Development of chimeric protein as a multivalent vaccine for human Kinetoplastid infections: Chagas disease and leishmaniasis

Leishmania spp. and Trypanosoma cruzi are parasitic kinetoplastids of great medical and epidemiological importance since they are responsible for thousands of deaths and disability-adjusted life-years annually, especially in low- and middle-income countries. Despite efforts to minimize their impact, current prevention measures have failed to fully control their spread. There are still no vaccines available. Taking into account the genetic similarity within the Class Kinetoplastida, we selected CD8+ T cell epitopes preserved among Leishmania spp. and T. cruzi to construct a multivalent and broad-spectrum chimeric polyprotein vaccine. In addition to inducing specific IgG production, immunization with the vaccine was able to significantly reduce parasite burden in the colon, liver and skin lesions from T. cruzi, L. infantum and L. mexicana challenged mice, respectively. These findings were supported by histopathological analysis, which revealed decreased inflammation in the colon, a reduced number of degenerated hepatocytes and an increased proliferation of connective tissue in the skin lesions of the corresponding T. cruzi, L. infantum and L. mexicana vaccinated and challenged mice. Collectively, our results support the protective effect of a polyprotein vaccine approach and further studies will elucidate the immune profile associated with this protection. Noteworthy, our results act as conceptual proof that a single multi-kinetoplastida vaccine can be used effectively to control different infectious etiologies, which in turn can have a profound impact on the development of a new generation of vaccines.

Nitric oxide contributes to liver inflammation and parasitic burden control in Ascaris suum infection

BACKGROUND

Human ascariasis is one of the most prevalent neglected tropical diseases worldwide. The immune response during human ascariasis is characterized by Th2 polarization and a mixed Th2/Th17 response during the pathogenesis of experimental larval ascariasis. Cytokines and other pro-inflammatory mediators, such as nitric oxide (NO), are involved in helminthic infections. However, the role of NO in ascariasis remains unclear.

OBJECTIVES

Given the importance of NO in inflammation, we aimed to determine the immunological and histopathological alterations in the livers of C57BL/6 iNOS^-/- mice during A. suum infection.

METHODS

In this study, parasitic load was evaluated in the livers of wild type C57BL/6 and C57BL/6 iNOS^-/- mice infected with A. suum. Histopathological and morphometric analyses and analysis of serum cytokines via Cytometric Bead Array were performed, and the activity of eosinophil peroxidase and myeloperoxidase of neutrophils in the tissues were determined.

RESULTS

The results showed that NO is important for controlling parasitic load during infection by A. suum. C57BL/6iNOS^-/- mice showed reduced inflammatory processes and less tissue damage during liver larval migration of A. suum, which is associated with a reduction in serum levels of pro-inflammatory cytokines.

CONCLUSIONS

We demonstrated that NO is a crucial inflammatory molecule during Ascaris sp. infection and controls the establishment of the parasite and the development of the host immune response in the liver.

Tissue eosinophilia correlates with mice susceptibility, granuloma formation, and damage during Toxocara canis infection

An increase in peripheral blood eosinophils in helminth infections is expected, and these cells are known to promote immunity against these parasites. However, studies have suggested that in some specific helminths, eosinophils may promote the needs and longevity of these parasites, and their role in these infections remains undefined, including in Toxocara canis infection. Thus, this study aimed to investigate the role of eosinophils in the context of larval migration of T. canis and the immunopathological aspects of infection. For this, we used wild-type mice and mice genetically deficient for the transcription factor GATA-binding factor 1 (GATA1−/−), infected with 1000 eggs of T. canis. At 0, 3, 14 and 63 days post-infection, parasite load, tissue cytokine production, leucocyte profile, bronchoalveolar lavage cells and histopathological analyses were carried out. Collectively, our results demonstrate that the presence of eosinophils mediates susceptibility to T. canis, inducing leucocytosis and the formation of granulomas, increasing the pulmonary and cerebral parasite load, and reducing the number of neutrophils, which may be necessary to control the infection.

