Morphological alterations in female litomosoides carinii after treatment with two benzthiazole derivatives in vivo.

Multimammate rats (Mastomys natalensis) infected with Litomosoides carinii were treated 65 days after infection with a single oral dose of 50 mg/kg of CGP 20308 or CGP 20376 (Ciba Geigy Limited, Basel). Autopsies were performed between 1 and 28 days after treatment. The numbers of worms and the numbers and condition of intrauterine developmental stages in the females were determined. Other female filariae were investigated by transmission electron microscopy (TEM). Female filariae were observed to be immobile on Day 2, later became encapsulated, and had almost disappeared on Day 28. The number of embryos had decreased on Day 6 and even more on Day 14, when only 5-10% appeared light-microscopically unaffected. TEM examination of the filarial midbody regions revealed, that the fine structures of all somatic muscle cells began to disintegrate as early as Day 4 after treatment with either drug. The breakdown of these cells was increased on Day 6 and Day 14. The cytoplasm of the nerve fibres was more electron-dense in treated than in untreated worms. No alterations were observed in the hypodermis, the cuticle, the intestine and the uterine epithelia. Sections from anterior and posterior regions of the parasites were studied after treatment with CGP 20308 only. Degenerating nerve fibres were found in the nerve rings of these filariae 4 days after treatment.