Reports of changes in snails’ cellular and humoral immune responses following exposure to pesticides are rare in literature, and we found no studies using phytochemical products. Our results show, for the first time, how the exposure to a phytochemical can change the profile of hemocytes and influence the host’s immune response to the parasite. In this case, we used S. mansoni-B. glabrata model with E. milii latex exposure. We observed proliferation of hemocytes (circulating and tissue-specific) and subsequently death of parasites in tissues with the presence of a granulomatous structure. The E. milii latex was able to influence the S. mansoni in the intermediate host, reducing the cercariae shedding in water, changing the parasite’s life cycle. The E. milii latex exposure stimulated hemocyte proliferation in the tissue after 24 hours. The presence of the product in the water may have affected sporocyst recognition as self and triggering snail response . This effect caused by this phytochemical, we are calling of the schistosomostatic effect. The immunological conditions observed in our study resembled those described in the literature for infection-resistant strains, especially the cell immune response with granuloma formation, which is characteristic of resistant strains [29, 30]. Therefore, our results agree with studies that have shown that several classes of stressors increase hemocyte proliferation in the tissue of B. glabrata, such as ferritin, synthetic latex and bacteria .
In the susceptible snails, the hemocytes presented low number, motility, phagocytic capacity and activation of new hemocytes, allowing the development of the parasite [32, 33], as observed in the Group I. Compatibility between S. mansoni and B. glabrata is directly related to the incorporation of soluble antigens present in the hemolymph by the primary sporocysts, [11, 29] a similar reaction to that observed in vertebrate hosts, called antigenic mimicry. The suppression of the cellular immune response is an adaptative process of the parasite . In our study it seems to us that the product somehow interfered in this process and further studies are needed.
In relation to characterization of the hemocytes, recently Cavalcanti et al.  studied the morphology B. glabrata hemocytes and observed three cell types: blast-like cells, granulocytes and hyalinocytes, the last divided into three subtypes. The hyalinocytes were the most frequent cell type, followed by granulocytes and blast cells. In the present study, hyalinocytes were most commonly found, followed by granulocytes and blast cells, except in the Group C, where the percentage of hyalinocytes was followed by blast-like cells and granulocytes, like observed by Cavalcanti et al. . Those authors did not report the relation between the type of hemocytes and susceptibility of the parasite. It seems that the hemocyte type does not influence the cellular immune response, but the number of hemocytes does.
In the relation the toxic effect of phytochemicals, several works have reported snail tissue damages caused by aqueous plant extracts [34–38]. Using aqueous extract of E. milii in Lymnaea columella, Pile et al. [37, 38] observed lesions characterized by degeneration, necrosis and accumulation of liquid in the digestive gland and kidney in specimens submitted to 0.47 ml/l of latex, similar to our findings. We also observed lesions in the digestive gland and mantle, close to the kidney, observed by different colorations in the digestive gland and by edema in the epithelium of the kidney, suggesting liquid accumulation. In addition, we also observed dark substances without structures in the digestive gland epithelium, similar to the substances described by Adewunmi and Ogbe . We observed in uninfected and infected B. glabrata the same toxic effect in the tissue described by Pile et al. [37, 38] in Lymnaea columella. In this study, using sublethal concentrations of E. milii latex, the intermediate host did not die, but the products altered the tissue structure, probably related to toxic effect of this product, which directly interfered in hemocyte profile of the tissues.