ASCVac-1, a Multi-Peptide Chimeric Vaccine, Protects Mice Against Ascaris suum Infection

Control of human ascariasis, the most prevalent neglected tropical disease globally affecting 450 million people, mostly relies on mass drug administration of anthelmintics. However, chemotherapy alone is not efficient due to the high re-infection rate for people who live in the endemic area. The development of a vaccine that reduces the intensity of infection and maintains lower morbidity should be the primary target for infection control. Previously, our group demonstrated that immunization with crude Ascaris antigens in mice induced an IgG-mediated protective response with significant worm reduction. Here, we aimed to develop a multipeptide chimera vaccine based on conserved B-cell epitopes predicted from 17 common helminth proteomes using a bioinformatics algorithm. More than 480 B-cell epitopes were identified that are conserved in all 17 helminths. The Ascaris-specific epitopes were selected based on their reactivity to the pooled sera of mice immunized with Ascaris crude antigens or infected three times with A. suum infective eggs. The top 35 peptides with the strongest reactivity to Ascaris immune serum were selected to construct a chimeric antigen connected in sequence based on conformation. This chimera, called ASCVac-1, was produced as a soluble recombinant protein in an Escherichia coli expression system and, formulated with MPLA, was used to immunize mice. Mice immunized with ASCVac-1/MPLA showed around 50% reduced larvae production in the lungs after being challenged with A. suum infective eggs, along with significantly reduced inflammation and lung tissue/function damage. The reduced parasite count and pathology in infected lungs were associated with strong Th2 immune responses characterized by the high titers of antigen-specific IgG and its subclasses (IgG1, IgG2a, and IgG3) in the sera and significantly increased IL-4, IL-5, IL-13 levels in lung tissues. The reduced IL-33 titers and stimulated eosinophils were also observed in lung tissues and may also contribute to the ASCVac-1-induced protection. Taken together, the preclinical trial with ASCVac-1 chimera in a mouse model demonstrated its significant vaccine efficacy associated with strong IgG-based Th2 responses, without IgE induction, thus reducing the risk of an allergic response. All results suggest that the multiepitope-based ASCVac-1 chimera is a promising vaccine candidate against Ascaris sp. infections.

Eosinophils mediate SIgA production triggered by TLR2 and TLR4 to control Ascaris suum infection in mice

Human ascariasis is the most prevalent but neglected tropical disease in the world, affecting approximately 450 million people. The initial phase of Ascaris infection is marked by larval migration from the host's organs, causing mechanical injuries followed by an intense local inflammatory response, which is characterized mainly by neutrophil and eosinophil infiltration, especially in the lungs. During the pulmonary phase, the lesions induced by larval migration and excessive immune responses contribute to tissue remodeling marked by fibrosis and lung dysfunction. In this study, we investigated the relationship between SIgA levels and eosinophils. We found that TLR2 and TLR4 signaling induces eosinophils and promotes SIgA production during Ascaris suum infection. Therefore, control of parasite burden during the pulmonary phase of ascariasis involves eosinophil influx and subsequent promotion of SIgA levels. In addition, we also demonstrate that eosinophils also participate in the process of tissue remodeling after lung injury caused by larval migration, contributing to pulmonary fibrosis and dysfunction in re-infected mice. In conclusion, we postulate that eosinophils play a central role in mediating host innate and humoral immune responses by controlling parasite burden, tissue inflammation, and remodeling during Ascaris suum infection. Furthermore, we suggest that the use of probiotics can induce eosinophilia and SIgA production and contribute to controlling parasite burden and morbidity of helminthic diseases with pulmonary cycles.

PERFIL EPIDEMIOLÓGICOS DOS PACIENTES ENCAMINHADOS PARA O LABORATÓRIO DE REFERÊNCIA DO GRUPO GSH NO ANO 2020

Introdução

O aumento crescente da complexidade de casos relacionados a hemoterapia e avanços tecnológicos nos diagnósticos das doenças onco-hematológicas, associado ao aumento da expectativa de vida desta população, tem permitido que pacientes cada vez mais complexos sejam encaminhadas as especialidades médicas para definir o melhor tratamento a ser realizado.

Objetivo

Realizar um levantamento do perfil epidemiológico das amostras de pacientes encaminhados para o laboratório de referência em imuno-hematológica para identificação de anticorpos irregulares devido transfusões ou sensibilizações.

