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Clinostomum complanatum is a digenetic trematode that causes yellow grub disease in some fish species and also shows zoonotic potential by sporadically infecting humans. In this study, progenetic metacercariae of C. complanatum were obtained from the fish Trichogaster fasciatus, and were aseptically placed in conjunctival incisions made in the superior and inferior fornices of the eye of rabbits, which served as the experimental hosts. Worms were harvested without necropsy of the host on days 4 and 8 post infection, to observe in vivo transformation of the progenetic metacercariae into ovigerous adult worms. The worms appeared to cause minimal damage to the host although they were tenaciously attached. In vivo maturation was evident by the development of the vitellaria, enlargement of gonads, the presence of a large number of shelled eggs in a distended uterus and ramifications of the intestinal caeca. Obtaining mature ovigerous worms without sacrificing the host clearly gives the rabbit eye model an advantage over those described previously. Due to the relative advantage of the short time required for maturation and the prolific egg production by C. complanatum, it is suggested that this host–parasite system could be used as an excellent model for classroom teaching of trematode biology and to investigate the cues involved in in vivo transformation and host–parasite interactions. [ABSTRACT FROM AUTHOR]

Infected hosts progressively decrease egg output during the chronic phase of Schistosoma mansoni infection. Ageing may be a factor that results in a progressive decrease in the ability to reproduce. This study was performed to gain insight into the effects of ageing on adult schistosomes, using confocal laser scanning microscopy. Adult worms were recovered from experimentally infected Nectomys squamipes (water rat). Viable eggs were voided in the faeces for 65 weeks and, thereafter, only unviable eggs were eliminated. The rat died after 70 weeks in captivity. Recovered worms (six males and one female) were prepared for confocal microscopy and images were obtained with an LSM 510-ZETA laser confocal microscope. The overall morphology of the adult worms (suckers and tegument) and reproductive organs were the focus of this work. The suckers, ovary, vitellaria and oocytes appeared to be apparently normal. The ootype was formed by flattened cells and unclear nuclei, suggesting that the mechanism for eggshell production by the ootype during organogenesis might have been impaired. Testicular lobes showed empty areas around the germinative cells. Male adult worms showed flaccid musculature of the dorsal surface. Taken together, the present results provided several indications of infertility in older male and female schistosomes. [ABSTRACT FROM AUTHOR]