Ultrastructural changes to the tegumental system and the gastrodermal cells in adult Fasciola hepatica following in vivo treatment with the experimental fasciolicide, compound alpha

Slice infected with the triclabendazole-susceptible, Cullompton isolate of Fasciola hepatica were dosed with 15 mg/kg of compound alpha at 12 weeks post-infection. Adult flukes were recovered from the bile ducts at 24, 48 and 72 h post-treatment (p.t.). Ultrastructural changes to the flukes were assessed using transmission electron microscopy (TEM), with a view tot gathering information oil the mechanism(s) of action for compound alpha and on the possible route of its entry into F. hepatica. The tegumental syncytium was more severly affected than the gut at all time-points p.t. with compound alpha, suggesting at predominantly trans-tegumental route of uptake. Disruption to the tegumental system became increasingly severe over time. A stress response was observed at 24 h p.t. and tool: the form of blebbing and increases in the production and transport of secretory bodies. By 72 h p.t., extensive tegumental loss and degeneration of the tegumental cell bodies had occurred. Degeneration of subtegumental tissues and internal flooding were also observed. (Changes in the gastrodermal cells were slow to develop: reduced secretory activity was evident art 72 h p.t. There was progressive disruption to the somatic muscle layers, with disorganization of the muscle block, and loss of muscle fibres.