Materais e métodos

Levantamento estatístico utilizando o banco de dados do sistema informatizado do Banco de Sangue de São Paulo grupo gestor em hemoterapia.

Resultados

1.023 amostras de pacientes foram contabilizadas neste período do ano 2020, dos 1.023 pacientes 638 amostras eram do sexo feminino, e 385 amostras do sexo masculino. Quanto a idade recebemos amostras de pacientes com 1 dia de vida até 102 anos, de 0–10 (3,2%); 0–20 (2,8%); 21–30 (6,8%); 31–40 (18,8%); 41–50 (14,1%); 51–60 (10,6%); 61–70 (14,0%); 71–80 (13,9%); 81–90 (13,4%); 91–102 (2,6%). Dentre as doenças relacionas estão aborto 45 (4,4%); Anemia hemolítica auto imune (IHAI) 6 (0,6%); Anemia sem especificação 105 (10,3%); Anemia Falciforme 36 (3,5%); COVID-19 53 (5,2%); Insuficiência Renal Crônica (IRC) 25 (2,4%); Leucemia sem especificação 87 (8,5%); Linfoma 55 (5,4%); Lúpus 5 (0,4%); Mielodisplasia 33 (3,2%); Mieloma Múltiplo 61 (6,0%); Neoplasia 16 (1,6%); Trombose 12 (1,2%); Transplante de Medula 11 (1,1%); Talassemia 16 (1,6%); Sepse 16 (1,6%); Sangramento 16 (1,6%); Parto 39 (3,8%). Nas identificações de anticorpos irregulares encontramos os seguintes anticorpos: D (162 – 15,8%); c (15 – 1,4%); C (8 – 0,8%); e (1 – 0,09%); E (75 – 7,3%); K (40 – 3,9%); Kp^a (4 – 0,4%); Di^a (28 – 2,7%); Fy^a (14 – 1,4%); Jk^a (10 – 1,0%); Jk^b (4 – 0,4%); P1 (1 – 0,09%); S (3 – 0,3%); s (3 – 0,3%); M (27 – 2,3); N (2 – 0,2%); Le^a (9 – 0,9%); Le^b (1 – 0,09%); Lu^a (1 – 0,09%); Lu^b (1 – 0,09%); Fenotipagem estendida (276 – 27%); tipagem ABO direta/reversa (26 – 2,5%); TAD+/Auto+ (209 – 20,43%); Ausência de anticorpos (92 – 9,0%); auto e (3 – 0,3%. Crio aglutinina fria (12 – 1,2%).

Conclusão

A maioria das amostras dos pacientes encaminhados ao laboratório de referência em imuno-hematologia para realizar os estudos imuno-hematógicos foram do sexo feminino, na faixa etária de 31–40 anos, as doenças com maior incidência foram leucemia, mieloma múltiplo, linfoma e COVID-19. Em relação aos anticorpos identificados o de maior prevalência foi D 15,8%. Esses resultados nos ajudam no planejamento e cuidado transfusional para esses pacientes.

Biology and External Morphology of the Immature Stages of Dirphia moderata Bouvier (Lepidoptera: Saturniidae: Hemileucinae) in Anacardium occidentale L

The genus Dirphia Hübner, [1819] presents Neotropical distribution. This genus, besides causing accidents of interest in public health, is a potential defoliator pest of cultivated plants, among them the cashew tree (Anacardium occidentale L.), a crop of great economic importance. This study describes the biology, external morphology of the immature stages of Dirphia moderata Bouvier, 1929 including the first instar larva chaetotaxy. The egg stage had an average duration of 15 days, larval stage 45 days and pupa 60 days, totaling 120 days in average temperature of 28.8 °C and 59.5% relative humidity. Six instars were confirmed by the Dyar rule, with a growth rate of cephalic capsule K = 1.4 times per ínstar. The results found in the first ínstar chaetotaxy follow the general pattern known for Hemileucinae.

