The effect of ambient temperature on biological properties and energy metabolism of Fasciola hepatica metacercariae.

Parasitic helminths mainly use carbohydrates for energy synthesis, of which glycogen is the main reserve polysaccharide. When its content decreases to the minimum value, helminths lose their invasive capability. The material for the research was F. hepatica metacercariae. The complete biological cycle of F. hepatica development, from incubation of adult helminth eggs to production of sexually mature trematodes in definitive hosts was reproduced in laboratory conditions using common methods of parasitic helminth cultivation. F. hepatica metacercariae were kept in petri dishes with distilled water on the leaves of Elytrigia repens under different temperature conditions. In experimental conditions, we observed a high stability of F. hepatica metacercariae. Their long-term storage at a constant temperature of 6 ± 2 ° C causes a gradual decrease in the biological properties of F. hepatica metacercariae: viability, invasive capability and glycogen concentration. The glycogen concentration from 0.115 to 0.061 μg in a metacercaria ensures the preservation of basic biological properties of the helminth. An increase in ambient temperature (38 ± 2 ° C) or freezing temperatures (-2 ± 2 ° C) cause a sharp decrease in the viability, the invasive capability and glycogen content. The invasive material becomes sterile after 72 h under high (38 ± 2 ° C) temperature conditions, and 96 days under freezing (-2 ± 2 ° C) conditions.