela, can be defined as those where the vector exists, the prevalence of active cases is under 25%, individuals with mild intensity of infection predominate and are mostly asymptomatic. These areas are the consequence of effective control programs, however, "silent" epidemiological places are difficult to trace, avoiding the opportune diagnosis and treatment of infected persons. Clinic and abdominal ultrasound have not shown to discriminate infected from uninfected persons in areas where besides Schistosoma mansoni, intestinal parasites are the rule. Under these conditions, serology remains as a very valuable diagnostic tool, since it gives a closer approximation to the true prevalence. In this sense, circumoval precipitin test, ELISA-SEA with sodium metaperiodate, and alkaline phosphatase immunoassay joined to coprology allow the identification of the "schistosomiasis cases". In relation to public health, schistosomiasis has been underestimated by the sanitary authorities and the investment on its control is being transferred to other diseases of major social and political relevance neglecting sanitary efforts and allowing growth of snail population. Some strategies of diagnosis and control should be done before schistosomiasis reemergence occurs in low transmission areas.