IgG Induced by Vaccination With Ascaris suum Extracts Is Protective Against Infection

Human ascariasis has a global and cosmopolitan distribution, and has been characterized as the most prevalent neglected tropical disease worldwide. The development of a preventive vaccine is highly desirable to complement current measures required for this parasitic infection control and to reduce chronic childhood morbidities. In the present study, we describe the mechanism of protection elicited by a preventive vaccine against ascariasis. Vaccine efficacy was evaluated after immunization with three different Ascaris suum antigen extracts formulated with monophosphoryl lipid A (MPLA) as an adjuvant: crude extract of adult worm (ExAD); crude extract of adult worm cuticle (CUT); and crude extract of infective larvae (L3) (ExL3). Immunogenicity elicited by immunization was assessed by measuring antibody responses, cytokine production, and influx of tissue inflammatory cells. Vaccine efficacy was evaluated by measuring the reductions in the numbers of larvae in the lungs of immunized BALB/c mice that were challenged with A. suum eggs. Moreover, lung physiology and functionality were tested by spirometry to determine clinical efficacy. Finally, the role of host antibody mediated protection was determined by passive transfer of serum from immunized mice. Significant reductions in the total number of migrating larvae were observed in mice immunized with ExL3 61% (p < 0.001), CUT 59% (p < 0.001), and ExAD 51% (p < 0.01) antigens in comparison with non-immunized mice. For the Ascaris antigen-specific IgG antibody levels, a significant and progressive increase was observed with each round of immunization, in association with a marked increase of IgG1 and IgG3 subclasses. Moreover, a significant increase in concentration of IL-5 and IL-10 (pre-challenge) in the blood and IL-10 in the lung tissue (post-challenge) was induced by CUT immunization. Finally, ExL3 and CUT-immunized mice showed a marked improvement in lung pathology and tissue fibrosis as well as reduced pulmonary dysfunction induced by Ascaris challenge, when compared to non-immunized mice. Moreover, the passive transfer of specific IgG antibodies from ExL3, CUT, and ExAD elicited a protective response in naïve mice, with significant reductions in parasite burdens in lungs of 65, 64, and 64%, respectively. Taken together, these studies indicated that IgG antibodies contribute to protective immunity.

Multiple Exposures to Ascaris suum Induce Tissue Injury and Mixed Th2/Th17 Immune Response in Mice

Ascaris spp. infection affects 800 million people worldwide, and half of the world population is currently at risk of infection. Recurrent reinfection in humans is mostly due to the simplicity of the parasite life cycle, but the impact of multiple exposures to the biology of the infection and the consequences to the host's homeostasis are poorly understood. In this context, single and multiple exposures in mice were performed in order to characterize the parasitological, histopathological, tissue functional and immunological aspects of experimental larval ascariasis. The most important findings revealed that reinfected mice presented a significant reduction of parasite burden in the lung and an increase in the cellularity in the bronchoalveolar lavage (BAL) associated with a robust granulocytic pulmonary inflammation, leading to a severe impairment of respiratory function. Moreover, the multiple exposures to Ascaris elicited an increased number of circulating inflammatory cells as well as production of higher levels of systemic cytokines, mainly IL-4, IL-5, IL-6, IL-10, IL-17A and TNF-α when compared to single-infected animals. Taken together, our results suggest the intense pulmonary inflammation associated with a polarized systemic Th2/Th17 immune response are crucial to control larval migration after multiple exposures to Ascaris.

Intraoperative radiotherapy in the conventional linear accelerator room for early breast cancer treatment: an alternative choice in developing countries

Intraoperative radiotherapy with a single dose of electrons (ELIOT) in the conservative treatment of breast cancer is a possibility under evaluation in clinical trials. The costs of the mobile linear accelerator with a robotic arm, used in intraoperative radiotherapy, are prohibitive for poor countries. The aim of this study was to evaluate the feasibility of ELIOT in the accelerator room of the Radiotherapy Service for early breast cancer treatment. We analyzed 40 patients submitted to breast conservative surgery and ELIOT, in the accelerator room of the Radiotherapy Service at the Hospital of Pontificia Universidade Católica do Rio Grande do Sul in Brazil from January 2004 to July 2005. Patients with unifocal breast carcinoma smaller than 25 mm, aged over 45 years, who were candidates for conservative surgery were selected and a total dose of 21Gy was delivered, without further radiotherapy. In the short-term follow-up (median 18 months), six patients (15%) presented with some grade of fibrosis under the scar. One case (2.5%) of local recurrence was reported. There are no cases of contralateral carcinoma or distant metastases so far. Our data show that intraoperative radiotherapy with electrons can be safely performed in an accelerator room with a conventional machine.

