Alterações imunológicas e histopatológicas em Biomphalaria glabrata SAY, 1818 (pulmonata: Planorbidae) infectada por Schistosoma mansoni Sambon, 1907 (Trematoda: Schistosomatidae) e exposta a concentração subletal do látex de Euphorbia milii (syn splendens) var. hislopii (Euphorbiaceae)

Abstract

In Brazil, schistosomiasis mansoni affects about 7 million people and other 25 millions are at the risk contrating a disease. One of the ways to control schistosomiasis is the use of molluscicides to control the intermediate host. Among the non-chemicals tested, latex Euphorbia milii var. hislopii showed molluscicide potencial in low concentrations following the criteria of WHO. This thesis aimed to verify Biomphalaria glabrata immunological and tissue changes caused by exposure to a sublethal concentration of E. milii latex for 24 hours. The analysis were made in 4 groups of mollusks : infected by S. mansoni and exposed to latex (IE) uninfected and exposed to latex (E), only infected (I) and control – neither infected nor exposed (C). The immunological analysis was made in 10 mollusks of each group through the quantification, chracterization of hemocytes and production of nitric oxide. In relation to histology, five mollusks of each group were separated to the analysis, through longitudinal sections. The results related to the number of hemocytes were: group I presented the lower number of hemocytes than others and group IE showed the significative increase comparing with the others. The groups E and C did not present significative difference. Three types of hemocytes were found: hyalinocytes, granulocytes and blast-like cells. In all the groups the proportion of hyalinocytes was superior, C (59,8%), E (47,5%), I (45,7%), IE (41,3%). In groups E (28,4%), I (36,8%) and IE (31,7%) the second greatest type was granulocytes followed by blast-like cells in lower proportion. In group C the blast-like cells represented 27,5%, followed by granulocytes 12,5%. There was no significant difference among the cell types and the different groups analyzed in 24 hours. Comparing the types of hemocytes in each group significant difference was observed between the number of cells of the type hyalinocytes and blast-like in the control and infected group. Concerning the NO production, the mollusks of group C showed an increase comparing with the others. There was no difference in the NO production comparing the group IE with the groups E and I. Whereas the group E presented a reduction in relation to the group I. The E.milii latex exposition promoted, in the group infected by S. mansoni a great proliferation of hemocytes in the tentacles, mantle, mufla, digestive gland, kidney and ovotestis. In the digestive gland and the kidney were observed granulomatous reactions around the sporocysts, characteristics of mollusks resistant to the infection. In the mantle, tissue destruction with dead sporocysts was observed. In the uninfected group and exposed, there was also proliferation of hemocytes in the kidney and the digestive gland, besides of this we observed edema in the mantle area. We conclude that the sublethal concentration of the latex of E. milii influenced the immune response of the suscetible lineage B. glabrata to infection by S.mansoni, promoving the destruction of parasites as observed in resistant snails.