Estudo do efeito moluscicida de espécies vegetais em embriões e caramujos adultos de Biomphalaria glabrata SAY 1818 (Gastropoda, Planorbidae) / Investigation of the effects of plant species molluscicides on embryos and adult snails of the species Biomphalaria glabrata

A esquistossomose é uma doença parasitária causada por helmintos trematódeos do gênero Schistosoma, que tem o ser humano como hospedeiro definitivo e os planorbídeos do gêneroBiomphalaria como hospedeiros intermediários. É a segunda doença parasitária mais importante nomundo, atingindo mais de 220 milhões de pessoas. A busca por moluscicidas derivados de espécies vegetais tem sido intensificada como alternativa ao uso de moluscicidas sintéticos. O objetivo destetrabalho foi investigar o efeito moluscicida de Annona muricata e Jatropha elliptica no caramujoadulto e em suas desovas. Nos bioensaios, observou-se que os extratos etanólicos das espécies A. muricata e J. elliptica apresentaram efeito concentração-dependente com valores de DL90 68,3 e 41,1 mg/mL-1 , respectivamente, sobre o caramujo adulto, e DL90 27,7 e 24,0 mg/mL-1 sobre as suas desovas. As espécies vegetais investigadas neste trabalho apresentam efeito moluscicida epossivelmente podem ser fontes de compostos no controle da esquistossomose.

Molecular Differentiation of Schistosoma japonicum and Schistosoma mekongi by Real-Time PCR with High Resolution Melting Analysis

Human schistosomiasis caused by Schistosoma japonicum and Schistosoma mekongi is a chronic and debilitating helminthic disease still prevalent in several countries of Asia. Due to morphological similarities of cercariae and eggs of these 2 species, microscopic differentiation is difficult. High resolution melting (HRM) real-time PCR is developed as an alternative tool for the detection and differentiation of these 2 species. A primer pair was designed for targeting the 18S ribosomal RNA gene to generate PCR products of 156 base pairs for both species. The melting points of S. japonicum and S. mekongi PCR products were 84.5+/-0.07degrees C and 85.7+/-0.07degrees C, respectively. The method permits amplification from a single cercaria or an egg. The HRM real-time PCR is a rapid and simple tool for differentiation of S. japonicum and S. mekongi in the intermediate and final hosts.

Recent studies on Schistosoma intercalatum: taxonomic status, puzzling distribution and transmission foci revisited

Schistosoma intercalatum, which causes human rectal schistosomiasis in Africa, still presents a great interest for its imprecise taxonomic status and its puzzling distribution in Africa. Two geographically isolated strains of S. intercalatum are recognized, the Lower Guinea strain and the Congo strain, which differ from each other in a number of morphological, biological and biochemical characteristics. Recent molecular data using RAPD markers indicate high divergence between the two strains, with values of Nei and Li's similarity indice allowing recognition of two genetically distinct taxa: experiments on pre- and post-isolating mechanisms are in progress in order to re-evaluate the taxonomic status of this polytypic species. With regard to its geographical distribution, S. intercalatum is characterized by the existence of two stable endemic areas (localized in Lower Guinea and North East of Democratic Republic of Congo) which correspond to the historical areas of species discovery, and the emergence during the last 15 years of new foci of the Lower Guinea strain outside previously known endemic areas. The absence of local adaptation of the Lower Guinea strain to its intermediate host, supported by experimental studies, may help to facilitate the spread of this strain. Nevertheless, the present restricted distribution of this species remains puzzling, because its potential snail hosts (bulinids) are widely distributed throughout much of Africa. Recent experimental and epidemiological studies suggest that interspecific sexual interactions between human schistosomes could have a role in limiting the distribution of S. intercalatum: the competitive sexual processes acting among human schistosomes show that S. haematobium and S. mansoni are always competitively dominant over S. intercalatum. These epidemiological observations lead the authors to distinguish three kinds of transmission foci for S. intercalatum

Schistosomiasis malayensis-like infection among the Penan and other interior tribes (Orang Ulu) in upper Rejang River Basin Sarawak Malaysia.

A serosurvey of various indigenous interior tribes (Orang Ulu) in upper Rejang River Basin Sarawak Malaysia, the site of a multibillion Ringgit hydroelectric power project, found 6.8% of the individual surveyed were seropositive for schistosomiasis, as determined by ELISA method using the soluble egg antigen of Schistosoma malayensis Baling strain. In all age group, the seroprevalence rate is higher (9.5%) in males than in females (4.5%) except for the 31-40 age group. Seroprevalence of schistosomiasis was found to increase with age with the above 60 age group having the highest rate followed by the 31-40 age group. Seroprevalence rate among the tribes ranges from 4.1% among the Penan to 11.6% among the Kajang. There was no seroevidence of schistosomiasis among the Ukits. A snail survey found four snail species including Brotia species, the intermediate host of the lung fluke Paragonimus westermani, however no schistosome snail host was identified. Although schistosomiasis malayensis-like infection may be endemic in the area, its public health significance remains undetermined.

Monoclonal antibodies against Schistosoma mekongi surface tegumental antigens.