[Ecoepidemiology of urban schistosomiasis in Itamaracá Island, Pernambuco, Brazil]

INTRODUCTION

In 1988, 22 autochthonous cases from accidental exposure were registered in Forte Orange beach, Itamaracá Island, Pernambuco, Brazil. All cases occurred in middle-to-upper class individuals who were vacationing in the island. After the cases were identified, the major objective was to find breeding sites of schistosomiasis vectors and correlate the biological factors with the environmental conditions.

METHODS

The environmental characteristics of the beach before human occupation were obtained from several documents. Also, a one-year malacological survey was conducted with monthly collection of mollusks, and the determination of their infectivity rates.

RESULTS/CONCLUSIONS

The malacological survey was able to identify 20 breeding sites of Biomphalaria glabrata and 28 capture station were set up. Snails were collected and examined each month throughout a whole year. The results show a seasonal variation in the mollusk population density associated with infection rates and types of breeding sites. The importance of this new epidemiological profile of schistosomiasis in the State of Pernambuco relies on the fact that it can be related with the drastic human interference on the environment. Ecological, environmental, and demographic factors as well as the epidemiological characteristics of the disease have social and economic repercussions.

Possible hybridization of Brazilian planorbid snails and its importance in population dynamics

This study focuses on the possibility of experimental hybridization among host snail species for Schistosoma mansoni in Brazil, with morphological characterization of the hybrids found. By using albinism as a genetic marker, intraspecific crossbreedings were performed between two strains of each species involved, in addition to interspecific crossbreedings; the only viable crossbreeding was between pigmented Biomphalaria glabrata (Paulista, PE) and albino B. tenagophila (Joinville, SC), with the formation of F1 and F2 generations. All offspring in F1 displayed black eyes and a renal ridge on the mantle, while F2 displayed dissociated morphological traits. With regard to reproduction, F1 was more efficient than F2. The experiment's results suggest post-zygotic reproductive isolation.

[Schistosomiasis: reproduction and expansion of the endemia to the state of Pernambuco in Brazil]

Schistosomiasis mansoni can be considered an important public health problem in Northeastern Brazil, in spite of the reduction in the prevalence of the hepatosplenic clinical forms which have been attributed to the large scale use of chemotherapy in this country. However, the rise in the prevalence rates and the spread of this endemic disease to new areas show that schistosomiasis is assuming its must cruel expression: less lethal but more greatly incapacitating in terms of irreversible physical and moral damage to human beings. The state of Pernambuco presents growing rates for schistosomiasis infection in humans. The epidemiological profile of this disease displays high and consistent prevalence rates (up to 80%) in rural areas, and new cases of acute infection on the coast, where schistosomiasis has recently been introduced. The reproduction and expansion of this endemic disease can be better understood on the basic of a conception of structural and historical causation. The disease construction process should be reconstructed in the light of biological as well as the social, political and cultural factors which are jointly responsible for the present endemic situation. Within that frame work, the historical and socioeconomic features that interact with the parasite and give rise to the present proportions of the schistosomiasis epidemic in Pernambuco are discussed. The mode of occupation and use of the land, unemployment, under-nutrition, migration, etc., raise the question of the growing difficulties confronting the control of the disease, both in rural areas where populations are extremely mobile as well as in the poorly organized urban population. Epidemiological investigation is fulfilling its role in its attempts to understand the complex relationships of an intrinsecally social nature of the health/disease process between health problems and the quality of life for the purpose of producing consistent disease control models.

Formas hepatosplênicas da esquistossomose mansônica no interior do Nordeste do Brasil

Estudos de campo sobre a morbidade da esquistossomose mansônica foram realizados em algumas áreas rurais do interior do nordeste do Brasil durante o primeiro semestre de 1991. Estes estudos seccionais foram limitados à determinação do gradiente clinico da endemia. Foram examinadas todas as populações presentes neste levantamento feito casa-por-casa. Os resultados mostraram a redução da prevalência da forma mais grave da esquistossomose - a forma hepatosplênica - quando comparados com estudos semelhantes feitos nas mesmas áreas durante as décadas de 60 e 70. As taxas de prevalência das formas clínicas graves da doença foram deslocadas dos grupos de idade mais jovens para os grupos mais velhos.

