LIGHT AND ELECTRON-MICROSCOPY STUDIES ON ONCHOCERCA-JAKUTENSIS AND O-FLEXUOSA OF RED DEER SHOW DIFFERENT HOST-PARASITE INTERACTIONS

Adult filariae of two intranodular Onchocerca species of red deer (Cer vus elaphus) were examined at the ultrastructural level. In all, 90 no dules of O. flexuosa and 20 nodules of O. jakutensis were studied by h istology. O. jakutensis caused cystic and pus-filled nodules in which the female and male worms were motile. Female worms possessed a thick cuticle and a well-developed somatic musculature. The basal lamina of the muscular syncytia was connected with the transhypodermal fibers th rough long protrusions. The epicuticle had only few protuberances and no visible surface coat. Female O. flexuosa showed morphological featu res similar to those of other intranodular filariae. A surface coat co uld not be detected. In 24% of 33 nodules with young live female worms and 40% of 38 nodules with older live female O. flexuosa the worms we re surrounded by giant cells apparently attacking a cuticle. This was found even in nodules obtained from animals no older than 9 months. It is probable that the lack of a surface coat protecting the female wor m and the inability to move due to the reduced somatic muscles lead to an early elimination of O. flexuosa by the host's immune system.