Biochemical and morphological pathology of the foot of the schistosome vector Biomphalaria glabrata infected with Schistosoma mansoni.

Infection by Schistosoma mansoni resulted in morphological and biochemical changes to the foot of its intermediate host, Biomphalaria glabrata. Migration through, and emergence of cercariae from, the foot was observed and evidenced by lesions on the ciliated foot surface. This was accompanied by a significant decrease in the velocity of movement by infected individuals. In vivo 31P NMR spectral analyses demonstrated that the foot of infected snails had a lower phosphoarginine (PA)/adenosine 5' triphosphate (ATP) ratio than that of uninfected controls. Moreover, kinetic experiments, employing saturation transfer, demonstrated the pseudo-first-order rate constant for the arginine kinase-catalysed exchange reaction in the forward direction, that is, PA-->ATP was decreased by infection. The reverse reaction was not observed by the NMR methods used. PA was depleted upon exposure to hypoxic conditions suggesting its traditional role in preserving ATP level. Partly oxidized metabolic end-products were not observed in snails maintained under aerobic conditions, but succinate, propionate, acetate and lactate rapidly accumulated under hypoxic conditions.