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.(ABSTRACT TRUNCATED AT 250 WORDS)

The bioecology of snail vectors for schitosomiasis in Brazil

This paper describes the ecology of two species of Biomphalaria: B.glabrata and B. straminea. These species have been intensively studied in Brazil and in other countries since the 1950s. The literature in this area can be broadly subdivided into three categories, linked to three distinct historical periods: 1) an accumulated store of early studies carried out in the laboratory and in the field; 2) the development of quantitative ecological models; and 3) the development of an alternative methodology for breeding snails under seminatural conditions.

Long-term controlled field experiment on the competition between two species of Biomphalaria (Mollusca, Basommatophora), the snail vectors of Schistosoma mansoni in Northeastern Brazil

A long-term controlled field experiment on the interactions of the populations of Biomphalaria glabrata (target population) and B. straminea (competitor) was carried out in the county of Alhandra, state of Paraíba, Brazil, during the period 1980 through 1989. Results obtained in the current paper show that the snail B. straminea has strong competitive advantages over B. glabrata. In six out of nine streams the native population of B. glabrata were totally excluded and replaced by B. straminea. There is evidence showing that seasonal dryness has marked influence on the phenomenon studied in this paper. In all the streams were B. straminea already predominated, return of B. glabrata was never observed.

Modelo alternativo para o controle da esquistossomose: estado atual do projeto no Estado do Espírito Santo, Brasil

O trabalho que vem sendo desenvolvido em uma área rural do município de Afonso Cláudio (Espírito Santo) representa uma proposta alternativa aos atuais programas de controle. Este é um trabalho de pesquisa controlado, em integração interdisciplinar e multi-institucional, envolvendo várias entidades de pesquisa e de serviços. O modelo alternativo de controle da endemia conta com amplo envolvimento comunitário e com a organização dos serviços locais de saúde a nível primário (SUS). A pesquisa participante tem sido o ponto de partida metodológico que baliza os procedimentos de coleta e análise de dados e os de intervenção na realidade local. Os métodos de controle estão limitados ao tratamento médico individualizado e à melhoria das condições de saneamento. Estes métodos estão, evidentemente, integrados às ações sociais acima descritas. O projeto está dividido em três fases: pré-controle, controle (intervenção) e avaliação final. No momento, o mesmo entra em sua fase de intervenção, com duração prevista de três anos.

Transmission of Schistosoma mansoni under experimental conditions using the bovine--Biomphalaria glabrata-bovine model

Three calves experimentally infected with Schistosoma mansoni, and passing viable eggs in feces, as well as 5 normal calves (coming from a non-endemic area for schistosomiasis) kept as controls, were maintained in an enclosure (850 m2 in area). In this enclosure, a tank with water received 500 laboratory reared Biomphalaria glabrata. All the control calves were infected for a period ranging from 79 to 202 days after the beginning of the experiment, and afterwards presented viable S. mansoni eggs in feces. The mean worm recovery was 555. The snail population increased throughout the experimental period, showing a high number of B. glabrata infected with S. mansoni (42% on average). According to the present study, bovine has been suggested as having potentially a role in the maintenance of the life cycle of S. mansoni.

Alternative approaches in schistosomiasis control

Measures for the control of schistosomiasis were implemented in Egypt beginning 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 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 focal 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 studies (Espírito Santo and Pernambuco). The adopted strategy aims to interfere in the complex relationships between man and his bio-social-cultural environment, without forgetting that the unequal distribution of the space is a consequence of the political and economic organization of the Society.

Competitive displacement of Biomphalaria glabrata by B. straminea

Data on the interaction between populations of closely related species of Biomphalaria, B. glabrata and B. straminea, are presented in the current paper. Laboratory and field observations and experiments have shown that B. straminea has competitive advantages over B. glabrata.

Competitive interactions between species of fresh-water snails. I. Laboratory. IC. Comparative survival of Biomphalaria glabrata and B. straminea kept out of water

Biomphalaria glabrata and B. straminea were submitted to an out-door laboratory experiment for testing their comparative ability to resist desiccation. Results have shown that B. straminea is significantly higher resistant than B. glabrata. After five months under such distressing condition the survival ratios were: B. glabrata 8.1 per cent and B. straminea 18.4 per cent.

