Histopathologic features associated with susceptibility and resistance of biomphalaria snails to infection with Schistosoma mansoni

Abstract

Resistance and susceptibility of Biomphalaria snails to Schistosoma mansoni sporocysts occur in different degrees. Histopathology reflects these diferences. In a state of tolerance numerous sporocysts in different stages of differentiation are seen in the absence of host tissue reaction. However extensive diffuse and focal proliferation of amebocytes with sequestration and destruction of many parasitic structures appear in resistant snails. Some snails are totally resistant and when exposed to infecting miracidia may never eliminate cercarie. Sequential histopathological examination has revealed that in such cases the infected miracidia are destroyed a few minutes to 24 hr after penetration in the snail. However, B. glabrata that were exposed to S. mansoni miracidia and three moths later failed to shed cercariae, exhibited focal and diffuse proliferation of amebocytes in many organs in the absence of pasitic structures. These lesions were similar to those observed in resistant snails that were still eliminating a few cercariae, with the difference that no recognizable sporocystic structures or remmants were present. Histological investigation carried out in similarly resistant B. tenagophila and B. straminea presented essentially normal histologic structures. Only occasionally a few focal proliferative (granulomatous) amebocytic reactions were seen in ovotestis and in the tubular portion of the kidney.Probably, there are two types of reactions to miracidium presented by totally resistant snails: one would implicate the immediate destruction of the miracidium leaving no traces in the tissues; the other involving late reactions that seem to completely destroy invading sporocysts and leave histological changes.

Angiostrongylus costaricensis (Nematoda: Protostrongylidae): migration route in experimental infection of Omalonyx sp. (Gastropoda: Succineidae)

“…4. Studies using different populations/strains of Biomphalaria and Schistosoma mansoni reported the variability in host responses, according to their geographical origin and species (Newton 1952;Guaraldo et al 1981;Godoy et al 1997;Borges et al 1998).…”

Effects of the desiccation on Biomphalaria tenagophila (Orbigny, 1835) (Mollusca) infected by Schistosoma mansoni Sambon, 1907

“…When the hemocytes concentrate around the larvae they form granuloma type structures (Borges et al 1998). The hemocytes are small phagocytic cells with basophil cytoplasm and varied forms, due to pseudopodia emission.…”

Histopathological study on susceptible and resistant Bulinus truncatus snails to infection with Schistosoma haematobium

“…Hematoxylin-eosin-stained 5-µM sections were examined microscopically for the histological condition of larval trematodes, as categorized by Borges et al (1998). Histological analysis was performed on about 38 and 45 susceptible and resistant snails, respectively.…”