Philophthalmus species, probablyP. palpebrarum, in Israel: description of the eye fluke from experimental infection

Abstract

Following a recent incident of human philophthalmosis in Israel, the intramolluscan larval trematode fauna in snails randomly collected from the suspected water source was checked. Of the snails examined, onlyMelanopsis praemorsa shed cercariae, including aPhilophthalmus cercaria. To identify the philophthalmid species involved, chicks were experimentally infected with metacercariae of the trematode, subsequently yielding mature trematodes resembling those ofP. palpebrarum. The majority of trematodes obtained, whether from one-worm infections or from multiple-worm infections resulting in a single trematode in one of the eyes, were relatively small and showed only immature eggs in their uteri. This finding suggests that the existing descriptions of two species ofPhilophthalmus purportedly harbouring eggs with non-oculate miracidia, namelyP. palpebrarum andP. nyrocae, are actually based on immature specimens from one-worm infections that precluded cross-fertilisation. If this be true, then all species of the genusPhilophthalmus produce eggs that, when mature, contain oculate miracidia. The species encountered in Israel is thus most likelyP. palpebrarum.