Monoclonal antibodies were produced from naturally infected BALB/c mice. Thirteen hybridomas which were found to produce monoclonal antibodies against surface tegumental antigens of Schistosoma mekongi by ELISA assay were used in this study. The antigen specificities of hybridomas reactive with surface tegumental antigens were characterized and localized by immunoblotting analysis and Avidin-Biotin method. Of the 13 hybridomas, only three produced monoclonal antibodies to the single epitopes in the surface tegumental antigens. These epitopes (125 kDa, 97 kDa and 38 kDa) have been found to be the major antigenic components of the surface tegument of S. mekongi. The 38 kDa antigen was found to associate with the surface tegumental layers, the muscular layers lying just beneath the tegument, as well as in the gut surface. The 97 and 125 kDa antigens were detectable only in the surface tegumental area. The biochemical identity of these proteins or glycoproteins is unknown. However, these antigens have also been described in S. japonicum and S. mansoni.

Pulmonary pathology in rabbits infected with the Baling and Koyan strains of Schistosoma malayensis.

Two distinct strains of Schistosoma malayensis exist in Malaysia (designated the Baling and Koyan strains). Both these strains show intraspecific variations in pathology (Greer et al, 1988). To evaluate the differences in the pulmonary pathology resulting from infections of the two different strains of Malaysian schistosome, a total of 20 experimental rabbits were infected, 10 each with cercariae of the Koyan strains. Pathological changes were studied over a period of 28 weeks. Granulomas in the lung occurring as a result of infection with the Baling strain were compared with those caused by infection with the Koyan strain. Although both strains produced parenchymatous and alveolar lesions, granulomas caused by the Baling strain of Malaysian schistosome were more numerous and larger (when comparing mean diameter as well as area of granuloma, p < 0.05). In addition, pulmonary vascular hypertensive changes were present in Baling strain infected rabbits. These comprised of pulmonary arteriolar endothelial swelling and damage, intimal elastosis and medial hypertrophy. Angiitis and pulmonary periphlebitis were also noted occasionally. In contrast, Koyan strain infection resulted in fewer and smaller granulomas. Pulmonary vascular changes were minimal.

Induction of intestinal lesions in rabbits with Koyan and Baling strains of Schistosoma malayensis Sp N.

Schistosoma malayensis Sp N is a putative new species of schistosome discovered in Peninsular Malaysia in 1973. This paper comprises the first report on the detailed gastrointestinal pathology present in rabbits infected with strains of the parasite. Two different strains of schistosome--the Baling and Koyan strains--from two different ecosystems were used to infect inbred rabbits and the resulting pathophysiology was studied. Our results showed that the Baling strain of S. malayensis was more virulent than the Koyan strain and produced nodular, segmental circumferential lesions and large bilharziomas measuring 1-7 cm in diameter in the distal jejunum, ileum and the ileo-caecal junction. The findings indicate that the Baling strain of S. malayensis was more pathogenic for rabbits as compared with the Koyan strain--in relation to the gross pathology of the gut and the tissue egg load. Earlier reports have shown that rabbits infected with S. japonicum induces significant intestinal lesions in rabbits (Cheever et al, 1980 a,b) but these animals are refractory to infection with S. mekongi (Byram and Lichtenberg, 1980). Our studies show that the two strains of S. malayensis adapted well in rabbits. It is also established that in rabbits, the virulence of the Baling strain of S. malayensis is greater than that of S. mekongi and approximates that of S. japonicum.

Investigation on immunity induced by Schistosoma spindale against S. mekongi in experimental mice.

An investigation on immunity induced by Schistosoma spindale cercariae (cattle and swamp buffalo schistosome) against S. mekongi (human schistosome) was conducted in Swiss albino mice. The studies comprised the development patterns of homologous immunity of S. spindale and heterologous immunity induced by S. spindale against S. mekongi. The development pattern of homologous immunity was studied in mice with an immunization of 100 S. spindale cercariae. At one week intervals, between 2 to 16 weeks after immunization, they were each challenged with 500 S. spindale cercariae. Significant homologous immunity, as judged by lung recovery assay five days after challenge, occurred from week 5 to week 16 with week 8 giving the highest homologous immunity (68.1% of schistosomular reduction). Using the above information mice, with an eight-week immunization period of 100 S. spindale cercariae, were tested for resistance to heterologous S. mekongi infection. The criteria used to evaluate their immune status was schistosomular lung recovery, daily egg output, worm recovery and tissue egg count. The results showed that mice immunized with S. spindale cercariae could develop heterologous immunity against S. mekongi infection. Manifestation of immunity was demonstrated by significant reduction in mean schistosomular recovery (31.4%), in mean daily egg output per female worm (16.7%), in mean worm recovery (64.2%) and in mean egg deposition in the liver tissue and intestines per female worm (37.05%).

Isoenzyme analyses of Malaysian Schistosoma, S. mekongi and S. japonicum by isoelectric focusing in polyacrylamide gel.

Isoenzyme patterns of adult Malaysian Schistosoma, S. mekongi and S. japonicum strains were analysed by isoelectric focusing (IEF) in polyacrylamide gel. Enzyme patterns obtained from Malaysian Schistosoma homogenates differed from those of S. mekongi and S. japonicum strains. Malaysian Schistosoma was found to differ from S. japonicum by 8 enzymes, namely phosphoglucomutase, phosphoglucoisomerase, malate dehydrogenase, acid phosphatase, hydroxy-butyrate dehydrogenase, hexokinase and alkaline phosphatase, and from S. mekongi by phosphoglucomutase, malate dehydrogenase, aldolase and alkaline phosphatase. These results and the distinct biology of the parasite suggest that Malaysian Schistosoma is a new species in the S. japonicum complex.

Present research on schistosomiasis in Thailand.

The current status of schistosomiasis in Thailand is briefly reviewed. Collaborative research on the Mekong Schistosoma in Thailand and the susceptibilities of the snail intermediate hosts of the schistosomes in Southeast Asia is reported.