The
glucose content in the hemolymph and
glycogen content in the digestive gland-gonad complex (DGG) and cephalopedal mass of Biomphalaria glabrata exposed to different parasite doses (5 and 50 miracidia) of Echinostoma paraensei as well as the activity of
lactate dehydrogenase were evaluated. HPLC (high-performance liquid chromatography) analyses were also performed to determine the concentrations of four organic
acids (oxalic, succinic, pyruvic and lactic) present in the hemolymph of infected and uninfected snails, to better understand the effect of
infection on the host's energetic/oxidative metabolism. The snails were dissected 1-4 weeks after
infection to collect the hemolymph and separate the tissues. There was alteration in the glycemia of the snails at both parasite doses, with a significant increase of glycemia from of the third week after
infection in comparison to the control group. Changes were also observed in the
lactate dehydrogenase activity, with increased activity as the
infection progressed. In parallel, there was a decrease in the
glycogen content in the storage tissues, with a markedly greater reduction in the digestive gland-gonad complex (larval development site) in comparison with the cephalopedal mass. Additionally, the
infection by both miracidial doses resulted in an increase of oxalic and
lactic acid levels, as well as in a decline of piruvic and
succinic acid levels in B. glabrata, thus explaining the reduction of the oxidative decarboxylation rate in the tricarboxylic acid cycle and acceleration of the anaerobic degradation of
carbohydrates in the snails, through lactic fermentation, which is essential to ensure energy supply and success of the
infection.