Competitive interactions between species of freshwater snails. I. Laboratory studies: Ib. Comparative studies of the dispersal and the vagility capabilities of Biomphalaria glabrata and Biomphalaria straminea

Experiments reported in the current paper, carried out under semi-field conditions created in the laboratory, have shown that B. straminea has competitive superiority when compared with B. glabrata. The former species has shown higher capabilities of both dispersal and vagility. In addition, B. straminea was able to compete successfully with B. glabrata.

New field observations on the competitive displacement between two species of planorbid snails inhabiting northeastern Brazil

Observations reported in the present paper have shown that Biomphalaria glabrata is being gradually displaced by B. straminea in coastal areas of two counties on the state of Pernambuco, Brazil, confirming former observations made in the same region.

Incapacitating effects of schistosomiasis mansoni on the productivity of sugar-cane cutters in northeastern Brazil

Studies were carried out on two sugar estates in the humid coastal forest region of northeastern Brazil, a highly endemic area of schistosomiasis mansoni. Results obtained in a retrospective study were not conclusive, but clear-cut results emerged from a prospective study. The latter was conducted on a sugar estate (Catende) where the severe hepatosplenic clinical form of the disease is seen in 4% of the field-working population. Comparison was made between two groups of paired subjects: one composed of workers with the hepatosplenic form of the disease and the other composed of workers with the intestinal form. Reduction of productivity among the hepatosplenic subjects compared to intestinal subjects was 35.1%. The loss to the Catende sugar estate from reduced productivity caused by schistosomiasis mansoni for the harvest season of 1978 was calculated as 0.93% of the estate's total production, or approximately US$135,000. When this figure is extrapolated to the State of Pernambuco (16 million tons of sugar total annual production), the annual loss in the state if estimated to be US$2 million.

[Schistosomiasis in workers of the Catende Sugar Mill, Pernambuco, Brazil]

Foi realizado estudo transversal sobre a esquistossomose mansônica em nove engenhos da usina Catende localizada na Zona da Mata sul do Estado de Pernambuco (Brasil). A prevalência foi 43,8% para a população geral dos engenhos e 64,6% para os trabalhadores de campo. A prevalência das formas hepato-esplênicas foi 4,1% sendo que em dois engenhos chegou a 8,7% e 9,1%. Biomphalaria straminea foi o único molusco transmissor encontrado na área; sua taxa de infecção natural por S. Mansoni foi 0,07%. Á esquistossomose pode ser considerada como doença grave na região estudada.

[Autochthonous schistosomiasis mansoni in the Federal District, Brazil]

Sete casos autóctones de esquistossomose mansônica são descritos no Distrito Federal (Brasil). Todos os casos são de crianças cujas idades variavam de 3 a 13 anos e que habitavam área suburbana da cidade de Planaltina. Cinco destes casos pertencem a uma mesma família vivendo às margens de um criadouro de Biomphalaria glabrata onde foram encontrados dois caramujos infectados por Schistosoma mansoni em 229 examinados.

Cross-sectional studies on Schistosoma mansoni infection in northeast Brazil

Studies on the prevalence and morbidity of Schistosoma mansoni infection were carried out in selected areas of northeastern Brazil. The study revealed that both prevalence and morbidity rates were significantly higher in rural than in urban areas. No statistically significant differences in prevalence and morbidity were found in relation to sex. The age-specific prevalence curve was found to be of the usual shape found in highly endemic areas of the country: it reaches its peak in the 10-14 group, and slightly decreases in the older groups. Although it is generally admitted that hepatosplenic forms of the disease occur more frequently between 10 and 40 years of age, the present study has shown that the proportion of these severe cases increases with increase of age.

Schistosoma mansoni: Natural Infection of Cattle in Brazil

In an area in Brazil where schistosomiasis has long been endemic, examination of cattle which were slaughtered for food disclosed the presence of adult Schistosoma mansoni in the mesenteric veins of four animals. Eggs of S. mansoni were found in the feces and rectal mucosa of one animal.