Schistosoma haematobium: amoscanate and adult worm ultrastructure

Amoscanate, when administered orally as an aqueous or "formulated" preparation, induced pronounced ultrastructural abnormalities in male and female Schistosoma haematobium. Higher dose levels of the aqueous suspension (300 mg/kg body wt) had to be administered to achieve the full range of effects induced by formulated doses of 2.5-8 mg/kg body wt. Worms were recovered from hamsters between 1 and 120 hr after treatment. Although the amount of amoscanate-induced damage varied considerably between worms, an overall pattern of damage emerged. Initially, 1 hr after treatment, amoscanate caused tegumental vacuolation and oedema. As the drug treatment period was extended to 24 hr, blebbing, exudation, collapse of sensory organelle bases, and abnormal mitochondria became increasingly evident. With exposure to higher drug doses (50-300 mg/kg body wt), the tegument became further distorted with the appearance of necrotic structures and myelin whorls, which appeared to represent various stages in lysosomal formation and digestion. Eventually, erosion of surface layers resulted in the breakdown of tegumental integrity. The caeca and vitellaria were also adversely affected by drug treatment. Basal vacuolation and the formation of myelin whorls occurred in the gastrodermis. In the mature S4 vitelline cells, coalesced vitelline droplets and myelin whorls were evident.